Hmm that's odd.

When I take a hard corner and purposely let the car slide (power oversteer), it seems easier to perform with AH OFF as compared to Competitive Driving mode enabled. Is that basackwards

 

O7zeeO6,

The documentation I've used includes
a. the Owner’s Manual, pp. 4-9 through 4-12.
b. The Service Manual p. 5-131 through 5-218; here Active Handling is called Vehicle Stability Enhancement System (VSES). A good explanation of the functioning of the: VSES is found on page 5-217 and Traction Control System is found also on page 5-217.

I’ve studied the Active Handling System carefully because it’s a safety issue for racing. And, having raced three Z06s, I needed to be sure I adapted to inherent differences in the new generation when my C6Z was delivered in February 2006.

The Traction Control System (TCS) “limits wheel spin.” [Source Owner’s Manual p. 4-9 and Service Manual p. 5-217]

“The Active Handling System (AH) is a computer controlled system that helps the driver maintain directional control of the vehicle in difficult driving conditions. This is accomplished by selectively applying any one of the vehicle’s brakes.” [source Owner’s Manual p. 4-10 and Service Manual p. 5-217]

The normal functioning of the Anti-locking Brake System remains in effect for at all times.

These are the four different handling settings on the C6Z.

(1) Normal driving (Traction System-On and Active-Handling-On in its aggressive form)

(2) “Traction System-OFF” (TC-Off and AH-On in its aggressive form); DIC message and the TCS dashboard warning icon are set. Entered via one push of the button. Turning off TCS allows the wheels to spin without changing any other handling characteristic of the car. That means that the aggressive form of Active Handling remains available.

(3) “Competitive Driving Mode” (TS-Off and AH-On in its less aggressive form); DIC message is set. Entered via two pushes of the button. “Competitive Driving Mode allows the driver to have full control of the rear wheels while the Active Handling System helps maintain directional control of the vehicle by selective brake application.” [source Owner’s Manual p. 4-12]

(4) Traction System and Active Handling Off. DIC message is set. Entered via holding the button down for five seconds. “The anti-lock brake systems remain on with the Traction Control and Active Handling Systems off.” [source Owner’s Manual p. 3-65]

Again, the Anti-lock Braking System (ABS) is always on and unaffected by selection of (1), (2), (3) and (4).

How Active Handling functions is sketched out here. http://forums.corvetteforum.com/show...80&postcount=9

That article is dated 2001 but the functions remain the same. What has changed is the speed of the communications channels between sensors on the C6 are more than ten times faster than on the C5. So now AH is perceived as smoother and more refined than before.

There are numerous undocumented features of the C6 platform. Some get discovered by owners and are written about here.

As you might imagine, there should be some difference between (1) Traction Control System Off and (2) Competitive Driving Mode; both turn off traction control.

The difference is in the degree of aggressiveness of AH. You can test that by tracking a turn (1) near the limit and watching AH intervene. Repeat the same turn at the same speed and steering angle but in (2). AH will probably NOT intervene. By this simple test, you have confirmed the difference. Dave Hill spoke about this AH difference in several lectures he gave after the Z06 was introduced.



Ranger

 

I had a PM exchange on this topic yesterday that bears repeating in part.

When we drag race, the driver intends to go straight. Momentary short-duration movement of the rear often occurs on power transitions involving shifts. In the C6Z we get wheel spin on every shift, even on heated drag radials. Logged data show plus 12-17 mph on both the 1-2 (60 actual) and 2-3 (89 actual) and 9-11 mph on the 3-4 (120 actual). That spin is momentary and the lateral component is usually very small, less than a foot.

On the 1-2 shift it's not unusual for my rear end to carve a gentle 20-40 foot arc about a 12-18 inches off the previous track of the car and hit the outer-edge of the rubber-lined racing groove. That movement doesn't upset the balance of the car, because the movement has a very minor yaw component and is generally graceful.

What set off the incident Monday at Atco was the rears spinning from actual 60 mph to 89 mph almost instantaneously but unevenly side-to-side. That put a significant yaw force at the rear. The speed of the comms path in the C6 is very fast and Active Handling reacted twice, once at the right limit and once at the left. Unfortunately I wasn't PCM-logging that pass. Would love to see the data on the car's and my (re)action times.

When the incident occurred, the actual speed was 60 mph. I knew that aggressive AH was there. I knew that the run was compromised and the risk of staying on the throttle was higher than lifting. Once I lifted the throttle, and had the AH assist, the car settled down back in the racing groove, but it's course in the two jigs deviated by an estimated three feet right and a bit less left.

The wall at the tracks I run on are about 8'-12' from the side of the car when it's in the groove. That's not much maneuver room at racing speeds.

Most pro drag racers attempt to recover from a loose condition during a pass. But they're racing for money; and if they hit the wall, the repair is covered by owners/sponsors. Most of us occasional racers bear all the risk and liability ourselves. That makes me more cautious in solving the risk v reward calculation.

I've seen seven C5/C6 hit the wall. All were running with AH turned off.

Appreciate the opportunity to elaborate on yet another learning experience at the track. C6 AH does does its job for us straight-line guys.

Ranger

 

Yes the manual is very badly written and it is crazy that CDM doesn't entail the traction warning light coming on the dash.

But Ranger is 100% correct: CDM allows a lot more sideways movement than just TC off, and less than "all TC and AH off" where it is all down to you.

Race circuit/street circuit is the only relatively safe environment to try CDM and only experienced circuit racers should try all AH off IMO.

I always try out the grip levels with CDM on first before turning all AH off for race circuits.

 

thats soo normal

 

Actually, that sounds correct. When you say AH Off, I assume you have everything off, as I don't believe there is a choice of using TC without AH. As the car slides laterally, AH will apply braking to the corner(s) as necessary to help restore straight line movement. If you are inducing power oversteer, you need the freedom of manual throttle control, and without the intervention of braking. My track use is strictly road course, so my opinion is a bit different regarding these electronic aids. I have used both CM and everything off, but I usually just leave it in the default all-on setting. My driving style on track doesn't require any greater freedom of slip and yaw angles than allowed by the car's systems. In other words, if I activate TC or AH, I have either done something wrong, or, something unexpected was encountered (fluid on the track). So, since it doesn't slow me down, I figure I might as well leave it on. Other folks enjoy sliding around more, but it's seldom faster. I realize drag racing is totally different, and I can see that you would need more wheel spin than TC allows.

 

This is exactly what I follow. CDM for most of the time and the first session of HPDE, then all off. I never drag race so I cannot comment there.

 

I've done only a couple of hundred laps, all on the same high speed road course: Texas World Speedway. The first 50 or so laps were with TC and AH full on. Then the next 50'ish in Competitive Driving Mode. The last 100'ish with all computers off (push and hold the buttom like 5 seconds). Here are my humble observations.

AH is very aggressive, and very effective. Without it there's no doubt Ranger would have had a bad day.

Interestingly, I found that CDM actually resulted in AH employing its braking algorithm longer for a given departure from controlled driving than it did with TC and AH fully engaged. After observing this a dozen or so times, I concluded that CDM allows higher yaw angles, higher yaw rates, and/or larger disparities in individual wheel speeds than with full AH. So you get both a more fully developed departure in CDM, and a more heroic intervention. Bottom line, the brakes stink more and your splits are slower.

For my driving style, I feel more in control of the car, and my laps times are consistently quicker, if TC and AH are completely disengaged.

BUT, to reiterate Ranger's point: leave AH fully on if you are going fast between two concrete walls.

 

Thanks Ranger for this detailed explanation. Having the experience and wisdom of guys like you is definitely saving lots of headaches for newbies like me. I feel like I should ask CF members first before I do anything on the car that I haven't done before. Had I known what I know now, I would have been a lot more scared in going 193 MPH on this thing. It is such a disappointment to learn the mounting shortcomings of GM in their feeble attempt to produce a decent quality product. I guess it will take a lawsuit from an unaware driver who gets into a serious wreck by having selected CDM over "traction control off" in an effort to drive safer in this car. I hope someone will take a big chunk of GM's pocket because of this since 3 years into production and not a simple half a page explanation on the manual which can make a world of difference in a mishap, is unacceptable. It makes me wonder what other hidden shortcomings/gremlins GM has that could result in a serious injury or worse even death. Stuff like this is what separates Japanese cars and American cars, I hate to sound bias but this is the first American made car I've ever owned in 20+ years. It seems to me that everyone else except American car companies listens to their customers when it comes to feedback regarding their products. I was a mechanic at one point in my life, so I know the huge difference between imported cars and Domestic cars when it comes to design and quality. The gap got closer in the past 10 years, but its not yet there and Toyota is only getting better. Ughh!! Sorry, just venting, I know I'm overreacting. I'll get over it Game on!!

 

Guys you gotta read about your car! This thread has 29 posts in it and 6 are from Ranger. Almost two thirds of the remainder are from people thanking Ranger for the info on how to work their own car! I don't understand how you could spend 70k on a high performance car and not know what all the buttons do or the reaction from pushing the buttons!!

You guys are driving a true performance car, learn how to drive it in a fun safe way. The majority of the owners here do not utilize the performance the car was designed for and those same guys want to get the new ZR-1 ??????????????

Learn the car.

 

I don't agree with your assesment of the car, it is a great car. My wife has a lexus GS and this car is built just as well.

-You should be scared going 193 in a street car. Especially on a public road.

-If anyone wrecks their car and blames it on the traction control, they need to blame themselves and then learn how to drive.

 

Posted below with permission by the driver is a picture from a video I shot at a spring rental I hosted.

Part of the driver briefing on procedures always covers the requirement to make passes in Traction System Off, one click of the console button. That setting allows wheel spin but retains the aggressive form of Active Handling.

This driver spun the launch and his rear wheels departed the racing groove, the change in traction was uneven side-to-side, introducing yaw. The car snake left then hard-right then left again as "aggressive AH" did its job.

The tell-tale signs of the movement of the car are shown in the marks left by the rear wheels on the racing surface. Note the crucial AH intervention on the hard-jig to the right. Had AH been relaxed (Competitive Driving mode) or off, this car would definitely have hit the right wall.



Hope the picture reinforces the need to retain aggressive AH at the drag strip.

Ranger

 

Seems that driver stayed in the run quite long after breaking loose, no?

Ron

 

Not the case in the video, Ron.

My belief is that the driver reacted OK. He appears to lift during the hard jig to the right. His speed and momentum then carried the car to the position in the picture. I captured it there to reveal the full path of the car in the track surface during the incident.

But without aggressive AH, he would have sustained damage to the car from a collision with the right wall.

Ranger

 

My C5 with 667 RWHP was a point and shoot A4, why is the C6Z so dangerous in non-professional hands? I've witnessed a few 1/4 mile C6Z runs where the car almost went into the wall.

 

Three factors play a role in the difficulty involved in driving any severely traction-limited car. (1) driver experience (2) traction and (3) the laws of physics.

For many owners, the C6Z06 is their first experience behind the wheel of a manual-tranny super car. Seat time needs to accumulate before driver reactions are honed. Even then, on the drag strip, turning AH down or off gives all risk and no reward.

Finally, I note with interest your car has an automatic tranny. Easier to drive, spared of the need to work the clutch and shifter and manage shift-points. That makes for less congestion in the driver's central processor, freeing up cycles to enjoy the view and play with the radio.

Ranger

 

Thanks for the clarification Ranger.
I don't happen to have the owner's manual at work with me and I was too lazy to bust it out of storage at the house. The scenario I must be experiencing when TC is turned off is that if the rear wheels are spinning there is little traction and yaw control won't have any chance to pull me out of yaw that's already happening.
I think I need to make an appointment in an empty parking lot v. soon.

 

Not doubting, but can you post the video John?
When you & I got sideways Monday, we lifted & the cars straightened after the one way sidestep. Just curious as to the events during this pass.


Ron

 

Don't have permission to post the vid on the net. Just a pic that obscures the tag.

Ranger

 

Please don't get me wrong. I think this car is great overall as well, but with many shortcomings. I can list all of the flaws that this thing has, but all you have to do is read the posts in this forum and you'll know what I'm talking about. I'm sure it will be longer than your wife's car shortcoming list. My gripe is the simple lack of extra effort by GM to ensure owners are well aware of the car's capabilities and limitations by having all it's features documented in the service manual. Obviously they know the car in and out by having people discuss what it does in public. This to me is a sign of lack of attention to details.

I make it a rule for myself that before I criticized anyone, I need to know all the details. With all due respect sir, I recommend you do the same. Yes you were right on your assumption that I drove this car at 193 MPH in a public highway, but I did it at the German Autobahn. And before you say that it is the same as it is in the US, I'm here to tell you that you are absolutely wrong. The Autobahn highways are designed for speeds of over 150 MPH, unlike in the US, and the people drive and are used to driving more than twice the speed here. Unless you have lived there for at least 1 year, then you are in no position to assess the Autobahn and its limitations and to dispute any of my claims.

If you read my previous post, I was not accusing the AH/TC being a possible culprit of an accident. Let me clarify myself better. When the folks at GM decided not to discuss what "TC off means" in the owner's manual, this give drivers a false sense of security by being on a setting that is less secure/safe than what he/she thinks based on what is written on the owners manual. This is similar to the problems when the anti-lock brakes first was introduced years ago, when it was not a common knowledge how it works. Imagine how much worse it could have been if the ABS wasn't discussed in the owners manual?

I'm sure there are owners out there who don't subscribe to the CF thus are not getting the unwritten information regarding this car. I just hope that no one will get seriously hurt for lacking the inside knowledge provided by skilled CF members.

Sorry Ranger for semi-hijacking this thread.