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What size exhaust system for VR4?


MiSTER2
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Galant VR-4 org Post #: 16976 posted 07/20/03 09:02 AM     Remind Me!  Send Private Message   Edit Post      
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.

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Matticus
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Galant VR-4 org Post #: 16977 posted 07/20/03 09:37 AM     Remind Me!  Send Private Message   Edit Post      
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.

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4orced4door Galant VR4.org Moderator
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Galant VR-4 org Post #: 16978 posted 07/20/03 09:47 AM     Remind Me!  Send Private Message   Edit Post      
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.

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MiSTER2
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Galant VR-4 org Post #: 16979 posted 07/20/03 10:12 AM     Remind Me!  Send Private Message   Edit Post      
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).

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Matticus
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Galant VR-4 org Post #: 16980 posted 07/20/03 10:18 AM     Remind Me!  Send Private Message   Edit Post      
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.

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4orced4door Galant VR4.org Moderator
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Galant VR-4 org Post #: 16981 posted 07/20/03 10:25 AM     Remind Me!  Send Private Message   Edit Post      
The never ending upgrades are what makes it fun. [Wink]

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. [Wink]

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gvr4ever
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Galant VR-4 org Post #: 16982 posted 07/20/03 10:46 AM     Remind Me!  Send Private Message   Edit Post      
Is boost creep and boost lag getting mixed up? How could you get boost creep from a 3"?

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4orced4door Galant VR4.org Moderator
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Galant VR-4 org Post #: 16983 posted 07/20/03 10:50 AM     Remind Me!  Send Private Message   Edit Post      
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.

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Matticus
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Galant VR-4 org Post #: 16984 posted 07/20/03 11:01 PM     Remind Me!  Send Private Message   Edit Post      
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.

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4orced4door Galant VR4.org Moderator
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Galant VR-4 org Post #: 16985 posted 07/20/03 11:02 PM     Remind Me!  Send Private Message   Edit Post      
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... [Wink]

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MiSTER2
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Galant VR-4 org Post #: 16986 posted 07/20/03 11:19 PM     Remind Me!  Send Private Message   Edit Post      
Coming back to the original topic....
Noise level? Resonator? 3inch to 2.5inch?

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Dan D
220, 221... whatever it takes
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Galant VR-4 org Post #: 16987 posted 07/20/03 04:10 PM     Remind Me!  Send Private Message   Edit Post      
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?

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blacksheep
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Galant VR-4 org Post #: 16988 posted 07/20/03 04:38 PM     Remind Me!  Send Private Message   Edit Post      
SEARCH!

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Hibrn8
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Galant VR-4 org Post #: 16989 posted 07/20/03 05:55 PM     Remind Me!  Send Private Message   Edit Post      
quote:
Originally posted by blacksheep:
SEARCH!

word!

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Jonvr4
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Galant VR-4 org Post #: 16990 posted 07/20/03 06:47 PM     Remind Me!  Send Private Message   Edit Post      
yes damn it

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SEVEN26
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Galant VR-4 org Post #: 16991 posted 07/20/03 06:56 PM     Remind Me!  Send Private Message   Edit Post      
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.

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a_santos
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Galant VR-4 org Post #: 16992 posted 07/20/03 10:40 PM     Remind Me!  Send Private Message   Edit Post      
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.

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SEVEN26
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Galant VR-4 org Post #: 16993 posted 07/20/03 11:03 PM     Remind Me!  Send Private Message   Edit Post      
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

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GeeRIDE
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Galant VR-4 org Post #: 16994 posted 07/21/03 02:10 AM     Remind Me!  Send Private Message   Edit Post      
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"!"

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scooter
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Galant VR-4 org Post #: 16995 posted 07/21/03 04:13 AM     Remind Me!  Send Private Message   Edit Post      
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.

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Ash
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Galant VR-4 org Post #: 16996 posted 07/21/03 05:42 AM     Remind Me!  Send Private Message   Edit Post      
quote:
Originally posted by MiSTER2:
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).

I've got a full 3" system from the turbo back with a ported b16g, no resinator & only a shite lukey straight through 3" muffler, it doesn't sound too loud or droney to me but different strokes for different blokes.

If I was you, I'd go 3" right to the remus seeing as you already have it, the 2.5" will quiet it down & hopefully not get you a defect - I don't really have to worry about exhaust DB testing up here in hicksville but you probably have to be a bit more worried.

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spoulson
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Galant VR-4 org Post #: 16997 posted 07/21/03 05:56 AM     Remind Me!  Send Private Message   Edit Post      
quote:
Originally posted by 4orced4door:
And by opening up your exhaust, you are helping to free that air. I'm afraid DSMBalk has corrupted you... [Wink]

I don't think that makes sense. If the wastegate is already being outflowed, creating less backpressure with bigger pipes is only going to make the problem worse.

My understanding: If the turbo is creeping with high backpressure from stock exhaust, then how could it be any better by putting on high-flow 3" exhaust? You're only allowing more gasses to make it through the turbine when the turbo is experiencing boost creeping.

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gvr4ever
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Galant VR-4 org Post #: 16998 posted 07/21/03 08:04 AM     Remind Me!  Send Private Message   Edit Post      
Boost creep is caused by installing a bigger turbo that out flows the wastgate flapper and 02 housing. The effect is the boost rising for your engine. You might try and set it at 16, but it will keep going up and you can't do anything about it untill the flow problem is fixed.

If you had a 20G with a stock exhaust (just a example) then I'm sure the stock exhaust would play a roll in boost creep too.

So how could putting a bigger exhaust on ever cause boost creep?!?!? It can't.

People don't just add external wast gate dumps to scare old people. Well, it's not the only reason.

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howard
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Galant VR-4 org Post #: 16999 posted 07/21/03 08:41 AM     Remind Me!  Send Private Message   Edit Post      
quote:
Originally posted by gvr4ever:
Boost creep is caused by installing a bigger turbo that out flows the wastgate flapper and 02 housing. The effect is the boost rising for your engine. You might try and set it at 16, but it will keep going up and you can't do anything about it untill the flow problem is fixed.

If you had a 20G with a stock exhaust (just a example) then I'm sure the stock exhaust would play a roll in boost creep too.

So how could putting a bigger exhaust on ever cause boost creep?!?!? It can't.

People don't just add external wast gate dumps to scare old people. Well, it's not the only reason.

That's not correct.

Boost creep is caused by the resistance in the exhaust being LESS than the resistance going through the wastegate valve. Exhaust takes the easiest route, which is through the turbine wheel, thus making more boost.

Problem can be remedied by
A) larger WG flapper
B) proper porting

See what I'm saying? The bigger exhaust can reduce backpressure so much that exhaust doesn't want to go through the wastegate and bleed off. W

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GalantVR41062
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Galant VR-4 org Post #: 17000 posted 07/21/03 10:21 AM     Remind Me!  Send Private Message   Edit Post   
Howard is correct. And with larger exaust you will get more lag, untill you get that first pound of boost your motor is NA and needs tuned exaust(not to big not to small). But when your in boost the best exaust is no exaust at all.

~John

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