What size exhaust should I go with? (pics of new exhaust!!!)

[MONTERACER]

What size exhaust should I go with, 2.25" or 2.5"? I have used the search engine but cant make up my mind, so looking for opinions. I am very close to booking my appointment to have it done at James Dean muffler. I have a 3.5 liter, but dont want to lose alot of low end, nor do I want to lose gas mileage. I currently have a Dr. Speed CAB. My setup will be basically a carbon copy of Arcanum and Tin Indian's setups (KMAN Style). Dont really plan on doing PCM upgrade. Opinions wanted, please!!!

Thanks, Bill.

[dre256]

You wont lose MPG, it will go up. Opens up the engine alot. I think you have 2.25 stock just like the GTPs. I would go with a 2.5 and a single muffler into two outlets. Like the GT-R kit, if thats too much noise you can also do a resinator to quiet it down. Just my oppinon though

[Toyz]

Im at 2.25 back to the Magnaflow Muffler, 2.5 dual to the tips It is all new plumbing, custom built. Factory is 2.25"
Sounds great at idle, high rpm gets a little raspy, but i am thinking it is my tips.

[disposablehero]

A true 2.5 is the way to go. That means no crush bend.

[PwrG6Guy]

I think i've got a 2.25 cat back, no resonator to a magnaflow muffler.

3" magnaflow tips.

[Arcanum]

Bill,

Tomorrow (10/21/06 @Noon) I am going to James Dean to have Jim replace the 2.5" pipe with 2.25" pipe from the CAT back to the dual MagnaFlow's. I am hoping this will restore some of the backpressure I lost with my setup.

I'll give you a call with my results....

P.S. I voted for the 2.25"

[Arcanum]

...Factory is 2.25

I measured 2.125" or 2 1/8" and it's not mandrel bent. ?????

[G6Performance]

I'd go 2.5. That showed the best gains on the Grand Am (the 3.4L engine, very similar to your 3500). It showed even better gains than a comparable 2.25 system.

[Interfire]

I'd def go with the 2.5 also.

^^ Factory is crush bent.

[GT-R]

The factory is 2.25", but where it connects to the muffler it narrows down to between 1.78-2.00". And in reality, that's all you got. When you take a 2.5 pipe and crush it, you can wind up with as little as 2.00"

Take the narrowests section on the systems, and that's all you have.

You can have 50' of 3" pipe, but if it narrows to 1" anywhere within that pipe, 1" is all you have.


This is why mandrel is the way to go, especially if you have plans for other mods in the future. Otherwise, you may be doing this again.

[gkr7007]

Keep in mind that when you go to high flow cat (or none), eliminate the res, and go to high flow muff; that you are increasing the flow quite a bit just from those changes. And then, like GT-P says, you are limited by the restriction of the smallest part of the pipe. So if you go to a mandrel bent exhaust, you also eliminate that restriction also. Going to a true 2.25 mandrel bent system with the high flow AC can really open up the exhaust flow quite a bit. Opening up the exhaust flow too much can cause you to lose some scavenging effect and cause you to lose some bottom end pull. Just food for thought.

[Eco_JUNK]

^ hit the nail on the head. I know the 3800 engine does wonders with 2.5" but Im not too familiar with the 3.4/3.5L engines. I do know this if your going for all out race, go with a bigger exhaust. Your engine is gonna spend a lotta time in upper RPM. If your looking for a street driver, stick with a perfecly bent 2.5" to keep some of that low end grunt.

[MONTERACER]

Here's a few pics of my new exhaust. I wound up going with 2.5" head pipe to a 18" long glasspack(resonator) to dual 2.25" pipe to (2)2.25" magnaflow offset inlet-offset outlet mufflers, 2.5" tailpipes and 4" magnaflow tips.

[beitodesstrafe]

looking good

[jnak]

Nice setup.