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Old 10-15-2015, 03:56 PM
  #21  
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Default Z06 at Motor Trend's "Best Driver's Car"

Original answer thread is here.

four0nefive asked:
I think many people want an answer to this question. I'm not sure if you are aware, but the Z06 that was supplied to Motor Trend for their Best Drivers Car competition finished as a DNF (last place). They noted that the car was supplied with worn brake pads and that the supercharger refused to make boost. We would like to know whether these press cars are checked to make sure if they are in proper condition before they are sent out? It seems like they haven't been checked considering that this is the 2nd time a car was sent to MT and didn't perform properly. To add to this, is it possible that Jim or someone from the racing team will do a hot lap at Laguna Seca since MT will most likely not retest the Z06 at LS?
Tadge answered:
The short answer to this question is, yes, we check our press cars before we send them out. However, you are probably looking for the full story and how to reconcile how a Z06, actually the exact same Z06, could do so well in Car and Driver's hands for the Lightning Lap and be such a disappointment weeks later in Motor Trend's Best Driver's car issue.

First a little background: Corvettes are highly sought after test cars for media around the world. The number of requests we get to evaluate cars is well beyond our ability to accommodate them. We have to pick and choose and set priorities. The natural question might be: "You are the manufacturer. Why don't you just make more cars and have a bigger press fleet?" The truth is we have limited resources to manage such fleets and since we are capacity-constrained in production at Bowling Green, every car we put into the press fleet is a car we take away from a paying customer. That means people who have had orders placed for a long time have to wait even longer. We try to accommodate as many media requests as we can and that means there is enormous pressure to minimize the prep time for cars between media loans. Media deadlines are absolute, just like race start times, if you aren't ready when the green flag drops, you don't run. The goal for media prep is always the same: Make the car like-new for each loan. Sometimes this is easy, sometimes there is a lot of work to be done. Magazines and other media rightly expect the cars to be perfect, both mechanically and aesthetically. They usually use the same car for photography and track testing. It would be great to send two cars for every loan, so we would have a back-up, but then we would have to double the size of our fleet (see above). Bottom line is that the Car and Driver loan and Motor Trend loan were scheduled back to back. What could go wrong, right?

A lot, as it turns out. During testing at C and D the car went off track into a tire wall. Stuff happens. It wasn't the first time this has happened and I'm certain it won't be the last. Fortunately, the damage to the car was cosmetic (rear fascia, supports and the energy absorption assembly). It didn't have any fundamental structural or chassis damage. The alignment was fine. Basically, zip ties and some duct tape was all it took to make it track-worthy. The car then went out and ran the second fastest Lightening Lap they have ever recorded.

Any time there is an incident like that, we have to tear the car down, replace broken parts and make it like-new again. In the few days we had to prep the car for Motor Trend, we did a tremendous amount of work to make sure the car was safe, capable and pretty. In our haste, two things were missed. We always replace brake pads before delivering a car, but this was missed. I can’t remember this ever happening before, but it did. We have since changed our pre-test check procedure so this can never happen again. Although Motor Trend made it a point in the article, they did not notice any issue with braking performance during their spirited street drives. Our engineer on-site noticed the linings were worn, and they were immediately replaced and burnished. This was done the day before the Z06 was run on track by Randy Pobst and had absolutely no bearing on the results of the test.

The second unfortunate occurrence related to the intercooler circuit. One of our pre-loan checks is to bleed the intercooler circuit to make sure there is no air in it. Some customer complaints about over heating Z06s have been traced to improperly bled intercoolers. The technician doing the work plugged in the electrical connector for the intercooler pump and it seemed to seat and "click" into position, but the secondary latching mechanism did not fully lock into position leading to intermittent operation. Without the pump running there is no coolant flow, no intake charge cooling and the engine pulls spark to protect itself. That is what Motor Trend experienced at random times during their testing. Unfortunately, the connector was seated enough that the pump and engine worked fine in all the pre-test driving done before trucking the car across the country to Motor Trend in California. Remember this is the same car that performed flawlessly a few weeks prior in sweltering heat during Car and Driver's Lightning Lap. The possibility of bad fuel was discussed because it was clear there was an abundant amount of spark retard, but we didn't discover the true root cause until the car had returned to the Milford Proving Grounds after the test. We have modified our procedure to run the pump remotely during the bleed process so this issue can be avoided in the future.

Bottom line is that like any team we have good days and we have bad days. We showed well at Car and Driver Lightning Lap and stumbled at Motor Trend. We engineers and technicians on the team are even more disappointed than any in the Corvette community. We are reviewing our prep processes, which loans we prioritize and even the size of our media fleet. We will get better. We will live to fight another day. Motor Trend is planning another test at Laguna Seca in a few months with some very, very capable competitors. We intend to be ready.

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Old 10-30-2015, 06:57 AM
  #22  
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Default Added cooler on 2016 Z51 A8 - Air Flow?

Original answer thread is here.

BrittHealey asked:
The added cooler lies parallel and very close to the bottom cover that would seem to minimize air flow and reduce its effectiveness. Please comment.
Tadge answered:
Good question BrittHealey.

Intuitively, it would seem that panel under the horizontal cooler blocks the exiting flow, thus reducing its effectiveness. We thought the same thing. And we wanted to maximize the cooler's effectiveness. We were also worried that dumping more air under the car would hurt front down force. So we tested it both ways. Tests with the bottom panel opened up didn't help cooling and resulted in lost down force. The reason it works that way is that hot airflow exiting the transmission cooler has enough open perimeter area above the bottom panel to keep from losing cooling effectiveness. That airflow exits from the spaces aft of the cooler and is reintroduced with underbody airflow without adding front lift.

If you look at the undersides of high performance cars, you will see that a lot of engineering work has been done to balance the aerodynamic priority of a smooth, closed-out underbody with the necessity of exiting cooling air from a variety of heat exchangers.

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Old 11-04-2015, 11:50 AM
  #23  
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Default Why aren't the C7's E85 compatible?

Original answer thread is here.

RC000E asked:
Allowing the Z06 or C7's the ability to use E85 seems like a fantastic option for track sessions to keep knock retard at bay, reduce EGT's, etc. Was there ever a consideration to make these cars flex fuel compatible and/or why was the decision made not to?
Tadge answered:
RC000E, as you correctly point out, higher octane of E85 is directionally correct in mitigating knock and resulting spark retard. We have recommended the use of racing fuel and octane boost for that very reason in certain situations. The issue with E85 in high performance engines is that there is less total energy per gallon, that is why fuel economy measured in miles per gallon tends to be worse with E85. While it is theoretically possible to build a 650Hp engine that uses E85, The challenge is getting enough fuel into the cylinders. The fuel flow rate to the injectors has to be higher in proportion to the energy content of the fuel. That means over 25% more fuel flow. Direct injection engines require very high fuel pressure to operate. At the time the LT4 engine was designed, there was no pump in existence that could manage the combination of flow and pressure. It is always possible to try to force a supplier into a unique low-volume solution to meet our needs however it would have been larger, heavier and much more expensive. In addition to the pump on the engine, the pump in the fuel tank would have to be up-sized and possibly even need twin pumps. Routing fuel from the tanks at the back of the car to the engine at the front is always a challenge. Higher volume of fuel flowing requires larger lines that are even more difficult to package. So, for a variety of technical reasons, we elected not to design for E85 on Corvette.

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Old 12-11-2015, 06:19 PM
  #24  
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Default New GM performance parts voids powertrain warranty!

Original answer thread is here.

AliZ51 asked:
GM performance part group is finally on the move and we are hearing one announcement after another with regards to the release of new components. This is great until we read the disclaimer and that all these parts would/ will void the powertrain warranty. How can GM justify voiding a powertrain warranty even for a carbon fiber cover? Please clarify. Thank you.
Tadge answered:
Great question from the forum. Although I am not directly responsible for performance parts, this question caused detailed conversation about the relationship between that business activity and our factory warranty. That is why this answer took longer to provide. As we continue to develop more and better performance parts we will strive for better clarity on impact to warranty, if any.

We assume that this question originated from the new SEMA offerings of Performance Parts for Corvette (cooling kits, aero kits, carbon fiber braces, brake kits, T1 suspension kit, and driveline kits) and the publishing of these parts in the 2016 Performance Parts catalog. The warranty disclaimer statement that is published in the catalog (see statement below*) was originally written for crate engines and engine parts, and had not been changed to reflect the differences between Powertrain Parts and our Vehicle Performance Parts offerings. We are in process of re-writing this statement and will publish the update in the catalog and online at the next printing.

Our intent is not to altogether void the New Vehicle Limited Warranty nor the Powertrain Warranty on our Vehicle Performance Parts, and most of the Performance Parts available for Corvette do not restrict these warranties at all. We will, however, need to restrict some aspects of these warranties, as noted below, given that installation of some Performance Parts will alter the intended uses of the production vehicles. There are also instances where Performance Parts take the vehicle out of compliance for public road use. These restrictions will be disclosed to Performance Parts consumers so that they can knowledgeably choose whether or not to install such parts. .

In the first printing of the catalog, the following parts were called out with the standard warranty disclaimer. We are now more clearly defining the specific restrictions and will publish these in the next catalog update:
  • Secondary Radiator and 600w fan – this was a misprint in the catalog – there are no warranty restrictions on these parts. These will not void the New Vehicle Limited Warranty.
  • Carbon fiber braces – these parts are intended for off-road use only. Our long term, 10 year corrosion testing is not complete and therefore warranty claims for corrosion at the attachments of the brace to body will be restricted. The remainder of the factory warranty is intact.
  • Z51 brakes for Stingray – in this kit, the mass dampers were removed from the stock Z51 pads in order to fit inside of the base Stingray wheels. Mass dampers are used to tune the system for brake noise, and therefore this kit is not warranted for noise performance. The remainder of the factory warranty is intact.
  • Z06 brakes for Z51 – this application is for off-road use only because the stock Z51 wheels do not fit over the Z06 brakes. We cannot test or certify to all of the potential solutions. Any failures occurring as a result of the non-production wheels selected by the customer would not be covered. The remainder of the factory warranty is intact.
  • T1 suspension kit – this suspension kit is designed for off-road, racing use only. Generally speaking we expect vehicles equipped with the T1 content would also be outfitted with track slicks and raced, both of which do void the general vehicle warranty.
Thank you for bringing this issue to our attention. You have made us realize that a generic disclaimer does not clearly communicate the reasoning and intent behind each of the Performance Part restrictions. We are pushing to continue to bring new, exciting parts to market, and we’d love to hear your feedback.

*Current Catalog statement (for reference only):
The use of this engine or component in a new Chevrolet vehicle voids the vehicle powertrain warranty and may result in adversely affecting vehicle performance. In some cases, use of certain Chevrolet Performance components may result in the failure of other components or systems, thus voiding the warranty of the failed component or system. Chevrolet Performance components installed in new vehicles do retain their regular warranty coverage unless otherwise noted.

These engines and components have not been tested or validated by GM Engineering for use in these vehicles. Installation of components or engines in non-original applications may require fabrication or modifications that affect other vehicle systems. Certain engines may require modifications to the vehicle for fit and operation.

The installation and operation of these components or replacement engines in new vehicles is intended for off-road operation only.

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Old 12-18-2015, 05:09 PM
  #25  
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Default Automatic Transmission Paddle Shift reaction time

Original answer thread is here.

dmhines asked:
Why does the time between depressing the paddle in manual mode and the Automatic Transmission shifting seem so long. Why can't it be instantaneous?
Tadge answered:
First of all, we on Team Corvette want to wish everyone in the Corvette community and on the Corvette Forum a wonderful holiday and a safe and happy new year!

Now on to the answer:

Although shift speeds have been a priority in racing for a long time, it is a relatively new focus in the mass production auto industry. For decades we had basically two transmission choices; a traditional manual transmission where the time to shift was 100% dependent on the driver’s skill level, and a torque converter automatic where the vehicle hardware and calibration determined the shift timing and speed. The main focus on the automatics was a smooth shift with little driveline or customer disturbance. Yes, there were niche products that featured different set ups, so pardon me for the generalization.

Some performance cars started to offer automated manual transmissions that used a traditional clutch but did the work of shifting robotically, but my experience with those early units was that they were slow and lacked the finesse of a well-shifted manual driven by a skilled driver. Over time the shift quality and speed was improved and manufacturers started talking about shift times as an important performance vehicle characteristic. For the most part auto makers have moved away from automated manuals and use sophisticated planetary automatics or DCT’s to get the best shift speed and quality. This question focuses on shift speed, so I will leave the pros and cons of the two automatic transmission types for another day.

So why can’t down shifts be instantaneous? Well, there is the transmission hardware side that faces the physical challenge of transferring the torque from one set of gears to another set of gears. That is the time most manufacturers quote when discussing shift times. Those times have been improved over the years to very small fractions of a second and the Corvette is competitive with the best on that score. To be honest, we have put a higher priority on upshifts because they occur while accelerating and will contribute faster lap times. Downshifts typically occur when off-throttle and on the brakes, so a slower shift is far less likely to affect lap times. Regardless, up or down, our 8-speed automatic transmission is capable of extremely fast shift speeds.

The paddle shifters on Corvette are controlled by on-board computers just like many other functions on the car. They are “intelligent” devices that seek to improve the safety and controllability of the car. When the driver requests a downshift, the car does not blindly obey (the same is true for throttle inputs). It checks a multitude of parameters to verify that a shift can be done safely, without risk of damage to the car and without upsetting the vehicle dynamics. The control modules work to match the speed and torque of the engine to the future gear state. Note that there are a number of ECUs (Electronic Control Units) involved communicating in a coordinated way across an on-vehicle network, not just a computation done in a single processor. The larger the engine, the more inertia and the more challenging perfect matching is. I’m sure you know that an abrupt shift and resulting torque spike while cornering quickly can unsettle the car, so the algorithms for shifting will take that into account. In addition to how the car is being driven, ambient conditions, driver mode selected and other factors are taken into account. Even the break-in state of the transmission matters. Over time the transmission actually learns about itself and seeks to improve shift performance. All this intelligence takes computational time by the on-board processors. The throughput of those processors is dependent on the workload at the time of the shift, so the latency from shift command to shift execution can vary a bit.

All manufacturers are working to improve the shift speed and quality of their transmissions. I foresee ongoing improvement in this area.

One last side note: Some companies do something that we do not do. They move the tachometer needle to the new rpm on a shift faster than the engine actually achieves it. This bit of electronic trickery improves the perception of shift speed without actually changing it. Although it seems to be effective, we don't do it because it is inconsistent with our philosophy on Corvette to convey the most accurate information possible in our cluster displays.

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Old 01-22-2016, 03:33 PM
  #26  
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Default Stiffer suspension for standard Z06

Original answer thread is here.

AliZ51 asked:
Can you explain the calibration differences between a standard Z06 and the Z07 package. We know that the Z07 (FE7) suspension is stiffer than standard Z06 (FE6) but many Z06 owners like to have a stiffer suspension without the Z07 package. Some forum members/ Z06 owners researched and found that the springs, shocks, and stab bar bushings are stiffer on the Z07 and these parts can be purchased from any GM dealer. The concern is with MR calibration or if there is any negative effect for adding these parts without proper calibration.

If calibration is in fact needed, would GM offer the calibration for purchase (similar idea to rough track calibration on Z07) through GMPP?

Can this be also available for Z51 owners with MSRC?
Tadge answered:

Chassis tuning is quite a complex melding of art and science. Despite our massive computational capability, no one has yet invented a way for computers to create the optimal combination of tire construction, bushing rates, spring rates, stab bar torsional stiffness, and shock tuning to ensure optimum handling in conjunction with great ride. Analytical techniques help us to define suspension geometry (kinematics), the stiffness of each individual component, and get us into the ball-park on spring and stab bar rates. However, much of the final tuning is still done the way it has been for over 100 years: Talented, skillful drivers use their subjective impressions supplemented with measured data to continuously improve our initial specification to achieve that elusive perfect balance of ride and handling. Of course modern cars, especially Corvette, then overlay enormously complex electronic controls of ABS, Traction control, launch control, stability systems, Elsd, and ride modes. Both the mechanical and electronic system are balanced to meet legal requirements and performance expectations from customers in all countries and environmental conditions. As the factory, we are obligated to thoroughly validate everything we sell, which requires a lot of engineering resources. That is why we sell packages of equipment and can't let customers order every imaginable combination of chassis set ups, brakes, tires and aero packages. We always shoot for the combinations that most customers will like and then tweak from there.

Jim Mero leads our chassis tuning work and is supported by many others. I asked him for a description of the Z06 Chassis options to clarify the content and talk a little about the philosophy:

Jim Mero writes:
The differences between the Z06 (FE6) and Z07 (FE7) suspension packages are:
  1. Spring rates – The Z07 spring rates were calculated to keep the cars attitude consistent at speed using the downforce loads from the stage 3 aero. Because of this, the rates and ratio of the front spring to the rear spring differ between the FE6 and FE7.
  2. MR Dampers and calibration – besides the enormous flexibility we have to add damping electrically, there are also mechanical components that can be changed to make the electronics even more aggressive. These mechanical components are used in conjunction with the proper calibration uniquely for FE6 and FE7 for optimum performance
  3. Stabilizer bar bushings - These have a significant amount of influence on the TLLTD (Tire Lateral Load Transfer Distribution) which is basically a ratio of the percent roll stiffness of the front relative to the rear. The roll stiffness is comprised of the springs, stab bars and stab bar bushings. We used the stab bar bushings to obtain the appropriate TLLTD for each chassis in conjunction with the different spring rates as mentioned in point 1.
You may ask why the stabilizer bars are not different between the 2 cars i.e. FE7 with larger front and rear bars. The answer is because we are packaging the largest rear stab bar we can in both the FE6 and FE7. Although there is a difference in TLLTD between the FE6 and FE7, the required balance was obtained using stab bar bushings in conjunction with the springs. Thus a different front bar was not required.

During the process of development of both these packages, our philosophy has remained the Z07 would be geared towards track performance with road behavior falling where it may, and the FE6 needs to be a more balanced car. Good FE6 road behavior in touring is a much more significant objective than that in the FE7. Using that philosophy, we feel we have met the objectives. Having said that, we worked very diligently to make the FE7 a well-rounded daily driver and the FE6 a very competent track performer.

In the thread nominating this question, it appears that the emphasis is more on track than sport or touring. Increasing the spring rates on the FE6, would not be allow us to meet our objective for the philosophy of that package as stated above.

Also, the Pilot Super Sport tire on the FE6 is a great tire but does not have the amazing grip provided by the PS Cup-2 tire. So when more roll stiffness is introduced to the car with a tire that is not as strong, tire saturation is a concern, which would be the case of the FE7 package paired up with the Pilot Super Sport tire.

Back to Tadge.
More from Tadge:
Thanks to Jim for that summary.

So to summarize, we can’t offer every imaginable combination because the resource cost and validation risk is too high. We try to focus on thoroughly optimized packages that address different customer’s needs. Since we introduced the Z06, we have already expanded our offerings to allow the CCM brakes on the standard car without spec'ing Z07. Those brakes do offer some attributes that customers desire without the super-aggressive tires and aero. Even though that is a "bolt on" combination, we had to go back and do all the testing to validate functionality. Note this does not mean iron and CCM brake are interchangeable. The CCM brakes have higher capacity than the steel brakes, so we don’t recommend putting the iron brakes on a "cup"-tired car.

And to answer the question directly: Yes, you could purchase the Z07 parts and bolt them on to a Z06, but we don't feel it would be worth the cost or effort. The initial perception might be that the car seems more responsive due to the high rates, but there won't be any real performance gain and it will definitely hurt the performance in other areas. It would cost-prohibitive for us to do the optimization work to offer custom shock and chassis controls to optimize that system through service parts. We do appreciate the thinking however, we are always looking for ways we can configure the car to satisfy customers.

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Old 02-12-2016, 04:08 PM
  #27  
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Default Latest Motor Trend Test at Laguna Seca

Original answer thread is here.

AliZ51 asked:
What is your take on Motor Trend latest head to head test against the ACR and GT3RS? The Z06 performed really well and made Corvette guys proud. MT pretty much loved everything about the Z06 with the exception of rear grip / oversteer issues. Randy said front grip was good but rear was very loose. Was the alignment checked on this car? Do you agree with Randy's comments that softening the rear will bring more grip for better corner entry/exit?


Tadge answered:
There are always interesting back stories associated with these tests, so I will share a few things. First of all, the alignment on the car was fine. The car handled great for our engineers performing 10 hard shake down laps at Milford before we shipped the car. The engine ran strong. We had no overheating or other performance issues in Motor Trend’s hands. So, I would like to address the handling comments, and answer the implied question, "Should the car have been faster?"

Regarding handling, we develop the Corvette at many tracks with the objective of finding a sweet spot for all from a vehicle dynamics perspective. It is evident from many other independent tests that the Z07 handling is spot on -- Super-capable without too much over steer or under steer. We do not want to overreact to comments about one vehicle, on one day, at one track at the risk of sacrificing handling for a multitude of drivers at many different tracks across the country.

That is particularly true in this case, as the story makes it clear the track conditions were far from ideal. Consider this quote about the Porsche:

“It says a lot about the GT3 RS that it’s the first and only car Randy’s ever spun while hot lapping MRLS,” Scott Evans says. “Not once but three times.”

Followed by these comments from Randy Pobst:

“I was struck by the wide gap in lap times between the Viper ACR lap record I set at Mazda Raceway with Dodge and the time I set for Motor Trend. The cars felt similar. It’s not a power issue. Top speeds on the straights and acceleration curves were similar. Grip was down. I braked earlier and had a lower minimum speed in nearly every corner. I attribute the difference to the track condition. Our MT test followed a motorcycle weekend, and those skinny bike tires don’t leave a nice layer of rubber the way race cars will. The track felt really green, as we say in racing. Perhaps it helps explain why the ‘Vette Z06 felt so unruly. The Viper had that great stable balance, same as at the lap record run, and data showed good power, just less grip. I blame the track.”

The Viper was set up for that track very well. Randy had just been in it one month earlier with SRT to set their claimed track record at Laguna Seca, so Dodge had the opportunity to fine tune the Viper for Laguna Seca. In the review, Motor Trend mentions that, "Dodge also gave us another ACR set up in Track mode — different compression and rebound settings for the dampers, a larger front splitter, a larger rear diffuser, and a different angle on the wing." One advantage of having a large rear wing, is that small changes in attack angle have a big impact to pitch moment, so you tune the aero-driven under/over steer balance at will. Of course, there are numerous disadvantages as well, such as the reduced practicality of the car.

So could we have gone faster? In a word, yes. In other similar comparison tests the two cars are much closer in lap times, but there will always be test-to-test variation. Bottom line is that the Z06 is one of the fastest cars in the world and can be used in so many more ways than a pure track machine can. That is something we are very proud of.

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Old 02-19-2016, 12:32 PM
  #28  
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Default Improving Paint Quality on Corvettes

Original answer thread is here.

RC000E asked:
Could you explain the factors/considerations/compromises that are made in determing the final paint finish on a Corvette versus its competition? Is the "orange peel" intended for durability (clear mil thickness) and has a hand finish dealer option ever been considered, etc?
Tadge answered:
Like most of the questions I get in this forum, the premise is that although people love their Corvettes, they can think of ways it could be better. Paint quality is a perfect example. First of all, Corvette paint has never been better. Even during the life of the C7 it has improved. We have reduced orange peel by 25% as measured by a Wave Scan. A Wave Scan is a certified measuring instrument the reads the spectrum of long and short waves. Analyzing the entire structure spectrum and evaluating the ratio of various structure sizes helps to explain the visual perception of the surface. We also have developed a new process for painting our Silver that produces a bright harmonious finish that accentuates the Corvette’s crisp lines. If you have not seen one in silver lately I would really encourage you to check it out, the car looks great and the color really pops. The entire Corvette Team is driven to make every Corvette we produce better than the one before it and our efforts at improving paint quality are just another example of that.

Unlike most other vehicles, Corvette owners scrutinize their cars from every angle and see it from very close range as they hand-wash their cars. As they should be, our customer's expectations are very high. We have benchmarked many premium cars and although paint quality varies quite a bit, we are solidly competitive. Yes, you can find some that are better, but you can also find many much worse. Although you mention orange peel specifically, there are many indicators of paint quality: scratches, debris in paint, swirls, drips, sags, thin spots, dry spray, color match, harmony, consistency of flake orientation and many others. We have to pay attention to all of them.

Orange peel is caused by many factors including: spray angles, temp and humidity, air pressures, flash off times, baking temperatures and how the solvent flashes off as the paint is flowing out. With the Corvette however there is another major factor not found on most other vehicles and that is our composite body. In fact Corvettes have had composite bodies since 1953. It is an awesome material for low mass, dent resistance, styling freedom and corrosion resistance. It does however, present challenges to paint. The surface is porous at a microscopic level and is non-conductive. Both of these make painting more difficult. The best way to get paint on a body panel is to use an electrostatic charge. Like most automotive paint shops, we use static electricity to attract the paint to the panels. When the panel is steel or aluminum, it is relatively easy. For composites we have to use what is called conductive prime. We first spray the panels with a primer that conducts electricity to help with the process. That same primer helps with the micro porosity issue too and so on many panels we actually spray 2 coats to help prep the surface for the color coat and the clear coat. It is a very involved process and it is made more complex by the variety of panel materials we use. Although most body panels are a form of fiberglass, we use more flexible materials to cover the front and rear bumpers and then use carbon fiber in strategic areas. Each material takes paint differently.

The question asks specifically about hand finishing. We already hand sand at many points in the process. Could it be made better with more? Yes, although vastly more resources and floor space would be required to execute a finish like the best custom paint shops. Bowling Green produces a car roughly every 3 minutes at the current line rate. You can imagine how tough it would be to replicate the finished achieved with hours of hand sanding for each car. Offering a premium finish has been considered before but has always been deemed impractical in a mass production facility. But as I say just about every week in this forum, we love to hear customer's requests so we can consider it in our forward planning.

Speaking of that, we have announced and have started construction of a new paint shop in Bowling Green. These major facilities have lead times even longer than that of a new car, so the decision to replace the facility was made years ago. The current shop is over 30 years old and is being replaced on the normal cadence to maintain our manufacturing infrastructure. Although the new shop won't come on-line until the fall of 2017, we have had significant input to its design to optimize it for painting the Corvette’s composite body. After we are done with construction, we believe we will have the finest possible paint shop for Corvette for the foreseeable future. After the new shop launches, we could highlight some of the changes we made and the new state of the art technology that will be in use. Remember our goal is to build a Corvette that will not only exceed your expectations, but one that requires no explanation. Our investment of 439 million dollars for our new paint shop is a strong example of our commitment.

I would like to recognize Chuck Valentini for his help in answering this question. He manages the paint shop in Bowling Green and works tirelessly to continuously improve Corvette paint. We owe much of the progress we have made to him.

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Old 03-08-2016, 08:53 AM
  #29  
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Default C7 A8 Transmission and Torque Convertor Questions

Original answer thread is here.

Maxie2U asked:
1) A8 Transmission: a) what changes and/or redesigns were made to the newly released A8 transmission (new part#24274892)? b) what is the date Bowling Green began to use the new transmission in production?

2) Torque Converter: why was it necessary to release a redesigned torque converter this year (as referenced in document id: 4373638)? How does this affect owners that have the old torque converters?
Tadge answered:
Before answering the questions directly, I will point out that the new 8-speed transmission has been very reliable. Our data indicate that the vast majority of owners have experienced no issues and, in fact, are enjoying the best balance of performance and efficiency we have ever offered. Although we strive for perfection, no person, company or machine is perfect so we, like all manufacturers (And not just autos…. How often is your cell phone upgraded?), practice aggressive continuous improvement. We did on our 4-speed trans years ago and likewise when we introduced the 6-speed more recently. We are doing it on the 8-speed currently. As I have answered in other questions on the Forum, we always try for backwards compatibility, but can’t restrict progress by making that a mandate.

Question 1} Part number 24274892 was released for use with the heavy duty cooling option which comes with Z51 and Z06 automatics (and will be for the just-introduced 2017 Grand Sport}. The transmission hardware itself is the same as the prior part number (24273222). The difference is that it contains more oil in it to compensate for the extra coolers and cooler line volume added to the vehicle. The 24273222 trans assembly remains released for use with the standard LT1 cooling package. The break-point for the new part number in Bowling Green was May of 2015.

Question 2) The service bulletin you cite says to perform a double oil flush if you suspect that the trans is exhibiting TCC (torque converter clutch) shudder. That procedure has been successful in fixing a few vehicles. This has primarily been a truck issue, pretty rare on Corvette. The bulletin is now being updated to have the converters replaced instead of just a flush since it has not been 100% effective. So the bottom line is if customers are not having any problems, they shouldn’t worry about that document. In the rare instance where there is truly a torque converter problem, there is new design that should help. That hardware became available in December of 2015. I want to make sure customers with the prior design understand that if there is an issue, symptoms will appear early in the car’s life. The design change was not to improve the performance of the car or it’s durability over the long term. Bottom line is that if customers are not having a problem now, it is very unlikely to occur later.

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Old 03-24-2016, 10:42 AM
  #30  
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Default Changing oil type for the track and for road use

Original answer thread is here.

descartesfool asked:
What is the effect of changing from Dexos compliant 5W30 to Mobil1 15W50 for the track and back for road use? Some cars which are used on track a lot such as Porsches and GT-Rs recommend Mobil 1 0W40 for all uses, with no changes required when driving on track. Would this oil be fine for track and street use in the C7? What are the negative effects of leaving the 15W50 after track days and driving on the road, and at what temperatures is it an issue, hot or cold?

Tadge answered:
GM Propulsion Systems has validated all Corvette engines to operate with the DEXOS 5W30 for all but the most extreme track conditions. We recommend the use of Mobil 1 15W50 when the vehicle is going to be used for high temperature track operation as the higher viscosity range provides a greater degree of protection under the extreme stresses of that duty cycle. We like the extra lube performance in those conditions because, unlike some other manufacturers, driving on the track does not automatically void the warranty. However, daily driving use of the Mobil 1 15W50 on the street has not been validated, and as such we do not recommend its use where the operating temperatures can run lower. Some contributors to the thread correctly point out that few Corvette drivers operate their vehicles at extremely low temperatures, but as the manufacturer, we have to protect for that possibility. Another issue is that the 15w50 oil has higher phosphorous and ash content than we specify for factory fill. That is ok for track usage, but in long term street usage, those chemicals can compromise catalyst performance. As the manufacturer, we are expected to meet EPA emissions for a very long time. Lastly, the higher viscosity will also result in a small loss of fuel efficiency.

As for the Mobil 1 0W40, it was not available when we validated these engines and, in its currently available formulation, it also contains more phosphorous and ash than we specify. So, even if we validated the 0W40 for track use, we would still have to recommend reverting to a DEXOS 5W30 for daily street use.

Like all aspects of the auto industry, lubricants continue to improve over time. We work with Mobil and others to elevate the performance of their products and hence ours. We will continue to do that and when we have a better oil to ship in our engines or recommend for use on the track, we will do so.

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Old 04-19-2016, 04:35 PM
  #31  
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Default Aerodynamic properties of the various C7 models

Original answer thread is here.

descartesfool asked:
In order to better understand the performance differences and goals of the C7 models, could you detail the values for the lift and drag coefficients and frontal areas for the base, Z51 and various Z06 versions and front to rear downforce ratios and total downforce at speeds, Lift/Drag ratios, and why they were chosen?
Tadge answered:
The standard Stingray has a drag coefficient of .30. Its frontal area is 2.02 square meters and has a lift coefficient of .20. Generally speaking, as you move up the Corvette model range, frontal area and drag go up and lift goes down. This is not just true of Corvette, but virtually all performance car lines. Frontal area goes up because tires get wider and you have more aggressive aerodynamic features. The aerodynamic aids that create downforce tend to disturb the air in such a way as to add drag. Directing air through heat exchangers and towards brakes to cool them also creates drag. As engines make more power, more energy needs to be dissipated in all cooling systems including coolant, oil, trans and differential lube, and in the case of charged engines, intake air.

Race cars have a lot of drag by street car standards, but they produce a lot of downforce. Race teams spend a lot of time optimizing this tradeoff for a given track. They also have to make sure the drivers like the way the car handles. It is no different for street cars, we are always looking for ways to improve down force at the minimum drag penalty. The Z51 option on the Stingray adds cooling content, a rear spoiler and modifies the aero panels under the nose of the car. It's Cdx moves up to .35 but lift drops to .03, which is very close to a zero lift car. Actually, we have tested Z51 cars with negative lift coefficients, which means those cars are producing true downforce.

The Z06, with its wider tires and flared body panels has a higher frontal area (up to about 2.1 square meters) and the standard car has drag and lift numbers similar to the Z51. The Z06 has available Stage 2 (CFZ or CFV Carbon Fiber Ground Effects) and Stage 3 (Z07 Performance package with the large end plate on splitter and the center bridge "wicker" on the rear spoiler) aero packages that further trade drag for additional downforce. Stage 2 has a "lift" coefficient of -.152 and stage 3 is -.279. The minus signs mean negative lift or down force. The trade off in drag means those coefficients move from about .40 to .50. In other words, the cars are starting to approach race car numbers. In our testing on many tracks, the improvement in corner speeds more than offsets the straight line speed loss from the higher drag. Depending on body style, our aero packages have lift to drag ratios ranging from 2.6 to 3.6. We consider anything over 2.0 (2 counts of lift reduction at the cost of a single count of drag) an efficient tradeoff.

You asked about front to rear down force ratios or what we call "Pitch moment". We have strict criteria for pitch moment. The ratio needs to be held within a fairly narrow range so that the vehicle handling remains consistent. Too much down force on the rear and the car will understeer at higher speeds. Too much on the front and the car will oversteer. We tune all our cars to maintain neutral handling biased slightly towards understeer.

I am sharing these specifics with you quite reluctantly. The reason is that there are many ways aero performance can be quantified. No two wind tunnels are exactly the same. Some have moving ground planes, some do not. Many correction factors are used because none of them replicates exactly what happens in the real world. They have finite test spaces while the world is far more open. Computation fluid dynamics (CFD) is getting so good, it is used widely and surpasses physical testing in some ways. Bottom line is that with so many ways to predict them, numbers from one manufacturer are only roughly comparable to another. In addition to the number of ways to measure, the cars themselves can be variable. Small changes in standing height or pitch (relative height of the front to the rear) can have a big effect on measured numbers. Thank you for the question. I have tried to keep the answer to a level everyone can understand. Aerodynamics can very quickly become a complex technical discussion.

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Old 05-06-2016, 02:01 PM
  #32  
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Default PDR Fix and Improvements

Original answer thread is here.

Poor-sha asked:
There appears to be an issue with the PDR system where it periodically and randomly winds back the lap timer while recording.

Multiple forum members have seen this happen and I've had this happen in both in my car and in the cars at Spring Mountain.

There is a detailed thread with screen captures already on the forum here: https://www.corvetteforum.com/forums...e-anomaly.html.

You can see in this post https://www.corvetteforum.com/forums...post1591345523 a screen shot of the Cosworth toolbox. Look at the time delta line. It goes near vertical at about the 30 sec mark even though I’m still running normally.

Also, you can watch this video at around the 1:52 mark. Just watch it in ¼ speed and you can clearly see the lap time go from 21s to 19s.
https://youtu.be/PRsLojTdA6Q

Is GM aware of this problem and is there a fix in the works? It's not the sort of thing a dealer is going to be able to replicate or fix on their own.
Tadge answered:
Several of us on the Corvette team learned a lot from researching this answer. We have known about the problem and technical folks were developing a solution before we heard from customers or got asked the question on the forum.

Most people think of time as a sort of universal constant, like a metronome clicking off the seconds with perfect regularity. Einstein is deservedly famous for showing that time is not constant, it is relative to the speed of the observer. I am not saying the Corvette is so fast that clocks run slower in the car (although that is true to a very small extent), but bringing this up to highlight the fact that are many ways to measure time.

What does this have to do with the PDR loosing 2 seconds seemingly at random? The answer lies in the coordination of different global time systems. Corvette’s PDR used GPS (Global Positioning System) to determine the location of the car on track. GPS uses extremely accurate clocks to measure the time it takes signals (traveling at the speed of light, 186,000 miles per second) to travel the distance between the vehicle and several satellites orbiting the earth. Knowing the distance to the satellites allows the system to triangulate and calculate an accurate position for the car. The clock system the GPS uses is known as UTC (Temps universel coordonné) and is based on a series of super-accurate atomic clocks around the world. Unfortunately, the world we live in is not as stable as the atomic clocks. Much of the world operates on solar time which is based on the rotation of the earth. The rotation of the earth varies over time but is on the general trend of slowing down. Periodically, these two time measurement systems fall out of sync and an adjustment has to be made. Every time your Corvette starts, the PDR system looks to see if an adjustment has been made through the GPS. Since the PDR software was created 2 seconds have been added to sync the clocks (June 30, 2015 and June 30, 2012). These adjustments to the UTC time are managed through the addition of “leap seconds”. Leap seconds are analogous to leap days added February 29 every 4 years to keep our calendars sync’d with the earth’s orbit around the sun.

When the PDR was created the UTC time adjustment was broadcast through the GPS system every 10 seconds, meaning almost immediately after vehicle start, the data was available to bring the clock setting up to date (With on-board processing time, the worst case was 10 minutes). In December of 2015, that update cadence was slowed to every 2 hours, vastly increasing the probability that an update could occur as someone is timing a lap. When the system updates while timing a lap the result is the loss of exactly 2 seconds. This explains why customers are seeing this occasionally in the field. We do have a solution for 2017 and the good news is that it is backwards compatible to all prior PDR-equipped vehicles. The software update should be available this Summer. Although it will reduce the likelihood of getting the time loss by orders of magnitude, there will still be a very small chance it could happen again depending on when the time systems get updated.

I have tried to describe this situation in layman’s terms. International time keeping is actually quite a complex subject. Anyone interested in more detail can find lots of info on-line.

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Old 05-13-2016, 07:16 AM
  #33  
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Default Can 'Performance Shift Active' be Explained in Detail

Original answer thread is here.

AllFlash asked:
Under certain conditions, accelerating ones Corvette will trigger 'Performance Shift Active' on Corvettes and a number of changes are observed, least of which is a delayed changing of gears in the A8 while acceleration or deceleration is present. Can Tadge and GM explain exactly what changes the car experiences, whether it be engine, transmission or suspension while 'Performance Shift Activated'...is active.
Tadge answered:
When you see the 'Performance Shift Active' message that means you have engaged a set of features we call PAS/PAL. PAS stands for Performance Algorithm Shift. PAL refers to Performance Algorithm Lift-foot. We, like many manufactures, try to have the car adapt to the way it is being driven. Sensors on the car detect things like the rate of steering wheel rotation, rate of change of throttle position and vehicle lateral acceleration. PAS/PAL are just a couple of features that fall into this category and they only affect how the transmission shifts gears.

The performance shift algorithm is an 8-speed paddle shift automatic feature that operates in Sport and Track mode with the shifter in “D”. Sport mode enables the lift-foot algorithm, Track mode additionally enables PAS which brings lateral acceleration into the equation. PAS is the more aggressive level of performance shift, it will force the lowest possible gear for a given speed range. Lateral acceleration plays a role in activating the feature and is also used to negotiate gear state, for example: Downshifts are not allowed above a certain lateral acceleration (don't want to have any abrupt torque changes that might disturb the chassis).

During an acceleration PAL is activated during a lift-foot throttle maneuver which is calibrated above a threshold pedal position and a calibrated pedal rate of return. These calibration values are set to prevent the algorithm from activating during normal driving conditions. Unlike PAS which selects the lowest available gear, the lift-foot algorithm will hold the gear the transmission is currently in until it times out (then normal shifting will begin).

There is a bit more to these features than I am sharing here and you can tell I'm not disclosing any specifics around the calibration for our algorithms. That is intentional. I always want to share as much as I can when answering these questions, but I have to balance customer's desire for specific information and spoon-feeding our competitors’ valuable proprietary information that would be expensive and difficult for them to obtain through other means.

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Old 05-26-2016, 02:02 PM
  #34  
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Default Track Alignment Problems

Original answer thread is here.

Bill Dearborn asked:
Many members are running into problems having dealerships set the track alignment as defined in GM Bulletins such as #16-NA-056. The dealerships do not have the tools to measure rear caster and some insist it doesn't need to be set.

Through discussions with various dealership personnel I found out the tools are not provided as part of the Essential Tools Kit. Thus they are not inclined to spend money purchasing the tools when only a few people request that rear caster be checked and adjusted.

Some dealerships tell me if I bring the tools with me they will use them to set rear caster but I am not sure why I should be purchasing GM Tools they should already have. It looks to me like the Corvette Team is out of sync with their Service and Support group.

I thought the rear caster adjustment was something that is supposed to be checked on all Corvettes receiving an alignment.

I live in the Charlotte area and 4 dealerships do not have the tools. One dealership has the gauge but they do not have the adapter that permits use of the tool on the Corvette.

Is there anything that GM can do to alleviate this situation?
Tadge answered:
Whenever we do a new car, there are learning curves for suppliers, customers and dealers. Although rear caster was not part of the alignment process on the 6th gen Corvette, it is on the new 7th gen car. Making it adjustable adds some complexity in the alignment process, but it also lets car be brought into ideal suspension geometry regardless of factory build variation. Rear caster accuracy and symmetry is important because it affects ride steer. Students of suspension geometry will understand that even small changes in rear steer angle can have big effects on vehicle handling.

The question suggests that customers are getting a variety of stories from dealers on our process and their readiness to do Corvette alignments, so I will describe that in detail.

As we were launching the Stingray in 2013, the following technical document was published to the dealer community:




For reference, here are images of the two tools described in the document:
Digital Angle Gauge CH 47960


CH 47960–10 Gauge Mounting Adapter


The term “essential tools” may be the source of some confusion. As used in every day language, both of these tools are essential to do the caster alignment. The GM technical meaning of the term is different, however. The dealer sales and service agreement states: "Dealer agrees to provide and maintain on dealership premises essential service tools as required by General Motors and such other tools and equipment as reasonably necessary to fulfill its responsibilities to properly diagnose and service Products." When GM classifies a tool as “essential” for authorized Corvette dealers, that means the dealers will automatically be shipped the tool for their use and the cost will be charged to their open account. The adaptor is custom-designed to fit the Corvette knuckle and cannot be purchased on the outside market. That is why it is classified as an essential tool. The high-precision digital angle gauge is a more generic tool with multiple possible sources. It is a bit expensive and can also be used for jobs other than Corvette alignment so some dealers already have one in the shop. As a result, GM service elected not to classify that gauge as an essential tool. You can imagine the discontent in the dealer forced to buy one when they already have one on the premises. So the bottom line is that adapters were sent to all authorized Corvette dealers a few years ago and it is up to the dealer to procure the tool to measure the caster angle. GM makes every effort to enable dealers to access to these tools. We have a tool loaner program that will send the need tool to a requesting dealer the next business day. Any dealer without the angle gauge can get one in 24 hours. The same is true for the adapter if it was not received or has been lost or broken.

This question is prompting us to take additional actions. Here’s what we’re going to do help:
  1. We will re-communicate in the TechLink mailout and the Emerging Issue video (monthly web-site training) the criticality of rear caster adjustment.
  2. We will re-communicate that the rear caster adapter tool is an essential tool and is required if you are an authorized Corvette dealer.
  3. We will communicate that both the adapter tool and the digital angle gauge are available through the GM Tool Loaner program.

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Old 06-09-2016, 01:57 PM
  #35  
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Default C7 Blind Spot Detection

Original answer thread is here.

tbogdan asked:
I am thoroughly enjoying the 2016 Z51 A8 I recently purchased. Very impressed with C7 interior and all of the features that come with the 3LT. I am curious why Chevrolet would not put blind spot detection on the Corvette, especially when the small window behind the driver is obstructed by the driver seat when merging left or changing to the left lane. This is available on other GM products (LTZ Tahoe, for example).
Tadge answered:
Many of the questions on this forum relate to trade-offs in the vehicle design process. Side Blind Zone is a perfect example.

Generally speaking, we tend to err on the side of not having a lot of alerts that would interfere with the joy of driving. The SBZ feature was just emerging as a feasible customer feature as we were designing the 7th generation Corvette. We thought very carefully about including it in the program since we knew other vehicles were going to offer it. SBZ uses sensors located on the rear outboard corner of the car, just behind the fascia. That is precisely the location we needed to package our race-derived transmission and differential coolers. Having heat exchangers in the back corners interfered with both the physical space need for the sensors and disrupted their performance. In the end, we prioritized vehicle performance over a new feature that we were not sure would be a strong customer desire. We have gotten similar feedback from several customers asking the same question. SBZ does seem to be gaining good acceptance from customers so, although not feasible in the short term, we will strongly consider that customer desire in our future plans.

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Old 06-22-2016, 11:10 AM
  #36  
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Default Why No Oil Catch Can on the LT1 Corvette Engine?

Original answer thread is here.

Maxie2U asked:
Why did the Camaro design team decide to design in an Oil Catch Can on the 2016 Camaro with the LT1 engine? Will the 2017 C7 with LT1 engines also come with an Oil Catch Can, if not why not?
Tadge answered:
To answer the second question first: No, the 2017 Corvette LT1 will not have the Camaro V8 PCV air/oil separator (what the questioner calls a "catch can") added to its oil management system. For those not familiar with the abbreviation PCV, it stands for "positive crankcase ventilation"

Even though the Corvette and Camaro share the LT1, they are very different in execution detail. The LT1 in the Corvette sits lower and very close to the ground to enable an industry-leading low profile hood and good sight lines despite a very low seated position. Having the engine close to the ground is great for keeping the vehicle's center of gravity down, but means the oil pan is relatively shallow. Having little depth in the oil pan means it is very challenging to scavenge oil in high G loading conditions. For this reason we add dry sump lubrication to our high performance models. The Camaro's higher engine position allows for a deeper oil pan and a reliable configuration for picking up oil for delivery to all parts of the engine. Thus the Camaro is able to avoid the cost and mass of the dry sump tank and resulting complexity of the lube system.

The Corvette's dry sump tank looks relatively simple on the outside but the internals are really quite complex. The top third of the tank contains a PCV air/oil separation system. On the Corvette, PCV lines route from the valve covers to the air/oil separator on top of our dry sump tank. Oil from PCV air is separated and returned to the lube system through the oil tank. The PCV separation system on Camaro V8 performs a similar function except oil is returned to the engine oil pan from the PCV separator's drain back tube. The Camaro V8 PCV air/oil separator is more complex than a "catch-can" since it not only separates oil from PCV air it provides a drain back path for this oil to be reused by the lube system. "Catch-can" systems that do not have a drain back path for separated oil run the risk of poor oil pressure performance over time as oil is removed from the lube system.

The bottom line is that both cars use optimized engineering solutions for their lube systems based on vehicle architectural considerations.

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Old 07-28-2016, 09:17 AM
  #37  
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Default Melting AFM Actuators

Original answer thread is here.

Along4theRide asked:
I hope you can clear up some questions about the AFM system and the use of plastic AFM Actuators. Some of us who purchased Z51 cars specifically to track the vehicle are disappointed that under heavy track load and temperatures the AFM actuators melt and fail. Besides throwing a check engine light and horrible noises during V4 ECO mode, could you explain what issues someone might have in just running these in this condition? What is GM’s position on replacing these? It’s my understanding from speaking to other affected users (some whom have had the AFM actuators replaced 5 times) that there is no fix for this condition. Is there a new part design coming soon for this? I’ve heard that Spring Mountain has seen this as well and it affects many of their vehicles. Can you offer advise to those affected? How do we fix this issue permanently?
Tadge answered:
Corvettes have long pushed the technology envelope to make a car that is both supremely fast and remarkably efficient. That often means we are doing things no other manufacturer would try. The combination of true cylinder de-activation (meaning keeping cylinder valves closed, not just turning off fuel injectors as many others do) in a track-ready car is an example. We did do our normal 24 track testing with the AFM valves in place without issue. Perhaps the way we run our test can help folks running on the track avoid problems.

A few important points: The valves are very sensitive to air flow under the car. Anything that restricts that airflow could increase the chance of an issue arising. These would include any aftermarket aerodynamic or cooling aides. Also, lowering the standing height (which many folks are tempted to do to lower the center of gravity) of the vehicle below spec has a measurable negative effect. We always run at least one complete cool-down lap before pitting. This is super-important because the relatively cool exhaust gases running at part throttle cool the AFM valve quickly. Finally, some tracks have noise regulations that cause people to run in stealth mode. That is a relatively recent trend, so we did not validate track durability in stealth mode. It was always intended to be a street feature.

The question cites the “plastic” actuator with the implication that we used non-robust materials in such a hot area. Although the accompanying photos show thermal distress in the glass-filled nylon case, that is an effect of the internal thermal failure , not the cause of it. Actually the internal magnets and electronics are the thermal weak link and there is no material substitution in the world that can be used to fix it.

So what can we do about it? For the 2015 model year we added insulating content into the muffler head to reduce the thermal load on the valve. That was a continuous improvement, but not a “clean kill” for every situation. For 2017, we have eliminated the valve on Z51 and Grand Sport (manual transmissions only). Manuals still have AFM, but the torque levels are low relative to the automatic so the N&V issues are manageable without it. Also, the AFM only works in Eco mode, so it is easy to avoid if you want to. The 2017 manual transmission hardware set is not an easy “bolt in” for prior year cars, so we are studying how to make that solution available. The automatic is likely to need the AFM valve for the foreseeable future. The great thing about this “Ask Tadge” activity is that it lets us hear very directly from customers. We will ramp up our efforts both in our mainstream engineering and our performance parts activity to see if we can have better solutions available in the future.

Last edited by jvp; 08-08-2016 at 09:40 AM.
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Old 08-16-2016, 10:45 AM
  #38  
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Default The Relationship of "Racecar to Streetcar" Within Corvette

Original answer thread is here.

RC000E asked:
Since Corvette/Chevrolet's direct involvement in ALMS beginning in 1999, could you describe the evolution/intensity/milestones of the relationship between the racing side of the Corvette and the factory side? We've seen multiple facets of the program have been transferred in house, from the engines (formerly Katech) to the frames of the C7.R being built in house, etc. Has the racing sides influence increased exponentially with time would you say, and as chief engineer, how critical do you feel the racing teams involvement is to the future of Corvette as a brand? If at all possible, some words from Doug Fehan as well, on this subject, would be fantastic!
Tadge answered:
Wow, what a question! After 16 years and over 100 victories, there is enough material to write a book, a pretty long one (and a good one!).

Traditionally racing programs are marketing activities. Companies would try to make a link between the race program and street program, but the strongest statement they could muster was that the street car was “racing inspired”. If you think about that it really means nothing tangible about the connection. And in fact, traditionally, there has been virtually no connection. Race teams were funded by marketing departments and contracts were awarded to independent companies who did their best given their budget to produce victories and airtime for their customers. Contracts tended to be short term with lots of turn over and virtually no interaction between the working level people on race and street car teams. Aside from VIP seating at races, there was no influence on the people responsible for the street car. The C5.R, C6.R and C7.R programs changed that in a fundamental way. Having a long term commitment to endurance racing has enabled us to tear down the walls between the race team and production team. It didn’t happen overnight and is still evolving today. I have been lucky enough to be on the Corvette team for the entire time and have had a front row seat for the show!

The question suggests input from Doug Fehan, our Corvette Racing Program Manager. Doug has been with the program since inception and was, more than anyone, the visionary and prime motivator to get the program where it is today. He is more than a business partner. Like many on the race team, I consider him a friend. I asked him for a quick take on this question and here’s what he had to say:
From Doug Fehan:
From the very beginning, the Race Program's objective has been to integrate itself into every aspect of Chevrolet's business. Clearly, the buy-in from Dave Hill's engineering group, at the onset of the program, was critical and served as our initial cornerstone from which to build. That, in turn, opened the doors within Tom Peter's design team and all of the Chevrolet sales, marketing and advertising groups. The Corvette Racing mantra has always been "racing is more than a checkered flag and a trophy". I think there is no better example of that than the current C7.R which is the embodiment of 16 years of effort to bring our customer a road-worthy product that is as close to the high-performance race car as possible. From its’ light-weight aluminum frame, composite body materials, advanced aerodynamics, performance-based seating to it's amazing drivetrain capabilities, the C7.R is truly representative of a meaningful collaboration between Tadge's design team and the race team. Our customers serve as an impressive testament to the success of our philosophy.

Tadge continues:
The truth is that the current 7th generation Corvette would not be what it is without the racing program. Even in its’ 4th model year, the Stingray, Z06 and now Grand Sport are selling in record numbers. The combination of performance, technology and function-driven good looks is compelling to customers. And using racing strategies is at the core of that appeal. The specifics are too numerous to go into fully, but almost every surface on the car and all the performance hardware has come from racing either directly or indirectly.

We share engineering development both ways…. Sometimes it is the production side doing the heavy lifting like in our light, stiff aluminum structure, engine development or in air conditioning systems. The race team takes the lead with the aerodynamic tools, brake cooling and tire technology.

Doug Louth is the Chief Engineer of the race program and has been my counterpart in this partnership for a long time. He is also a friend and had this to say about what we are doing:

From Doug Louth:
From the start of the program, sharing of objectives and design concepts between the road car and race car teams led to better cars on both sides. This evolved into the sharing of engineering processes and tools. One of the earliest examples was the use of the race program’s CFD tools, processes, and personnel to support Tadge’s team in finding a solution to an urgent brake cooling challenge. This was the first of many programs where the racing engineers worked closely and collaboratively with the road car engineers and leveraged the strong capabilities from both groups to be successful. Now this collaboration has evolved into a wide array of projects/programs and is fundamental to the development of both the road and race cars. It has been extremely rewarding for motorsport personnel to participate and contribute as regular members of the road car development team in recent years. The immense array of objectives and requirements involved in fielding a new road car, and the organization, people, processes, and tools used to integrate and deliver on these have been an extremely positive influence on the way the race cars are developed. In turn, the tools and processes developed around racing’s relatively single-minded approach to performance have in turn been valuable additions to the road car program. Finally, this collaboration extends more and more beyond the Corvette road car team to the greater GM and some of the core engineering groups that develop all of GM’s products. Racing is exciting and rewarding in many ways, but the knowledge that the hard work to perform on track may be improving the cars that thousands of people drive every day is a major source of gratification for our racing team members.
Tadge again:
You put all that capability together and we get a synergy that makes us more than the sum of our people and organizations working independently.

My bottom line is that our future is intimately linked together and I predict great things to come!
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Old 08-31-2016, 10:25 AM
  #39  
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Default PDR Pre-Record and Quick Record Button

The original answer is here.

slickstick asked:
While the PDR is cool for the track, it would be nice if it had a street mode as well. It could be set to record constantly, and add a recording 'hotkey' to the infotainment home screen. If anything noteworthy happens on the streets, pushing the record button would instantly enter record mode, and with a configurable pre-record (ex: 30-60 seconds) would capture what happened prior to the button push.

Can this feature we added via software update? It seems very simple and straightforward to provide owners.
Tadge answered:
Thank you for the question, slickstick. Since introducing the PDR as a first-in-the-industry feature, we have had a lot of input on possible upgrades and use-cases. You now see PDR starting to proliferate to other GM vehicles, so those customers are also providing feedback.

You are right that, although PDR was originally imagined as a track feature, there are many possible uses on the street. We will be prioritizing all the customer feedback in addition to our own ideas and you will see a continuous evolution of the PDR functionality in the coming years. In fact, we have discussed features very similar to what you describe. As I have described in answering many other questions on the Forum, we always try to make software (and sometimes hardware) backwards compatible, but it is not always possible.

Another challenge we have is that there are privacy laws that vary by state and country that may prohibit recording without specific direction from the customer. I'm not saying we can't do as you describe, but nothing is ever as simple as it seems and we have to get many legal interpretations of the global regulations as we bring new features to market.

Last edited by jvp; 08-31-2016 at 10:26 AM.
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Old 09-12-2016, 01:25 PM
  #40  
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Default Introduce the Corvette Engineering Team

The original answer is here.
jvp asked:
Would you be willing to introduce us to the team of engineers and others that work on the Corvette? I'm curious as to how many folks are directly tied to the Corvette.


Tadge answered:
We pride ourselves on Corvette for being uniquely accessible to our customers. Many members of our team support Corvette events around the country whether it is race weekends, museum events or shows like Corvette's at Carlisle in Pennsylvania. I can't think of another example in any industry where customers can talk directly to the folks who make virtually all of the product decisions. Most large companies have layers of "customer service" or "customer relations" departments (and many out-source that function). The bottom line is that many on our team are known very well by customers and have ongoing relationships far beyond the traditional manufacturer/customer definition.

When I talk about the Corvette team I include everyone who has a part in getting cars to customers. For the most part, we engineer the car (and I am including both the street car and the C7.R race car here) in Michigan and build it (the street car) in Kentucky, but there are people around the world supporting us in functions like Marketing and Distribution, Sales and Service and Global Purchasing. If you came to visit us in Michigan, you would see our program team is comprised of representatives from all the traditional corporate departments: Program management, Manufacturing, Marketing, Design, Engineering, Purchasing, Finance, Quality, Customer care & Aftersales, Test & Validation, Vehicle Development and others. Each representative on the team is supported by large departments with functional expertise and responsibility for their particular area of the car. Also, those are not listed in any priority order. Like every good team, everyone holds equal responsibility for a successful product.

Within Engineering there is a further division with representatives from Body Structure, Exterior panels, Electrical, HVAC (Heating Ventilation and Air Conditioning), Interior, Propulsion Systems and Chassis. Again, each lead engineer is supported by a functional department with vast expertise and resources that GM can bring to bear on developing a new vehicle. Propulsion systems, for example, is a huge organization designing engines and transmissions for all GM vehicles. The Small Block team is just one part of that organization that engineers our V8 engines.

Within Manufacturing there are further divisions between technical specialists like the Body shop, Paint and General Assembly. Manufacturing engineers have to design tools and processes to build Corvettes efficiently. They also have to coordinate the installation and tune-in at our manufacturing site in Bowling Green. Bowling Green Assembly, led by Plant Manager Kai Spande, assembles the cars (and LT4 engines) and ships them to customers all around the world.

The number of people working on Corvette varies tremendously over time. When an all-new car is being developed, we have hundreds of people working full time and more than a thousand working part time (shared resources with other projects). And that does not include our suppliers or the second and third tier companies shipping components to our first-tier suppliers. If you added them all up there would be close to 10,000 names on the list. After a "Major" program like the C7, most of the resources migrate to other projects and a core team with maybe a couple dozen full-time employees remain supported by a couple hundred part time folks. That smaller team manages all the annual changes and continuous improvement.

The automobile is the most complex, highly regulated consumer product, so takes a small army to put a modern vehicle on the road. Here is a picture from one of our regular "All People" meetings. This one is from last year celebrating our Le Mans victory and includes both the race and street car team. I do not believe it has been shown publicly before.
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