Backfire at 1-2 Shift with FRPP Tune

[M1GarandGuy]

All:

I've got a 2008 GT, automatic, 23k miles, fresh plugs with the Bullitt CAI, FRPP tune, and FR500S mufflers. About a month after I installed the tune, it started to backfire at WOT (or from a slow roll) when it makes the 1st gear to 2nd gear shift.

Any idea what I could be?

 

[kevinatfms]

those mufflers will "pop" when letting off after WOT. change the muffler type. look on youtube, plenty of videos of people just blipping the gas and you hear it "pop, pop, pop".

 

[M1GarandGuy]

But I'm not letting off since it's an automatic. Its at the point where the computer shifts the gear.

 

[S197GT07]

Are you sure its not just popping?

When the car shifts the now colder air will rush inside the exhaust pipes, and when the hot air from combustion meets it there will be popping. Thats why on decel with some mufflers you'll get that sound.

Are you 100% sure its a backfire? It would be as loud as a gunshot (I have a WOTBOX so I know what a backfire sounds like).

What area of NH are you from?

 

[brnmw]

Are those the same as the Ford Racing M-5230-5GT* mufflers for an '06 Mustang GT. If they are I do not know what to tell you.... Mine is an Auto. trans. and do not pop. I switched out to the Ford Racing Ceramic headers with Bassani "Pwr.-X" mid pipe and those mufflers mentioned I think I used the stock FRPP for only a few days with just the exhaust added still no pop... then took it to Mike Murillo @ MMS Powerhouse in San Antonio, TX. to get it dyno tuned with a Diablosport after I added everything else and still no pop. Again I do not know if they are considered the same muffler set up that mine has but "no pop". I have heard that though on several other cars, and it is annoying IMO.

 

[5pointohh]

my auto car use to do this...
it would tickle the rev limiter right before it shifted.

 

[vic_s197]

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