Exaust Modifications worth a decent performance boost?

[94CutlassSLCoupe]

I was rotating the tires on my Cutlass today and was looking at the exhaust, which is something I would like to improve.

 

My two plans of attack could be:

 

Option 1:

 

Remove stock system from cat back and replace with 2.5" pipe, y-ing off and using some performance mufflers (I like flowmasters but i know everyone here hates them), cut in the factory openings for duals and use some stainless tips (looks like stock LQ1 exhaust only shiny)

 

Option 2:

 

Change exhaust system from the bottom of the downpipe (necks down from 2.5" to 2" on my car), use a high flow cat, and 2.5" all the way to the splitter and using the same kind of stuff as in option 1.

 

I would really like to do something with the exhaust as the 2" pipe, stock cat, resonator, and ultra quiet muffler cant be helping performance or gas mileage

[slick]

I know the downpipe on the 3.4 equipped cars is already 2.5", i'm unsure on the 3100. Most people do a 2.5" cat-back exhaust.

[94CutlassSLCoupe]

My downpipe is 2.5" and then it necks down BEFORE the cat which seems really crappy to me.

[gp90se]

2 1/4 mandrel bent pope from the downpipe 2 the flowmaster, high flow cat

[94CutlassSLCoupe]

anybody else? what's best for performance?

[manitcor]

I have a full custom exhaust with headers and a 3" cat w/ 2 1/2" all the way back. Honestly your not going to see a huge improvement over stock except in your top end untill you get more mods.

[pwmin]

as is, i would go with 2.5" single for the best performance. high-flow cat and magnaflow muffler and 4" resonator. that should give you some leeway for some mods. i wouldnt mess with dual exhaust, but if its what you want, 2.5 to dual 2.25

[gp90se]

the 3.1 mpfi really doesnt have the compression/flow needed for 2 1/2" mandrel bent, you'll loose more low end then gain top, but if its shitty bent (forget the name) then 2 1/2 will be okey

[TeeJay3800]

Everyone says use a high-flow cat, but unless your state has emissions testing, you can save money but just using a straight pipe there. As long as your exhaust isn't too large in diameter, the straight pipe won't hurt your low-end much at all, and it can only help your top end.

 

The only downsides are definitely a louder exhaust, and of course worse polution. But what difference does one car make?

[pwmin]

the 3.1 mpfi really doesnt have the compression/flow needed for 2 1/2" mandrel bent, you'll loose more low end then gain top, but if its shitty bent (forget the name) then 2 1/2 will be okey

 

good point. plus its a lot cheaper. i didnt mean mandrel, thanks for pointing that out (as if you were referring to me - i'm so self-righteous -- j/k)

[gp90se]

Everyone says use a high-flow cat, but unless your state has emissions testing, you can save money but just using a straight pipe there. As long as your exhaust isn't too large in diameter, the straight pipe won't hurt your low-end much at all, and it can only help your top end.

 

The only downsides are definitely a louder exhaust, and of course worse polution. But what difference does one car make?

 

 

have a cat there provides a little backpressure which is needed for more low end power, and being a high flow unit, you wont loose any power top end. Cat converters really dont change the sound by much.

 

 

good point. plus its a lot cheaper. i didnt mean mandrel, thanks for pointing that out (as if you were referring to me - i'm so self-righteous -- j/k)

 

the 2 1/4" mandrel bent piping will provide fast flow out of the pipes over the 2 1/2" standard bent, which means more power and better mpg.

[TeeJay3800]

Everyone says use a high-flow cat, but unless your state has emissions testing, you can save money but just using a straight pipe there. As long as your exhaust isn't too large in diameter, the straight pipe won't hurt your low-end much at all, and it can only help your top end.

 

The only downsides are definitely a louder exhaust, and of course worse polution. But what difference does one car make?

 

have a cat there provides a little backpressure which is needed for more low end power, and being a high flow unit, you wont loose any power top end. Cat converters really dont change the sound by much.

That's what a lot of people told me before I took my cat off, but it was not true AT ALL. With my Flowmaster 40, it made the exhaust literally over twice as loud in volume! I just wanted to put that disclaimer in so he wouldn't be surprised when his exhaust volume doubled.

[gp90se]

then your stock cat was clogged, I went from stock exhaust to straight pipe and dynomax mufflers to high flow cat with dynomax. When I pulled the stock cat, it got a little louder and with the high flow cat, noise didnt change at all.

[TeeJay3800]

then your stock cat was clogged, I went from stock exhaust to straight pipe and dynomax mufflers to high flow cat with dynomax. When I pulled the stock cat, it got a little louder and with the high flow cat, noise didnt change at all.

I don't think it was clogged, but it sure rattled like crazy. So either way it was shot. I'm still surprised as many people insist on using a "high flow" cat when there are virtually no adverse effects to a straight pipe. And the big positive is reduced cost!

[Brian P]

the 3100 stock downpipe is 2" maybe even less. Looking at it from the outside it seems 2.5" but don't be fooled, it's "double walled" aka that's acting like a heat shield. I have a 2.5" DP made by my muffler shop to a tune of $40