4" turboback?

[sho_tyme_psi]

Just wondering if anyone has ran a 4in. turboback or if anyone even makes them. I have priced out a little less then $600 to do the whole thing in stainless. I don't need any hate replies on why I don't need 4" , Its easier to do this than 3". open DP plus all the noise and fumes go out the back. Any help greatly thanked.

 

[timloomis]

ive never heard of a 4" system on a dsm.i know shep runs or did run 3.5.you might wanna talk to the supra guys,4" is pretty common for them.but i guess if its easier/cheaper for you,the do it.

 

[sweet97]

4" has been done, there's a pic around here somewhere. Not needed unless you are in the 4 figure HP range though. Like the last poster said go ahead and do it if it's easier. mark

 

[~laser_craver~]

them school busses have 4 inch exhaust and are only making 250 hp and 480 ft lbs so dont just state that you only need it if your int he 4 digit power area.... it all depends on the motor/setup, but they are correct 4'' is way to big really over kill, just out of curiosity what turbo is gonna be trapped to this 4'' exhaust?

 

[sweet97]

C'mon this is a DSM forum not a school bus forum which are deisels making a lot of sooty volume exhaust. I still say 4" is not needed. 3" is overkill for half the guys using that size. Velocity helps also and bigger pipes cool the gas slowing it's exit. mark

 

[staticbrainwash]

ya know, im not trying to start shit here, but im curious as to where people keep getting this info.

"exhaust gasses cool as they exit the pipe." yes, it makes sense that the would a little. but it's just hard to believethat it could EVER mke that much difference. espically on a turbo car. i want numbers on cooling rates down the pipe. because, and espically, if a car is running in the range of anything over 3000rpm's it seems to me that in reality, gasses will NOT have that much time to cool down the pipe. everything will be flowing like crazy through a turbo, which is also just making things hotter as they exit.

like i said, im not trying to start shit. i just want to see numbers on this "mystery" cooling exhaust. if someone gets mad by this post, please, prove me wrong. i just can't see that it makes that much of a difference.

 

[Bastard1g]

What about getting an intercooler for your exhaust then? How about water injection?

 

[mntalon_05]

ya know, im not trying to start shit here, but im curious as to where people keep getting this info.

"exhaust gasses cool as they exit the pipe." yes, it makes sense that the would a little. but it's just hard to believethat it could EVER mke that much difference. espically on a turbo car. i want numbers on cooling rates down the pipe. because, and espically, if a car is running in the range of anything over 3000rpm's it seems to me that in reality, gasses will NOT have that much time to cool down the pipe. everything will be flowing like crazy through a turbo, which is also just making things hotter as they exit.

like i said, im not trying to start shit. i just want to see numbers on this "mystery" cooling exhaust. if someone gets mad by this post, please, prove me wrong. i just can't see that it makes that much of a difference.

how can you say exhaust doesn't cool much? you can put your hand in the tip of your exhaust and not get burned, now try that right when it comes out of the turbo? what's your egt guage reading, a little warmer than what it is at the end. The ideal exhaust setup is one that keeps velocity up, without creating a restriction, not so big that the volume of air in the pipe creates a restriction, and keeps the heat held in the pipe to keep velocity up also. Some big company needs to make a turboback that is ceramic coated and starts big and slowly gets smaller to keep velocity up to compensate for the heat loss. think of all the r&d it'd take to get the ideal setup there, haha. Until that happens, 2.5" or 3" mandrel is the tried and true.

 

[sweet97]

how can you say exhaust doesn't cool much? you can put your hand in the tip of your exhaust and not get burned, now try that right when it comes out of the turbo? what's your egt guage reading, a little warmer than what it is at the end. The ideal exhaust setup is one that keeps velocity up, without creating a restriction, not so big that the volume of air in the pipe creates a restriction, and keeps the heat held in the pipe to keep velocity up also. Some big company needs to make a turboback that is ceramic coated and starts big and slowly gets smaller to keep velocity up to compensate for the heat loss. think of all the r&d it'd take to get the ideal setup there, haha. Until that happens, 2.5" or 3" mandrel is the tried and true.

Thanks as I stated my thought poorly except the exhaust gas needs some velkocity to exit the engine/exhaust. Too large a pipe allows the gases to cool thus slowing their velocity. Yes it's a tough R&D enterprise and the 2.5-3" have served well. I don't want to argue either and if anyone wants to build a 4" exhaust more or less power to him!

 

[staticbrainwash]

like i said, i wasn't trying to start anything. im just curious about numbers.

i do agree about 4" being overkill. and even 3" is overkill for some people.

i also see what you're saying. i didn't even think about the heat out the tip. but are you refering to idle? or high rev? i imagine the difference would be made (at least for power) in the high rev category. hmmmm. . . looks like i have a new research project.

 

[bastarddsm]

ya know, im not trying to start shit here, but im curious as to where people keep getting this info.

"exhaust gasses cool as they exit the pipe." yes, it makes sense that the would a little. but it's just hard to believethat it could EVER mke that much difference. espically on a turbo car. i want numbers on cooling rates down the pipe. because, and espically, if a car is running in the range of anything over 3000rpm's it seems to me that in reality, gasses will NOT have that much time to cool down the pipe. everything will be flowing like crazy through a turbo, which is also just making things hotter as they exit.

like i said, im not trying to start shit. i just want to see numbers on this "mystery" cooling exhaust. if someone gets mad by this post, please, prove me wrong. i just can't see that it makes that much of a difference.

What are you going to do with these numbers? even if you get them chances are they are not gonna mean dick to you, because you don't have a clue what going on anyway. I think its hilarious all these import racers trying to be all scientific about things they don't even understand. Honestly what good is data going to do for you if you don't know what it means. Ive been around cars my whole life, and i mean fast cars, and i honestly can't make head or tails out of this cooling effect you guys are jabbering on and on about.

but back to the original poster, 4 inch isn't very common, but go for it, on a turbo car it won't matter because the scavenging effects are minimal anyway. So once you get the exhaust to the turbo you want to get it away with the least amount of restriction. do remember that you want to start out with your exhaust at the size of the turbine outlet and them increase it at a 7degree angle. you can use simple trigonometry to figure out the length of your transition.

 

[Coup D E'Tat]

This thread makes my head hurt. I remember back when everyone swung from the 50-trim's nuts, and people running 550's with 20g's were common as daylight. Why must everyone on this site insist on a 3"? Who cares what the shit he wants to run, or what size exhaust Shep runs. Everyone knows everything.

That being said, I run a 3.5" with a Dynomax straigh-thru muffler welded maybe halfway through the system, along side of the driveshaft. It starts at 3" off of my O2 housing and expands to 3.5" right after the oil pan. Clearance was no big deal, and I ran it under the pumpkin. Coming out of the back is just a 3.5" pipe, and I think it sounds great. Not too loud, nice and deep, and cruises really quietly.

I wouldn't think 4" would be much harder to fit. My only concern was the muffler. Because the can is maybe 6" in diameter, is does hang a little lower than I'd like. I haven't scraped it yet, though.

 

[staticbrainwash]

listen here astard dsm. who the hell are you to say weather or not ill be able to understand the numbers. i didn't request them to be a "cool import guy" i was honestly curious.

and maybe if you've been around "fast, and i mean fast cars" your whole life, you should take a look at what info you've truly assimilated. so don't come into here spouting bull about how I won't understand. because i will.

honest curiosity is typically the only way to learn. maybe you should give it a chance. and give other people a chance when they want to learn.

all in all, you don't know me. you have no idea what i do and do not know. so don't come in here and talk shit to me like i know nothing.

the funny thing is, i even prefaced this all with "i don't want to start anything". it was genuine curiosity. i have now said my peace, put in my 2cents about 4" maybe being overkill. espically if you look into boost creep. im done, and i am espically done with you bastarddsm.

 

[bastarddsm]

listen here astard dsm. who the hell are you to say weather or not ill be able to understand the numbers. i didn't request them to be a "cool import guy" i was honestly curious.

and maybe if you've been around "fast, and i mean fast cars" your whole life, you should take a look at what info you've truly assimilated. so don't come into here spouting bull about how I won't understand. because i will.

honest curiosity is typically the only way to learn. maybe you should give it a chance. and give other people a chance when they want to learn.

all in all, you don't know me. you have no idea what i do and do not know. so don't come in here and talk shit to me like i know nothing.

the funny thing is, i even prefaced this all with "i don't want to start anything". it was genuine curiosity. i have now said my peace, put in my 2cents about 4" maybe being overkill. espically if you look into boost creep. im done, and i am espically done with you bastarddsm.

Thats just it, there *might* be one person on this board who would know what the numbers mean. asking for some numbers isn't the way to go about figuring out how shit works, I hate to break it to ya but if you don't know that the post turbo exhaust on a turbo motor has exactly dick to do with the powerband ( except in extreme circumstances) you got a lot of learning to do before you go and start asking for numbers. you need to stop asking questions and start reading, lots and lots of performance books. and no I am not trying to be god of all here, but this is stuff you need to know before you start spouting off. but hey what do i know i'm only 20, and on my way to a Phd in physics, it's not like i deal with data and numbers all the time or anything.

 

[staticbrainwash]

thats a gross generaliaztion about everyone on this board. so why to be a dick.

and how would numbers not help someone learn. it's all information, and it's all application.

and you've got to be kidding me that post turbo exhaust means nothing to the powerband. if that was the case everyone would stick with stock exhaust. and that would be fine. but now people move to full turboback systems which are yielding 15+ hp, PROVEN hp, on the dyno.

im done, if you truly care to continue this debauchery of forum posts keep it to pm's, i don't want to get this persons thread closed.

 

[BGRIPTP]

First off, honestly does it really matter how much the exhaust cools the air coming out of the exhaust?

Secound, time after time on DSM's a 3" downpipe, 3" test pipe, and a 3" catback has been proven with DSMs day after day, year after year, time after time, and dyno after dyno. People have made 800+ horsepower with the 4g63 with just the 3" exhaust. Just get with what everyone uses, and hell, if your under 350whp, Id probably only get a 2.5 inch, which would be plenty effecent enough. However, if it is cheaper to do the 4inch, you could do it. Your turbo is making enough backpressure for your engine, so however fast you can get the gasses out after the turbo, do it. Thats all that really matters, not if its 2 inch or 4 inch ehxaust, how fast you can get those exhaust gasses out of the way for the gasses behind it.

 

[suicidal2af]

how can you say exhaust doesn't cool much? you can put your hand in the tip of your exhaust and not get burned, now try that right when it comes out of the turbo? what's your egt guage reading, a little warmer than what it is at the end. The ideal exhaust setup is one that keeps velocity up, without creating a restriction, not so big that the volume of air in the pipe creates a restriction, and keeps the heat held in the pipe to keep velocity up also. Some big company needs to make a turboback that is ceramic coated and starts big and slowly gets smaller to keep velocity up to compensate for the heat loss. think of all the r&d it'd take to get the ideal setup there, haha. Until that happens, 2.5" or 3" mandrel is the tried and true.

Starts big and gets smaller?

Um, sorry, no. That will create what we call a restriction.

Keep in mind how a turbo works, people. As part of its nature it will do MOST of the exhaust cooling. Tapering your exhaust down will only create a restriction.

Like the old saying goes, your exhaust is only as big as its smallest point.

 

[bastarddsm]

thats a gross generaliaztion about everyone on this board. so why to be a dick.

and how would numbers not help someone learn. it's all information, and it's all application.

and you've got to be kidding me that post turbo exhaust means nothing to the powerband. if that was the case everyone would stick with stock exhaust. and that would be fine. but now people move to full turboback systems which are yielding 15+ hp, PROVEN hp, on the dyno.

im done, if you truly care to continue this debauchery of forum posts keep it to pm's, i don't want to get this persons thread closed.

once again get a clue!

 

[totaleclipse_05]

To the OP, stick with a 3" exhaust. Like everyone has said here, it is tried and true. If you were to come up to me and tell me you have a 4" exhaust I, honestly, would probably laugh at you because imo that is way to big, even for turbo.

 

[sho_tyme_psi]

Wow, I didn't think my little thread get everyone this worked up. I need to clarify a few things, I'm not doing this for cool the exhaust thats the last my worries. as far as my turbo here are the specs.

WET FLOATING BEARINGS
A/R .84 TURBINE HOUSING
A/R RATIO .70 COMPRESSOR HOUSING
SHAFT & WHEEL TRIM 64.5mm
COMPRESSOR WHEEL 60.5mm
I'm just getting the car running on it and hope to step up to a gt40R. Before I start getting neg. feed back on the turbo size remember this, this car will be street legal but not a every day driver. I know I wont be in the 4didgit club but would like to be damn close with spray.

 

[peregrine]

dont listen to these guys. if you do it and it doesnt work well, just go back to 3". i dont see a problem with it except for low end response and ground clearance. i myself will be going with a 3" downpipe and 3.5" exhaust. good luck

 

[fatafall]

4" is too big. You dont need it. Its unnecessary... Do it anyway. Haha. If its cheaper for you then what does it matter. Plus, Id like to see some pics of a 4" exhaust on a DSM.

 

[Coup D E'Tat]

I'm really interested to hear why everyone thinks 4" is "too big."

 

[ISUJakey]

I'm really interested to hear why everyone thinks 4" is "too big."

So would I. There appears to be a number of computational fluid dynamics, thermodynamics, and heat transfer experts here but yet nobody has posted some hard numbers. I look at as if sho_tyme_psi wants to run a 4" SS exhaust, go right ahead if he can make it work. I can forsee him running into some clearance issues but I'm sure they could be worked out.

 

[green92gsx]

I would say go for it. You'll never make a 4"in o2/downpipe combo though without relocating your alternator.
Do a 3'in o2/downpipe, then once past the oilpan and x-fer case expand to 4'in.