Launch Control for Evo 8 Drag Car (link g4+)

Could use some guidance here. The turbo on the car is extremely large (76mm) and I am having issues with the car bogging. Car is on a fuel cut pulling about 5 degrees of timing revving to 7000. Should I look at switching to an ignition cut or rotary style cut? What is a safe range on the ignition retard? I came here due to the fact I know Andre has been in this territory before and I'm hoping he can shed some light that can help me.

I did on evo8 with same size turbo and g4+ next:

launch rpms - 7000

launch limit mode - ign cut

advanced mode - on

limit range - 250rpm

cut effect - adaptive

start cut tp100 - 40%

end cut - 85%

exit decay - 100%/20ms

about 17-20 degrees of absolute ignition retard

and some Fuel trim if needed

also!!! I set target boost from speed chanel, and when wheel speed is 0 - you need to choose how much boost you want at launch

it can build more than 2bars in 1.5 secs, but too much boost on launch also may be a problem.

Can you post your map and log file with launch try?

-17 to 20 degrees seems like a LOT. Was that car a solid lifter car or a hydraulic lifter car?

hydraulic lifter.

You're in a difficult position as with a turbo that large you're almost certainly going to need to run an aggressive launch control strategy in order to build reasonable boost. This will require an ignition cut and a reasonable amount of ignition retard (I'd expect you'll need to retard the timing past TDC to get reasonable boost response). The problem you'll then face is that you will almost inevitably end up with the hydraulic lifters pumping up.

You may get away with this if you use a very stiff valve spring in the exhaust to try and combat the pressure pulsations in the exhaust popping the valves back off their seats, however all the drag engines I personally built we swapped to solid lifters to avoid complications. In the perfect world this also requires a solid profile cam as the lead in as you transition off the base circle of the cam is different between hydraulic and solid. I have however got away with using solid lifters on a hydraulic cam profile by setting the lash clearance very tight (0.002-0.003" cold).