back fire

intense 7MGTE · 09-23-2005, 07:41 PM

I have a MKIII turbo w/ a full race exhaust and no cats. When I shift gears and only build about 5psi of boost my car will back fire a little in between shifts. Any idea what would be causing this??

rnoswal · 09-23-2005, 09:22 PM

I am not positive on this one, but with that little back pressure making the head perform a lot better, some of the unburnt gasses are finishing in the exhaust system and causing the popping noise you are hearing. I think that is normal usually, but with all the normal cat. and muffler system, it gets muffled out. You will notice most NASCAR cars doing this while letting off the gas in the turns. They don't get the best fuel milage, but for the power they produce, they do run as lean as they can and have that nice flame due to the overlapping of the cam intake and exhaust openings and not as much air due to the carb being closed.

Just a thought though.

Russ

joel w · 09-25-2005, 03:36 AM

also its been my experience that any exhaust leak ftom the turbo back can create a exhaust backfire noise between shifts. even pinholes ive noticed, what size "race" pipe are you running?

intense 7MGTE · 09-26-2005, 05:37 PM

Tanks I do have a few small exhaust leaks in my cat back do to rust holes and a gasket that just will not seal. Hope fully that is what is causing the back fire. Other than that my MKIII runs greats with out any hicups. So I dont think I have any problems elsewhere. Thanks again.

09-23-2005, 07:41 PM	#1
intense 7MGTE Stock Join Date: Jul 2005 Posts: 20	back fire I have a MKIII turbo w/ a full race exhaust and no cats. When I shift gears and only build about 5psi of boost my car will back fire a little in between shifts. Any idea what would be causing this??

09-25-2005, 03:36 AM	#3
joel w Lexus & 550's Join Date: Aug 2005 Location: In the shadows Posts: 506	Pop also its been my experience that any exhaust leak ftom the turbo back can create a exhaust backfire noise between shifts. even pinholes ive noticed, what size "race" pipe are you running?

09-26-2005, 05:37 PM	#4
intense 7MGTE Stock Join Date: Jul 2005 Posts: 20	back fire Tanks I do have a few small exhaust leaks in my cat back do to rust holes and a gasket that just will not seal. Hope fully that is what is causing the back fire. Other than that my MKIII runs greats with out any hicups. So I dont think I have any problems elsewhere. Thanks again.

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09-23-2005, 09:22 PM	#2
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	I am not positive on this one, but with that little back pressure making the head perform a lot better, some of the unburnt gasses are finishing in the exhaust system and causing the popping noise you are hearing. I think that is normal usually, but with all the normal cat. and muffler system, it gets muffled out. You will notice most NASCAR cars doing this while letting off the gas in the turns. They don't get the best fuel milage, but for the power they produce, they do run as lean as they can and have that nice flame due to the overlapping of the cam intake and exhaust openings and not as much air due to the carb being closed. Just a thought though. Russ