Advance for engine braking

[tortfeaser]

I'm tuning a Celica GT4 (3S-GTE) with 34mm restrictor and have come across a situation where above 5500rpm and under boost when the throttle is released to change gears the engine won't quickly die down in rpm.

Below 5000rpm everything is normal. Its not a question of flywheel weight. I wonder whether advance at low MAP/high RPM is stopping the motor from reducing RPM.

Any ideas?

[bigmuz]

Fuel cut on the over run is not aggressive enough? No fuel to burn, no makee power. Then spark is irrelevant.

What is the ecu?

[tortfeaser]

No fuel cut 'cos that would interfere with antilag. Its a Motec M4.

When antilag is active revs drop as you'd expect. The only difference is that ignition is retarded 60 deg from the 40ish at low map/high RPM. But when antilag isn't active the revs won't drop making it a challenge to change up a gear quickly.

I'd think it was the fuel tuning, except we didn't touch it in that region.