Backfiring after exhaust work done.

[twokingsracer]

I recently had an O/R H pipe and dumps put on. I am running Flowmaster Series 40's. The car sounds really great but I have now gotten a backfire when shifting during a race. I did not have this before the install. I got under the car and found where the dumps are not completely welded to the mufflers at the top. I have been told by a couple of people that the dumps not being completely welded are causing the backfire. I have also been told that Flows will tend to backfire when dumps are put on. Is it that I am sucking cold air in during those high RPM shifts? These are the mods I have so that you have a better picture of what I am running. Thanks for any help.

1997 Mustang GT 4.6L 2V
C&L 80MM MAF w/True Flow inlet pipe
K&N Air Filter with fender relocation
MAC 70MM TB
Superchip with mail order tune
MAC O/R H pipe w/dumps and Flowmaster Series 40's
4.10 gears
Granatelli Solid Upper and Lower Control arms
B&M Ripper Shifter

Parts I have that are going on this week:
PI Cams
Aluminum U/D Pullies
Steeda full length SFC's
Battery relocation kit

 

[68's Revenge]

Fresh air hitting too rich exhaust wil cause a pooping in the exhaust, I would look at tuning, does your car have asmog pump?

 

[twokingsracer]

Its a 97. I dont think so. But I dont know. Anyone...anyone.

 

[97rioreddohc]

Thats happened to me many times and still does, after installing the o/r x pipe, its a caused by a rich condition and it seems to only happen when the weather is cold or when the car is extremely cold

 

[1fast03pony]

its normal. its a free-er flowing exhaust. my fathers c5 backfires like a mutha and it was just dynotuned. hes running a corsca indy cat back and magnaflow o/r x.

if its too much then i suggest switching exhausts it might be the way your catback routs the exhaust.

 

[2k2SilverBullet]

i would worry about it,my friend had the same problem with his flows dumped, hopefully i will see you oct. 3 at mokan

attila

 

[2k2SilverBullet]

i meant i wouldnt worry about

 

[Jr2fast]

its the exhaust mine started it when I put the O/R on then the flows made it worse and I dumped mine last week. Its nothing, just tell them your motor i smaking so much power its bursting out the exhaust

 

[87PonyBoyGT]

Fresh air hitting too rich exhaust wil cause a pooping in the exhaust, I would look at tuning, does your car have asmog pump?

im curious what does the smog pump have to do with the popping because iim having similar problemos. i have bbk unequals with a mac xpipe and american thunder flows. i know i have an exhaust leak and was told that was causing the backfireing. but how does the smog pump play a role in this?

 

[shawnster]

If you watch the movie "Bullett" when Steve Mcqueen is chasing the black Charger, His car is backfiring between gears too and I was told, when that movie was made that was a brand new 68 Mustang..so I would think thats normal..personally, I'm running Flowmasters American Thunders dumped and mine don't backfire..I guess it depends on the car..

 

[streetstang03]

If you watch the movie "Bullett" when Steve Mcqueen is chasing the black Charger, His car is backfiring between gears too and I was told, when that movie was made that was a brand new 68 Mustang..so I would think thats normal..personally, I'm running Flowmasters American Thunders dumped and mine don't backfire..I guess it depends on the car..

THe sound of McQueens 68 was a GT40, not the fastback. They layed the audio track of a GT40 over it.

 

[shawnster]

Really? That would be a cool trivia question..did they do that to the charger too? I think that car had a 440 but Im not sure

 

[doogz]

My offroad h-pipe + flowmasters began popping extremely loud at high-rpm quick shifts. If I powershift, it won't backfire and if I take my time getting back into it after a high-rpm upshift, it won't backfire either. I don't think putting the tailpipes helped any if I remember correctly. I'll see if the longtubes made a difference with the popping.