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4wd Launch Control

Launch Control

Discussion and questions related to the course Launch Control


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Setting up the launch control on my Subaru Sti, and have the attached log of a launch on my medium boost setting. Car bogged slightly and then spun a bit as it was wet, however in the dry the car bogs a bit more, In this situation would I first try raising the Launch RPM limit from 6500 to 6800rpm? Or would it be better to retard the ignition further to try get more boost? Or lastly on my high boost setting 300kpa, this should overcome the bogging? Its at 14 degrees retard at the moment. 6500rpm limit with a -500 control range. Turbo is an EFR7670 and an ej207, ported heads etc..

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There isn't necessarily one single way to deal with your situation - You could try raising the rpm for the launch or you could try increasing the boost at your current launch rpm and both could give you reasonable results.

Personally how I would try dealing with it is first by keeping the launch rpm where it is and then using a little more retard to try and raise the boost you're launching from. While your log is in the wet, it looks like you're pretty close. The other thing that is really valuable to learn in a 4WD (well actually any car really), is to slip the clutch slightly as you launch rather than to just dump it. This will reduce drivetrain shock and also help maintain engine speed and reduce the tendency to bog.

Thanks for the reply and advice, I will try extra retard. I think part of my issue was the launch control was set to disarm 1 second after the car reached 15kph, so it was staying on up to about 60kph. So ignition was staying retarded. Have changed to disarm in 0.2 seconds, or would you normally just have it at a 0 second delay? On my highboost map i get about getting 32psi by 30-40kph.

I would suggest removing the retard immediately, however in some of the drag cars I tune I use a timer based ignition trim to remove timing through 1st gear which is really a different thing entirely. Depending how aggressively you're retarding the timing on launch control, you may struggle to actually launch the car at all if the retard stays active - The engine may be making lots of boost but it will be producing no real torque due to the combustion happening well after TDC.

Thanks again Andre, had the competition yesterday, launch control worked well except there may have been a little bit much spin, I could have probably gained a second or so changing into 2nd gear a lot sooner? Need some advice on how to read the log and adjust. Times were a lot slower than I expected based of previous road data, although it was damp. Still managed to win my class. This log was a race against the V8 in the video below. Nearly spun slowing down too fast after the run.

https://youtu.be/3B9YxNzUA0g

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