New injectors, now FEELS like fuel cut??

[Spoolin92GSX]

I just got some RC 750cc injectors installed the other day, got them dialed in with TunerProRT and got the car running great at 14psi. Bumped up my NLTS from 6krpm to 7krpm, and went to do a full 3rd gear pull. As soon as I hit ~6150rpms on the log, it FELT like fuel cut. Very violent power loss, stutter, only way I can describe it is the feeling of fuel cut. However, I have fuel cut disabled via hex editor. Injector duty cycle was only about 75% when it happened, MAF wasn't being overrun, I've looked through my entire tune with a fine-tooth comb and everything looks spot on. I know it's not spark plug/gap related, I've dealt with that before. I would post a log, but TunerPro log files aren't recognized. Any help on what could be causing this would be greatly appreciated!

 

[rEclipserGST]

I just got some RC 750cc injectors installed the other day, got them dialed in with TunerProRT and got the car running great at 14psi. Bumped up my NLTS from 6krpm to 7krpm, and went to do a full 3rd gear pull. As soon as I hit ~6150rpms on the log, it FELT like fuel cut. Very violent power loss, stutter, only way I can describe it is the feeling of fuel cut. However, I have fuel cut disabled via hex editor. Injector duty cycle was only about 75% when it happened, MAF wasn't being overrun, I've looked through my entire tune with a fine-tooth comb and everything looks spot on. I know it's not spark plug/gap related, I've dealt with that before. I would post a log, but TunerPro log files aren't recognized. Any help on what could be causing this would be greatly appreciated!

Without posting a log. All I can ask is how many lbs did you boost leak test to?

What global setting & deadtime are the 750cc injectors set to?

Also, what was the MAFraw reading? Some #'s would help us. As we are just guessing that everything is spot on without actually knowing.

 

[Spoolin92GSX]

Well, like I said I'm on TunerPro so it's a little different than link. But my injector comp is set for 750's, added 320deadtime, MAF Hz (assuming that's the same as MAFraw for link) topped out at ~2300 on that pull. I can safely say it's not airflow related; since then I've kept it under 6000rpms and got the boost up to 19psi. I can pull right up to 6000 at 19psi with no problems, but as soon as it goes over 6100 it hits the wall. I'm suspecting the CAS since it seems RPM dependent..
EDIT: Forgot to mention, I boost leak tested to 30psi with zero leaks.

 

[rEclipserGST]

Well, like I said I'm on TunerPro so it's a little different than link. But my injector comp is set for 750's, added 320deadtime, MAF Hz (assuming that's the same as MAFraw for link) topped out at ~2300 on that pull. I can safely say it's not airflow related; since then I've kept it under 6000rpms and got the boost up to 19psi. I can pull right up to 6000 at 19psi with no problems, but as soon as it goes over 6100 it hits the wall. I'm suspecting the CAS since it seems RPM dependent..
EDIT: Forgot to mention, I boost leak tested to 30psi with zero leaks.

You do know that pulling higher rpms means you are usually flowing MORE air right? This could still be a MAF overrun issue. Are you on the 1g maf still? Thought I saw a MAFT, but that must of been another thread.

 

[Spoolin92GSX]

You do know that pulling higher rpms means you are usually flowing MORE air right? This could still be a MAF overrun issue. Are you on the 1g maf still? Thought I saw a MAFT, but that must of been another thread.

Yes, I understand that and yes I'm on the stock 1G MAF. I don't suspect airflow because it cuts at the exact same RPM regardless of boost (airflow). 14psi-19psi, it still cuts at 6150rpms. The first time it cut out, all that had changed was the injectors and related settings; plus the extra 150rpms.. For all I know, I could have had this with the old injectors too but I never revved it past 6000 so I never saw it.. I don't mean to sound argumentative, but with different boost levels I know it flows different amounts of air at a given RPM. Odd.. I'm going to test sensors and check connectors just to be sure, and run another BLT for the hell of it.
EDIT: Also, the NLTS works at 7000rpms; I can push the clutch or go in neutral and free rev and it will rev to 7000 no problem.

rEclipser, I owe you an apology bud.. Did a bit more research and found that 1G MAFs are only reliable up to ~2000Hz. Guess where my fuel cut happens? Right about 2300! I watched my WBO2 and sure enough, 22.4; looks like I'm in the market for a 2G or EVO MAF now. Sorry, you were right!

 

[rEclipserGST]

Haha. Glad you solved it. Was going to say free reving isn't exactly pressuring the system either.

But yes indeed, two shortcomings of owning a 1g is the MAF overrun issue & aggressive timing curve. Good luck with the tuning. Let me know if you need a 2g maf. I don't have the pigtail adapter though.

 

[Spoolin92GSX]

Thanks, yeah I mentioned the free revving when I was still thinking it was RPM based I'm going to look into a 3g/EVO MAF since they're physically a little easier swap. I'll mark this resolved once I make my way to the computer