What causes a back-fire?
09-29-01, 02:32 AM
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What causes a back-fire?
Just wondering what makes the car back-fire, because with all my mods that I have listed I sometimes get popping at lower RPM's and when I'm at WOT and take it to redline, everytime I shift there is a loud backfire between gears....
Am I running too rich? Can this damage my car? How can I fix it?
Am I running too rich? Can this damage my car? How can I fix it?
09-29-01, 05:36 AM
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that's what a backfire is, unburnt fuel igniting in your exhaust. It, in itself, is not harmful. If you ditch the hi-flo for a midpipe, you can turn them into flames! 
If you get it alot, it can be because you're running too rich. Do you notice smoke along with the backfire? (dark smoke)
If you get it alot, it can be because you're running too rich. Do you notice smoke along with the backfire? (dark smoke)
09-29-01, 11:49 AM
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Banned. I got OWNED!!!
Originally posted by bploz RX7
running rich?? I have downpipe, hi-flo cat, hks cat back, pettit intake and my car backfires w/ the stock ecu... this has always baffled me
running rich?? I have downpipe, hi-flo cat, hks cat back, pettit intake and my car backfires w/ the stock ecu... this has always baffled me
GOOD LUCK!
09-29-01, 02:40 PM
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Yeah....there is always a lot of exhaust(smoke) when it backfires at WOT....when I look in rearview it's like a fog behind my car....
I mean I know there's nothing wrong with my car mechanically, I know the excess exhaust and smoke is from running too rich...
What can I do to prevent this? Run a midpipe instead?
M2 said their ECU won't support a midpipe, only a highflow, but from what it looks like, it's too rich with the highflow....
Btw, one thing that I have noticed lately, after installing all these mods, the 3k "hesitation" is different. When I first got the M2 ECU it almost completely fixed the "hesitation", then I added some more of my mods and now the "hesitation" is greater and it feels different too, almost like the car is bogged down with gas....maybe it is running a little too rich.
I mean I know there's nothing wrong with my car mechanically, I know the excess exhaust and smoke is from running too rich...
What can I do to prevent this? Run a midpipe instead?
M2 said their ECU won't support a midpipe, only a highflow, but from what it looks like, it's too rich with the highflow....
Btw, one thing that I have noticed lately, after installing all these mods, the 3k "hesitation" is different. When I first got the M2 ECU it almost completely fixed the "hesitation", then I added some more of my mods and now the "hesitation" is greater and it feels different too, almost like the car is bogged down with gas....maybe it is running a little too rich.
Last edited by Pressurized; 09-29-01 at 02:46 PM.
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09-30-01, 02:05 AM
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If you're getting at WOT when you're shifting, that does not mean you're running too rich. You may or may not be running too rich, but a backfire at shifting won't tell you that.
When you let off the throttle to shift, the throttle body closes its butterfly, so there's a sudden drastic reduction in the amount of air going into the engine (especially since we're talking about a turbo application). But, there fuel injectors are still delivering as much fuel as they were a microsecond ago when there was more air, since they haven't had a chance to adjust yet (them and the ECU and the rest of the fuel system). So, you've got very little air, and a whole lot of fuel, which is a mixture the spark plugs can't quite ignite, so it just gets dumped into the exhaust. Your exhaust is REAL hot, and the fuel mixture is real heavy, so, when it touches metal, it explodes. Pop. Or, more frequently, BANG. Remove the main cat and that bang is just a fireball in a pipe going straight to the back of your car, so, you get flames shooting out.
Now, if you're at WOT, and you get backfiring when you're NOT shifting, that could mean you're running too rich. Or it could mean you're plugs are fouled. Or it could mean you're ignition is breaking up. I'm sure it could probably mean something else also, but I'm no expert, so I don't know what that would be.
When you let off the throttle to shift, the throttle body closes its butterfly, so there's a sudden drastic reduction in the amount of air going into the engine (especially since we're talking about a turbo application). But, there fuel injectors are still delivering as much fuel as they were a microsecond ago when there was more air, since they haven't had a chance to adjust yet (them and the ECU and the rest of the fuel system). So, you've got very little air, and a whole lot of fuel, which is a mixture the spark plugs can't quite ignite, so it just gets dumped into the exhaust. Your exhaust is REAL hot, and the fuel mixture is real heavy, so, when it touches metal, it explodes. Pop. Or, more frequently, BANG. Remove the main cat and that bang is just a fireball in a pipe going straight to the back of your car, so, you get flames shooting out.
Now, if you're at WOT, and you get backfiring when you're NOT shifting, that could mean you're running too rich. Or it could mean you're plugs are fouled. Or it could mean you're ignition is breaking up. I'm sure it could probably mean something else also, but I'm no expert, so I don't know what that would be.
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