High Flow Catalytic Converter and Performance

Linewalker

Member
Joined
Dec 3, 2007
How much will a high flow catalytic converter slow me down?

Right now, I have a gutted cat on my car for visual reasons. I would like to be in compliance with emission laws. Not just at inspection time, but all the time. I just don't want to kill the performance of my car.

Btw, I'm running mid twelves in the quarter with SMC's alky kit.

Thanks,
Jeff
 
I can't give you specifics, but..... I have a high flow cat that I only used for smog certs in CA. otherwise I run an identical gutted version for daily use.

I thought I would try and run the real cat for a while and quiet my car down a little.

I was quite surprised at the "butt dyno" power loss. Throttle response was not as good, low/mid/high end power were all down. Turbo spool was also negatively affected.
A loosing proposition all the way around. Not a HUGE difference but enough to be very noticeable.

But no numbers to back it up.

Positives: car was quieter. Smelled cleaner.
 
I would also would like to know, since now I use alky and not race gas any more, I'm thinking about putting on a cat in place of the THDP test pipe, and who can or where can I get the replacement cat that was offered in place of the test pipe when you bought the down pipe, thanks.

Ron
 

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I don't have any apples to apples before-after numbers to present, but I've been running thru a a real functional cat now for a few years and I don't think it's slowed me down at all. I've run my fastest time (see sig) with the cat in place.
 
Can anyone recommend a source for the buick 4 bolt cat flange?

RJC sells many different types of flanges. No numbers here, but I agree with TurboDave, for the hour or so I have a high flow cat on the GN, it seems sluggish. Pretty much kills off about 5# of boost, usually run 28# with the dump pipe and it was down to 23# with the cat on, that alone has to be 50HP:eek:
 
I had a hi flow cat on my car.I was amazed when i put the test pipe in.I then opened up the cut out and was amazed again. I don't know hp.#'s but if u can feel that big of a difference the hp #'s are big.
 
I'll tell you what baffles me. There are numerous new cars running around with 400/500 + horsepower. They run through the cats without it killing their performance. How come we can't?

Jeff
 
3" Hi Flo Cat

Here's what I'm running. It's a 3" Stainless Hi Flow Metal Core Cat....#7102 and made by Vibrant Performance. I just had the muffler shop weld up the 4 bolt flange from an old straight pipe I had lying arouund.

This thing flows really well.....am using it in conjunction with my 2.5" ATR exhaust and pit bull mufflers, Kenne Bell Headers and 3" SE Turbo Down Pipe.

Couldn't be happier with the performance and drone has been kept to a minimum. I'd highly recommend this for turbo buicks.

Here's a link.

Vibrant Performance ::.

dave
 
I'll tell you what baffles me. There are numerous new cars running around with 400/500 + horsepower. They run through the cats without it killing their performance. How come we can't?

Jeff


How do you know this????:confused: Have you personally seen how they perform without the cats???

I didn't say it kills power, and I didn't say one can't make horsepower in the 500-600 range. I merely stated that it had a small affect on response and drivablility. I can say this, because I've been driving this very same car for over 20 years. I know every nuance of this car, and can immediately tell when something is different, if even slightly.
When you get a few more years of seat time with your car, you'll understand what I mean.
 
I've been told the only difference between a "Hi Flow" cat and a regular one of the same diameter is the price. YMMV.
 
How do you know this????:confused: Have you personally seen how they perform without the cats???

I didn't say it kills power, and I didn't say one can't make horsepower in the 500-600 range. I merely stated that it had a small affect on response and drivablility. I can say this, because I've been driving this very same car for over 20 years. I know every nuance of this car, and can immediately tell when something is different, if even slightly.
When you get a few more years of seat time with your car, you'll understand what I mean.
I am the original owner of my 1986 T-Type. I just thought there might be some new technology in cats out there that I wasn't aware of.

Thanks,
Jeff
 
I am the original owner of my 1986 T-Type. I just thought there might be some new technology in cats out there that I wasn't aware of.

Thanks,
Jeff


Good grief, where've you been for the last 20+ years? Usually when I see 9 posts, I assume(ya, ya I know) a new buyer.
 
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