Engine miss/stuttering.

[fanman223]

After a recent RCC Stage one turbo install on a Gen II bike it seems to start and run fine up to 7K rpm. Then the engine stutters like it is missing unless at or near full throttle. Then it pulls great. It dynoed at 301 with stock injectors but had the waste gate spring changed to 255 which is more useful for me. It is a street bike so partial throttle setting are the norm. The ignition seems squared away with new plugs and coils. I use pump 93 oct. First turbo for me but I suspect a tuning issue. Any help would be appreciated.

 

[Mr Brown]

It's in the tune.

 

[Boosted Cycle Perf]

After a recent RCC Stage one turbo install on a Gen II bike it seems to start and run fine up to 7K rpm. Then the engine stutters like it is missing unless at or near full throttle. Then it pulls great. It dynoed at 301 with stock injectors but had the waste gate spring changed to 255 which is more useful for me. It is a street bike so partial throttle setting are the norm. The ignition seems squared away with new plugs and coils. I use pump 93 oct. First turbo for me but I suspect a tuning issue. Any help would be appreciated.

Holy crap. 300hp is a lot of power on a stock compression gen 2 on 93 octane. It made that on what? 8-10psi? NOT a good idea at all.

What did you use to tune the bike? Stock ecu? Wouldn’t happen to have a picture of the plugs you pulled out of it do you?

Its almost certainly in the tune. Likely, it’s loading up on fuel. But it could potentially going dangerously lean at that point too.

 

[fanman223]

Yes 301 HP at about 8-10 psi, perhaps a bit more but presently tuned back to 255 which better suits the way I ride. BUT. The engine is not stock. Wossner Gen I rods, Wossner turbo pistons, Gen I block with correct gaskets and spacer, ARP cylinder studs, Ported head, Stainless valves, High pressure valve springs, Ti retainers. Stock cams, High volume oil pump gear, Modded clutch, Energy coils, Full exhaust system and the small air filter that fits behind the body work. But stock injectors. If/when I want more power, I take the red spring out and put the yellow spring in and another dyno tune. No worries about the motor being able to take it.
The stock ECU is used for tuning. No pics of the sparkies.
Yes, I think it is loading up in that 6500-7500 band at partial throttle.
It is going back to the dyno soon to get it squared away.
Just wanted to get an experience opinion. It confirms what I suspect.