[ASKED] Explanation of Launch Control

[midas@bellnet]

+1 please fix this, at a drag strip it is very embarrassing!!

[Zach495]

+1
Not to mention it's embarrassing in front of friends when leaving gatherings. FYI, I feel that the eLSD system is engaging too much at all times. You can be at 20 mph in 4th gear hit the throttle and it reads 19% wheel slip. That part doesn't make sense to me and I think that slows down my power across the whole power band. I also found out that there is some procedure about bleeding the ICHE system that engineering recommended that my dealership do to my car. It does seem a little better since they did this but I can't tell for sure as it's too cold in the northeast to really test the system until spring time.

[BSR-1]

I have problems with this as well.

[ZED SLED]

+1. I would like an explanation of this as well, especially now that I'm past break-in.
Thanks

[LSmith353]

I'm in......

[soceur77]

+1 this thread, even as an A10 owner Id like to know more.

[Norm Peterson]

Originally Posted by Zach495

You can be at 20 mph in 4th gear hit the throttle and it reads 19% wheel slip. That part doesn't make sense to me

I hope that any answer we get includes the definition of "wheel slip" that GM/Chevy is using.

Zach - read on.

Originally Posted by spotswood

I view several of the monitors in performance settings as useless especially the wheel slippage. I do not need a meter to tell me when I have the rear tires slipping.

Tire grip is hardly a 100% fully stuck down or 100% sliding/wheelspinning. It may help to consider wheel spin as the forward/backward counterpart to slip angle when cornering. As long as there is a load on the tires causing acceleration (or braking), the tires are not rotating in perfect sync with the road speed. And just like slip angles that have an angle corresponding to peak grip, forward/backward tire slip also has a peak slip% value (above which it rapidly gets easier to put them into full-blown spinning or even a smoke show).

Nothing about tire performance is "linear", let alone "constant". All or nothing behavior is for doorbell switches.

You'd really like to be able to stay right at that peak the whole time you're accelerating but doing so is probably beyond human capability. If anything, your feedback loop from sensing a little too much slip and lifting ever so gently - or not sensing enough and adding a little throttle - is simply too slow.

I guess I am just too old fashioned to want all these computer programs interfering with my car control.

You and me both.

But I do want to understand what's going on behind the curtain even if all that does is confirm or deny my own suspicions and maybe point me in some direction for how to best cope with it. I'm not going to assume that this particular piece of technology will remain exclusive to the ZL1 and cars of similar performance capability.


Norm

[Infern0]

Originally Posted by Norm Peterson

I hope that any answer we get includes the definition of "wheel slip" that GM/Chevy is using.

Zach - read on.



Tire grip is hardly a 100% fully stuck down or 100% sliding/wheelspinning. It may help to consider wheel spin as the forward/backward counterpart to slip angle when cornering. As long as there is a load on the tires causing acceleration (or braking), the tires are not rotating in perfect sync with the road speed. And just like slip angles that have an angle corresponding to peak grip, forward/backward tire slip also has a peak slip% value (above which it rapidly gets easier to put them into full-blown spinning or even a smoke show).

Nothing about tire performance is "linear", let alone "constant". All or nothing behavior is for doorbell switches.

You'd really like to be able to stay right at that peak the whole time you're accelerating but doing so is probably beyond human capability. If anything, your feedback loop from sensing a little too much slip and lifting ever so gently - or not sensing enough and adding a little throttle - is simply too slow.


You and me both.

But I do want to understand what's going on behind the curtain even if all that does is confirm or deny my own suspicions and maybe point me in some direction for how to best cope with it. I'm not going to assume that this particular piece of technology will remain exclusive to the ZL1 and cars of similar performance capability.


Norm

Well said.

[6spdhyperblue]

+1

[HAHA I 1]

+1 I actually had significant bogging happen in 2nd gear, too. Its driving me nuts and making me regret getting an M6, which is really crazy because my 67 Nova wagon and 68 Camaro are T56 cars because they are my favorite.

[S.T.A.R.]

+1 here as well...

ZL1 A10 owners be like, hey little brother (1LE), one day you to can run with the big dogs!

[Ankh599]

You my vote. I don't think you need to change anything.

I've met with the corvette tech at my dealership and he stated GM wanted the car drivable even for grandma. He says he cam put a tune on it that can eliminate the bogging down. Once I have mine done I'll report back

[travislambert]

Originally Posted by Norm Peterson

I hope that any answer we get includes the definition of "wheel slip" that GM/Chevy is using.

Zach - read on.

Tire grip is hardly a 100% fully stuck down or 100% sliding/wheelspinning. It may help to consider wheel spin as the forward/backward counterpart to slip angle when cornering. As long as there is a load on the tires causing acceleration (or braking), the tires are not rotating in perfect sync with the road speed. And just like slip angles that have an angle corresponding to peak grip, forward/backward tire slip also has a peak slip% value (above which it rapidly gets easier to put them into full-blown spinning or even a smoke show).

Nothing about tire performance is "linear", let alone "constant". All or nothing behavior is for doorbell switches.

You'd really like to be able to stay right at that peak the whole time you're accelerating but doing so is probably beyond human capability. If anything, your feedback loop from sensing a little too much slip and lifting ever so gently - or not sensing enough and adding a little throttle - is simply too slow.


You and me both.

But I do want to understand what's going on behind the curtain even if all that does is confirm or deny my own suspicions and maybe point me in some direction for how to best cope with it. I'm not going to assume that this particular piece of technology will remain exclusive to the ZL1 and cars of similar performance capability.


Norm

Thanks Norm! A lot of good points made. This one seems particularly important for folks to understand:

Originally Posted by Norm Peterson

As long as there is a load on the tires causing acceleration (or braking), the tires are not rotating in perfect sync with the road speed.

GM must feel that "peak slip %" is usually somewhere between 5% and 15%. However, from what I've seen, a percentage-based launch control system over penalizes slip at very low speeds. Therefore I don't feel a constant target wheel slip % value can be used to keep the tires at optimal acceleration.

The proof is in the case when the car first begins to accelerate. Since the car isn't moving, any slip of the tires will exceed the 15% of allowable slip. Trying to keep the slip limited to 15% at low speeds will require significantly reduced engine power at the worst possible time. By the time the car gets going fast enough for the 15% to become meaningful/stable, it's too late for launch control to provide value.

Although maybe not a perfect solution, I would think a distance-over-time (e.g., MPH) target slip metric would at least not have this issue.

I'm really hopeful we can get the Camaro team to help explain their rational for their design.

[S.T.A.R.]

Originally Posted by Ankh599

You my vote. I don't think you need to change anything.

I've met with the corvette tech at my dealership and he stated GM wanted the car drivable even for grandma. He says he cam put a tune on it that can eliminate the bogging down. Once I have mine done I'll report back

Ankh, and not void the warranty ?

And thanks for that info.

Tony