CATS OR NO CATS

When talking about good, high flow cats on a Street Car application

I've seen some say a loss of 2 or 3 rwhp
and
Some say maybe as much as 5rwhp

I don't know for sure myself
but
I kinda think the above is about right

No more than a loss of 5rwhp

Of course ... if you're talking about a pa combo ... the loss would be more

Grady

When I went from my stock h to an o/r h, I felt a HUGE difference.

Go for the sound... No Cats....

In all honesty my car has a HORRIBLE resonance in the car with the high flow cats (also back when I had tailpipes)... No cats = quieter in the car and sound better out of the car....

I have to agree with the above. I went from a mac high flow h pipe to an offroad vrs x pipe. I don't think i gained any power, but the sound of my cam really came alive. The car gets a TON more attention when im idling. However, it can be a pain either finding a hookup or switching the pipe out come inspection time..

Does ANYONE have PROVEN dyno difference between cat and NON-cat?

Here's something I found from a co.called www.bieberfever.com - stock stang with shorty headers:

a. MAC high flow catalytic h-pipe: 6-8 rear wheel hp gain over stock
b. MAC high flow off-road h-pipe: 9-12 rear wheel hp gain over stock
c. MAC high flow Pro Chamber™: 23+ rear wheel hp gain over stock

hmm... so a high flow pro-chamber and shorty header with Off road h-pipe = 23rwhp? Incidently what is a pro-chamber? and is that ?

Based on below b. and c. look like

Ok...finding more... Below is a 2001 GT:
"We left the stock mufflers in place so as not to get the awful drone associated with "cat back" muffler systems. On the dyno the restriction free X-pipe showed a 6-8 horsepower gain from 3000 to 5000 rpm, with a 2-3 HP loss on the low end. Torque was up a max of 10 lb. ft. at 4400 rpm."

http://www.fordmuscle.com/archives/2004/12/Xhale/index.php

Looks like 6-8rwhp gain is about right WITH low end loss of 3rwhp. Is that enough worth to blow me ear drums out and scare neighboorhood cats? No.

i dont have any proof, but our cars have 4 friggen cats....not to mention our high mileage cars are slowly clogging them up more im sure...i felt a difference in upper rpm after removing them......id like to say realistically i bet its about a 10rwhp gain or in that ballpark...

plus stock midpipe is damn heavy compare to catless one

The only way I'd ever run cats is if I lived in Cali or had to pass emissions. Even still, I would have a catted pipe to throw on for emissions, then yank it and put the O/R pipe back on after. I hate catalytic converters.

I LIKE cats. When prepared properly, they taste like chicken.

igotyofire said:

i dont have any proof, but our cars have 4 friggen cats....not to mention our high mileage cars are slowly clogging them up more im sure...i felt a difference in upper rpm after removing them......id like to say realistically i bet its about a 10rwhp gain or in that ballpark...

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Posting guesses is great but again I look for proof if I can find it. The 10rwhp you are suggesting would be after a minus of rwhp if suggesting cats get build up and lose HP. Still, in the article they are testing a 2001 which also has 4 cats and buildup over a few years. They only got 6-8 rwhp. 10rwhp is not that far off though.. But yo uknow how internet myth goes...one guy says 10 and the next say 12, 14 all the way up to 23rwhp from a prochamer on e7's!

reddy351 said:

I LIKE cats. When prepared properly, they taste like chicken.

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I prefer mine on the BBQ with lots of sauce!!

I'll see if I can find my book on dyno pulls. It's the one with like a 1000 pulls on small block fords. It shows shorty vs equal length vs. long tubes.....stock cats, vs. high flow vs no cats. etc, etc. If I remember right the Off road h-pipe didn't give up anything and was around 8-10hp more than high flow cats.

I know I FELT the difference between my factory cat pipe and my high-flow cat pipe. Then I again felt a difference (slight though) between my cat pipe and my O/R H-pipe... But this was only slight.

So I would say that with pretty bad cats a 15 HP delta is possible... but most would be less...

It really depends on the condition of the cats you are replacing/removing.

However the sound of an O/R pipe speaks for itself...

reddy351 said:

I LIKE cats. When prepared properly, they taste like chicken.

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I have no cats now but Im thinking of putting some on just b/c my car is so damn loud w/ no cats on it

Redline_351R said:

I have no cats now but Im thinking of putting some on just b/c my car is so damn loud w/ no cats on it

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oh stop it!

blink327 said:

I have to agree with the above. I went from a mac high flow h pipe to an offroad vrs x pipe. I don't think i gained any power, but the sound of my cam really came alive. The car gets a TON more attention when im idling. However, it can be a pain either finding a hookup or switching the pipe out come inspection time..

Click to expand...

I didn't feel too much of a change but it was loud as hell w/ my offroad X and H. It became a PITA @ smog time to swap out, plus I smelled like gasoline wherever I went... so I spent the $$$ and got a quality piece

The hippie in me says go with the high flow cats and save the trouble

A while back my friend dynoed his mustang with both a high flow catted H pipe and a off road H pipe .The off road H pipe only made 4 more horsepower than the high flow but lost low end torque .I have both the high flow catted and the off road H pipe and I feel my car stronger with the high flow catted H pipe and the sound is almost the same between the two .