DCT Launch Control Update

[MarkR171]

Just finished another autocross event today. Normally, I never bothered to use launch control since there were tight corners so close to the start. Today, I decided to give it a shot and I finally have the answer to the question "What is the minimum travel distance required to use Launch Control again?"

The answer: Very little distance!

We had a short course this week, ~35-40 second range, I used launch control 5 runs in a row with the only driving in between runs being the time on course and driving back to grid, probably just over a quarter mile. Effectively, a drag racer could use launch control every pass.

I also found out it's very quick to engage. I pulled up to the start with the trans in M1, DCT and Sport buttons. Holding the brake at the start, and to launch I just slammed on the gas and immediately took my foot off the brake. The car didn't move until the revs reached launch revs (does not take long, obviously) THEN launched, even though my foot was already off the brake.

On another note, my car was parked with the engine off for 2 hours before my heat. I took it easy for 1 run to get the temps up, and was able to use launch control for the rest of the runs. I didn't try to use LC on the first run.

Took 1st in class D-Stock again today and people are starting to comment on how well the car is doing in stock form on run flat tires. I absolutely love it. It needs nothing!

[TreDirtyFive]

Did the flag icon come up when you nailed the accel to the floor while holing the brake? There should be no delay once you let off The brake if it's done correctly as its similar to slipping a manual clutch... U get tire squeal!! Congrats on placing 1st!!

[MarkR171]

The flag icon came up every time. There was a delay because it was still revving up to launch RPM. Basically just a split second delay, equal to a manual car with the clutch in revving to launch RPMs.

Basically:

1. Foot on brake
2. Quickly floor gas pedal
3. Immediately release brake as soon as you touch gas pedal
4. Transmission keeps clutch engaged as RPM rises to launch
5. Immediately launches as soon as 3500RPM hits

Instead of keeping both pedals pressed, then releasing the brake to launch.

[MarkR171]

Video from today:

[plasar]

Wow, congrats, awesome YouTube vids, and thanks for sharing.

I could really see different lines around the 180 degree turn that you have to brake for mid-course. Your last run did look quickest.

BTW, did you trounce that yellow Vette that we see at the end of the vid in the parking lot?

[Xylarax]

Thanks for the video, and congrats

[MarkR171]

Originally Posted by plasar

BTW, did you trounce that yellow Vette that we see at the end of the vid in the parking lot?

He's fast. He drove a Scion xB (first gen) last race because he had a hole in his Hoosiers. He beat around ~60-70 drivers with a stock xB. It was pretty funny to watch him in that car! He's one of the instructors for novice drivers.

It was surprisingly close though!

Z06 on Hoosier race tires: 36.397
Factory Stock 135i on Run Flats: 36.557

I ran a 36.209 in fun runs at the end of the day, with a passenger I got faster every run and I really think if I put my best sections all together in a run I would have broken into the mid to high 35s. I thought I was at the limit of my tires on my first 3 runs which were 37.8, 37.6 and 37.5 but since another D-Stock class car ran 37.1 (on Hoosier R Comps!) I had to just go for it. Knocked off a full second on my last run for 36.5 when I kept the pedal floored through the slaloms. I was really surprised with how stable and completely neutral the car handled. I still think it does not need a stiffer front sway bar for stock class at all. I'll officially trounce that vette z06 next event, I promise


The biggest surprise of the day: My Stock 135i was faster than all 9 STU cars!

[warmtoes]

Thanks for the vids. Excellent view to see the quick and hard launch the car performs. I'm guessing that's the Aloha stadium parking lot? Looks familiar from all the flea market shopping I've done.

[MarkR171]

Originally Posted by warmtoes

I'm guessing that's the Aloha stadium parking lot? Looks familiar from all the flea market shopping I've done.

That's the one. The only legal venue on the island since the track closed a few years back (poor maintenance and lack of funds from the owners)

[warmtoes]

Where was the previous track?

[RPM90]

Originally Posted by MarkR171

The flag icon came up every time. There was a delay because it was still revving up to launch RPM. Basically just a split second delay, equal to a manual car with the clutch in revving to launch RPMs.

Basically:

1. Foot on brake
2. Quickly floor gas pedal
3. Immediately release brake as soon as you touch gas pedal
4. Transmission keeps clutch engaged as RPM rises to launch
5. Immediately launches as soon as 3500RPM hits

Instead of keeping both pedals pressed, then releasing the brake to launch.

Nice work.

However, in a timed 1/4 mile, you'd want to keep your foot on the brake, press the throttle to the floor, revs rise, when the lights blink to green, release brake.
In a 1/4 mile timed run, you'd blow the light using your above posted method.

#4- clutch is kept dis-engaged

[MarkR171]

Originally Posted by RPM90

Nice work.

However, in a timed 1/4 mile, you'd want to keep your foot on the brake, press the throttle to the floor, revs rise, when the lights blink to green, release brake.
In a 1/4 mile timed run, you'd blow the light using your above posted method.

Absolutely. Main point was to show that drag racers can still use DCT launch control on multiple consecutive passes and that it's really not time consuming to launch in a hurry if someone so chooses.

#4- clutch is kept dis-engaged

oops, I meant similar to clutch pedal being pressed (disengaged)

[woner]

Just curious, how many miles were on the car when you first used launch control? I hit 1200 today and was excited to try it out, but I can't get it to work. I'm 99% sure I did the right procedure. I could just feel the car trying to move forward everytime I gave it any gas and no flag appeared.

[MarkR171]

If there was no flag icon, LC didn't activate. My first one was right around 1250 miles. Remember the car has to be warmed up to allow you to use LC, and a minimum of 6.2 miles (that day, not necessarily that trip.) 2 of my runs with launch control were after the car was sitting for around 45 minutes with the engine off.

The full procedure:

- Stop the car
- Press DTC button once so "DTC" comes up on dash
- Press Sport button
- Move lever left to S1
- Click Downshift paddle to switch to M1
- Brake
- Gas to full
- At this point revs will increase and flag icon appears
- Release brake to launch

[woner]

Ah do you need to push the gas pedal all the way down? That's the only thing I didn't try..I was afraid if i did that and it didn't activate then I would be sitting there spinning my tires looking like an idiot or I might damage something. Does it matter what order I activate dtc etc.? (surely not)

[MarkR171]

It shouldn't matter. In between runs, my car is parked in Park with DTC still on. so that's already changing the order.

The car won't let the revs go up while the brake is engaged unless launch control is engaged, so don't worry about pressing the gas and brake at the same time until you see the flag. Again, make sure you've driven ~6 miles and the car is warmed up (~235-240 degrees on the oil gauge.)

Also, your tires will spin and squeal a little so don't be alarmed when it happens

[woner]

Okay I'll give it another shot tomorrow if I get a chance, this time giving it more gas. It was definitely warmed up after a 2 hour trip! Thanks for the tips.

[JB135MDCT]

Mark, You are the DCT God.

[MarkR171]

Originally Posted by maxnix

I don't understand how increasing front roll stiffness would not increase understeer, either.

What suspension modifications can you get away with?

Stiffer shocks (stock length and mounting points) and a front sway bar. That's all for D-Stock suspension. Catback exhaust and tires are the only other allowed mods.

Maybe removal of the alignment pin for ~2 degrees camber but not sure if I want to bother with that.

[Limpopo]

Originally Posted by MarkR171

Just finished another autocross event today. Normally, I never bothered to use launch control since there were tight corners so close to the start. Today, I decided to give it a shot and I finally have the answer to the question "What is the minimum travel distance required to use Launch Control again?"

The answer: Very little distance!

We had a short course this week, ~35-40 second range, I used launch control 5 runs in a row with the only driving in between runs being the time on course and driving back to grid, probably just over a quarter mile. Effectively, a drag racer could use launch control every pass.

I also found out it's very quick to engage. I pulled up to the start with the trans in M1, DCT and Sport buttons. Holding the brake at the start, and to launch I just slammed on the gas and immediately took my foot off the brake. The car didn't move until the revs reached launch revs (does not take long, obviously) THEN launched, even though my foot was already off the brake.

On another note, my car was parked with the engine off for 2 hours before my heat. I took it easy for 1 run to get the temps up, and was able to use launch control for the rest of the runs. I didn't try to use LC on the first run.

Took 1st in class D-Stock again today and people are starting to comment on how well the car is doing in stock form on run flat tires. I absolutely love it. It needs nothing!

I have a 2010 135i N55 DCT
I switch off the Traction control
Move the lever to sport
Pussh it forward
Step on the brake
Push the throttle

It goes to 1300rpm
and no flag no nothing
I then release the brake and it seems for a second as if it gears down and the it goes.

Is Launch control in all the cars
My salesman tells me that I can only use it from 2000 km onward ????

[Limpopo]

Originally Posted by woner

Okay I'll give it another shot tomorrow if I get a chance, this time giving it more gas. It was definitely warmed up after a 2 hour trip! Thanks for the tips.

Hallo Woner

Did you get it right?

[MarkR171]

Originally Posted by Limpopo

Is Launch control in all the cars
My salesman tells me that I can only use it from 2000 km onward ????

Read your manual. It states very clearly how to use it, and that you can only use it after 2000km.