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3 Rotor Won't Quite Start (G4 xtreme)

James Simpson

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Really struggling to get a 20b to start up here, 

We have a ported 3 rotor wired into a G4 xtreme, and it won't start (almost kicking in)

Have tested compression,  ignition and fuel and its all there, just not right.

Im using LS2 coils and they are firing fine, however I think it might be over fuelling considerably.  Currently the o2 sensor (Lc-1) is not functioning for some reason so its running without it enabled, would this be a problem?

I have a feeling its something with the fuelling as its dumping un-burnt fuel out and occasionally backfiring, its running on 850 primaries, can anyone recommend a fuel pressure and master fuel setting to begin with?

Triggers seem OK, however I had to lower the cranking trigger arming threshold to 0.3.

Timing could be off, as there was no timing mark, so we tried to figure out TDC from apex seals in sparkplugs holes- is there a more effective way without taking the front cover off?

Any ideas welcome!



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Get your apex seal no1 rotor at the spark plug hole and mark the pulley where its easy to see. Move back 5 degrees and mark again to give you 5deg BTDC then forward 20 degrees to give 15deg ATDC.  Get a timing light and see if your anywhere close. Also if you think its fuel related why not lower master fuel

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Progress! So I changed the settings on the Ignition to settings mentioned here:


For the LS2 type coils, e.g

Dwell between 8v-15v set from 6.9-3.8v,

Spark Duration 2ms

Falling Edge (Can someone confirm this is correct for me as I think this is the cause the most improvement?).

Still problems keeping running, which I am not attributing to fuel and amount of air being let by the throttle body.

Still wondering what a "rough" figure should be for Master fuel given I am running 850cc injectors.  Considering the rx7 base map is 12-15ms, running at like 6 seems a little low.  



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