Exhaust size question.

[Jim]

I have an '88 GT (FE motor) and am considering changing my exhaust and was thinking about going with a 2" pipe and maybe a turbo muffler. Does anyone have any recommendations on an exhaust size? The car is mainly my daily driver, to and from work is mostly highway, 65(+) mph, but the car is also used to autocross. I would also like to know the reason for the exhaust size you recommend. I don't need a cat. were I live, so I plan on excluding it with the new exhaust. Also a recommendation on a good inexpensive muffler that will not make my car sound ricey would also be appreciated.

The car is an auto (until the tranny goes out) and so far, the only mods. are a MSD blaster 2 coil and an MSD 6A. I just blocked the vacuum to the ERG valve and am checking to see if this makes on difference. Air cleaner is next.

Thanks, Jim

[taticelica]

I have a 3" on mine and it has a nice deep sound. I do have a GT-S 5spd though. I think if you go over 3.5 then you pretty much will be losing HP or not gaining it. I would say dont make it bigger than 3.5 cause of the HP. If you do then it would be louder and more "ricey" sounding, and it will oook fugly.

[4thgenceli]

I have the same engine, and I'm going w/ a 2.25 full exhaust.

I'm moving over to mods....

[Luc]

taticelica said:

I have a 3" on mine and it has a nice deep sound. I do have a GT-S 5spd though. I think if you go over 3.5 then you pretty much will be losing HP or not gaining it. I would say dont make it bigger than 3.5 cause of the HP. If you do then it would be louder and more "ricey" sounding, and it will oook fugly.

where did u get yours from the only cat-back i can find is the gay pace-setter cat-back

[taticelica]

All I did is get a muffler and a high flow cat and had a shop here weld them on.

[Luc]

how much did it cost u

[dansgts]

i've got 2.5 (or 2.25, forget which) catback with a cf muffer, i love it.

[dansgts]

Luc said:

where did u get yours from the only cat-back i can find is the gay pace-setter cat-back

go to a shop and have them custom do one, i know a place that wont charge more than 150, all piping and install, all you need is a muffler. just look for a place in your area.

[Jim]

3.5"? What difference have you noticed? Did you lose some bottom-end? Are you using a stock manifold and if so, did you open the outlet hole?

Has anyone done any bac-to-back tests with different exhaust pipe sizes? Like maybe a 1/4 mile time with stock then upgrade to a bigger size?

4thgenceli, what made you decide to go with 2.25", since you say you are going to have that size done? What kind of muffler are you going with?

[4thgenceli]

It's a general size that I usually get for 4-banger's. I can go 2.5 if i wanna. It's just some performance muffler this shop carries. This shop did Jeremy's exhaust, and his buddies 198? Supra w/ i think a 3" exhaust..

[Luc]

if i bought the piping it should be cheeper right? i know jcw sells pipinghow much was the high flow cat?

[taticelica]

I got a high flow for less than a hundred from a store here in my area. I got everything done for $150 US, and thats muffler and high flow and ne pipe from the cat to the muffler.

I have a 3" outlet and I have not noticed a difference from my old one when i had a 2.5" muffler on. It just sounds a little deeper, surprisingly.

[blck87gtconv]

4thgenceli said:

It's a general size that I usually get for 4-banger's. I can go 2.5 if i wanna. It's just some performance muffler this shop carries. This shop did Jeremy's exhaust, and his buddies 198? Supra w/ i think a 3" exhaust..

2.25" is the absolute best size for our N/A 4 bangers. It's best to maintain this size throughout the entire exhaust, although I realize it's next to impossible to find a muffler with anything smaller than a 2.5" inlet and a 3" outlet.

Despite popular believe, the brand of muffler you buy actually does make a difference. Those e-bay mufflers look good, and they sound good.... for about a month before the material starts to corrode. I'm not saying everyone should go out and buy the most expensive muffler you can find. I honestly think that a 2.25" setup with a high flow cat and something like a cheap domestic performance muffler for close to $20-$30 is a great setup. You don't have to worry about being too loud, it looks stock, and it's a killer setup.

It keeps the exhaust temps high, and thus the exiting velocity varies the least amount possible.. which is exactly what you want.

The problem with oversized exhaust tubing on an N/A, is that there just isn't enough force from the exhaust on the car to make a consistent flow of gases through the system. This causes the exahust gases to slow down, and thus get a bit cooler.. this all has the effect of actually producing MORE backpressure.

The concept that our engines need a little bit of backpressure is a myth.. it stems from a lack of understanding the physics of a performance exhaust system and going with a "rule of thumb" policy. Just keep the sizes right with the least curves possible in the tubing, and you'll have a really good setup.

If you really want mandrel bends, I would suggest you get them from JCWhitney and have a shop weld them in with the rest of the system.. but maintaining the 2.25" ID sizing.

Knowledge is power.

[jbone2322]

Knowledge is power.

but good writeup jason. thanks.

[Jim]

Great job on the write-up. This is my first experience working with 4 cylinders. Most of my life I have built and drag raced Pontiacs were header pipe and collector pipe size is very important to getting the full HP from the motor. We obviously don't use full exhaust on the cars. I'll give the 2.25" size and the domestic muffler a try.

Thanks, Jim