up and down pipe

hey there I would like to ask what is the

best up pipe and down pipe to use to upgrade my legacy gt

and my is a 2006 with 189050 on her

It doesn't make too much difference which brand for those things. For the uppipe you can even find an OEM used STI or Legacy GT catless uppipe. Popular brands for uppipes and downpipes on these cars are GrimmSpeed, Cobb, Invidia. I have an Invidia downpipe and I'm happy with it.

 

The truly important thing will be making sure you have your car tuned as soon as the parts are on so the engine doesn't fail from running too lean.

Not trying to hijack the thread, but this seems like an appropriate thread to ask in.

 

I've tried doing research but wasn't able to come up with much definitively. As far as aftermarket downpipes go, is there a great difference performance-wise between a catted and catless dp? From what I've seen so far it looks like there's little difference. I am not worried about the price difference or about emissions as my state only does ECU testing so I won't have to worry about what's coming out of the pipe as long as the computer says it's cool, but am thinking I'd rather have the catted pipe simply because I assume it will be a little quieter? I don't want a super loud rumble exhaust, but with no cats on the car whatsoever I fear it will sound super shitty. On the other hand, my stock dp is my single largest restriction that I want to tackle before I tune. I'm leaning towards a catted pipe, unless it will be more restrictive and not worth the money. Any first hand knowledge is greatly appreciated

OTS tunes (Cobb's, anyway) are written for catted DPs only, so if you go catless, include a pro tune as part of your upgrade plan.

The catted DP is less noise, the same exhaust on the catless wagon was to loud until I put it on my catted Spec B. The Q300 is nice and easy to live with on the Spec B.

 

Get a catted DP.

 

The catless wagon is to loud with a stock mid pipe and straight through mufflers. Fun in the summer time with the windows down, but to loud for a long drive with the windows up.

You also risk boost creep with un-catted DP, plus need a tune to get rid of CEL from o2 sensor.

Catless exhausts stink, we have no emissions where I live, but I refuse to run catless (even on my weekend racecar) because the stank. Plus it is illegal and our state inspections can get picky.

Thanks guys, that's pretty much what I assumed but I wanted to ask people who know.

 

I'm not going to be running an OTS map so I'm not worried about boost creep, gonna have them do a full dyno tune. Not sure if I'm even going to get an AP at this point, probably just open source because the car already does not have a factory tune from the PO as it is.

 

I just really did not want a catless down because they sound like shit imo (and yes the smell too). The car is not going to sound stock as it is, but I don't need to be obnoxious with it setting off car alarms in the parking lot at work and waking up my newborn when I leave for work in the middle of the night.

I've been planning on going for a catless downpipe, what exactly is boost creep? I do plan to get a tune through the tactrix cable and online software done by a professional.

I just finished installing a catless up and down pipe. I regret the catless downpipe for the smell but the price couldn't be beat. With the stock cat back it's really no louder than stock.

Imo, yo uonly really need a catless pipe if you are trying to be competetive at the strip where fractions of seconds count. Other than that, the sound and smell (and apparent danger to our atmosphere or w/e) are not worth it.

I've been planning on going for a catless downpipe, what exactly is boost creep? I do plan to get a tune through the tactrix cable and online software done by a professional.

 

Boost creep essentially means your boost will slowly rise higher than you would want it, due to unrestricted exhaust flow/undersized wastegate. If your engine is tuned to run at 10 PSI and it creeps up to 17 PSI, bad things will happen.

I like the smell of catless lol.

I've been planning on going for a catless downpipe, what exactly is boost creep? I do plan to get a tune through the tactrix cable and online software done by a professional.

 

The wastegate on the stock turbo is pretty small, with a free flowing setup it is possible to create more boost than the turbo is able to control by releasing pressure through the wastegate causing boost pressure to continue climbing even with the wastegate fully open. This boost gain is unpredictable and with no real way to control it one risks engine damage if it gets too high over what the car was expecting to handle (I really doubt one or two lbs will hurt much but when you start pegging over 20 psi and the car is expecting 16.5 it's no good). Except for in extreme cases it can generally be prevented/corrected with a good protune. Otherwise you need to start looking at getting a different turbo, or just be prepared to drive around at half throttle everywhere.

 

This is one of the many reasons I am hesitant to get a DP, but I plan to talk more with my tuning shop to see if they think my planned setup will be reasonable.

 

Someone please correct me if I'm wrong, but If I remember correctly it is best to have your car tuned in colder temps as boost creep is much less likely to happen in warmer months when the air is less dense and oxygen rich?

 

 

I like the smell of catless lol.

 

It's not a terrible smell, but I definitely wouldn't want it on this car.

I guess it's all in how you want to use the car.

 

My old jacked up Chevy K10 and my stripped Datsun 280ZX I use for auto-x don't have cats, they sound cool and the smell suits them. But that's not what I desire for my nice comfortable Legacy sedan. I have loud stinky fun things in the driveway already (and have had plenty of others over the years), for my DD I'd like it to be a reasonable vehicle. This is not a race car for me, nor is it a toy. Fast and fun for sure, but still able to blend in with traffic and capable of being comfortable when I'm half asleep ho-humming my way into work.

If I remember correctly it is best to have your car tuned in colder temps as boost creep is much less likely to happen in warmer months when the air is less dense and oxygen rich?

 

Yes, for the most part. I believe cold air has my O2. Seem to recall an Afterburner on a jet engine will use more fuel in cold weather because there's more O2. I used to be a Jet Engine Mechanic, Flight Line in the USAF, yea I worked outside in all kinds of weather.

 

Oh look what I googled,

 

https://www.google.com/search?source=hp&ei=6p4lWq_VOoOWjwO7xJ6IAw&q=does+cold+air+have+more+oxygen+than+warm+air&oq=does+warm+air+have+more+O2+then+cold+air+&gs_l=psy-ab.1.0.0i22i30k1.1697.16998.0.22770.41.36.0.3.3.0.386.5845.0j19j4j5.28.0....0...1c.1.64.psy-ab..10.31.5924...0j0i131k1j33i22i29i30k1.0.NrszoiFvKl8

Well I already know for a fact air is more dense and has more oxygen at colder temps, no google needed there.

 

I was simply trying to remember if it was optimal to tune the car when it was cold out rather than spring/fall temps (obviously summer heat is bad). One would possibly assume that neutral "middle of the road" temps would be ideal, but if you have your car tuned during "normal" temps it will possibly be unprepared for cold temps and may still boost creep in the winter. So I was asking if it's best to tune it in the most oxygen rich scenario (winter) so there will be no issue down the road when it gets cold. You may run rich in the summer, but at least you won't burn your shit up when it gets cold? That's all I needed clarification on

I don't touch the tuning side of things, but with modern engines, I would imagine the ECU takes into account the Air Density change at lower temperatures. I think why those old "+100HP Ebay Chips" came about. I would be more concerned with altitude change having an effect on air density. I would throw that question at someone familiar with open source tuning, they might have an exact answer on that.

Well I already know for a fact air is more dense and has more oxygen at colder temps, no google needed there.

 

I was simply trying to remember if it was optimal to tune the car when it was cold out rather than spring/fall temps (obviously summer heat is bad). One would possibly assume that neutral "middle of the road" temps would be ideal, but if you have your car tuned during "normal" temps it will possibly be unprepared for cold temps and may still boost creep in the winter. So I was asking if it's best to tune it in the most oxygen rich scenario (winter) so there will be no issue down the road when it gets cold. You may run rich in the summer, but at least you won't burn your shit up when it gets cold? That's all I needed clarification on

 

Your thinking is correct based in the fact that a "standard day" is something like 69F with a standard for the other two parameters too. Sorry it's been about 40 years since I needed to know that.

 

The ECU should learn after the first boost spike in cold temps. I just push in the clutch, turn the car off/on 4 times, it clears the CEL and keep driving. Haven't had to do that in a long time.