Backfire at redline/high rpm's

[FASTSPOOLINGST]

Me and about five of my friends were out on the highway last night doing rolling runs. I was racing a corvette and I was in 3rd gear at about 3k. We both took off, i started to pull away from him, but then once my car got up to about 5500-6000 rpm, it let out this loud as hell backfire????? WTF???? It does it too whenever I am dragging and my 1st and 2nd gear revs up to fast when my stock clutch slips all to hell and my motor bounces off the rev limiter. Is this due to still running the stock fuel set up? I am running 15-17 psi on stock injectors.

AFC on the way today, next payday I want to order injectors. I want to run 20 psi on 93 octane, what size to i need. Will 660's work for this, or will they be runnin maxed out? If so, i will get something bigger.

btw-i shifted to 4th and still left him.

 

[talontsi01]

I have the same problem. Fuel cut. I am also in the market for upgrading my stock fuel system to something with a little bit more flow. I have gotten fuel cut in every gear except 5th. I also get it at about the same rpm's as you. I am thinking about upgrading my injectors and fuel pump. I'm not sure what else exactly I would need.

 

[FASTSPOOLINGST]

It isn't fuel cut, maybe just running too lean. I know what fuel cut is and what it feels like (engine falling on it's face slamming hard) when i hit it and it wasn't it. It was just a loud ass backfire and the dude in the vette said he saw a flame shoot out my muffler. I'm sure upgrading my injectors will get rid of this, that is my next step in my Stage 2 upgrades.

I already have a walboro 255 fuel pump w/ re-wire installed

I ordered my SAFC today from ebay

Next payday (1st of Feb) I will be ordering my injectors.

I'm pretty sure this will solve the problem after i get all of it on and tuned out right.

 

[talontsi01]

 

[talontsi01]

I get the same thing. I'm most likely running to lean too. Thats why i need to add fuel.

When I've hit my fuel cut (or whatever it is), friends tell me that they have seen a large puff of black smoke come out of the exhaust.

What I think I might have is both fuel cut AND what you're talking about (running to lean). Atleast that is what it seems like. At times, I will hit fuel cut (I will feel the jerk). And other times, I will just backfire and shoot out a puff of smoke out the tailpipe (but not the intense jerk of power).

Hopefully a fuel pump and injectors should solve both of these.

Couple questions: Why did you go with the 250 rewire?
How hard was it to install?
Have you decided what size injectors you are going to get?


I apologize for wrongly informing you. I didnt fully read the post. But I do know what you are dealing with.

Thanks, Jim

 

[98eclipseRS]

back fire plus flame = not lean. The reason you back fire and/or shoot flames is when you are running too rich and some how the unburt fuel in the exhuast is ignited. My friends cobra started doing it after he switched over to an off road h-pipe(no cats). He later got it dyno tuned with wideband o2 sensor and it was running extremely rich.

 

[FASTSPOOLINGST]

Yeah, i believe you are correct, i know i am running rich as hell. I hear the popping in the exhaust at idle and the it smokes cuz it's too rich and you can smell it like crazy from the fumes.

I am going to be running 550's or 660's I haven't decided yet, I will probably go with the 660's. I am going to be looking at running 20psi on pump gas, that's why and I am also going to be upgrading to the T3/T4 50 trim in the future after I get my FMIC.

I have a 255 fuel pump and it is easy as hell to install, it takes about 15 minutes. The rewire is just replacing the skinny ass wire they put on it stock, cuz if you ever heard a pump without it, when u turn on your blinker you can hear the power loss in it. Headlights too for that matter. Just goes to a thicker gauge wire. I think there is some dsmers even selling a rewire kit on ebay. Way overcharging for some wire and splices though. It is in your Haynes manual how to do it, but there are also links and a few websites that have articles on it on the web. Check around in the forums i'm sure you can find it.

 

[FASTSPOOLINGST]

Originally posted by 98eclipseRS
He later got it dyno tuned with wideband o2 sensor and it was running extremely rich.

After I get my injectors, i am going to have my afc tuned by wideband o2 sensor, but it will not be on a dyno. The performance shop here doesn't have a dyno, they road tune. How big of a difference will it be between the two, cuz i know another guy that is mostly domestic race cars that has a dyno, not sure if he tunes afc's on his dyno, but if it is worth it i will give him a call and check it out.

I am not a serious drag racer yet, i mostly streetrace, so if it will save me the dough and be suitable to my needs, i'll stick with the road tuning.

 

[bigjangin]

i use a safc and pocketlogger to street tune and I think ive got it tuned pretty good. With a wideband o2 and a logger you should be able to tune it well.

 

[98eclipseRS]

there is no difference in the actual outcome of tunning. However when using a dyno to tune it is alot more convenient. You don't have to worry about all the hazards of doing it while on the road. That's pretty much the only thing.

 

[ennioGST]

do you get whiplash when it "backfires"? also what turbo are you running? it sounds like boost cut. Your ecu keeps your car from over boosting. need to get a tune