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Backfire after spraying

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Old Dec 31, 2011 | 11:44 AM
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Default Backfire after spraying

Just wanted to see if this is normal...When I spray my 125 wet shot w/ my cutout open, after I'm done and the RPM's are coming down, it sounds like its backfiring and my buddy said flames were coming out. As cool as that might look, I don't think its normal. I'm thinking that its just unsprayed fuel going through the intake, but wouldn't that blow my hood off like some people have done? No window switch btw, only a WOT switch and a flip switch in the cab

Any thoughts?
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Old Dec 31, 2011 | 11:48 AM
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Does it only happen on the spray? My car runs a little rich and does this n/a with bolt ons when I let out at like 6k and dont push the clutch in...
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Old Dec 31, 2011 | 12:30 PM
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Thats normal for my last 3 nitrous cars. Just extra fuel from running rich being on nitrous and backfires when you stop or get off throttle.
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Old Dec 31, 2011 | 01:54 PM
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ok, thats what I was thinkin. But it is bad for the motor at all? I'm thinking its just the extra fumes from the nitrous and fuel being heated up from the exhaust and then it gets ignited and blown out.
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Old Dec 31, 2011 | 01:55 PM
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Originally Posted by coolmanvette75
Does it only happen on the spray? My car runs a little rich and does this n/a with bolt ons when I let out at like 6k and dont push the clutch in...
and yes, its only when I spray, run it to high rpm's, and then let off
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Old Dec 31, 2011 | 05:28 PM
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I have yet to hear of flames on decel in mine. Ya'll must be uber rich.
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Old Jan 2, 2012 | 09:00 PM
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What is your airfuel?

Dave
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Old Jan 2, 2012 | 11:20 PM
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Mid 11's @ WOT...the afr is good, its only doing it on decel and pops once or twice. I'm A4 btw
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Old Jan 3, 2012 | 12:57 AM
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mine does this every time i spray it did it on the 100,150 and my current 175 shot hasn't hurt anything in mine.
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Old Jan 3, 2012 | 12:43 PM
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Originally Posted by jrzdude
Mid 11's @ WOT...the afr is good, its only doing it on decel and pops once or twice. I'm A4 btw

mid 11's and a/f is good contradict each other....
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Old Jan 3, 2012 | 02:55 PM
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Its not normal, probably from being way to rich.
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Old Jan 3, 2012 | 03:17 PM
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What A/F should it be then? I thought 11's are where you want it
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Old Jan 3, 2012 | 08:13 PM
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What ever the plugs/et/mph tells you it wants. there is no magic number but id bet anything its not mid 11's on any shot let alone a 125 on an ls1.
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Old Jan 5, 2012 | 09:45 AM
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Originally Posted by jrzdude
pops once or twice.
Okay is it popping or backfiring? Big different. Popping on Decel is normal with headers and especially with cut-outs. Turn off or adjust DFCO in the tune.
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Old Jan 5, 2012 | 10:59 AM
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It's popping, but I figured with the flames coming out, it was a backfire
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Old Jan 8, 2012 | 12:16 PM
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Originally Posted by SargeZ06
Turn off or adjust DFCO in the tune.
That's what I was thinking...make DAMN certain you're tuner adjusted this to a respectable level for your setup. I would recommend you turn it off completely on nitrous runs personally.
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Old Jan 8, 2012 | 07:47 PM
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When we were dialing in the nitrous tune on the blazer we had the issue. after reading the plugs and all we ended up leaning it out some. Picked up et and mph. Plugs cleared up and the very same issue you have went away.

So I agree with everyone else. You are running way rich. I even have it on video while we were tuning it and you can hear what you are describing.


during tuning

http://www.youtube.com/watch?v=CRl8S...4&feature=plcp

notice it real good here. That popping was me

http://www.youtube.com/watch?v=YWqY_...6&feature=plcp

and now. Best video I have to show no more popping

http://www.youtube.com/watch?v=pJHu_...eature=related
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Old Jan 10, 2012 | 07:42 PM
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When you close the throttle and decelerate, the vacuum jumps way up and flash vaporizes the fuel that had puddled on the floor of your intake's plenum.

You know those controversial fuel puddles that are claimed not to exist when using wet systems?
Yep, those very same ones.

The rich misfires causing the popping in your exhaust are just the puddles letting you know what you're in for one day when the vacuum eventually pulls combustion flame back up into your intake.

FYI, most of the factory stock cars/tunes I've tested have the AFR dipping into the 11's already, so no you're really not that far off on average AFR.

The problem with wet systems is that because of very poor fuel distribution, and fuel drop-out, they have to run richer that optimal in order to prevent some lean cylinders.

You could try leaning your wet tune down a bit, and may pick up power and all is well. Be careful and keep an eye on each spark plug and hopefully you will catch any lean cylinders before it is too late.
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Old Jan 10, 2012 | 08:29 PM
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Originally Posted by white2001s10
fuel that had puddled on the floor of your intake's plenum.
Would a guy still have this problem with a wet plate system?
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Old Jan 10, 2012 | 09:07 PM
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Originally Posted by white2001s10
When you close the throttle and decelerate, the vacuum jumps way up and flash vaporizes the fuel that had puddled on the floor of your intake's plenum.

You know those controversial fuel puddles that are claimed not to exist when using wet systems?
Yep, those very same ones.

The rich misfires causing the popping in your exhaust are just the puddles letting you know what you're in for one day when the vacuum eventually pulls combustion flame back up into your intake.

FYI, most of the factory stock cars/tunes I've tested have the AFR dipping into the 11's already, so no you're really not that far off on average AFR.

The problem with wet systems is that because of very poor fuel distribution, and fuel drop-out, they have to run richer that optimal in order to prevent some lean cylinders.

You could try leaning your wet tune down a bit, and may pick up power and all is well. Be careful and keep an eye on each spark plug and hopefully you will catch any lean cylinders before it is too late.

Instead of tuning, could I maybe step a size down on the fuel pill to lean it out a little bit?
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