backfire in boost

[VergeTSi]

What are the common causes of having backfire when in boost? It happens when at full boost and it shoots a flame out the exhaust and the car falls flat on its face when it does. Can boost leaks cause this? What about the fuel pump? Can I get a list of what can cause backfire when in boost please? Thanks

 

[sonik619]

Check the coil pack and check the gap on spark plugs.

 

[gofer]

back firing occurs when theres a rich condition in the motor... the flame shooting out the exhaust is a sweet side effect. boost leaks can cause it to run a little rich but so can SAFC's without a tune... i know this isn't your car alex so whos cars doing it? mine was doing it for awhile until i fixed a few boost leaks, hence the black stain on my bumper for the last few months.

 

[VergeTSi]

This is mikes Gsx. Lost my account information. Anyway the car doesn't boost. When I even go into boost it hits an invisible wall and backfires. Going to do a blt at alexs house this weekend.

 

[kahl23]

Boost leak test. Sounds similar to when I had an injector seal torn, turbo would spool and pull for about a half second, then fall flat on its face. Definitely do a BLT and then get back to us.

 

[talonsteve25]

Fuel cut?

 

[92awddsm]

Fuel cut?

Yep, due to a boost leak more than likely.

 

[rush2252]

vented BOV will cause one to run rich it will backfire surely you arent venting?

Kolby

 

[kahl23]

Vented BOV would only do that after it opened, which would mean after he had lifted off the throttle, and would not cause the car to bog like that unless it was a massive boost leak.

 

[gofer]

OIC. well somehow your account is still on my friends list in my profile... alex did say you fixed that clutch issue you were having, i told you!
get out that soapy H2O and start testing, its probably your IM since gavin never tightened those things down? Id start all the way up at the TB and work your way down since who knows where to even begin. you better get that thing ready to roll before mid june because your not the only 16g powered GSX rolling through socal anymore.

 

[sonik619]

OIC. well somehow your account is still on my friends list in my profile... alex did say you fixed that clutch issue you were having, i told you!
get out that soapy H2O and start testing, its probably your IM since gavin never tightened those things down? Id start all the way up at the TB and work your way down since who knows where to even begin. you better get that thing ready to roll before mid june because your not the only 16g powered GSX rolling through socal anymore.

Isn't alex's car fwd?

 

[Bud92gsx]

Ya know this seems to happen to me too at like 5k under boost..All of a sudden backfire, loss of boost, then everything comes right back to,life.. I do have new plugs ready to be dropped in, I'm just lazy and havn't put them in..Also your plud gap should be under.028 or a turbo dsm..Factory says .032, but everybody know thats wrong..

 

[94awdcoupe]

most likley exhaust leak. fresh air getting sucked into exhaust can cause the unburnt fuel to backfire in exhaust. thus the flame. the excessive back pressure during explosion sends very hot gasses back through motor during valve overlap for a split second causing car to run ruff for a few seconds.

or is backfire in intake manifold?

 

[kahl23]

Even if there was an exhaust leak, wouldn't there be too much positive pressure in the exhaust for any fresh air to be sucked in? I know air can be sucked in at lower load and RPM conditions due to the pulses of exhaust gas, but at 5k WOT I would think that the exhaust would be under enough pressure so that fresh air wouldn't be able to come into the exhaust

 

[Bud92gsx]

Ya I'm thinking it's just either the old plugs or, possibly my bov leaking..This is the 3rd bov I have tried, and this one is the most uncrushed I have..I do have one more that is uncrushed, but those leak at higher boost unless crushed right( and maybe dode mod)??

 

[94awdcoupe]

Even if there was an exhaust leak, wouldn't there be too much positive pressure in the exhaust for any fresh air to be sucked in? I know air can be sucked in at lower load and RPM conditions due to the pulses of exhaust gas, but at 5k WOT I would think that the exhaust would be under enough pressure so that fresh air wouldn't be able to come into the exhaust

pressure makes no difference.
ever seen a hand held sand blaster? 150psi air sucks sand right into the flow.

about ten years ago I thought I would be smart. I cut a hole in my exhaust about where the cat would be. and made a flap to cover the hole.. with a light spring I held the flap shut. I figured under boost the exhaust pressure would open it up and I would go faster and it would be quiet under normal cruise conditions....two things happen I didnt expect. it was loud at idle as it opened and closed. and bone quiet under boost. the flow sucked it shut.

 

[VergeTSi]

Hey I'm back. been super busy working all the time. Yeah alex and I have previously tried to do a blt on my car with a small compressor, starting at the tb and it would not even try to build pressure, just go to 7 psi and within 2 seconds die down. But I borrowed my friends 20 gal 5 hp compressor with a regulator so that thing will be on all the time. how much should I regulate the compressor to? Like 25 psi? Before I checked the intake mani and the bolts were tight but I didn't spray the bottom. I will definitely do a full BLT today and get back with the results.