backfire

[Atsushi7mgte]

when i drive my supra fast like when i spool my turbo up to 7psi and rev to redline before i shift itll let out a big backfire. Im not sure about this but i think it throws fireballs some times cause me and my friends were driving a mountain road and my friend said that he saw a light flash from around the corner.

so question is...

what causes this?
is it bad??

 

[Jason T]

when i drive my supra fast like when i spool my turbo up to 7psi and rev to redline before i shift itll let out a big backfire. Im not sure about this but i think it throws fireballs some times cause me and my friends were driving a mountain road and my friend said that he saw a light flash from around the corner.

so question is...

what causes this?
is it bad??

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=19

 

[Poodles]

do you have a vented BOV?

 

[Atsushi7mgte]

nope all i got is straight pipe exhaust no cat with and 5zigen muffler apexi power intake and front mount intercooler.

 

[supraguru05]

mines pops on decel one or twice occansionally when its warm. i think thats relativly normal i definitly dont think its a lean backfire.

if anything check your tps adjustment

 

[TurboWarrior]

a backfire is serious. a rich "pop" is fine

 

[Poodles]

mine pops like that too sometimes... could be boost leak, or any number of things...

 

[Atsushi7mgte]

its not like constant its just like a fairly loud POP.

 

[supraguru05]

ok maybe we need to define backfire and pop here i think he is "popping"

what do you mean by back fire i was under the impression backfireing is simply igniting unburnt fuel in the exhaust

 

[Atsushi7mgte]

oh sorry for the confusion guys but its just like one loud pop.

theres this long straight before all the turns and thats where we hang out and i punched it in that straight and in the shift between 3rd and 4th its popped but it was loud as hell like i had my windows up and i heard it loud and it scared the shit outta my friend who was standing on the side haha

i just wanted to know what it was.

 

[buldozr]

sounds like 'fun', its normal. After I installed my A/f ratio guage, I noticed it was pretty rich when shifting(blow off valve is recirced) I get a slight pop with full 3" with a flowmaster muffler. If you are pretty concerned about it, check plugs and wires and check for boost leaks.

 

[jetjock]

ok maybe we need to define backfire and pop here i think he is "popping".

Backfires are induction events. They have nothing to do with the exhaust system. What is being talked about in this thread is afterfire. Also called muffler explosion.

 

[MA70Snowman]

Backfires are induction events. They have nothing to do with the exhaust system. What is being talked about in this thread is afterfire. Also called muffler explosion.

nice answer JJ, can you explain what might cause such conditons. Mine "Pops", or uh.. afterfires, but i chalk it up to a rich condition and fuel igniting somewhere along the exhaust. but if there are other culprits that might need to be checked please enlighten us.

 

[jetjock]

It's caused by what you said. Assuming fuel control is working in this car it's usually associated with a maladjusted TPS combined with an exhaust leak. The dashpot can also contribute. Overly rich open loop mixtures combined with exhaust leaks will cause it too. Lean mixtures with high HC is another culprit. Basically anything that combines excessive O2 with excess fuel.

 

[starscream5000]

nope all i got is straight pipe exhaust no cat with and 5zigen muffler apexi power intake and front mount intercooler.

So you've got an aftermarket front mount Intercooler with stock Intercooler pipes and a stock bypass valve?

 

[themadhatter]

mine does t on decel i always just figured it was bechause of the fact i have no cats and a can muffler lol and a light exhaust leak

 

[starscream5000]

The only time mine ever backfired was when I was venting my BOV. Never had this issue since it's been recirculated...

 

[MA70Snowman]

It's caused by what you said. Assuming fuel control is working in this car it's usually associated with a maladjusted TPS combined with an exhaust leak. The dashpot can also contribute. Overly rich open loop mixtures combined with exhaust leaks will cause it too. Lean mixtures with high HC is another culprit. Basically anything that combines excessive O2 with excess fuel.

so yeah my 550s w/ lex and no tune, as well as open vent are deffinatly my culprits.