Am I correct in that....

[QWKSNKE]

backfiring out the tail pipe when going WOT is referencing a lean condition?

I know that backfiring through the intake is referencing that timing is off.


Took Dskeet for a ride today and around 4k rpm (9psi) car started a light stumble and then backfired through the exhaust

[Italian LX]

Originally Posted by QWKSNKE

backfiring out the tail pipe when going WOT is referencing a lean condition?

I know that backfiring through the intake is referencing that timing is off.


Took Dskeet for a ride today and around 4k rpm (9psi) car started a light stumble and then backfired through the exhaust

Yeah, that's what my car does a lot of times at low rpm WOT pulls. During that time, the O2's are pegging lean.

[QWKSNKE]

I have got to start tuning again before the next weekend's trip to the dyno

[Italian LX]

Originally Posted by QWKSNKE

I have got to start tuning again before the next weekend's trip to the dyno

Yeah, you need to drive it everyday to work and datalog while staying out of the throttle; get some good MAF transfer tunes done.

If you need me to, I can do some 100mile/day tunes.

[QWKSNKE]

Originally Posted by Italian LX

If you need me to, I can do some 100mile/day tunes.

ok

[1Quik85GT]

Rocker adjustment can be off!!! and I dont know if you guys know this, but you can also be too rich, and this happen, it gets deep so I might off to try to keep it simple..........

[QWKSNKE]

yeah Stephen, that's what Edgar told me last night. She will be put on the dyno next week, so I'll know for sure then

[93Cobra#2771]

HMM, I have always thought that backfiring through the tailpipes (barring mechanical problems such as rocker adjustments) were due to a rich condition. So rich, in fact, that the unburnt fuel gets into the hot exhaust system and then combusts all on its on.

[Wicked]

Originally Posted by 93Cobra#2771

HMM, I have always thought that backfiring through the tailpipes (barring mechanical problems such as rocker adjustments) were due to a rich condition. So rich, in fact, that the unburnt fuel gets into the hot exhaust system and then combusts all on its on.

edit: bump

Same here.

After hearing both reasons though, I'd say they are both possible. One way, you have unburnt fuel(rich), the other you have unburnt oxygen(lean). Either way you create an condition where there is a fuel source in the exhaust.

Also, backfires through the intake are usually lean condition related, not just timing. I had a friend who had a damage o2 sensor connector. It allowed him to connect it wrong. Well the result was a lean condition at part throttle that caused lean pop in the intake under acceleration. But the same way, you can get abackfire in the intake from fuel puddling.

[93Cobra#2771]

the other you have unburnt oxygen(lean). Either way you create an condition where there is a fuel source in the exhaust.

Just so everyone is on the same wavelength, you meant to say "excessive oxygen", right? Oxygen itself does not burn - all it does is allow the fuel to burn. Without enough oxygen, the engine won't ignite/burn the fuel properly. This is called a "rich" condition, as there is excessive fuel making it into the exhaust system where it is promptly ignited by the heat in the mufflers. Then you get the backfire through the exhaust system. Carbed cars that aren't tuned well are known to do this during deceleration, and in the old day, people would start slowing down, then kill the ignition, only to fire it back up - A BOOMING backfire would often result, sending people in town scurrying for cover.

A lean condition (too much oxygen) cannot cause a rich/fuel backfire.