Gutted cat = backfire?
01-26-2007, 06:34 PM
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Gutted cat = backfire?
I just recently gutted the cat and installed a flowmaster 40 series. Will the gutted cat make the car backfire? It is not a loud backfire, but more like spitting or loud gurgling, during upshifts at rpms above 4000. Seems to only happen from 1-2. It never happened prior to gutting and muffler.
I am new to the 951, so this may actually be a "normal" sound from the release of the back pressure.
If it makes any difference, the mods to the car are, Autothority stage II chips, shimmed wastegate, boost controller running 16psi, K&N drop in, gutted cat and flowmaster 40.
I am new to the 951, so this may actually be a "normal" sound from the release of the back pressure.
If it makes any difference, the mods to the car are, Autothority stage II chips, shimmed wastegate, boost controller running 16psi, K&N drop in, gutted cat and flowmaster 40.
01-26-2007, 06:57 PM
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It's the chips. On my grey car I have a gutted stock cat, 3" catback to a freeflow muffler and Guru 1.8chips otherwise stock - no decel backfire. Nice "worble" though.
01-27-2007, 02:28 AM
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I'm running roughly 19psi, and I get a pop from 3rd to 4th with it opened up all the way (and every now and then in normal driving)... I've got full B&B exhaust w/o a cat and the comp's tuned for the set-up I've got.
01-27-2007, 02:36 AM
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Originally Posted by Porschephile 924
*giggles like a school girl* I can't wait to get my new exhaust...
01-27-2007, 02:46 AM
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I'm planning on taking it to a local shop. they do fabrication, and dyno testing. they assess my needs, and build an exhaust to my specs, with mandrel bends. pretty comperable to a lindsey system or something. I'm planning on going with the Borla XR-1 muffler.
They mostly do a lot of Nissan work, but from what I've seen, their work is awesome, and I'll definately give it a shot. here is their site: www.macautosport.com
I got a ride in a nissan that they did the intercooler, exhaust, and turbo plumbing on... that car was friggin amazing.
They mostly do a lot of Nissan work, but from what I've seen, their work is awesome, and I'll definately give it a shot. here is their site: www.macautosport.com
I got a ride in a nissan that they did the intercooler, exhaust, and turbo plumbing on... that car was friggin amazing.
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01-27-2007, 02:51 AM
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Originally Posted by Porschephile 924
I'm planning on taking it to a local shop. they do fabrication, and dyno testing. they assess my needs, and build an exhaust to my specs, with mandrel bends. pretty comperable to a lindsey system or something. I'm planning on going with the Borla XR-1 muffler.
01-27-2007, 02:52 AM
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Originally Posted by sduceatt
I just recently gutted the cat and installed a flowmaster 40 series. Will the gutted cat make the car backfire? It is not a loud backfire, but more like spitting or loud gurgling, during upshifts at rpms above 4000. Seems to only happen from 1-2. It never happened prior to gutting and muffler.
I am new to the 951, so this may actually be a "normal" sound from the release of the back pressure.
If it makes any difference, the mods to the car are, Autothority stage II chips, shimmed wastegate, boost controller running 16psi, K&N drop in, gutted cat and flowmaster 40.
I am new to the 951, so this may actually be a "normal" sound from the release of the back pressure.
If it makes any difference, the mods to the car are, Autothority stage II chips, shimmed wastegate, boost controller running 16psi, K&N drop in, gutted cat and flowmaster 40.
You need to take it in to be serviced by a professional porsche dealer right now.
01-27-2007, 02:56 AM
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Originally Posted by porshhhh951
you're car isint supposed to spit fire much less anything else.
You need to take it in to be serviced by a professional porsche dealer right now.
You need to take it in to be serviced by a professional porsche dealer right now.
Run Rich at full throttle + big boost + shift = exhaust flames
01-27-2007, 12:19 PM
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Before I installed my Autothority chips I feel like I got more backfire (stock w/ no cat) than I do now with them in...
I plan on doing a night run tonight with someone behind me w/ camera just to be sure....
I plan on doing a night run tonight with someone behind me w/ camera just to be sure....
01-27-2007, 01:09 PM
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It's not "backfiring," and it's certainly nothing to be concerned about. Your car is running rich, and if you shift quickly under high load, the change in spark and fuel curves, along with the built up fuel mass in the pipe's gases at that moment send a quick "thooonk" of a fireball out. Sometimes it ignites in a gutted cat, as the gas expands, and sometimes it fires later on... and makes it out the tailpipe. It's not a problem with the car, it's just a nicely rich postfire. Backfiring is detrimental to your motor's longevity, and involves intake pops, or firing back into the intake... postfires are simply cool phenomena that give a good show to those behind you. 
