no cat
Thread Starter
Teching In
Joined: Apr 2005
Posts: 9
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no cat i have a 94 lt1 with cai, and a flowmaster muffler, i just recently bought a stock cat from the exact same car, and with my exhaust setup ill rev it up, and it will sound good, but as the rpm's start to drop it makes a poppin sound and livin in lebanon tn, im tired of sounding like all the redneck trucks, if i was to install that cat would it reduce that sound, also i have some headers sittin in my room, would this setup sound good
The cat should fix it. Mine sounded great when I had a cat on it but when I took the cat off, it sounded like crap on decel. That was of course when I had a muffler on my car. 
TECH Enthusiast
Joined: May 2004
Posts: 549
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From: St. Peters, MO
It's mostly due to the chambers of the flowmaster exhaust itself. It's not a really good design...i know i have one and mine pops w/o headers and stuff. The loudmouth, borla, flowmaster all do the same thing. To cure the problem, get a hooker, magnaflow, gmmg, corsa or true duals. It won't pop on decelleration. Oh and yeah, I go down to lebanon quite often, and I know about the trucks. All the damn dodge rams with no exhaust, it sucks. Rednecks. True duals and a cam would def set you apart. But I think I'm coming down for that big car show this summer, I forget the name, but I was there for it last year where everyone just cruises around at night. If I come down, we can meet up and swap stories etc. my .02
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Verdad Gallardo Thread Starter
Teching In
Joined: Apr 2005
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jordan i know exactly what your talkin about...the car show is slammin and jammin and it starts may 27....your right we do need to meet up, and i was wonderin if u know of any f-body shops around here........thanx
An LT1 running on a stock tune will pop alot. No matter what exhaust setup.
This is due to the fact that LT1s run rich from the factory. The extra, unburnt, fuel in the exhaust expands in gaseous form, and in expanding and changing shape, creates the popping. A tune fixes this popping.
Some exhausts will pop more than others as well, but the main problem with our cars is the tune. In my experience the more wide open the exhaust, the more it'll pop (also having to do with running rich).
This is due to the fact that LT1s run rich from the factory. The extra, unburnt, fuel in the exhaust expands in gaseous form, and in expanding and changing shape, creates the popping. A tune fixes this popping.
Some exhausts will pop more than others as well, but the main problem with our cars is the tune. In my experience the more wide open the exhaust, the more it'll pop (also having to do with running rich).
I had my PCM reprogrammed but I didn't get any air/fuel mixtures tuned and my car still pops but not on deaccel. It only does on deaccel. if my engine isn't warmed up. I have a Random Tech cat back.
On The Tree
Joined: Jun 2005
Posts: 147
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yea the more i took off of the exhaust the more mine popped too. and i have also noticed that i happens more when it is cold. my cat has been hollow for ever and when got rid of the muffler it seemed to happen more which backs up the back pressure idea. 
TECH Fanatic
Joined: Nov 2001
Posts: 1,098
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From: I-L-L-I-N-O-I-S
Originally Posted by 25thAnnivTransAm
An LT1 running on a stock tune will pop alot. No matter what exhaust setup.
This is due to the fact that LT1s run rich from the factory. The extra, unburnt, fuel in the exhaust expands in gaseous form, and in expanding and changing shape, creates the popping. A tune fixes this popping.
Some exhausts will pop more than others as well, but the main problem with our cars is the tune. In my experience the more wide open the exhaust, the more it'll pop (also having to do with running rich).
This is due to the fact that LT1s run rich from the factory. The extra, unburnt, fuel in the exhaust expands in gaseous form, and in expanding and changing shape, creates the popping. A tune fixes this popping.
Some exhausts will pop more than others as well, but the main problem with our cars is the tune. In my experience the more wide open the exhaust, the more it'll pop (also having to do with running rich).
Yes, all LT1's run rich from the factory to the point that they'll "pop" on the way down if you rev them up high enough...When my '95 Z28 had only a Hooker cat-back, it still popped like mad on the way down after I had revved it up nicely...The GMMG system I eventually replaced it with almost sounded like it was popping popcorn after I did that, LOL. NOT a good sound at all, IMO...Neither of my two LS1's have ever done anything like this...As for the tune, yeah, a good one that balances out the Air/Fuel ratio properly will negate most of that popping...Just depends upon the system...The more unmuffled it is, the more likely it is to pop some...After my MadZ28 tune, the GMMG + MAC headers/highflow cat doesn't pop as bad, but still does a little if I rev it up high enough...
Mike
What kind of "tune" is needed, and how much would it cost for it to stop running rich/lean? I'm bringing mine to Ion from madz28.com to get my rear O2's deleted, is there a way he can make it run better by not running too rich/lean?
