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GSpeed C7 Z06 Cooling Development

 
Old 07-07-2016, 02:15 PM
  #41  
SBC_and_a_stick
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Originally Posted by JoesC5 View Post
I don't recall anyone having to cut up the front bumper of the C6 Z06 or ZR1 to solve any cooling problems(but some did remove the stock fog lights and install secondary coolers, or brake cooling ducts).




Originally Posted by GSpeed View Post
Quite possibly. When we calibrate both sensors, that would be my guess. Our sensor we added is isolated by a rubber hose from the engine, whereas the GM sensor is screwed into the head.
Great to know! I never knew where the sensor is placed.

FWIW my OBDII reader gets exactly the same temperature as the car is displaying in Tour mode, to the same degree. Maybe in other modes there is averaging but if you set the display to show you actual readings to the degree there is no discrepancy whatsoever between the OBD port and the dash. I've been logging the same temps for about a year now.




Originally Posted by dar02081961 View Post

The OP's efforts are to be applauded. What it has proven thus far is when keeping the appearance of the car and mass marketing in mind GM did a pretty decent job to satisfy fit form and function.
Could they have added more cooling? Yes but it would have been at the expense of the cars appearance or size. The other option would have been to give us the original 625hp/tq they planned for. I am glad they gave us the 650hp/tq instead.
You are mistaken's GMs efforts to cut costs with the appearance of the car and size.

First remember that the C7 platform is longer, there is a ton of room. TIKT, DP3 and LG have proven there is room for coolers. So we don't need to discuss size. There was even room for extra coolers in the ZR1, see the pic I posted above.

Second, there have been countless cars with side mounted coolers, floorpan mounted coolers, and so on. Actually, the most desireable sports car of the last decade all have massive cooler cutouts. It makes them more beautiful, not less. Forget about function, people love the form!
911 GT3,
911 GT4,
BMW M4,
AMG GT S,
Ferrari F12,
Jag F type R,

etc.

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Old 07-07-2016, 02:25 PM
  #42  
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I think I have the solution to overheating. Move somewhere that's cooler! Lol I'll shut up now and wait for the next installment of 'How to tune a car properly' by GSpeed!!!.....

Talking seriously for a min. Do you think the small intercooler bricks could be hindering rejecting the heat in the charger cooler system? Most heat in OEM systems is rejected back into the intake air by the chargecooler brick(s) themselves. Maybe adding bigger bricks would help pull more heat out the system when at closed throttle. It would also lead to higher system loads when WOT though as well. Hmmm

On the engine cooling, have you guys thought about measuring air speed through the core? Could help with understanding any if any aero mods are actually working for or against you. Could the rad simply not have enough frontal area and it's the lack of airflow that's strangling the system. Have you tried running the primary and secondary dads in parallel to see if that help (both having higher delta T then) - same could be said for the low temp intercooler rads as well.

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Old 07-07-2016, 02:41 PM
  #43  
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On the intercooler side of things, it would be interesting to see the flow rates for the system. I think I read that anything between 7 and 12 leter per min is about optimum and what the OEMs aim for. Would be interesting to see what the Z06 system is delivering.

Alternatively just develop a massive rear mounted secondary radiator like the time attack / drift guys use! Sorry stupid ideas wil stop now.
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Old 07-07-2016, 02:50 PM
  #44  
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Originally Posted by SBC_and_a_stick View Post
Great to know! I never knew where the sensor is placed.

FWIW my OBDII reader gets exactly the same temperature as the car is displaying in Tour mode, to the same degree. Maybe in other modes there is averaging but if you set the display to show you actual readings to the degree there is no discrepancy whatsoever between the OBD port and the dash. I've been logging the same temps for about a year now.
Yeah, that makes sense. From our datalogging, it looks like what's being reported over OBD is identical to what's displayed on the dash, but that doesn't necessarily match exactly with what we're seeing on our additional sensors. Check this out. When you look at analog temperatures vs. the OBD reported temperatures, there's more than a linear offset going on. I suspect we're measuring a little cooler since we're measuring JUST water temperature, as previously mentioned. But if you look at the shape of the curves, it's clear the OEM sensor (as processed) is slower to respond. But like we said, that's not news to anyone.



Originally Posted by chuntington101 View Post
I think I have the solution to overheating. Move somewhere that's cooler! Lol I'll shut up now and wait for the next installment of 'How to tune a car properly' by GSpeed!!!.....

Talking seriously for a min. Do you think the small intercooler bricks could be hindering rejecting the heat in the charger cooler system? Most heat in OEM systems is rejected back into the intake air by the chargecooler brick(s) themselves. Maybe adding bigger bricks would help pull more heat out the system when at closed throttle. It would also lead to higher system loads when WOT though as well. Hmmm

On the engine cooling, have you guys thought about measuring air speed through the core? Could help with understanding any if any aero mods are actually working for or against you. Could the rad simply not have enough frontal area and it's the lack of airflow that's strangling the system. Have you tried running the primary and secondary dads in parallel to see if that help (both having higher delta T then) - same could be said for the low temp intercooler rads as well.
We already know mass airflow since we've got engine displacement, RPM, and manifold pressure.

The largest problem with the OEM heat exchanger setup is the stacking of cores. Every core preheats the air for the one behind it, so by the time it gets all the way back there's very little Delta-T left.

Jake

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Old 07-07-2016, 02:51 PM
  #45  
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Non conductive carbon fiber or xytel supercharger housing....get the heat sink outta there.
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Old 07-07-2016, 03:01 PM
  #46  
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Sorry GSpeed I meant the ambient airflow speeds not that of the intake air. totally appreciate maintaining good delta t is the key. If you go back in history to the old Group C days there were 1000bhp turbocharged monsters going down the Le Mans straight flat out for 24 hours and they kept everything (bar the driver from what I have heard) perfectly cool! Lol
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Old 07-07-2016, 03:06 PM
  #47  
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Originally Posted by NemesisC5 View Post
Non conductive carbon fiber or xytel supercharger housing....get the heat sink outta there.
Wouldn't help! The heating of the air is thanks to compressing it not the housing that it's sat in!

In fact you could see higher IATs with a none conductive supercharger casing as the high temp air after the supercharger could not shed some (not a lot) of its heat out the SC casing.

What you really need to do is go all mad max and mount a top down blower setup that stick the hot bit (the SC) outside the hood in the nice cold airflow!
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Old 07-07-2016, 03:12 PM
  #48  
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Originally Posted by GSpeed View Post
Okay, so check this out. When you look at analog temperatures vs. the OBD reported temperatures, there's more than a linear offset going on. I suspect we're measuring a little cooler since we're measuring JUST water temperature, as previously mentioned. But if you look at the shape of the curves, it's clear the OEM sensor (as processed) is slower to respond. But like we said, that's not news to anyone.
This is a very juicy finding indeed. This may very well be the reason GM's overheating threshold is so high at 262* where other cars give warnings at just 235* coolant.

What I was referring to was reading the OEM sensor through the OBD port vs. reading the same OEM sensor by looking at the display. I'm sure you know that but I believe we're talking about two different things in the thread and people are confused. What you are comparing is the OEM sensor to your own sensor.

Brilliant! I'd try digesting the results more so folks understand what you are doing, like explaining to a 2 year old. For example, I would say why you are looking at difference in air temperature in addition to fluid temperature. The heat exchanger, literally exhanges fluid temp with the air. Hotter air coming out of the HE is a good thing. Therefore, you were happy to see reversing the fluid direction resulted in hotter air temperature behind the main radiator. Things like that. BTW this comparison is a tricky one. What if it was just hotter outside or your driver drove harder after you reversed the flow. Hotter temps after the main radiator may be a result of ambient temps, or more heat build up in the engine.
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Old 07-07-2016, 03:16 PM
  #49  
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We opened up the bumper cutouts all the way to allow as much airflow through there as possible. We also moved the trans cooler forward, and the aux radiator back a little bit to increase airflow over the trans cooler.

In order to further increase the available airflow across the heat exchangers, we're planning on drawing brake ducting air off the back of the intercooler radiators. Not optimal, but the air coming off the back of those is maybe 150 or so. That's still plenty of temperature differential to cool down the 1000 brakes.

We added a larger oil cooler inboard of the left side intercooler radiator to bring oil temps down further.



Then we went testing.

Lap 1- 1:33.5
Lap 2- 1:28.7
Lap 3- 1:32.4
Lap 4- 1:25.8
Lap 5- 1:23.4
Lap 6- 1:23.7
Lap 7- 1:26.9
Lap 8- 1:24.6
Lap 9- 1:23.5
Lap 10- 1:32.7

The goal was to run low 20s as often as possible, which our driver did pretty successfully. There was a bit of traffic, which slowed him down with limited passing zones.

Here's the data we got:







We hooked up the MXL2 to the OBD system, so now we're logging trans and engine oil temps realtime as well. You can see the granularity of the OBD system that rounds to the nearest 0.5C compared to the smoother analog sensors.



Here's the temp differential calculations:





You can see we've still got some issues with the intercooler fluid circuit. We're investigating what it could be, but it's causing us problems. We lost power on track because post-charger intake temps got too high. Time to figure that one out.

Jake

Last edited by GSpeed; 07-07-2016 at 03:17 PM.
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Old 07-07-2016, 03:20 PM
  #50  
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Originally Posted by chuntington101 View Post
Wouldn't help! The heating of the air is thanks to compressing it not the housing that it's sat in!

In fact you could see higher IATs with a none conductive supercharger casing as the high temp air after the supercharger could not shed some (not a lot) of its heat out the SC casing.

What you really need to do is go all mad max and mount a top down blower setup that stick the hot bit (the SC) outside the hood in the nice cold airflow!
My comment was more about removing the metal mass that holds engine heat conducted from the block and heads. However, I don't agree that the heat generated inside supercharger housing by compression of air is great enough to heat the housing more than the conducted heat from the engine block and heads. N/A engines have benefited from the plastic / Xytel manifolds not holding heat and I believe a composite housing for a supercharger of this type and mounting location would benefit as well. We don't see turbo systems or centri superchargers have the same heat sink issues that Eaton units have.
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Old 07-07-2016, 03:21 PM
  #51  
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Originally Posted by chuntington101 View Post
Sorry GSpeed I meant the ambient airflow speeds not that of the intake air. totally appreciate maintaining good delta t is the key. If you go back in history to the old Group C days there were 1000bhp turbocharged monsters going down the Le Mans straight flat out for 24 hours and they kept everything (bar the driver from what I have heard) perfectly cool! Lol
Beyond ground speed, I'm not sure we need it. In this heat transfer problem, heat is only going to one place; into the air. We know it's leaving the water, and if we know water flow rate and air temps on both sides of the radiator, we can infer mass flow rate of the air.

Originally Posted by SBC_and_a_stick View Post
This is a very juicy finding indeed. This may very well be the reason GM's overheating threshold is so high at 262* where other cars give warnings at just 235* coolant.

What I was referring to was reading the OEM sensor through the OBD port vs. reading the same OEM sensor by looking at the display. I'm sure you know that but I believe we're talking about two different things in the thread and people are confused. What you are comparing is the OEM sensor to your own sensor.

Brilliant! I'd try digesting the results more so folks understand what you are doing, like explaining to a 2 year old. For example, I would say why you are looking at difference in air temperature in addition to fluid temperature. The heat exchanger, literally exhanges fluid temp with the air. Hotter air coming out of the HE is a good thing. Therefore, you were happy to see reversing the fluid direction resulted in hotter air temperature behind the main radiator. Things like that. BTW this comparison is a tricky one. What if it was just hotter outside or your driver drove harder after you reversed the flow. Hotter temps after the main radiator may be a result of ambient temps, or more heat build up in the engine.
Good point, I added another sentence to my previous post to clarify things a little more.

I'll try to make things simpler in the future.

Jake
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Old 07-07-2016, 03:23 PM
  #52  
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Refresh rate
Here is what I get out of the OBD port on Harry's laptimer in one 3.5 minute lap. As you can see to me it clearly updates a few dozen times a lap which is sufficient I'd say. I can't tell if your sensor updates more often. The OEM plot you are showing is actually a bit smoother to my eyes, so higher refresh rate. In either case I think both the OEM sensor and yours update often enough.

Delay
You mentioned the OEM sensor is slow. Since there are no major peaks and troughs in the plot you showed I can't tell which one reacts quicker. In a way the refresh rate shows the delay is only a few seconds, and that's not much when we talk about coolant temp.

Difference in levels read out by the sensor

This is the big finding imo. The OEM reads higher and you have a good theory of why that is.



Eager for more findings!
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Old 07-07-2016, 03:32 PM
  #53  
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Originally Posted by SBC_and_a_stick View Post
Refresh rate
Delay
You mentioned the OEM sensor is slow. Since there are no major peaks and troughs in the plot you showed I can't tell which one reacts quicker. In a way the refresh rate shows the delay is only a few seconds, and that's not much when we talk about coolant temp.

Difference in levels read out by the sensor

This is the big finding imo. The OEM reads higher and you have a good theory of why that is.

Eager for more findings!
Thanks! To add to that:

Delay- It's a software delay, not a sensor one. The digital values to the dash are heavily filtered, which is why you don't see the same response time as the unfiltered Aim logger.

Refresh Rate- The Aim logger records OBD data at 10 Hz (10 times per second), which is the maximum possible. I believe that's an OBD (J-2234) limitation, but I could be wrong.

Jake
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Old 07-07-2016, 03:40 PM
  #54  
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Originally Posted by GSpeed View Post
Beyond ground speed, I'm not sure we need it. In this heat transfer problem, heat is only going to one place; into the air. We know it's leaving the water, and if we know water flow rate and air temps on both sides of the radiator, we can infer mass flow rate of the air.

Jake
Good point! If you can calculate the ambient airflow through the cooling lack then that's as good as measuring it. I have seen measured airspeeds through intercoolers and its supprising how low they are (single cooler with lots of space at the back for airflow) compared to road speed!
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Old 07-07-2016, 03:47 PM
  #55  
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Originally Posted by GSpeed View Post



You can see we've still got some issues with the intercooler fluid circuit. We're investigating what it could be, but it's causing us problems. We lost power on track because post-charger intake temps got too high. Time to figure that one out.

Jake
The blower in temp looks funky as hell. Do you think this is a sensor problem or an actual temp reading?

Maybe the pump stops at times due to some sort of harness connection fault. Not sure what else it could be.

Otherwise the results look fine to me. I'd say you nailed it.

Ambient temps? Do you guys still have that driver that tests for OEMs behind the wheel?

Originally Posted by GSpeed View Post
Thanks! To add to that:

Delay- It's a software delay, not a sensor one. The digital values to the dash are heavily filtered, which is why you don't see the same response time as the unfiltered Aim logger.

Refresh Rate- The Aim logger records OBD data at 10 Hz (10 times per second), which is the maximum possible. I believe that's an OBD (J-2234) limitation, but I could be wrong.

Jake
Another reason why I think you are right is that Harry, the guy who designs Harry's Laptimer, said that most OBD ports are limited to 10 Hz. That's why he said most bluetooth OBD readers are not limiting the refresh rate, but rather it's the OBD limitation like you say.

Oh, here is the OBD refresh rate for the '09 corvette:
"2009 Chevrolet Corvette - 8.0 Hz"

We're up there with the best although my 2001 Honda s2000 refreshed at 10hz lol

http://www.gps-laptimer-forum.de/viewtopic.php?t=1880

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Old 07-07-2016, 03:52 PM
  #56  
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Originally Posted by NemesisC5 View Post
My comment was more about removing the metal mass that holds engine heat conducted from the block and heads. However, I don't agree that the heat generated inside supercharger housing by compression of air is great enough to heat the housing more than the conducted heat from the engine block and heads. N/A engines have benefited from the plastic / Xytel manifolds not holding heat and I believe a composite housing for a supercharger of this type and mounting location would benefit as well. We don't see turbo systems or centri superchargers have the same heat sink issues that Eaton units have.
You might be right! But what's the temp of the air post supercharge / pre intercoolers? I'm pretty sure they will be as hot as the mating surface bettween the SC and the intake manifold.
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Old 07-07-2016, 03:56 PM
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Originally Posted by SBC_and_a_stick View Post
The blower in temp looks funky as hell. Do you think this is a sensor problem or an actual temp reading?

Ambient temps? Do you guys still have that driver that tests for OEMs behind the wheel?
We're confident it's an actual reading. WHY it's reading like that is another question entirely.

Ambient temps were about 90F, maybe a little higher. Track temp was about 110F. Ha, our driver wishes he was an OEM test driver.
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Old 07-07-2016, 04:40 PM
  #58  
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Originally Posted by chuntington101 View Post
You might be right! But what's the temp of the air post supercharge / pre intercoolers? I'm pretty sure they will be as hot as the mating surface bettween the SC and the intake manifold.
While driving steady state on a public road pre-supercharger ~10* above ambient. Compressed to factory max in single gear pull I would guesstimate ~150-165* before entering intercooler bricks.
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Old 07-07-2016, 05:26 PM
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Originally Posted by SBC_and_a_stick View Post





Great to know! I never knew where the sensor is placed.

FWIW my OBDII reader gets exactly the same temperature as the car is displaying in Tour mode, to the same degree. Maybe in other modes there is averaging but if you set the display to show you actual readings to the degree there is no discrepancy whatsoever between the OBD port and the dash. I've been logging the same temps for about a year now.






You are mistaken's GMs efforts to cut costs with the appearance of the car and size.

First remember that the C7 platform is longer, there is a ton of room. TIKT, DP3 and LG have proven there is room for coolers. So we don't need to discuss size. There was even room for extra coolers in the ZR1, see the pic I posted above.

Second, there have been countless cars with side mounted coolers, floorpan mounted coolers, and so on. Actually, the most desireable sports car of the last decade all have massive cooler cutouts. It makes them more beautiful, not less. Forget about function, people love the form!
911 GT3,
911 GT4,
BMW M4,
AMG GT S,
Ferrari F12,
Jag F type R,

etc.
I guess I should make myself clearer.

I don’t recall any ZR1’s that were 100% showroom stock that were daily driven, and occasionally taken to a road course to do a HPDE on a day that was hotter than 86 degrees and was expected to last for more than three laps before shutting down, that had the front bumper cut open for additional heat exchangers, etc.

Last edited by JoesC5; 07-07-2016 at 06:07 PM.
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Old 07-07-2016, 05:48 PM
  #60  
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We submerged two sensors in boiling water, one Bosch NTC sensor hooked up to an Aim analog input, and one OEM temperature sensor hooked up to the factory wiring harness, which we read via OBDII on the Aim dash.

The Bosch sensor stabilized at 207.1F, and the OEM temp sensor stabilized at 206.6F, both in actively boiling water. They were sticking in from the top, which could explain the temperature readings slightly below 212F. More importantly, though, the Bosch sensors are reading within a half of a degree of the OEM temperature sensor. Therefore the temperature difference between the OEM water temp reading at the water pump and our measurement at the radiator inlet is accurate. 15, give or take, is already lost by the time the coolant reaches the radiator.
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