Cat-back Exhaust
#1
Seasoned Member
Thread Starter
Cat-back Exhaust
I hear of people putting cat-back exhausts on there jeeps. I have a 1990 Jeep Cherokee. I can get a deal on a Dynomax Cat-back 2-1/2" diameter cat-back with a turbo muffler. should I go for it? or is it not worth it? because wouldnt jeep have designed the jeeps with a 2-1/2" diameter pipe out of the cat if it was more efficient?
#2
Senior Member
Join Date: Jul 2009
Location: San Diego, CA
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1996
Model: Cherokee
Engine: 4.0 HO
Many times, car designers will build a car on how cheap they can do it rather than for performance. As long as the 2.5" pipes are from the cat back, you're okay.
#3
CF Veteran
Join Date: Aug 2009
Location: Herriman, Utah
Posts: 1,534
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1994
Model: Cherokee
Engine: 4.0
I dont know how much difference it would make considering you've still got the stock puny stuff coming off the manifold. Might make a little difference, but I wouldnt think too much.
#4
Seasoned Member
Thread Starter
I've heard it makes a good amount of difference because it reduces the back pressure. Doesnt it have a 2-1/2" pipe going from the manifold to the cat? Then it goes to a smaller pipe out of the cat? Thats what I think is goin on I havent really looked yet its been rainy and cold here.
#5
Senior Member
Join Date: Jul 2009
Location: San Diego, CA
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1996
Model: Cherokee
Engine: 4.0 HO
I read somewhere that there needs to be a certain amount of back pressure for the engine to work right and that maintaining the stock size from the manifold to the cat will do that. I think you can upgrade to 2.5" all throughout, but I think you'll need to retune after that.
#6
CF Veteran
Join Date: Sep 2009
Location: ☼ Blackhole Sun
Posts: 8,567
Likes: 0
Received 18 Likes
on
16 Posts
Year: My Jeep is a GMC
I think it all depends on the application. If you just go to a larger diameter pipe you'll lose scavenging & volumetric efficiency. In other words the exhaust pulse traveling down the pipe causes a negative pressure which helps to clear the next cylinder when that exhaust valve opens. If you increase rpms or CI with the same diameter pipe that will cause a bottle neck. If you just uncork the exhaust on a stock motor when you stab the gas pedal, it's like stepping on a wet sponge.
#7
Member
Join Date: Sep 2009
Posts: 239
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1985
Model: Cherokee
Engine: 2.5 liter
I think it all depends on the application. If you just go to a larger diameter pipe you'll lose scavenging & volumetric efficiency. In other words the exhaust pulse traveling down the pipe causes a negative pressure which helps to clear the next cylinder when that exhaust valve opens. If you increase rpms or CI with the same diameter pipe that will cause a bottle neck. If you just uncork the exhaust on a stock motor when you stab the gas pedal, it's like stepping on a wet sponge.
nicely worded
Trending Topics
#9
Junior Member
Join Date: Jul 2009
Location: Glen Burnie, MD
Posts: 47
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1986
Model: Cherokee
Engine: 2.8
I have the dynomax cat-back system on my 2.8. Not sure if it makes a difference over stock or not cause my whole system was rusted out when I bought it, so obviously I noticed a HUGE difference. It sounds pretty sweet on my Jeep so it probably sounds a lot better with a 4.0 in front of it.
#10
Seasoned Member
Join Date: Sep 2009
Location: Coventry, CT
Posts: 273
Likes: 0
Received 1 Like
on
1 Post
Year: 2000
Model: Cherokee
Engine: 4.0 high output, Alabama Cylinder head, 60mm bored TB
I think it all depends on the application. If you just go to a larger diameter pipe you'll lose scavenging & volumetric efficiency. In other words the exhaust pulse traveling down the pipe causes a negative pressure which helps to clear the next cylinder when that exhaust valve opens. If you increase rpms or CI with the same diameter pipe that will cause a bottle neck. If you just uncork the exhaust on a stock motor when you stab the gas pedal, it's like stepping on a wet sponge.
#12
Seasoned Member
Thread Starter
I think it all depends on the application. If you just go to a larger diameter pipe you'll lose scavenging & volumetric efficiency. In other words the exhaust pulse traveling down the pipe causes a negative pressure which helps to clear the next cylinder when that exhaust valve opens. If you increase rpms or CI with the same diameter pipe that will cause a bottle neck. If you just uncork the exhaust on a stock motor when you stab the gas pedal, it's like stepping on a wet sponge.
#13
Registered Users
Join Date: Nov 2008
Posts: 181
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1996
Model: Cherokee
Engine: 4.0l
i put a 2.5" hi flow cat with 2.5" pipe to a new flowmaster knock off muffler and then a 2.5" tail pipe. put new O2 sensors in and gained about 2 mpg. Did a complete tuneup after that and gained like another 2 mpg. i went from about 13mpg to 18 with all that. then i put a lift and bigger tires on and it dropped back down to like 15 or 16. the exhaust didn't give me a ton of power but it definately helped. plus its one of them supporting mods so once i starting playing with the motor the exhaust is taking care of!!
Thread
Thread Starter
Forum
Replies
Last Post
jmsummers2012
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
53
04-30-2021 02:35 PM
libengan
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
14
11-06-2015 09:16 AM
MightyMouse8
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
14
10-08-2015 08:57 AM
Crimmy
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
8
10-01-2015 06:43 PM
shadowmoses
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
6
09-30-2015 01:34 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)