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What technically happens when the car backfires???

The reason I ask is, when I run 10psi and push the clutch in, I hear the loud pop from the muffler (backfiring) but when I run 15psi, I every now and then do. Not as much as when I run 10psi.

I'm wondering why my car backfires when all I have is an exhaust. I would thing the cat will some how "stop" the backfire, but once again what is a backfire???

One more question: When upgrading to a dp and high flow cat, will the backfiring be any louder??

Thanks
ed

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'99 GST
http://www.geocities.com/mospeed9844
Akimoto Air Fitler
GReddy BOV
GReddy Intercooler Piping
GReddy Cat-Back
GReddy Profec B
GReddy Boost and EGT Gauge
Autometer Air/Fuel Meter
Front and Rear Strut Bars
 

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Backfiring is caused by unburnt fuel entering the exhaust and igniting in the exhaust system. IMO, at 10 psi your car's exhaust is running richer than at 15 psi boost. There is more air at 15 psi to insure that your fuel is properly ignited in the combustion chamber. When you let off the gas and shift you decrease velocity in the exhaust and temporarily create a vacuum that gets air to this unburnt fuel and ignites it.
I would think that you might be able to see this with your egt gauge. I don't have mine yet, so I don't know if they are that sensitive, that fast. I would check out the plugs, timing, etc. Also, I would tend to believe that it might be a decibel or few louder with the bigger dp, etc. Kinda like a .38 vs a .44? In the meantime, just run 15psi. :D
Hope this helps. Good luck!

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Rocky Mountain
'91 Talon Tsi AWD

[This message has been edited by Van (edited September 17, 2000).]
 
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