What gains would I see?

[Mudman]

Hey guys, my car is an '89 Lancer Shelby and I currently have straight through exhaust with a 2.5" magnaflow muffler. However most of the piping is the stock 2.25" stuff. I was thinking when I get some extra spending money to open it up to 2.5" all the way but I wanted to make sure the gains would be worth the money.

Mods are: FWD Stage 3 cal, 15psi, rebuilt turbo by TU with quickspool, I lightly ported my head, intake, and exhaust manifold (but I mean very lightly, it was my first time and I didn't want to take too much material off where I shouldn't) A fresh bottom end I just got done putting back together, and of course the exhaust I stated above.

She runs strong on the new motor and I was curious if that extra quarter inch piping would really make a difference.

Thanks guys, Zach.

[Directconnection]

Your stock exhaust should be 2-1/2" right after the cat, then it shrinks down after that, and mostly.... over the axle.

FWD and TU sells a catback exhaust that is 2-1/2" from the cat all the way over the axle to your muffler. That is what I would do. That 1-7/8" I think piping right before the muff/over axle area needs to be gone;)

[turbovanman²]

For sure, going a true mandrel 2.5 with a matching high flow cat or cat delete will make a big difference.

[Mudman]

Well my car is cat delete, and has a straight through muffler. I just need the piping to match, does it really bottle neck down to under 2" over the axle? I knew that was the main problem but I didn't know it was that restrictive.

[shadow88]

Maybe you should measure what's on there now. It's very unlikely that is still has the factory exhaust after 21 years. When I went from 1 7/8 to 2 1/2 inch, the power went up, the lag went down and the noise went up too. I thought it was worth the money. If you want some extra fun, maybe add in a cut-out.

[Mudman]

It had the factory exhaust before I cut the cat out and had a muffler put on hehe. I just didn't have the money at the time to do a full exhaust.

[ShadowFromHell]

I would go to 3" if you are going to spend the $$$.

[Mudman]

Would I really need 3" though? This is my DD, and it's probably never going to see more than 15psi. I'm probably done modding it after the exhaust really. Plus I already have a pretty new muffler that's 2.5"

[cordes]

Would I really need 3" though? This is my DD, and it's probably never going to see more than 15psi. I'm probably done modding it after the exhaust really. Plus I already have a pretty new muffler that's 2.5"

With those goals I wouldn't bother with 3". Too much trouble to get it over the axle without rattling for 15PSI IMO.

[OmniLuvr]

if your gonna spend the money, id go with 3" also. people "think" there done modding there cars at certain levels. but after being there for an extended period of time they feel its time to turn up the wick, if its for more fun or a better E.T. at the track.

the 3" dp and exhaust will give you quicker spool up, support further power goals, and the noise isnt bad when using the correct muffler.

[Mudman]

I've had this car at 15psi running the way it is for a few years though, I want reliability over performance because it's the only car I have. I understand the concept behind going big and getting the 3", I just don't see the practicality for me.

[turbovanman²]

Stick with 2.5, for what you have, that is fine.

[dwh4784]

2.5" is fine as mentioned.

I have almost the same setup as you, how do you like the FWD stage 3 cal compared to stock?

[Juggy]

id go 3"

do it right the first time...why spend money twice. youll get quicker spool and the 3" will support more power in the future.

[Mudman]

I love the stage 3 cal, but my stocker was broken...it had some issues. When it was really cold outside it would lose ignition randomly lol. Like the car would just fall on it's face and then pick up like nothing happened. Didn't have to be in boost, it was just weird.

[ShadowFromHell]

id go 3"

do it right the first time...why spend money twice. youll get quicker spool and the 3" will support more power in the future.

Thats my thought. I had a crush bent 3" system made for my shadow that fit perfectly. I have never had a after market assemble your self system, so I dont know how those fit. I would think any good exhaust shop could make you a 3" crush bent system cheap. I paid $100 for mine, but those days are long gone :(

[BadAssPerformance]

The 3" muffler shop bend (not mandrel bend) with 3" Dynomax Race Magnum oval and no cat on my T2 Shadow is just as good as the open downpipe.

EDIT: Just as good means both have run 12.89 @ 104.5

[OmniLuvr]

^bap, but what size sv? and your saying crush tube 3" is as good as open downpipe? what size downpipe?

mudman, why do you want to buy a 2.5" mandrel exhaust in the first place?

also, if you have an 89 lancer shelby, that means you have the higher flowing 2.5" sv right?

if you have a hookup on 2.5" mandrel bends and someone to install them for cheap, then go for that. but if you are going to pay for a NEW, FULL PRICE, FULL MANDREL exhaust kit, then purchase the 3". it will "almost" be the same price, give you more power and quicker spool, support more power, and it "will" be reliable (i dont know how an exhaust would give you un-reliable power?), it should make it more reliable...

[Mudman]

I didn't mean that the 3" exhaust would make my car less reliable, I was just saying that it would be cheaper for me and because I already have a muffler for 2.5" that's another expense I wouldn't have.

So here's my question, the way my car is "now" (with the mods I've stated before) would it really be worth it to go 3"?

[Vigo]

I think no. I think the majority of people would tell you to just upgrade the rest of your exhaust to 2.5".. and if you want to go faster later you can. Its not like the 2.5" exhaust will stop you. People have gone plenty dang fast on 2.5" exhaust.

[Juggy]

I didn't mean that the 3" exhaust would make my car less reliable, I was just saying that it would be cheaper for me and because I already have a muffler for 2.5" that's another expense I wouldn't have.

So here's my question, the way my car is "now" (with the mods I've stated before) would it really be worth it to go 3"?

SO GO 3" and get a 3" to 2.5" reducer for the muffler until you can find something else. all you need is a 3" straight through. even a cherry pack would work lol

[Juggy]

^bap, but what size sv? and your saying crush tube 3" is as good as open downpipe? what size downpipe?


when you say crushed tube? are you referring to the oval style exhaust tubing??? the oval stuff WILL NOT flow as good as the round tubing...i dont care what anybody says :nod:

[Vigo]

i think he means crush bent.

[Juggy]

ahhhh as in not mandrel, gotcha

[BadAssPerformance]

^bap, but what size sv? and your saying crush tube 3" is as good as open downpipe? what size downpipe?

'87 T2 Shadow is stock '87 stuff so 2.25" SV and DP... good enuff for 12's

Yeah, muffler shop bend is decreased area in the corners instead of mandrel bends... not talking about the accordian looking parts store garbage

[turbovanman²]

I didn't mean that the 3" exhaust would make my car less reliable, I was just saying that it would be cheaper for me and because I already have a muffler for 2.5" that's another expense I wouldn't have.

So here's my question, the way my car is "now" (with the mods I've stated before) would it really be worth it to go 3"?

No, 3" is harder to route over the back axle and can be a pain to stop rubbing. From what you've said, 2.5 mandel is all you need and even if you turn it up, it will still be fine.

[kuzman83]

I have a shelby lancer with a full 3 inch, no muffler, high flow cat and 2.5 inch SV, its running around 15lbs aswell with very similar mods as yours. I honestly regret going with the 3 inch sans muffler because its loud as hell, i've never had any trouble with the axle vibrations but it is definately a tight fit. It did however make a very noticable difference in power over the stock system. I bought my system from turbos unleashed about 3 years ago and it is holding up quite nicely, no rust and it fits like a glove. pretty reasonable price too if I remember correctly.