Help! Flames shooting out my exhaust??

[Nvsyet]

Hey guys, so I usually only fill up with BP 98 and I only get back fires when i change 1st-4th very lazily from 4000rpm?

About three times i've been up north, and needed gas but the only 98 octane fuel I could find was gull force pro 10% ethanol, so i've filled my tank 3x with this stuff.

Recently (last three nights) on the motorway, driving it hard, during gear shifts the exhaust would spit a longish flame , as i had people following me, they said i was shooting flames..

Is this bad for my car (engine)? Is this caused by the gull force pro since i've never shot flames before?

Cheers guys

[lachlan]

nah ****s mint .

my v3 used to do it fairly consistent if i wanted it to .

other than a new ecu(tune) theres not much you can do about it anyway

[boon]

Have you got a venting blow-off valve? That'll do it.

Or a Link with lots of overrun

Burrrr pop pop crackle burrrrrrrrr.

[94 Leone]

Lol standard v5 sti will spit fire occasionally on 95 haha. My mates 12a monster bridgeport will spit flames on demand haha

[ADIKT]

Mine doesn't spit flames

[kamineko]

mechanically, could it be a leaking injector/seal? my legacy has a bad earth somewhere and the TPS signal randomly goes high, resulting in extra fuel at throttle off = pop fart bang on overrun

i guess see if its still a problem after a few tanks of your usual fuel

[Nvsyet]

 boon said:

Have you got a venting blow-off valve? That'll do it.

Or a Link with lots of overrun

Burrrr pop pop crackle burrrrrrrrr.

I am running a Link G4 with a tune from gary capper. and yeah my BOV is venting to atmosphere, no cat full 3" straight exhaust.

could you please explain overunn?

[boon]

When you quickly close the throttle the engine requires much less fuel (obviously, less air coming in)

The Link takes a moment to notice this and is still fueling away like crazy. Result is unburnt fuel through the exhaust, popping flames etc.

Also happens under engine braking.

[Guest]

It's probably the anti lag

[Nvsyet]

I dont run antilag, so you think its my link overrunning? is this bad for my engine or exhaust?

cheers for the help guys

[Timmah]

Sounds like your car is running nice and rich, I'd be getting your tuner or laptop out to see what's going on.

Remember when you're driving around that you have a ClubSub banner so you're essentially representing the Club.

[pixelplay]

Its unburnt fuel getting burnt in the hot exhaust. Its normally caused by valve overlap which is where the exhaust valve is partially open and allow a little gas to escape, normally an exhaust is tuned so that the resonance in the exhaust pipe will push some of the unspent fuel back into the chamber, where it should be, before the valve fully closes. When the engine is running hard the gas flow is not as efficient as at lower revs so the fuel stays in the exhaust and gets burnt creating flames out the exhaust. Turbo exhausts tend to be more free flowing also so they are more prone to this at high revs.

Generally the more tuned your car is for performance the engine tolerances are smaller so this happens more during hard driving. As somebody said above if the cars running a little rich that will also cause it, the ECU will try to compensate for this but depending on the cars setup, sometimes it cant. It wont hurt your car if its rich but it will foul plugs and sensors if its like that for a long time. But since as it just happens when your going hard its probably not an issue.

Edited January 14, 2015 by pixelplay

[boon]

 pixelplay said:

Its unburnt fuel getting burnt in the hot exhaust. Its normally caused by valve overlap which is where the exhaust valve is partially open and allow a little gas to escape, normally an exhaust is tuned so that the resonance in the exhaust pipe will push some of the unspent fuel back into the chamber, where it should be, before the valve fully closes. When the engine is running hard the gas flow is not as efficient as at lower revs so the fuel stays in the exhaust and gets burnt creating flames out the exhaust. Turbo exhausts tend to be more free flowing also so they are more prone to this at high revs.

Generally the more tuned your car is for performance the engine tolerances are smaller so this happens more during hard driving. As somebody said above if the cars running a little rich that will also cause it, the ECU will try to compensate for this but depending on the cars setup, sometimes it cant. It wont hurt your car if its rich but it will foul plugs and sensors if its like that for a long time. But since as it just happens when your going hard its probably not an issue.

Yeah, nah, if this was the case the cars would do it from standard.

It's down to the tune, and a propensity for Links to overfuel at certain points, plus if he's still running a MAF (not all Link setups are speed-density) it will be due to the atmo venting BOV.

[Nvsyet]

 pixelplay said:

Its unburnt fuel getting burnt in the hot exhaust. Its normally caused by valve overlap which is where the exhaust valve is partially open and allow a little gas to escape, normally an exhaust is tuned so that the resonance in the exhaust pipe will push some of the unspent fuel back into the chamber, where it should be, before the valve fully closes. When the engine is running hard the gas flow is not as efficient as at lower revs so the fuel stays in the exhaust and gets burnt creating flames out the exhaust. Turbo exhausts tend to be more free flowing also so they are more prone to this at high revs.

Generally the more tuned your car is for performance the engine tolerances are smaller so this happens more during hard driving. As somebody said above if the cars running a little rich that will also cause it, the ECU will try to compensate for this but depending on the cars setup, sometimes it cant. It wont hurt your car if its rich but it will foul plugs and sensors if its like that for a long time. But since as it just happens when your going hard its probably not an issue.

Thanks for that extensive response! It backfires, and spits small flames if i change gears at like 3-4000rpm lazily?

[Nvsyet]

 boon said:

Yeah, nah, if this was the case the cars would do it from standard.

It's down to the tune, and a propensity for Links to overfuel at certain points, plus if he's still running a MAF (not all Link setups are speed-density) it will be due to the atmo venting BOV.

im running a link g4 if that helps? it may just be the ****ty ssq style bov?

[Guest]

Itl be the fuel over run like boon was saying. G4 doesnt give a fck about your bov unless youre still running maf based.

[Nvsyet]

 evowrx said:

Itl be the fuel over run like boon was saying. G4 doesnt give a fck about your bov unless youre still running maf based.

cool. i just wanted to know just incase it was bad cause sparks were comming out one night. my mate said it was my extractors getting red hot nd its cleaning it out?

[Guest]

Time for new mates.

[94 Leone]

Or maybe time to teach mates?

Unburnt fuel burning in exhaust.

Not red hot headers cleaning it lol.

[Guest]

Rear mounted ***** magnet. Boom.

[pedro]

Flames are cool...ironically..