Do Cat Back Exhausts give more hp?
04-17-2013, 06:57 AM
#1
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Do Cat Back Exhausts give more hp?
Specifically, are there any proven aftermarket exhausts out there that give a small (5 - 10 hp) boost?
Initially, I thought there must be. After all, we've all heard the supposed "stock exhausts are designed for noise reduction, and rob power".
But after alot of searching and thinking on the matter, I'm beginning to think aftermarket exhausts do nothing.
Case in point. One manufacturer only provides dyno reports for their complete package: CAI, exhaust, and throttle body spacer. I'm sorry, but I'm not intersted in a CAI or a totally useless TBS, I just want to know what your exhaust sounds like and if it actually results in more HP, on it's own. In fact, I don't think I want to buy anything from a manufacturer that makes a TBS for anything that doesn't have a carbuerator.
Another case in point. A manufacturer has pretty much the same exhaust for the 3.8 as the 3.6 and makes the same HP gains claims for each. How can that be possible for two totally different powertrains?
Finally, the skeptic in me says that any change in the airflow is going to be read by the computer, and - following what may be a brief period of increased HP - adjust for the increase to bring performance back in line to original parameters.
Look, if I knew I was getting some ponies from a new exhaust, I'd lay the coin down. But I'm starting to think it's a bunch of malarky. And while some of those exhausts sound awesome, sound alone is not enough for me to part with my money.
Aaaaand, go!
Initially, I thought there must be. After all, we've all heard the supposed "stock exhausts are designed for noise reduction, and rob power".
But after alot of searching and thinking on the matter, I'm beginning to think aftermarket exhausts do nothing.
Case in point. One manufacturer only provides dyno reports for their complete package: CAI, exhaust, and throttle body spacer. I'm sorry, but I'm not intersted in a CAI or a totally useless TBS, I just want to know what your exhaust sounds like and if it actually results in more HP, on it's own. In fact, I don't think I want to buy anything from a manufacturer that makes a TBS for anything that doesn't have a carbuerator.
Another case in point. A manufacturer has pretty much the same exhaust for the 3.8 as the 3.6 and makes the same HP gains claims for each. How can that be possible for two totally different powertrains?
Finally, the skeptic in me says that any change in the airflow is going to be read by the computer, and - following what may be a brief period of increased HP - adjust for the increase to bring performance back in line to original parameters.
Look, if I knew I was getting some ponies from a new exhaust, I'd lay the coin down. But I'm starting to think it's a bunch of malarky. And while some of those exhausts sound awesome, sound alone is not enough for me to part with my money.
Aaaaand, go!
04-17-2013, 07:13 AM
#2
JK Enthusiast
Specifically, are there any proven aftermarket exhausts out there that give a small (5 - 10 hp) boost?
Initially, I thought there must be. After all, we've all heard the supposed "stock exhausts are designed for noise reduction, and rob power".
But after alot of searching and thinking on the matter, I'm beginning to think aftermarket exhausts do nothing.
Case in point. One manufacturer only provides dyno reports for their complete package: CAI, exhaust, and throttle body spacer. I'm sorry, but I'm not intersted in a CAI or a totally useless TBS, I just want to know what your exhaust sounds like and if it actually results in more HP, on it's own. In fact, I don't think I want to buy anything from a manufacturer that makes a TBS for anything that doesn't have a carbuerator.
Another case in point. A manufacturer has pretty much the same exhaust for the 3.8 as the 3.6 and makes the same HP gains claims for each. How can that be possible for two totally different powertrains?
Finally, the skeptic in me says that any change in the airflow is going to be read by the computer, and - following what may be a brief period of increased HP - adjust for the increase to bring performance back in line to original parameters.
Look, if I knew I was getting some ponies from a new exhaust, I'd lay the coin down. But I'm starting to think it's a bunch of malarky. And while some of those exhausts sound awesome, sound alone is not enough for me to part with my money.
Aaaaand, go!
Initially, I thought there must be. After all, we've all heard the supposed "stock exhausts are designed for noise reduction, and rob power".
But after alot of searching and thinking on the matter, I'm beginning to think aftermarket exhausts do nothing.
Case in point. One manufacturer only provides dyno reports for their complete package: CAI, exhaust, and throttle body spacer. I'm sorry, but I'm not intersted in a CAI or a totally useless TBS, I just want to know what your exhaust sounds like and if it actually results in more HP, on it's own. In fact, I don't think I want to buy anything from a manufacturer that makes a TBS for anything that doesn't have a carbuerator.
Another case in point. A manufacturer has pretty much the same exhaust for the 3.8 as the 3.6 and makes the same HP gains claims for each. How can that be possible for two totally different powertrains?
Finally, the skeptic in me says that any change in the airflow is going to be read by the computer, and - following what may be a brief period of increased HP - adjust for the increase to bring performance back in line to original parameters.
Look, if I knew I was getting some ponies from a new exhaust, I'd lay the coin down. But I'm starting to think it's a bunch of malarky. And while some of those exhausts sound awesome, sound alone is not enough for me to part with my money.
Aaaaand, go!
I'm not an expert nor claim to be, in my "sports" car days cat back only changed the sound with no real changes in HP. The HP changes came from new Headers coupled with new larger exhaust systems. I'm not sure how it would work out for a jeep as they are not "high reving" and this is generally where the horsepower gains from exhaust would be found.
I'm sure someone will post a Dyno with some specs to show that there are gains at 5400 RPM but to be honest i don't think i've got mine that high ever...
but I do plan on replacing the rust bucket muffler on my Jeep with something a little more throaty, but like you I feel it is only for the sound. If do stomp on it i'd like to hear it. So lots of my money will not be spent on this.
04-17-2013, 07:18 AM
#4
Your thinking is correct. The gains are minimal and certainly no where near the manufacturers claims. If you want to increase HP/TQ your going to have to regear.
Or you could do the Hemi conversion
I wouldn't however put on a new exhaust expecting anything much more then a different sound.
Or you could do the Hemi conversion
I wouldn't however put on a new exhaust expecting anything much more then a different sound.
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04-17-2013, 07:42 AM
#8
So on our various systems for the 2007-11 JK platform we have seen gains, some high single digits some low double digits. We haven't dynoed a 2012- yet.
This is in MI on stock JK with stock exhaust, vs stock JK with our cat-back systems.... now add tires, lift, bumpers etc and gains will start to disappear.
What an after market muffler really does is provide a smaller size, in general not as restrictive as stock, and allows some gains over stock in most cases. But as I say no gains like adding two more cylinders.
This is in MI on stock JK with stock exhaust, vs stock JK with our cat-back systems.... now add tires, lift, bumpers etc and gains will start to disappear.
What an after market muffler really does is provide a smaller size, in general not as restrictive as stock, and allows some gains over stock in most cases. But as I say no gains like adding two more cylinders.
04-17-2013, 08:39 AM
#9
JK Freak
Catback systems work best on forced induction applications. I drive two turbo cars and catbacks work well on them because the turbine wheel of the hotside makes your backpressure. Turbo back systems work even better. Normally asperated engines need a certain amount of backpressure from the exhaust system and therefore you can go too big on pipe size. For a JK, those catbacks are going to be close to stock size pipe diameter. Most of any gain will probably be the muffler, and we're not talking double digits here.
