MagicRat

Righ then, while my tuning shop's dyno gets repaired (something that I'm told may take some time) I've been looking at ways to do some science to find out whether my Cobb remap has improved performance. It's certainly made the car feel and sound nicer, but has it actually made it faster?

The good news is the Cobb box measures 0-60 times, so on the right road I can carry out some testing without breaking the law. Tried it over the weekend though was a bit pressed for time and so the road I found had a bit of an uphill slope. But I figured if I started from the same bush each time then that would do.

So I plugged in the Cobb box, put the car in sport plus and initiated launch procedure. Tuned, and uphill, the car pulled 4.271s. I went back and did it again, and it did 4.180. What I noticed though was that the upshift to second gear wasn't clean on either occasion. It felt like the car was bouncing off a limiter (though I don't think it was high enough to be *the* limiter if you see what I mean) in first gear several times before second gear 'took'.

I then took the tune off (went back to Cobb Stage 0) and launched the car again. This time it upshifted cleanly and clocked a 3.935. So on the one hand cool that I have a sub 4-second car going uphill, but not such good news for the tune. Or so I thought. When I repeated the run, the catching on the upshift was bad again, and we did 4.322, so it seems the tune was not the problem.

At this point I ran out of time and had to head home but...what gives? Is there a way to launch the car that is 'better'? I just floored the gas and dumped the brake when the 'launch control activated' light came on. I could try upshifting manually, but the sticking seemed to happen before the redline so not sure that would help. Maybe a smoother release of the brake? Smoothness is generally encouraged.

Any ideas?

99999

I haven't had launch control work right once. only tried about 5 times so far. I put the brake on, floor the gas, it says "launch control activated", it revs up, i release the break, and NOTHING. car sits and stalls, every time. i have to re pump the gas or fiddle with the break again before it goes. really frustrating. I keep intending to play with it some more.

Dewinator

IIRC the gas to floor and brake release have to both be very rapid or else LC will not activate. When I did it there was a lot of rubber on the track so 1st took a bit to hook up but all the rest of the shifts were instantaneous.

9914s

try to shift manually around 500 rpm before redline.

saeyedoc

It sounds like you're doing it correctly, maybe the tune messed up the shift parameters.

Homeles

Try releasing the "brake"

NVRANUF

It's more.... full brake pressure, full throttle, then "side-step" the brake pedal.
Worked every time on my TT.

Sounds like a trip to your dealer may be in your near future. Something is not right.

Al.Fresco

Perhaps you need to try a different bush.

GTOWN83

I just got a lesson from my service tech (Nick at Livermore Porsche). I had to disable the traction control, enable sport plus, fully depress the brake, fully depress the throttle, the orange light comes on and I slide the foot off the brake. It works perfectly.

dflowerz

Odd that you would disable the traction control, as the point of launch control is to not spin the tires off the line?

skiahh

Steering wheel perfectly straight?

99999

This worked great for me! just went out and tried it twice. Not sure if i was taking my foot off the "BRAKE" too fast before or if it is really all about the traction control being totally off. But this worked. thanks.

StormRune

The couple of launch failures I had in my first PDK car I finally figured out was due to a slightly slow brake pedal release. Just letting the pedal pop up seems to have been the fix for me. Traction control on is fine.

As to OP's Cobb test, I don't know why you aren't getting a proper shift either but as long as you are consistent in your manually forced early shift point (as 9914s recommends), I would think your test would be valid.

Al.Fresco

Per 991.1 iManual.... no mention of traction control needing to be turned off.....

Preconditions:
– Launch Control should only be used when the engine has reached operating temperature.
– "Sport Plus" mode must be switched on (indicator light on the button comes on and SPORT PLUS appears on the
digital speedometer or on the steering wheel).

1. Press the brake with your left foot.
2. Quickly press the accelerator down fully (kickdown activated) and hold it.
   The engine speed will level off at around 6,500 rpm.
   "Launch Control active" is displayed on the multi-function display.
   Depending on equipment, the "LAUNCH CONTROL" logo appears on the steering wheel.
3. Release the brake within a few seconds.

Remaining stationary for a long time with LAUNCH CONTROL can lead to overloading of the transmission.
To protect the transmission, the engine power is then reduced and the LAUNCH CONTROL process is cancelled.

Valvefloat991

Best traction is achieved with limited wheelspin, about 15%. That's what launch control achieves.