v8vette84

I just installed Flowmaster Catalytic converters on my C4. Before the cats I had LT headers into an X-pipe then back into the Magnaflow mufflers (All 3"). Was a little too drony for me and i decided to put cats back on to try to kill some of the resonance. Anyways yesterday I drove the car and it drove with the same ***** as usual and had the same go it had just with a little less volume. Today I'm idling the car after pulling her out of the garage and all of the sudden I notice the car get louder.... So I took a peek underneath and all the pipes were still connected, nothing fell off. I started driving and the car sounded a little louder than I remember from the day prior but I brushed it off as my mind was probably making me feel like it was indeed louder. I took a drive and she car felt slower, less "right there at your foot performance" Feels like she moved her powerband farther up in the RPM band. Not only that but now the car won't idle correctly. No check engine lights, come up to a stoplight push in the clutch and the car idles down to around 400-500 then either catches itself and idles back to 900 or just dies out (Dieing more likely). The car did not have ANY issues until I put these cats on the car. The tuner told me before that it doesn't really matter if I have cats of not. (Madtuner). The cats are probably a good 1.5' from the headers but that's the ONLY spot I have available for them.

When I had the car idling SOMETHING DID change that made me feel like the exhaust got louder. IDK what is was but the car lost some power I feel like. Sorry about the long post, wanted to cover all the bases. Any ideas?

v8vette84

If the rain holds off i'll do some datalogging tomm (technically today) to see if I see any issues. Thanks and let me know if you have any ideas!

v8vette84

Any ideas?

blackjack325

iTrader: (1)

From what i understand, it does matter whether your tuned with or without cats. As far if it changes the sound all of a sudden im not sure

cardo0

Can't really understand your observations. Its getting louder and slower but day by day - not all at once? Well the cats add restriction. And the loss of the X pipe adds more restriction. But if the car is losing tune at low rpm then maybe something is damaged? O2 sensors or wires? Any welding with the batt connected (PCM scrambled)?

cardo

v8vette84

No, the car sounded like it got louder all of the sudden. I have the x-pipe right behind the cats. The car is not throwing any codes, I didn't touch anything in the front of the car only the exhaust from the headers back. It just feels slower from my sea of the pants gauge. I will confirm when I have nice weather again.

NewOrleansLT1

Maybe the ceramic in the cats broke apart

v8vette84

I mean they are new Flowmaster units but anything is possible.

englundjd

key word there ... flowmaster