Hi-Flow Cats worth it????

DrewsSC

Registered User
Whats up guys, I just bought some Flowmasters for my 93 SC, and I want to get those Hi-Flow cats listed on supercoupeperformance.com,,,but I'm not exactly sure how they would work w/ the exhaust system since the stock ones bolt directly onto the exhaust manifolds. I'm gonna take the Flow's to the muffler shop and have them weld everything up, so would they take care of the cats or what? Anyways, if any of you SC'ers have bought those Hi-Flow cats, let me know how you had them installed and if they are worth it. Thanks in advance!!!


Drew
 
If I'm not mistaken, stock cats flow around 200CFM where high flow cats flow around 500+ CFM.

I would suggest trying to get your local muffler shop to get you a set of Carsound high flow cats. If they can't get them order the SCP ones as they're probably the same.

If you do high flow cats, spend the extra and get 2.5" downtubes from the manifold, those stock downtubes are garbage.

Yes, high flow cats are worth it!
 
high flow cats

i JUST got my exhuast done today. june 25, 2003. a day to remember for me. i got 2.25 down tubse. i WAS goin to get 2.5 but i went to a single 3" to the back. and a 3" will be out "flowed" by hte dual 2.5's. so 2.25 was fine for me. i got catco high flow cats. all high flow cats are hte same. they are all smog pieces. waht make sthem high flow is the straight design. but its still a smog piece of equipment. yeah they flow WAY better than stock. ESPECIALLY because the stock ones take a sharp 90* angle. the flow of my car now is incredible. if you were going to do dual i would try for 2.5 inch. but yet it only flows 2" out hte manifold so i don't know how much 2.25 vs 2.5 would be. but its all upto you. i went with 2.25 to a single 3" borla xr-1 mufflers. the sound is crazy. but im a borla fan so...yeah. high flow cats FOR SURE tho. hope this helps. steve.
 
To stay emmisions legal yet still have power Id get two 2 1/4 into 2 2 1/4 high flow cats into a y pipe sigle 3 - 3.5 inch to the back then to the flowmasters. I tend to keep the cats instead of the resonator..Stock resonator and cats =garbage..You can also get a replacement resonator after cat sif you do notlike the sound
 
I'd go for the high flow cats for sure. You can get them from Jegs or Summit for around $50 each. I'd reccomend 2.25" downtubes and 2.5" cats. Going to want to replace the stock resonator also. It is very, very restrictive!!

Thomas
 
WAIT!!! Question!!??

No disrespect meant but…
Opinions are like As#^$*#s. Everyone has one. Is there any hard science or facts to support what size downtubes, cats, etc.. (the whole exhaust system) is going to give the best power for a stock engine. A system that is legal and will pass inspection.

Thanks guys!

Duane
:D
 
Well if we wanted to get scientific about it..Wed do testing at different altitudes, different % of humidity, all various setups dynoes at each location...Of course using all the various different dyno methods different..And we still wouldnt have everything...

So basically what you might consider an opinion based on non scientific data is based on real life performance gains..Of course sound is a personal opinion..However There are many here that can tell you what works..WHat doesnt work..And there are many different combinations,,,

Being the stock manifold has smaller then a 2 inch opening...Going larger then 2 1/4 inch is just silly..Plus it wont seal..Ya like exhaust leaks?..Of course ya can go from 2-2.25-2.5 in steps....why ..I dont know

Teh factory cats are on a 90 degree bend..You get rid of them with nice 2.25 downtubes with high flows...Your definately helping....

Stock resonator..Its a boat anchor as well as having somewhat of a single 2 inch outlet..chuck it altogether or get a high flow resonator

My experience with stock cammed SC's is that so long as you run cats removal of the resonator doesnt make the sound all that ba..If you dont liek it..Put a new one on later.

Definately do not go with no cat sno resonator and flowmasters..You most likely will not be happy..Unless you like your car sounding like a john deer on steroids

Personally I wouldnt go with flowmasters..Id do borlas or dynomax( they rot quick) for sound


Regardless good luck :O)
 
Actually, there was a technical analysis done:

http://www.sccoa.com/articles/cwexhaust.php

Note in the article the author used 2.5" pipes with 3.5" center section. Using calculations for Horsepower Output from other websites it's been found that (Dynomax Info ) 3" is good for up to 300 HP.

Using a larger than 3" pipe is overkill for the limited down pipe diameter you can seal with the stock manifolds.

Certainly headers with 2.5" down pipes and 3.5" single exhaust would be better, but it isn't going to make as dramatic a difference going from 2.25 to 2.5 as it will going from stock 1-7/8 to 2.25 and replacing the resonator.
 
cats

hey guys, thanks for the advice. I know most are opinions but that is what I was looking for...guys who have bought them and liked them. Obviously scientific evidence would be great but all im looking for is a little bit better ability for the SC to exhaust itself. Thanks again!

Drew
 
Thanks!

This is great!

Certainly experience mixed with facts makes for some good information! This is exactly what I needed.

Thanks,
Duane
 
I know laws are different for each state, but in general (or if anyone knows Maryland Laws), do you really need a resonator at all? I asked the person at my emissions place and he had no idea. I was thinking about just replacing mine with a straight pipe and going with some Dynomax Superturbos.
 
The laws only govern the use of cats,not resonators. That's not to say that you won't break your local noise ordinance laws if you run w/o a resonator!
 
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