Launch control is a optional feature on pdk cars(op has a pdk), it goes with the sport chrono package. I am not certain if it is also on manual cars. I have a pdk with chrono and it is there at the bottom beside the sport buttons. But it can also be a technique to use. I have never used it ($).

 

Understood...I've launched a manual shift car using throttle, brake & clutch control similar to how you'd do on a motorcycle when racing a 1/4 mile. But I agree, it might result in $$$ if done incorrectly.

 

Relax guys! I find it hard to fault someone for testing their car in a controlled environment...I even asked permission!!

On a more serious note, I'm a bit perplexed as to what actually happens during launch control. The car was in launch mode - I recall seeing it in the dash and have confirmed it after watching the higher res source video.

Being in launch mode, I expected PSM to control slip/throttle = it should NOT have been bouncing off the limiter (especially being in automatic). It felt more like I was attempting a burnout. From a few examples I found of other 997 PDK launch control videos, it certainly didn't act the same.

I wasn't just wrecklessly going WOT - I was trying to see what launch control does, and part of that involves holding the throttle down. It's hard to tell, under launch conditions, when PSM is on and when it reverts to being back off. Is it 2nd gear? Certain amount of steering input? Certain amount of slip? I'm still thinking over what happened and I can't put my finger on the exact sequence of actions. It seems almost contradictory that launch mode is enabled with PSM OFF rather than ON

 

Ok,watching it on the phone,I thought it's a manual...

 

I don't understand what you thought launch control would do for you on a slalom course. Looking at the video you may have initiated it right but then you started flailing again and came off the throttle. With that your launch was over so looks like the system worked as it should.

 

LC is a PDK (automatic double clutch) capability with Sport Chrono ONLY. The proper sequence as "outlined" in the owner's manual is: " Warning, there is a risk of endangering other road users if you use this Control in an improper location or in a situation where other persons might need to take evasive action due to the rapid acceleration that this technology permits". 1) Press the brake with your left foot 2) Quickly press down the accelerator fully. The engine speed will flatten out at around 6500 rpm. "Launch Control active" is displayed on the on-board computer. 3) Release the brake within a few seconds. Note: Sport Plus must be pre-selected and the engine must be at operating temperature before attempting LC. Remaining stationary for a long time can lead to overloading of the trans. USE OF LAUNCH CONTROL WILL INEVITBLY REDUCE THE LIFE OF THE ENGAGED ENGINE AND TRANSMISSION COMPONENTS.

 

+1
The OP initiated launch mode correctly up until the launch mode light came on. At that point he should have simultaneously let off the brake and mashed the throttle. The nannies and PDK would have taken over an snapped off redline up shifts and keep it going in a straight line. Lifting or braking put it back into normal mode.

I've never used mine but have done it in a Turbo S several times at the PSDS at Barber. Not on the autocross course though.

 

I guess I was more referring to this thread of yours from a few days ago. Sorry for the confusion.

https://rennlist.com/forums/997-foru...he-slalom.html

I'm all for finding the limits in a controlled environment but I think you'll get a more accurate portrayal of the cars limits by being smooth instead of causing the car to loose control.

 

I didn't hear the beep in your launch. The car beeps when it's time to lift off the brake. Keep the accelerator floored the whole time. I've never heard of turning PSM OFF.

 

Pho King Fast, I think some of the things you try are a bit crazy!

BUT, I give you a great deal of credit and respect for trying things and sharing your experiences and quest for knowledge in environments where you are unlikely to injure or damage anything other than your pride.

 

Okay I think launch control is not intended to work with the PDK in automatic. From the instructions that's the only variable I can see and it also partially explains the banging off the limiter. Weird why 'launch control mode' would still give every indication it's activated though, even if I was missing a crucial first step (put gear in 1st rather than D). Throttle was all the way down (floor button included) until you hear the rpm drop before 2nd corner.

1. Sport Plus ON
2. PSM OFF
3. Both feet down
4. Beep and Launch Control Mode - Enabled
5. Left foot up
6. PSM says JUST KIDDING HERE PLAY WITH THIS

Now I'm confused - was launch control disabled because of automatic? Or was automatic mode disabled because of launch control? Little bit of both?

Alright I re-read the instructions, looks like being in 1st gear only applies for manual. Launch control should have worked in this case. More confused.

 

Are you SURE you didn't come off the accelerator trying to navigate those cones rocketing to 60 in 4 sec? Watching your video it looks like you had to.

 

Launch Control is explicitly designed to work with PDK in auto mode. It is the faster shifting of auto that allows for LC to maximize acceleration. If, however, you lift off the throttle you will not achieve maximum acceleration (if you lift off then why even do a LC?). I suppose LC can be used in manual mode but you will hit rev limiter unless you are super fast with your shifts. If you hit rev limiter, you will experience hesitations/power loss until next upshift. In auto mode the PDK will shift continuously a fraction prior to redline. I know this from personal experience.

 

1. You do NOT need to use Launch Control at AutoX, maybe on a drag strip?
2. You didn't correctly engage the Launch Control
3. You actually need less power application to be fast around AutoX
4. You must take those turns in smooth transitions, as opposed to power, correction, power, steering, correction, etc...
5. START SLOW, and build speed
6. Again, you do NOT need to use Launch control at AutoX

 

Thanks for the kind words, we should have a beer one day. Also no room here for pride, only momentum!

Yeah I'm sure. People don't seem to realize that I was following instructions, paying particularly close attention to Step 5
It hit the limiter 3 times, auto-shifted into 2nd, rpm's continued to climb for a little until I finally lifted. Speed looks to be 57mph at time of lift, about 5-6 seconds in.

I came across this article on traction control and launch control. It's brief but fairly insightful, I recommend the read.

http://www.motortrend.com/features/p...ction_control/

My understanding of PSM
A = Slip
B = Wheelspin
C = Out of control
If B leads to C, and A could lead to B, then PSM will step in before A can even lead to B.
Based on my experience with PSM On, this is how I understand the computer to think. PSM usually seems to be able to think at least a step ahead before things get too messy.

Launch Control
I'm starting to settle on the idea that the tires were simply too worn for the launch control to be effective. Launch control worked in this case, it just wasn't effective. Launch control also appears to behave with a more reactionary approach, unlike PSM On which seems to have a more proactive behavior;
*Notice PSM is OFF = no traction (wheelspin) control
A = Grip (matching vehicle and wheel speed)
B = Disruption in acceleration (wheel hop/NOT wheelspin)
C = Reduce engine speed
If A leads to B, and B leads to C, then LC will step in at C and react accordingly to get back to A.

What happened in the video:
1. Since PSM is OFF, traction (wheelspin) controls remain off.
2. LC functions primarily by reacting to wheel hop/disruptions in acceleration.
3. As LC senses a disruption, it reduces engine speed appropriately for vehicle/wheel speed to match. Notice it does not actively manage engine speed - it only reduces it momentarily to match vehicle/wheel speed.
4. The wheels spin a little every time you hop, and since traction controls are off, they will spin as fast as physics allow for the brief moment they are hopping and trying to regain grip.
5. My tires were bad enough that the wheels could never catch enough grip to hop, never triggering LC to reduce engine speed.
6. It was not until hitting the limiter that LC sensed a disruption in acceleration, appropriating a reduction in engine speed to match vehicle/wheel speed.
7. This occured 3 times as I was in 1st gear. Every time the car hit the limiter, LC sensed a disruption in acceleration, and matched vehicle/wheel speed accordingly.

In conclusion
-Launch control does NOT proactively control engine speed
-Launch control does NOT directly control wheel spin.
-Launch control works by temporarily reducing throttle in moments of disruption in acceleration. That is the ONLY thing it does (aside from dumping the clutch).

Of course this is just my theory, but so far it seems to be consistent with everything that happened.