What size exhaust system for VR4?

I've already bought a remus 2.5inch muffler with twin tips for my 1991 galant vr4. I'm wondering if i should get the dump pipe and the rest of the system 3inch going down to 2.5inch after the cat or should go all the way 2.5inch?

So far the car is standard but sooner or later a 16g or a 20g will find it's way to the engine bay. And right after i get the exhaust system a FMIC, air filter, boost increase and ECU mods will follow.

 

[Matticus]

It sounds like you are still running the 14B stocker. With a 3" DP you will experience boost creep unless the turbo and O2 housing is ported around the wastegate. A 2.5" DP won't be as bad, but it will still be an issue. Keep that in mind, and 2.5" will be plenty big enough unless you really want the car to be a monster. Plus 2.5" will be a bit quieter too. Alot of folks will say to just get 3" all the way because that way you want have to replace the 2.5" when it becomes too small. They, however, don't ever mention the boost creep that comes with the 3"er.

 

[4orced4door]

quote:Originally posted by Matticus:
They, however, don't ever mention the boost creep that comes with the 3"er. I've had no boost creep issues with my 3" turboback setup, even when it was the only real mod the car had. At stock boost it was fine, and at 18 or so psi it is fine, it never creeps. All I have ported is the turbine housing where it bolts to the exhaust manifold.

 

Well as i mentioned sooner or later i'll be doing more serious mods to the car so i wouldn't wanna pay twice.

In terms of noise level, i picked remus 2.5inch muffler thinking it'll quiten the 3inch system before the gasses come out. Am i wrong? I don't want to put a resonator on. Do i really need one or can the car still be quiet without one? (considering 3inch all the way going down to 2.5inch after the cat converter).

 

[Matticus]

That is good to hear. I need to buy a new downpipe, my stocker one has a small hole near the flex section. I was afraid of boost creep associated with a larger downpipe.
These cars can be such a pain sometimes, once you start modding, it snowballs into a never ending saga of upgrades. New downpipe, port O2 and turbo, replace cracked manifold, port new manifold. Replace the clutch becuase it is done from the new power, fuel management.... But it is fun.

 

[4orced4door]

The never ending upgrades are what makes it fun.

This topic has actually been covered a lot. Just get 3" all the way back. Don't put a smaller muffler on, or the restriction will just hurt the power you could be making. My car is 3" all the way back, with a Magnaflow muffler and a test pipe, and most people comment on how quiet my exhaust is. Interstate crusing is rough, but around town it is fine. It really only gets loud when you go WOT, then it really opens up.

Even with 3" all the way back, your car is never going to be close to these loud ass Hondas buzzing around. Inside the car, you will quickly get used to it. Quiet = power being robbed.

 

[gvr4ever]

Is boost creep and boost lag getting mixed up? How could you get boost creep from a 3"?

 

[4orced4door]

quote:Originally posted by gvr4ever:
Is boost creep and boost lag getting mixed up? How could you get boost creep from a 3"? Neither one is even an issue. Boost comes on stronger and earlier with better flowing exhaust. Boost creep would definitely not be an issue. Boost creep is when the exhaust system can't get the air out fast enough, so excess pressure builds up, raising your boost. For example, running a huge ass turbo with a stock O2 and stock exhaust, you would boost creep like crazy. Correct?

Bigger exhaust can only help you.

 

[Dan D]

I don't think (?) you need to have taken any fluid dynamics classes to realize whether or not it is good for flow to go 3" into 2.5". Backpressure anyone?

 

[blacksheep]

SEARCH!

 

quote:Originally posted by blacksheep:
SEARCH! word!

 

yes damn it

 

matticus and 4orced4door are both right, but i think matticus' proposition is occurs more often than 4orded4door. cause 4orced4door's propostion would occur if someone had an upgraded turbo with a stock exhaust. either way, you would benifit a lot by getting a new o2 housing, which we all know will make boost creep a thing of the past.

yeah i think that all exhaust questions like this should just be closed after telling them to search and of course telling them why they have to do so.

 

[a_santos]

I have 2.5" Dp and cat and 3" from there, and I can honestly say that my car was one of the quietest cars at the shootout. I have a Borla race muffler.

I have had a Remus before, not on the Galant, and it is a really good sounding muffler. Go three inch and then reduce before the muffler. I wouls also recommend a high flow cat, I have one even though we don't have emissions testing in MI. It is better for the environment and it will quiet the car down some.

 

[Matticus]

From what I understand, boost creep is when the wastegate can not flow enough exhaust to bypass the turbine. When this happens, the only place for the exhaust to go is through the turbine, creating more boost. It can be more common on larger turbos that are running low amounts of boost with no modifications to the wastegate passage. Most of your bigger turbos should be run with an external wastegate, which nearly eliminate boost creep.
Go to www.dsmtalk.com/forums and do a search on boost creep, you gets lots of different scenarios of boost creep.

 

[4orced4door]

quote:Originally posted by Matticus:
From what I understand, boost creep is when the wastegate can not flow enough exhaust to bypass the turbine. When this happens, the only place for the exhaust to go is through the turbine, creating more boost. It can be more common on larger turbos that are running low amounts of boost with no modifications to the wastegate passage. Most of your bigger turbos should be run with an external wastegate, which nearly eliminate boost creep.
Go to www.dsmtalk.com/forums and do a search on boost creep, you gets lots of different scenarios of boost creep. And by opening up your exhaust, you are helping to free that air. I'm afraid DSMBalk has corrupted you...

 

i'm glad i'm not the only one who cares about the environment.

a kid i know is removing every cat from his wrx (yes a kid. he's only 17). i say he should at least keep two but whatever. there is no way in hell that he is passing emissions down here in the old Tx.

anyway

 

Coming back to the original topic....
Noise level? Resonator? 3inch to 2.5inch?

 

quote:Originally posted by 4orced4door:
quote:Originally posted by Matticus:
They, however, don't ever mention the boost creep that comes with the 3"er. I've had no boost creep issues with my 3" turboback setup, even when it was the only real mod the car had. At stock boost it was fine, and at 18 or so psi it is fine, it never creeps. All I have ported is the turbine housing where it bolts to the exhaust manifold. Right now I have a stock ported turbine housing on the 14b and run 18psi daily w/ 3" turboback no cat.. I get no boost creep what-so-ever.

As you do a search, you'll find that at the end of each 'exhaust' discussion, it ends up, "GET 3"!"

 

[scooter]

boost creep is caused by the exhaust outflowing the wastegate. like as in its easier for the exhaust gas to flow out the turbine exit hole and into the downpipe, instead of some flowing out the wastegate hole. it all just wants to flow out where its easiest to get out.(3in downpipe would be way easier than the 29mm wastegate hole.) with the stock exhaust it would back the flow up and cause some gas to go out the wastegate hole. not everybody will have boost creep, but some will have it bad. you can port out the wastegate hole and install a 34mm flapper though and you should be fine if you do have it.