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small backfire cause - running rich VS bad exhaust gaskets

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Old 01-01-03, 06:38 PM
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DragonFly

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Question small backfire cause - running rich VS bad exhaust gaskets

A pretty well versed rotor mechanic mentioned that some small backfires can be caused by faulty exhaust gaskets that, upon deceleration (or shifting) air gets sucked in the gasket leak and makes a mini explosion...thus the backfire.

Is that correct? .... or....

I always though that small backfires are caused by the car running very rich, so rich that significant unburn fuel makes it to the exhaust during decel or shifting and blows up in the exhaust...thus a backfire.


....anyone want to validate either of these?
Old 01-01-03, 06:44 PM
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An exhaust leak could be the source of a backfire, yes. Under significant vacuum, like deceleration, the leak could be the source of air entering the exhaust system.

Kyle
Old 01-01-03, 06:51 PM
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ahh, thanks kyle....so I may be able to reduce some small backfires by replacing all my worn gaskets and making sure I get a good seal between downpipe-cat-catback
Old 01-01-03, 07:02 PM
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If your gaskets are, in fact, bad, then yes. If the gaskets are still sealing well, you obviously won't see any changes. Good luck.

Kyle
Old 01-01-03, 07:04 PM
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thanks
Old 01-01-03, 07:07 PM
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I don't think you'll completely get rid of your backfires if you have removed the pre-cat. I believe you'll still have some backfiring.

My backfiring reduced quite a bit when I did my normal maintanence over the summer (O2 sensor, spark plugs & wires).

Still some backfiring on deccleration...
Old 01-01-03, 07:20 PM
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Blowing flames is fun though!
Old 01-01-03, 07:23 PM
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good point mahjic....so any backfiring that is not caused by air leak is caused by too much fuel?
Old 01-01-03, 07:24 PM
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LOl leprechan :-)
Old 01-01-03, 07:28 PM
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Originally posted by damian
good point mahjic....so any backfiring that is not caused by air leak is caused by too much fuel?
Well, honestly, I have no technical data for this topic, only guesses and theories...

I think it's caused by both, running rich and removing the cats. Our rotaries run pretty rich in stock form, however you usually don't notice any backfiring until you remove at least the pre-cat.

I know I never heard any backfiring on my car until I did my exhaust upgrades. I've also read about people programming less fuel upon deceleration to reduce the backfires on programmable ECU's.
Old 01-01-03, 07:57 PM
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>>I've also read about people programming less fuel upon deceleration to reduce the backfires on programmable ECU's.

ahh, thats what I like to hear, .....I plan on going to a larger IC and apexi power FC in the next year, maybe I can tweak the fuel deliver y to eliminate the 'pops' :-)
Old 01-02-03, 12:59 AM
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Originally posted by Leprechaun
Blowing flames is fun though!


Old 01-02-03, 08:16 AM
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Originally posted by oneflytrini




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