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Old 02-07-2018, 07:21 PM   #1
Mr. Wyndham
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[ANSWERED] Explanation of Launch Control

Quote:
Originally Posted by travislambert View Post
Hey Al,

Can you talk to us about the details of launch control and share any tips for effectively launching the 6th Gen ZL1 with a manual transmission?

For those of us with a custom launch control configuration, we can choose a slip target between 5% and 15%. When the car first begins to launch the front wheel-speed is near zero, so any slip of the rear tires will exceed the 15%. How was the car designed to react in this scenario? If there is some mechanism to conditionally apply the slip target as the car begins to move, can you share the details of this mechanism? Are there any factors, such as tire wear, wheel-speed sensor accuracy, sensor latency, etc. that may significantly impact the wheel slip % calculation at very low speeds?
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.

Name:  targeted slip 2.png
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Quote:
Originally Posted by travislambert View Post
What effect does each PTM Mode/Surface Type configuration have on the launch control?
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.

Quote:
Originally Posted by travislambert View Post
With high-traction surfaces many owners have experienced what’s being described as “bogging” while launching. Can you help us to better understand how the torque management systems are applied during launch to reduce as well as reintroduce power (assuming wheel-slip/traction is not an issue)?
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.

Quote:
Originally Posted by travislambert View Post
Can you share with us how the advertised quarter-mile times are determined? According to our “Official 6th Gen 1/4 Mile V8 Fast List”, only one member has been able to achieve the advertised 11.8 second quarter-mile time for the ’17 ZL1 M6 coupe, but many members have far exceeded the 11.4 advertised for the ’17 ZL1 A10 coupe.
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.

Name:  launchrawdata.png
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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.
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Old 02-07-2018, 07:43 PM   #2
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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.
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Old 02-07-2018, 08:02 PM   #3
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Sweet. Hopefully that advice leads to real improvements for members!
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Old 02-07-2018, 08:34 PM   #4
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Good stuff.
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Old 02-07-2018, 08:55 PM   #5
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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.
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Old 02-07-2018, 09:11 PM   #6
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Lol practice makes perfect
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Old 02-07-2018, 09:52 PM   #7
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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.
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Old 02-07-2018, 10:06 PM   #8
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Interesting response. Really need the seat time to learn this car. Helpful information to get to the end goal faster
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Old 02-08-2018, 12:35 AM   #9
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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.
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Old 02-08-2018, 03:01 AM   #10
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subscribed for reference.
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Old 02-08-2018, 08:03 AM   #11
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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?


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Old 02-08-2018, 08:05 AM   #12
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Quote:
Originally Posted by ninetres View Post
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.
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.

Name:  chart.JPG
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Old 02-08-2018, 04:06 PM   #13
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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.
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Old 02-08-2018, 06:36 PM   #14
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Quote:
Originally Posted by travislambert View Post
I appreciate the response Al.

The chart that was included from "one of the better launches" only shows about a 2.3 second 60'. Doesn't this confirm the problem? Or maybe the engineers at the proving grounds simply need more practice with the clutch?...

If it's so difficult to get a good launch that after a year in the public's hands practically nobody has learned to consistently launch the car, and the manufacturer's provided example of "one of the better launches" has a 2.3 60' time, then maybe the problem isn't the driver?

Also, if I understand correctly, the published performance numbers are derived from averages from actual runs... Since this run was from "one of the better launches", and there were no missed shifts or anything, I assume this was also one of the better 1/4 mile times. Therefore, I'd expect this run to be faster than an 11.8, but it isn't.

Here are the numbers I derived from the chart. I believe them to be accurate to +-0.02. (After I calculated the numbers, it became clear why the numbers weren't shared in the response.)

Code:
60'    2.30 @  36.33 MPH
330'   5.42 @  78.34 MPH
660'   7.94 @ 100.04 MPH
1320' 11.89 @ 125.86 MPH
This certainly is an exceptional run that beats my best time by a couple tenths (of course I don't have a private track though). Given the high MPH, I'd say the car had some pretty cool air to work with, but unfortunately, it still didn't reach the advertised 1/4 mile time for the ZL1 M6 Coupe.

You'll have to forgive me for not celebrating this response. I appreciate the effort that the team put into the response, but I don't think it proves in any way that the M6 ZL1 doesn't have an issue. If anything, it confirms it.

I really wish the Camaro team would just admit that this car has an issue and offer a fix.

If anyone would like to check my numbers, here's a zip of the excel file I used.

Attachment 919213
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'.
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