Whats the diff horsepower wise between 2 cats and no cats on x-pipes?

LordJish · Mar 19, 2004

Hi,

Still trying to decide on my mid pipe. I have the Magnapack and am concerned about crazy noise levels with no cats at all, so I'm wondering if someone could give me an estimate on what kind of hp I'd lose going with a catted x pipe vs a non-catted one.

Thanks!

JM

02 GT 5 speed

hognutz · Mar 19, 2004

I don't think there is much hp diffenece it is more of a cost/sound diff. I mean catted pipes are quite a bit more than O/R. O/R will obviously be a bit louder. Most good manufacturers are going to have very high flow cats.

b1gp1mp1n247 · Mar 19, 2004

i was running an o/f x-pipe for around a year or so and had to put cats back in for the damn emissions tests. i recommend if you have an almost stock motor, leave the cats on you feel a lot more torque. i actually like it better with cats then without. taking the cats off gives you no back pressure what so ever so you will lose a ton of torque if you have an almost stock motor. if you have added heads, cam, and intake then take the cats out. otherwise i say leave them in

red98_gt · Mar 19, 2004

personally...i think any v8 car will run somewhat better without cats..the difference in hp however will most likely be very insignificant, and you will loose a slight amount of torqu..
I have a buddy who has a car with practically the same miles and same mods..I added my BBK O/F X pipe (we had identical cat backs), and I pulled 2 cars on him from a roll. We have the same gear and drive the same.
My advise...get the off road pipe if you dont have to go through emissions testing, this saves a ton of money. If you have emmisions testing....I would jus go to an exhaust shop and have em hack all but one cat on each side! Jus my .02!

98GTVortech · Mar 19, 2004

I have heard that catted x/h pipes only take away 2-4 horses not much at all. But if you want some ear popping exhaust go for no cats but good luck with emissions.

LordJish · Mar 19, 2004

So basically..

2 cats = torque

no cats = hp

?

JM

00VERT GT · Mar 19, 2004

b1gp1mp1n247 said:
i was running an o/f x-pipe for around a year or so and had to put cats back in for the damn emissions tests. i recommend if you have an almost stock motor, leave the cats on you feel a lot more torque. i actually like it better with cats then without. taking the cats off gives you no back pressure what so ever so you will lose a ton of torque if you have an almost stock motor. if you have added heads, cam, and intake then take the cats out. otherwise i say leave them in

so in buying an offroad x pipe i have just lost a "ton" of torque? is this true?

b1gp1mp1n247 · Mar 20, 2004

00VERT GT said:
so in buying an offroad x pipe i have just lost a "ton" of torque? is this true?

in my personal experience yes. but that might just happen to me for some odd reason. but i have heard with a stock or almost stock motor you will lose a lot of torque when going with an o/r h-pipe or x-pipe and it is only a signifacant gain in motors that are built up. again though thats just my experience i have gained a lot of torque by putting 2 high flow cats on mine

b1gp1mp1n247 · Mar 20, 2004

LordJish said:
So basically..

2 cats = torque

no cats = hp

?

JM

through my experience yes

jrc_03_gt · Mar 20, 2004

I lost some torque just by welding in flowmasters original 40 series mufflers. Not lots of torque but it was a noticeable amount. I think it was worth it though the sound is awesome.

FallenPhoenix · Mar 20, 2004

I can't see how losing the cats will result in less torque. I'm not sure exactly how the power/torque is related to exhaust but the exhaust would slow down a lot when it got to the cat since it's basically just a large tube with catalyst (simplified). Back pressure is never good, slow exhaust gases are what makes you lose power.

sickstickGT03 · Mar 20, 2004

LordJish said:
So basically..

2 cats = torque

no cats = hp

?

JM

This doesn't make much sense, I don't know how the cats affect the power band, but most likely if you are losing torque you are losing horse power. Could someone specify whhat kind of horse power you are losing, high end, low end, peak?

jrc_03_gt · Mar 20, 2004

The 4.6 motor actually likes backpressure. That is what I have been told by a speed shop in cincinnati. I was describing to them how my car felt like it lost some snap to it after weld in flowmasters were installed he said it is normal for a little loss. That motor does well with backpressure. Its the same when you open up the the exhaust by going with bigger pipes or with no cats, you will loose some noticeable torque there too. Especially if you have no other mods to boost it back up.

DBMSTNG · Mar 20, 2004

FallenPhoenix said:
I can't see how losing the cats will result in less torque. I'm not sure exactly how the power/torque is related to exhaust but the exhaust would slow down a lot when it got to the cat since it's basically just a large tube with catalyst (simplified). Back pressure is never good, slow exhaust gases are what makes you lose power.

hp = (tq x rpm) / 5252

an engine sucks in air, and spits it out. if your engine can't suck in the air as fast as it's spitting it out, you aren't building as much pressure as you could. at low rpms, you aren't sucking as much air in as high rpm. so you lose power at low rpms. but when you start hitting the high rpms, a higher flowing exhaust can match the higher intake flow and produce more hp.

WRXracer · Mar 20, 2004

oh

I didnt lose any torqe and my car isnt loud either..

00VERT GT · Mar 22, 2004

So what's the advantage (if any) of going with an offroad (catless) midpipe?
Any? Cause it sounds like i jsut hurt myself rather than improved anything.

LordJish · Mar 22, 2004

I'd like to know also, as I've already ordered my off road mid pipe

JM

Blev · Mar 22, 2004

Here we go again...

Someone explain the whole Delta pressure thing again. I would but I can't remember. There were a few posts about this whole "back pressure" thing. You ENGINE is where the pressure is and matters. The exhaust does not play a part in it. I thought the idea was crazy at first, but then again so are engineers. I'll try and find the thread that goes into detail about this, but from what was said you do not lose HP or TQ by any changes to exhaust. You can flame me all you want, but the facts are what they are. Once again, I'll try and find the post were this was discussed.

LordJish · Mar 22, 2004

That would be great if you could bro,thanks

JM

Blev · Mar 22, 2004

Found it. The 7th post down really describes the Back Pressure and Delta pressure concept. I hope this helps to clear up any questions.

Delta Pressure

Whats the diff horsepower wise between 2 cats and no cats on x-pipes?

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