2004 Group N STi - Antilag Airflow with Idle Stepper Valve only?

Hi Guys,

i have basically no experience with Antilag Systems in particular, but i'm helping a friend with the calibration of his 2004 Group N rallye STi. He's running the very basic setup with an idle screw holding the throttle at almost 30% TPS and maintaining idle speed with massive ignition retard. Since no "kicker valves" or DBW Systems are allowed in Group N, if they don't come with the stock engine, this was the only option. Has somebody experience with antilag using the stock idle stepper valve to provide airflow during overrun? If yes: is it large enough to get a decent boost in overrun? I really want to get rid of the lumpy idle and poor driveability on transition between the rallye stages so any help is appreciated.

Thanks in advance!

The stock idle valve won't be able to make any real boost, especially if your running a restrictor.

Are you running a cyclic idle at all?

When you say dbw systems, could you run a dbw peddle activating a cable puller?

Unfortunately not, we cant change anything on the stock intake and throttle system. I'm running the ORB Mode 2 in the Motec M800. When ORB is switched of the Idle is maintained with the cyclic ignition cut to maintain idle speed of around 1800rpm.

Unfortunately there are no simple solutions to your problem. The idle control circuit alone isn't going to bypass enough air for worthwhile antilag operation. If you're running under Group N rules then the permanently open throttle plate with cyclic idle is really the only viable option. It actually works perfectly during a rally stage but it's horrible during touring stages.