Cyrus951

Okay, so I was driving onto the freeway onramp while accelerating in 3rd, then some car gets in front of me, and I let go of the gas, and I hear a loud POP from the exhaust. I thought I'd experiment with this after I exited the freeway, and I did. Here's what I did, I gave gas in 2nd took it to 4k rpms, let go of gas, and I hear a POP. Then did the same in 3rd, and I hear another POP. Any ideas?

tia

mochman

Mine does that I think it's a combo of no cat, a/m chips and turbo and a bov that vents to the atmosphere. Oh yeh it shoots flames too.

Chas

a free flowing exhaust will pop...not sure exactly what does it...something with how it comes off the fuel and the change in pressure in the crossover

Cyrus951

thank god I'm okay, one more problem with this car, and it would of been in the autotrader first thing tomorrow.

turbo944

The way I've come to understand it is that there is still residual fuel going through the system after you let off the gas accelerating hard that comes out of the system into the exhaust and gets lit by the hot exhaust and sends a fireball back through the exhaust and occasionally out of the tailpipe. If you have a cat it pretty well covers it up by catching it, but cat-less (or gutted) it is much more prevalent. My brother has actually seen the fireball comes out of my tailpipe between shifts Wish I had that on video!

Cyrus951

Ok, my cat is pissing me off. My po changed it about a year ago, it's probably whats causing my no boost, and my ****ty MPG, and now this..
hmm..anyone got a step by step to remove the cat?

tia

adrial

Yeah, step by step to remove the cat...

Get under the car and take off the 3 bolts holding it to the downpipe, the 4 holding it to the cat-back, the 2 holding it to the wastegate dump (it will slide forward off this) and the 2 exhaust hangers, believe 2 bolts on each hanger.

mochman

additional steps place on floor vertically and bash out all material use prybar etc. work from both ends it's a ghetto style test pipe but it works

OriginalSterm

...and voila! You created more turbulent flow in your exhaust! Just buy a cat-bypass or real test pipe. If not gutted properly, you can give yourself more issues.

mochman

seeing as I made more power on the dyno I got sheets somewhere with this method I still think it's worth a try. I've yet to hear of anyone making less power. BTW this was a temp. answer to collapsing cat then I test-piped it.

cheetah chrome

leaky injectors will also contribute to this problem. i had RC engineering clean/bench flow test mine and no more popping while downshifting. no free flow exhaust here...yet

Eyal 951

he cant gut his exhaust, he needs it. We live in California here. He can however buy a test pipe.
~Eyal

mochman

Gee PA has emissions too, Does the test-pipe eliminate the cat...on mine it does. At least if you gut the cat it looks like one's on there.

Eyal 951

Wait, you mean to tell me other states have emmissions too??? In California, as you may know, they are strict bastards. Stricter then ANY other state. Even PA! His car wont pass smog without the cat he has on there. Who cares if it looks like ones there or not. When was the last time a cop looked under your car? I was simply making a statement, not attacking your idea. that works in many states, but not here is basically what I was saying.
~Eyal

mochman

Uh didn't think you'd take it that way, what I was trying to say is a lot of us on this board run w/out cats even in cali. Also most test pipes bypass the cat so you're kinda back to square one anyway. BTW nice canyon pics