2.5" or 3"

[greg donovan]

so i am considering keeping the stock downpipe w/functional cat+02 sensorand having a straight pipe w/a resonator or two to keep the noise to a dull roar.

is it even worth it? i know a larger better flowing DP would be ideal but that is something i just dont want to deal w/now.

would 3 be better than 2.5?

i dont rallyx this car but i may autox it or take it to a track day.

my biggest concern is an improvemant in my acceleration from 0-40. which isnt too shabby in stock form but it can always be better.

[BAC5.2]

If you aren't going to do the downpipe now, then just go 2.5.

3" would be wasteful, and far to large to mount for a stock downpipe. Exhaust velocity would suffer greatly.

Why, out of curiousity, do you not want to do the downpipe now?

[greg donovan]

If you aren't going to do the downpipe now, then just go 2.5.

3" would be wasteful, and far to large to mount for a stock downpipe. Exhaust velocity would suffer greatly.

Why, out of curiousity, do you not want to do the downpipe now?

thats what i fugured about the 3". so 2.5 it is then.

money, money, and money. or rather the lack thereof is the reason why. and i feel it would be a bit of overkill for a street driven family mobile.

[BAC5.2]

Just remember, without the downpipe, you won't be getting as much performance as I think your expecting out of it.

[greg donovan]

Just remember, without the downpipe, you won't be getting as much performance as I think your expecting out of it.

but it will be slightly better than it is now i would assume.

i will also be installing a high flow panel filter and a lightened crank pulley before that.

i may not even do anything to the exhaust in the end as i am very happy w/the car in stock trim. but its fun to plan out stuff to do and know as much as i can about things before i get started.

[BAC5.2]

The little mods can add up, but add an intercooler, and a few PSI, and notice a significant difference.

[scottzg]

I suspect that a bigger exhaust might actually hurt 0-40 times in a mt SS, at least from a roll.

[BAC5.2]

Everything else being stock (including downpipe), then Scott is probably right. A larger exhaust, theoretically, would decrease exhaust velocity, and increase backpressure. Backpressure is the absolute enemy of an exhaust system.

Modded, though, and larger pipes are required to flow the air efficiently.

Exhaust is all about the highest velocity possible with the least amount of backpressure. To big a pipe will have to low velocity (and a slight increase in backpressure). To small, and you have moderate velocity, but really high backpressure also. Perfectly chosen pipe diameter and design give you really good velocity with very little backpressure.

[greg donovan]

The little mods can add up, but add an intercooler, and a few PSI, and notice a significant difference.

those things are all on the list too.

i am trying to put this stuff in some sort of order. going for a best bang for the buck while not compromising the durability of things too much.

all the mods will go together as a system eventually but i want to do the most cost effective ones first.

i know that ideally i should just save my pennies and wait a while and do it all at once. thankfully that is a bit easier w/this car as it is so much fun to drive.

here is the power plan so far:

1. lightened crank pulley, i have a perrin one in a box in my garage.

2. GN engine mounts and pitch stopper, also in previously mentioned box.

3. GN tranny mount, in a box in a store somewhere yet to be purchased.

4. Boost gauge

5. K+N type panel filter.

6. coffee mug? maybe?

i think this is where i will stop for a while and focus on the body of the car, it is a bit rusty in the typical places so i want them fixed up before next winter. also fix the antenna and get the headlights taken care of and do general maintenance on it. wiring and what not.

then i will probably do all of this at once:

7. boost controler

8. TMIC

9. DP+2.5" TBE

10. set it to 11 and have some fun. maybe 12.

[BAC5.2]

Even intercooling the stock setup would be beneficial at stock boost.

I noticed a difference when I went intercooled.

[greg donovan]

Even intercooling the stock setup would be beneficial at stock boost.

I noticed a difference when I went intercooled.

really, thats good to know. i may change my order a bit and bump the TMIC a little earlier on the list. the cooling effect makes that much of a difference? and im guessing pressure drop on a TMIC isnt THAT big of a a factor then, is it?

[BAC5.2]

Just get an MBC and raise compressor outlet boost to compensate.

The ECU SHOULD learn around the IC with the stock boost control after a little while though. I remember Vikash said his car quickly learned to go back to ~9psi.

[greg donovan]

Just get an MBC and raise compressor outlet boost to compensate.

The ECU SHOULD learn around the IC with the stock boost control after a little while though. I remember Vikash said his car quickly learned to go back to ~9psi.

stock is 9 PSI? for some reason i thought it was only 6.5?

[scottzg]

i doubt you gained anything with the intercooler, prolly just turbo lag messing with the calibration of the butt dyno. Stock boost is 8.7.

[BAC5.2]

I don't agree with you Scott. I don't get a chance to get to the dyno with every mod I do, so I can't give you exact numbers, but I can tell you that the car was faster.

Speaking from personal experience, I noticed a difference, and it wasn't because of turbo lag.

[greg donovan]

iff boost didnt drop i would expect an improvement due to the cooler intake temps.

[BAC5.2]

The turbo is still efficient to the MAYBE 10psi that will be asked of it to compensate for any pressure drop, so turbo outlet temps won't skyrocket, and the intercooler will do it's job by cooling the charge.

[scottzg]

I don't agree with you Scott. I don't get a chance to get to the dyno with every mod I do, so I can't give you exact numbers, but I can tell you that the car was faster.

Speaking from personal experience, I noticed a difference, and it wasn't because of turbo lag.

shrug, im just talking outta my butt.

[vrg3]

My ECU didn't learn around the pressure drop. It tried, failed, and gave up. With pretty much any air/air intercooler, you're gonna need some kind of aftermarket boost control.

[Brat4by4]

You want a 3" downpipe. Trust me. What you do with the rest of the exhaust doesn't matter as much. But you need to get the gasses away from the turbo in an efficient manner.

Pretty much all I have power-wise is the 3" turboback. I also have a lightweight flywheel and group-n mounts. The difference in feel is phenomenal, especially at higher rpms. Before the exhaust, the car absolutely dies above 4500 rpm and drops 1-2 psi. After the exhaust it holds full boost all the way to rev limiter, you can feel the slight loss of power from it being a smaller turbo if you are racing someone, otherwise it feels beautiful.

And don't forget. Eventually you will want more power and will be able to get it. You find killer deals on stuff because of WRX owners shedding off performance stuff like its yesterdays toilet paper. That being said, make sure you put stuff on that will handle the eventual power gains you will net. I would just go ahead with a 3" turboback and call it a day. They can be had for really cheap brand new (<$400), I'm sure you could get one at a phenomenal price used.