In my opinion i'd just get a 2.5 inlet/outlet muffler and just throw a reducer on it to fit the 2.25 back pipe, or if you have the money take it to an exhaust shop and just have them weld the muffler on and run a new 2.5 back pipe, thats what i did but i didn't have a backpipe at all, it cost me $80 tho for them to do it...so if you wanna stay cheaper just do the reducer and clamps. Not sure if you picked a muffler yet, but i just got my flowmaster 10 series muffler installed today and it sounds awesome a nice clean throaty sound. Little loud when on throttle but not very loud at all at a steady pace or idle, and down the highway just cruising you cant hardly hear it untill you hit the throttle then it opens up and sounds good It sounds best when your at a dead stop or slow roll and hit the throttle then it really sounds AMAZING

 

Dynomax has their rebate deal going again. Go to Summit Racing or any number of other on-line parts places and order the whole cat-back system for around $150. The rebate is $75 in the form of a debit card. I Ijust got one the other day and plan to install it this coming weekend.

My understanding is that these mufflers are louder than stock, but not obnoxious.

 

Different length exhausts create different resonant frequencies and have different effects on the motor's ability to scavenge. Typically, the longer the exhaust, the more bottom end, the shorter, the more top end. You can buy resonators which as well as quiet the exhaust down, altar and enhance the vacuum affect that engine resonance produces.

 

I've heard of scavenging in dirt bikes and motorcycles but does that apply to automotive engines over 2 liters?

I understand where your coming from but I think someone would have to either cut off the exhaust at the headers, or alternately weld a 15-20 foot exhaust to have any worthy effect on low or top end performance? The exhaust only effects the cars ability to release the expended gas and air, with a good flowing exhaust it doesn't matter how long or short it is

 

For those of you who are dying to know what set up I ended up choosing, I went with a 2.25" magnaflow performance muffler (because it was the most heavy duty muffler available at the local parts store). I just ended up cutting off the longest bit of the rear turndown of my exhaust pipe and clamped it onto the back of my new muffler so it dumps out right before my rear axle. The muffler sounds good, only a notch louder than my stock muffler, and a little lowered tone. I noticed a little better top end performance ( passing power) but a little less low end torque (which is what I didn't want...unfortunately) although that means I might get slightly better gas mileage (we'll see) which might be a better trade off with the rise of gas prices.
Overall I'm pleased with my choice, though I miss that torque below 2k rpm. Thanks so much for the input it was really helpful

 

Scavaging works on all motors.

When you see a set of headers that are "tuned length" That means each tube is designed for the firing order of the motor to take full advantage of the venturi effect.

Exhaust plumbing is a black art. You can't go by what drag cars and race cars go for because they are all about top end power and high rpms.

Here's a good read

http://www.nsxprime.com/FAQ/Miscella...austtheory.htm

 

You can't rely on the butt dyno.

 

thats a really good link

 

my buddy has a 2.5l 5 speed tj with a magnaflow glasspack, shortest size and it sounds great imo. I think it sounds as good as a 4 banger could. My friends father has a 4.0 tj with a borla and it sounds awesome, and my 5.2 zj is straight piped and people say it sounds amazing.

 

...thanks for the input...

 

Cool, good link. You learn something new everyday!

I've watched someone put together a custom set of headers for a dirt track racecar (not street legal of course) and I know what you mean. It's definitely not an easy task to do and he wasn't exactly engineering up a set of tuned headers. he just made it so that the pipes were all the same length by the time it got to the outlet. I'll just stick to buying headers from a performance shop

 

Buy the system from summit its cheap has a good sound when it gets broke in,Why put a cherry bomb on it and become a wiggle ,Its sounds like crap on a six cylinder, but your choice.I would get the right kit and do it right.

 

Dyno-max headers and a flowmaster exhaust = mean sound

 

It absolutely matters. My brother is an engineer at BAE whom, among other things, build the Bradley. One day my brother and his boss were discussing the exhaust on one of the vehicles they were designing and my brother asked if less back pressure is good, and volume isn't an issue on a tank, why not run straight pipes. His boss, who was a lead engineer on the v10 in the original Viper explained that engine resonance and scavenge is very important and that's why they were taking the time to design the right length and diameter exhaust to make the vehicle's motor as efficient as possible in the desired RPM range.

So what this means to you? I don't exactly know what to tell you except that size DOES matter, and if you want more bottom, I'd leave the system long as possible, and if you want more on top, slap a glass pack right after the cat and call it a day.

I hope my babbling has provided at least a little insight into the matter.

 

I would love to see some tests on a dyno to see what sort of performance difference longer or shorter pipes would bring on these jeep engines.

A Bradley v8 diesel engine tank and a v10 viper engine is very much different than anything typically bought from the dealerships in my area... I would consider those the opposite extremes of what anyone on this forum would buy and drive (either of em would be dam fun though) so unconventional upgrades in those make sense to me... But still not totally convinced for my lil heep