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      07-24-2014, 10:25 AM   #1
GTB/ZR-1
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'Sympathetic' DCT Launch @ Strip

Done some searching, but have not been able to find if the car can be brake-torqued @ the line, in interest of not getting wheel hop/instant spin? (On streeties)

I've not tried it yet, as I'm planning on taking the car to the strip to see how it does with the bolt-ons.

Is this an alternative, or does the computer not allow it?

Forgive me if this was covered in another thread... TIA
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      07-24-2014, 10:53 AM   #2
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Quote:
Originally Posted by GTB/ZR-1 View Post
Done some searching, but have not been able to find if the car can be brake-torqued @ the line, in interest of not getting wheel hop/instant spin? (On streeties)

I've not tried it yet, as I'm planning on taking the car to the strip to see how it does with the bolt-ons.

Is this an alternative, or does the computer not allow it?

Forgive me if this was covered in another thread... TIA
You can hold the brake with left foot and gas with right and then release, but what that gets the computer to do is basically dump the clutch and spin the tires. Your only way to do a mechanically-sympathetic launch IMO is just get on the gas with no LC and no brake torquing.

I did the left foot on the brake right foot on the gas launch (but w/o using launch control, and DSC off) a few times at autocrosses and it made for sweet smokey launches but not the fastest or easiest on the car...
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      07-24-2014, 01:18 PM   #3
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^^^

Even if you were only to give it slight throttle (~1/8th)?

Thx for the response...
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      07-24-2014, 01:20 PM   #4
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^^^

Even if you were only to give it slight throttle (~1/8th)?

Thx for the response...
I don't know the exact amount of throttle, but I wasn't giving it a whole lot. I only let it get up to maybe 2.5k rpm or 3k, but it seemed to just dump the clutch(es).
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      07-24-2014, 01:23 PM   #5
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Ok, gotcha... We just need AWD to solve the wheelspin issue... lol
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      07-24-2014, 03:01 PM   #6
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No you cannot brake-torque the DCT. There is only three ways to launch the DCT.

1) Use launch control. But in order to do this, you will need sticky DR's or slicks. This process feathers the clutches at 5,500 rpm and is not all that bad for the DCT.

2) "Floorboard" method. Not that great for the DCT. But when the light goes green, pretend you are trying to put your foot right through the floor. It will trigger the "kickdown" button and dump the clutch at 3,000 rpm. For a NA m3 with street tires, this may optimize the launch. Just don't do it a bunch of times or you will wear your clutches.

3) Floor it but don't hit the kickdown button. Probably the safest method but won't optimize launch.
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      07-24-2014, 03:19 PM   #7
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I wonder if mine is different because my car has M3 GTS software. Mine I just held brake and throttle and it revved it slightly and dumped the clutch, taking off in a mess of wheelspin.
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      07-24-2014, 04:14 PM   #8
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I have the GTS DCT upgrade as well--forgot to mention if that makes a difference?
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      07-28-2014, 05:15 PM   #9
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Quote:
Originally Posted by Longboarder View Post
No you cannot brake-torque the DCT. There is only three ways to launch the DCT.

1) Use launch control. But in order to do this, you will need sticky DR's or slicks. This process feathers the clutches at 5,500 rpm and is not all that bad for the DCT.

2) "Floorboard" method. Not that great for the DCT. But when the light goes green, pretend you are trying to put your foot right through the floor. It will trigger the "kickdown" button and dump the clutch at 3,000 rpm. For a NA m3 with street tires, this may optimize the launch. Just don't do it a bunch of times or you will wear your clutches.

3) Floor it but don't hit the kickdown button. Probably the safest method but won't optimize launch.
Can you explain what the "kickdown button" is? I've heard of that before.
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      07-28-2014, 07:59 PM   #10
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Quote:
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Can you explain what the "kickdown button" is? I've heard of that before.
Before you turn on your car, put your foot on the accelerator pedal and then push it to the floor. Now push it harder and you will feel it travel a little further toward the floor and you will hear and feel a "click". That is the kickdown "button". Button in quotes because it's not really a button at all.
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      07-29-2014, 10:47 AM   #11
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Quote:
Originally Posted by Longboarder View Post
Before you turn on your car, put your foot on the accelerator pedal and then push it to the floor. Now push it harder and you will feel it travel a little further toward the floor and you will hear and feel a "click". That is the kickdown "button". Button in quotes because it's not really a button at all.
Oh that. The "detent" - I gotcha.
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