[ANSWERED] Explanation of Launch Control
 

Al's Answer:

The 5-15% was simply the range selected by the Camaro team. You are 100% correct, any rear wheel slip from 0 speed would result in a wheel slip percent much greater than 15%. In fact, we could have just offered different levels of launch control numbered 1-20 and it would have done the same thing. Essentially 10% is where we normally tune launch control, and any move from 10% is just a scalar changing the slip profile. None of the factors mentioned (tire wear, etc) will affect the wheel slip % calculation, as it is merely parameter setting, not real-time compensation. Likewise, we cannot control how the driver releases the clutch, but we will protect the engine, transmission and clutch as a result of their driver action.

The custom launch control is best explained with a drawing:

The red line below is the target slip the system will control to. Then the 'modified' targets from 15% and 5% are shown.

Attachment 919129

Al's Answer:

PTM 1-4 is tuned for 'street surfaces' (unprepped). PTM5 is for drag strip 'high traction'. There is a noticeable difference between these two settings.

Al's Answer:

With respect to “bogging” on high traction surfaces, due to the stickiness of the tires and the tall first gear ratio, we drag the engine down once clutch is fully engaged. Currently we only use throttle and spark during pre-launch phase to control to requested engine speed which limits how quickly we can recover boost. We understand that a particular launch may result in a “bogging” condition, but much of that can be eliminated by practicing different styles of clutch ‘dumping’. See the answer below on how we achieve our quarter mile times to see the effects of different launch styles. One thing to note, that may not be obvious to the customer, is that the clutch release is still fairly quick - too slow of a clutch release will result in exiting of launch control and the engine reducing torque for clutch protection.

Al's Answer:
The advertised 0-60 and quarter mile times are determined by testing all available vehicles built with production intent hardware and calibrations throughout the development of the Camaro. As we get closer to production, and improvements are made, we will do our final measurements just prior to our press release. This is why you will never see early postings of our performance times, because we will push to the very end to get the fastest times possible. We also determine an average using multiple drivers and vehicles. The process starts by inspecting the vehicle for production intent calibrations, placard tire pressures, and recommended fuel type (Premium for ZL1).

Our testing takes place on an unprepped surface straightaway at the Milford proving grounds. It is the preferred location due to length of track and similar characteristics to magazine tests. If timing/weather are a factor, we will use our Yuma proving grounds.

The process starts with a few burnouts to warm up the tires (being careful not to overheat), followed by multiple quarter mile “runs”, two in each direction, multiple times. For the ZL1 manual on an unprepped surface, traction off (one button press) was found to be the fastest, however launch control is the easiest way to be consistent because you go to 100% throttle, let off the clutch, and let the car manage torque for you.

After testing, each session is analyzed and a time for that session is determined. The data is adjusted for ambient conditions and then the averaging of four runs, two in each direction, determines the session results.

Each published specification is the average of multiple sessions to eliminate any flyers that would be unattainable. The ZL1 Manual required significant practice of clutch pedal and throttle pedal application due to the tall first gear and the high grip tires. We experienced situations where the tires would light up with too much throttle and a slow clutch release, or grip too much with too quick of a clutch dump and not enough or too slow throttle, while we learned to maintain the right amount of stick/slip for best times. Also, shifting before 60 is worth about .2 seconds on the 0-60 time but does not impact ¼ mile. Don’t forget, the ZL1 will do 0-63 mph in first gear, to give you those 0.2 seconds back if you are just doing 0-60’s.

As we mentioned in the last question, the clutch release is still fairly quick, too slow of a clutch release will result in exiting of launch control and the engine reducing torque for clutch protection

The chart below shows the raw data of one of the better launches, including engine RPM.

Attachment 919128

The bottom line is this – We publish numbers that we feel confident are attainable (with practice) by our customers, and because we take a “best average”, we know many will also exceed our results. A driver also needs to understand how to properly use the clutch, to avoid the protection software intervening to protect the engine, transmission and clutch. These ‘nannies’ will often slow down a quarter mile time, which could be the nature of many not being able to achieve our times. My advice is to have a great time trying to learn your Camaro, because it is an awesome car, and will perform for you.

That's....pretty dang thorough!

I must also note, the Camaro Team has requested that we consider this the comprehensive answer on this topic so the Ask Al section will continue flowing. Basically: no follow-ups, please. :thumbsup:

Sweet. Hopefully that advice leads to real improvements for members!

Good stuff.:thumb:

So if I read between the lines a little bit, this was a very nicely put, politically correct way of saying, "you guys are crappy drivers - quit whining about a "bog" and learn your car better". LMAO!

Interestingly, in the graph the RPM line shows what we may be perceiving as the "bog" occurring as well.

The clutch release is very interesting. The release is very quick and deliberate, less than half a second - but the last 5% release takes a full second beyond that. I also take special notice to the related, and the only underlined statement above, "too slow of a clutch release will result in exiting of launch control and the engine reducing torque for clutch protection".

Oddly when considering launch control requires full throttle, you can see the accelerator was feathered and was never pegged to begin with. This looks like a manual launch.

NLS all the way through with a second gear shift at about 60.5MPH (~90Kph).

I wonder what the ET was for that run - looks like they did a quarter mile and just kept going.

Lol practice makes perfect

Great info
 

Thanks for answering Al. As a rookie driver with an SS not all of the information applies to my particular situation but I really appreciate the opportunity to learn from the design team and those drivers with more experience. :)

Interesting response. Really need the seat time to learn this car. Helpful information to get to the end goal faster

I must say, regardless of which question gets selected to be asked each time....this is quite the amazing “service” we are all blessed with. Thanks to all involved both on the forum and Camaro team! This answer definitely exceeded my, admittedly, pessimistic expectations.

subscribed for reference.

Thanks for such a detailed response, and for a graph that shows small details (such as the minor mph losses during upshifts).

I'm also seeing slight drops in rear wheel speed at the beginning of each upshift. Might this be a consequence of the amount of tractive force needing enough rear tire slip to show up on the graph, that would obviously disappear when declutching?


Norm

All three answers topped my expectations. Never thought we would get this type of time/effort put into these answers. When you all see them at the fest be sure and say thanks.

Here's a little blow up of the chart.

Attachment 919172

Not buying it...
 

Sorry, but not buying the answer. I want the ability to launch with NO nannies/electronics, etc. “Old school” style. I (we) know how to drive a stick, but the electronics are pulling power. I would happily pay any tuner listening who can defeat the torque control so I can then enjoy my car. Yes- I am willing to forgo my warranty to do it, too. My 2 cents. I paid for a quick car, but did not get one. Make it right, Al.:mad2:

Travis,

Thanks for posting that data.

Did you account for a 1ft roll-out (like at a dragstrip)? With that, I calculate a 1/4 mile time of 11.62s @ 125.9mph, with a 2.03s 60'.