Free flowing CATS?
Safety Car
Joined: Oct 2001
Posts: 4,763
Likes: 1
From: Connectivette
Re: Free flowing CATS? (cajun86)
I did also. At the same time I put in a front Y-pipe without pre-cats. I felt and heard a difference. With 112k on the clock when I did this clogged precats may have been the reason I "felt" a difference.
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: Free flowing CATS? (1991C4)
I certainly felt a difference with my long tube headers, which in turn removed the cats. I can't say for stock manifolds. There are stories of people actually gaining power by adding high flow cats over no cats. I don't know if I would believe it. If somebody can show me a dyno graph on the same day, same dyno of a high flow cat vs. no cat, then I'll believe it.
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Re: Free flowing CATS? (Nathan Plemons)
I certainly felt a difference with my long tube headers, which in turn removed the cats. I can't say for stock manifolds. There are stories of people actually gaining power by adding high flow cats over no cats. I don't know if I would believe it. If somebody can show me a dyno graph on the same day, same dyno of a high flow cat vs. no cat, then I'll believe it.
Le Mans Master
Joined: Aug 2000
Posts: 6,738
Likes: 76
From: Bloomington IL
Re: Free flowing CATS? (Glock'94)
I certainly felt a difference with my long tube headers, which in turn removed the cats. I can't say for stock manifolds. There are stories of people actually gaining power by adding high flow cats over no cats. I don't know if I would believe it. If somebody can show me a dyno graph on the same day, same dyno of a high flow cat vs. no cat, then I'll believe it.
I think they are probably talking about the small amount of torque that is gained back from the backpressure. They probably were just talking about a seat of the pants feeling. (my guess)
I think they are probably talking about the small amount of torque that is gained back from the backpressure. They probably were just talking about a seat of the pants feeling. (my guess)
Burning Brakes
Joined: Nov 2000
Posts: 1,040
Likes: 2
From: BowlingGreen KY
Re: Free flowing CATS? (91Vette)
I removed my precats and gutted my main cat. I didn't lose anything. I noticed a substantial improvement in throttle response and sound. The engine pulls much higher rpm's now. I'd say that any performance exhaust mods would give you a SOTP gain. :cheers:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Free flowing CATS? (91Vette)
Both Vic'89 and I have the same exhaust mods: 2 1/2" front Y (no precats), Random Tech cat, TPIS custom FlowMaster cat-back with similar performance gains. I did the entire system at once; you can check the time slip gains on my site.
Recently I ported the stock manifold but don't have time slip data due to a knock count issue holding back my trap speed.
I wouldn't worry about lower back pressure causing a loss of low end torque. Though it starts at about 3,000rpm check out my dyno pull; it pulls a lot harder off the line (I launch my A4 at 900rpm).
If you do just the cat you may feel some difference but it realy takes the system to get max gains on an L98, even without long tubes.
Recently I ported the stock manifold but don't have time slip data due to a knock count issue holding back my trap speed.
I wouldn't worry about lower back pressure causing a loss of low end torque. Though it starts at about 3,000rpm check out my dyno pull; it pulls a lot harder off the line (I launch my A4 at 900rpm).
If you do just the cat you may feel some difference but it realy takes the system to get max gains on an L98, even without long tubes.
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