Engine cuts out under high boost

[turbosam6]

I went to the track tonight, and was running 24-25 psi. At one point near the top of second gear on my second pass, the car just cut out, lost power, popped a little, then came right back in. What should I look for? Coincidently, my Direct scan stopped recording somewhere around that point, so no data. I had fuel pressure, no knock, and it picked right back up. I'm thinking ignition, maybe plugs? Ideas?

 

[TURBO 6]

Try gapping your plugs at a tight .030. That should clear it up.

 

[REDS HOT AIR]

what is the car running mph wise??

and i agree with .030 gap thats were mine are and no problem

 

[bruce]

Originally posted by turbosam6
I went to the track tonight, and was running 24-25 psi. At one point near the top of second gear on my second pass, the car just cut out, lost power, popped a little, then came right back in. What should I look for? Coincidently, my Direct scan stopped recording somewhere around that point, so no data. I had fuel pressure, no knock, and it picked right back up. I'm thinking ignition, maybe plugs? Ideas?

Try and get a DS of it doing that or something similiar.

 

[turbosam6]

MPH was 94 in the eighth. It doesn't show up on the DS. I'll try the plugs, I think they are gapped at .035 now.

 

[REDS HOT AIR]

i take it you were on a race chip?

if on street chip maybe it dont have enough duty cycle in the injectors and they are fallin off


did the pop come from intake side or out the exaust?

 

[TurboDave]

I doubt you'll cure anything fooling with the plugs. They aren't going to cause a loss of power like that. Ignition problems, or other main power gremlins however will.

 

[turbosam6]

I have an extender chip for my 50# inj. I didn't hear the "pop", my buddy was watching me run and said he heard it pop. I didn't hear anything. The duty cycle on the injectors was up to 102% at some points. Think they are too small? I will try the plugs, but I may not get back to the track till the midwest challange at morocco. Any more thoughts?

 

[turbosam6]

I did some reviewing on that run on the DS, and I was wrong, it did not shut off. My buddy was riding along and hit the space bar to stop recording. Should I do anything else besides plugs?

 

[REDS HOT AIR]

i just went 100.7 mph in the 1/8 and i was out of injector with 50's so your close to needing bigger

that was on my 127 mph 1/4 mile pass.

did your 02's drop mine were down in the low 600's on that pass with fuel at 63# static

i made the jump to 75's now and it dont have that problem now. cant wait to get it tuned in and see what it will do now..

 

[turbosam6]

Yeah, the o2's were at a low of 660, but my o2 was probably fouled out. The computer still shows a good a/f ratio on the direct scan, and my egt was high, but someone told me that my egt of 1699 was probably because I was rich, and was burning fuel in the exhaust. Basically it wasn't likely I had an egt of 1699 and no knock, which there was no knock. I'm confused because on one hand it looks lean, and the other rich. I get no knock at all, so what do you think? Should I go leaner or richer? I'm scared to lean it out because at that boost level detonation is a killer. Thanks for the help!

 

[REDS HOT AIR]

high egt's come from being lean

and your direct scan is getting its info from the 02

so looks like you leaned it out pretty good.

if fuel pressure stays up without dropping at all and it does it then its time to step up injectors

i havent seen any 50's that actually flow 50# most flow mid 40's normally unless you crank alot of pressure to then and if you do that they have the tendency to lock up and not want to start.

 

[Jimn8or]

It's too bad your buddy stopped the recording on the run in question. Were you manually shifting the car, or in 'D'? I didn't note your chip before I started this reply but there is a fuel cut-out command in most chips that occur at a preset rpm. If you were shifting at 5800-6000 I'd say that with ANY flare in the shift you'd be in the 'fuel cut-off' range of several chips. The result would be very similar to what you described above. With a complete run on Direct Scan you will actually see FUEL CUT-OFF illuminate on the replay. This is only one of several possibilities avail to your problem as a source. I would however recommend that you don't go throwing a bunch of money at injectors and alike as 009's have gone 10's with proper tuning. Do not disregard the words passed along regarding too rich creating high EGT's either, these are good words of advice. If I were you, I'd put my lap-top on the seat, and my buddy in the stands, and run it the way it was for a run with DS recording it all. There is a risk here, but you can't fix what you don't know is wrong.
Good Luck.
Jim

 

[turbosam6]

Jimn8or, are you spying on my garage? I just got back in from re-reviewing my ds file on that run, and thats EXACTLY what happened. The fuel shut off at the top of second gear at 5775 rpm. What happened is on the 2-3 shift, it appears the tranny flared, because the ds is showing 3rd is engaged, but the revs keep climbing, then fall back down. The car really hangs the 2-3 shift out, its probably going bad (stock tranny, except for shift kit, cooler, and deep pan). The fuel shut off light came on, just like you said. I missed that before, sorry guys- I'm a rookie at tuning! Guess the tranny needs rebuilt? Theres no way to fix that flare, is there? Crap, the way the shift feels, theres a tenth or two right there!

 

[turbosam6]

Oh, and I was wrong about the ds recording getting cut short. Its all there, he just stopped right when I got through the traps. I was messed up because the "feet traveled" was only 649, which is short, but I got 28" tires, and can't seem to make the ds read that way. I'll post that in scan tool tech.