Backfires while going WOT?

[TJC]

One more thing...if I did nothing, would the fuel trim automatically adapt over time?

Quick question.... Is this occurring when you come off throttle? I suspect so.

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[OGMix376]

Take a video we want to hear it

Yes we do.. I like the popcorn sounds (during deceleration)…
But I don’t like replacing valves so I don’t want it

 

[OGMix376]

Get a BOV and then be on and off the gas all the time. You’ll be the envy of all the cool kids down at the AutoZone parking lot.

“Hey, everyone, here comes Sid!”

Pssshh, pakka, pakka, pakka, pak.
Pssshh, pakka, pakka, pakka, pak.
Pssshh, pakka, pakka, pakka, pak.

It’s true..

I know from experience
Waiting for the Chris Farley and Adam Sandler clip to post now

 

[Grandaccess]

When ever you change something "anything", it will always change something else somewhere down line "always"
the whole thing was designed, tuned and tested to work the way it came off the line within normal driving habits... granted most of us are way outside "Normal" and we put up with what ever it breaks
I would think a muffler delete would change how the brain sees things would change it more than 3% out of spec. and the brain somehow would compensate somewhere else to bring it back in design spec....

 

[Msfitoy]

Quick question.... Is this occurring when you come off throttle? I suspect so.

No...only on WOT...

 

[TJC]

No...only on WOT...

That blows my theory out of the water...

 

[Msfitoy]

When ever you change something "anything", it will always change something else somewhere down line "always"
the whole thing was designed, tuned and tested to work the way it came off the line within normal driving habits... granted most of us are way outside "Normal" and we put up with what ever it breaks
I would think a muffler delete would change how the brain sees things would change it more than 3% out of spec. and the brain somehow would compensate somewhere else to bring it back in design spec....

It was designed to be "normal" but the tranny couldn't identify with that and left the party...

 

[TJC]

One other thought, we used a rich mixture to keep knock under control during boost. We had knock sensors on our aftermarket ECUs that would retard timing and enrich the fuel to keep boost knock under control.

Ford must be doing the same as the physics hasn't changed.

Are you truly getting backfires up through the intake? As opposed to bangs coming out the exhaust?

If it is backfires (coming up through the intake) it is a timing or intake valve (not closing in the compression / combustion stroke) issue.

If the bang is coming out the exhaust I'd bet it is excess fuel igniting in the exhaust pipe. If it is excessive unburnt fuel, your catalytic converter is at risk of damage. Add a muffler to slow the exhaust flow or lean out the A/F mixture.

I have no idea just how much A/F ratio auto compensation Ford has built into the ECU system, but I'd wager it may not be enough.

Take this for what it's worth as I'm drawing from my early to mid 90's days tuning turbo and supercharged 1.6L and 1.8L Mazda Miatas.

 

[Msfitoy]

One other thought, we used a rich mixture to keep knock under control during boost. We had knock sensors on our aftermarket ECUs that would retard timing and enrich the fuel to keep boost knock under control.

Ford must be doing the same as the physics hasn't changed.

Are you truly getting backfires up through the intake? As opposed to bangs coming out the exhaust?

If it is backfires (coming up through the intake) it is a timing or intake valve (not closing in the compression / combustion stroke) issue.

If the bang is coming out the exhaust I'd bet it is excess fuel igniting in the exhaust pipe. If it is excessive unburnt fuel, your catalytic converter is at risk of damage. Add a muffler to slow the exhaust flow or lean out the A/F mixture.

I have no idea just how much A/F ratio auto compensation Ford has built into the ECU system, but I'd wager it may not be enough.

Take this for what it's worth as I'm drawing from my early to mid 90's days tuning turbo and supercharged 1.6L and 1.8L Mazda Miatas.

Hi Tony...yes, backfires noise definitely coming from behind me from the exhaust...I had to do a Mdelete because the I bought rusted it way to the recycling dump...I'll probably fix this with a resonator insert later...maybe a SuperTrapp?

 

[Ninong]

By definition a "backfire" occurs in the intake side of the engine, not the exhaust. the popping you are hearing is caused by unburnt fuel entering the exhaust and then being ignited. I suspect this is due to lower back pressure from you deleting your muffler. The engine needs a certain amount of back pressure to keep the combustion flame in the cylinder as the exhaust valve opens. The other remote possibility is that you are experience some valve float at high RPMs. I would lean towards the muffler since the problem only showed up after you removed it.

 

[Msfitoy]

By definition a "backfire" occurs in the intake side of the engine, not the exhaust. the popping you are hearing is caused by unburnt fuel entering the exhaust and then being ignited. I suspect this is due to lower back pressure from you deleting your muffler. The engine needs a certain amount of back pressure to keep the combustion flame in the cylinder as the exhaust valve opens. The other remote possibility is that you are experience some valve float at high RPMs. I would lean towards the muffler since the problem only showed up after you removed it.

Is there another term to describe this exhaust "backfire"? I was under 6K rpm so valve float can be ruled out...the consensus seems to be add a muffler...

 

[airline tech]

Backfire can be in either Intake or Exhaust manifold.
Anything outside of the combustion chamber (uncontrolled)

 

[airline tech]

I think a good post for this thread would be to post Live Data of fuel related PIDs, when I get some time, I may just put something together.

This way there would be a (somewhat) baseline to compare with and without muffler, and will it show a big difference?
Then with a KAM reset - it would highlight if the PIDs come back to near normal even with the muffler delete.

This is only going by a (ASSUMPTION) we will see a noted difference - Mainly the STFT & LTFT as those will show (Rich or Lean) trends, at this point I am only (GUESSING) that the O2 sensors are being possibly thrown off and the PCM is commanding more fuel (Positive - Fuel Trims).
I cannot confirm that without comparative data.

Granted there are factors of difference between the comparisons which will slightly differ.
Mileage, Fuel Grade , Spark Plug Age etc. - Stock vs Stock Engines.

I am only assuming that a KAM Reset may help - I would try that before I would Tune it.
This is where a (Tuner) guy who has more in-depth knowledge of the PCM (internal software) can shed some input on the matter.

I will try to get something by the weekend.

 

[TJC]

Having a real world baseline sample is a good beginning. It will be interesting to see the delta differences as you suggested.

 

[Ninong]

Is there another term to describe this exhaust "backfire"? I was under 6K rpm so valve float can be ruled out...the consensus seems to be add a muffler...

In the drag racing world we called it "shooting ducks"

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