# turbooo



## themudboy (Sep 5, 2002)

Do i need to worry about having 2in piping from cat-back with a turbo?


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## chimmike (Oct 17, 2002)

you've got a lot more to worry about with turbo than cat-back piping.


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## Hawaii_SE-R (Apr 30, 2002)

themudboy said:


> *Do i need to worry about having 2in piping from cat-back with a turbo? *


If you are planning to turbo later, yes, 2" would still be too small, just ask any girl.


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## samk (Feb 26, 2003)

hahahah yes...gotta let it flow out.


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## Katana200sx (May 13, 2002)

u need atleast 2.5" but best would be 3"


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## urbanracerone (Apr 25, 2003)

most defenitly 3' TEAM G4L NYC


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## Hawaii_SE-R (Apr 30, 2002)

urbanracerone said:


> *most defenitly 3'*


3 feet diameter may be about 12 times too big. Like others have posted, 3 inches would be fine. Turbo'd cars will not be negatively affected by larger exhaust systems as N/A cars would due to positive and negative backpressure.


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## rios (Jun 10, 2002)

besides power loss, what else would a 2 inch exhaust do to a lighlty boosted car?


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## javierb14 (Jul 9, 2002)

more lag and it would probably be a little quiter....with a muffler of course.


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## By Nature (Apr 30, 2002)

remember with turbo you want to make size as large as possible (unlike N/A).. It's just anything more than 3" wont fit


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## 1fastser (Sep 30, 2002)

2" diameter piping would cause too much backpressure on the thrust bearing in the turbo and would eventually lead to turbo failure.

3" works great.

Jody


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## ForsakenRX7 (Mar 14, 2003)

Yea you would definatly wanna open that up a half inch. But I'd say go with 3. Are you running internal waste gate or external? Cause with a 3 inch exhaust on an internal wastegate boost creep can be a problem unless you get a god port job done.


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## Henry8866 (Apr 11, 2003)

2.5" is big enough. 3" is too big unless you're gonna be putting out 300+ rwhp.


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## anthony jackson (Jul 16, 2002)

Henry8866 is right, i mean why would you want to but two and a half in. pipe on a stock civic, when it is only putting out about 120bhp. Its the same thing with the turo. if your only gonna hit about 200hp, your sill gonna need a little bit o back pressure for that little 4 banger. in my opinion 2.5 is enough. that is unless you plan on going T3 or higher with your turbo set up.


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## By Nature (Apr 30, 2002)

I believe back pressure concept doesn't apply to turboed engines.. whatever goes in the exhaust pipe is just a waste and you just want to get rid of it... you don't care about exhaust velocity or pulse or anything like that.. most optimal setup is open downpipe...
what matters now is intake and intercooler piping to reduce the lag, while not choking the turbo


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## Henry8866 (Apr 11, 2003)

yah but why waste the extra money on 3" when 2.5" would flow just as good. The 4 cylinder won't be putting out enough exhaust to cause backpressure on that. He would be saving a few hundred on the exhaust going 2.5" too.


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## javierb14 (Jul 9, 2002)

u want the biggest differences of temp, pressure, and velocity between the manifold/turbine and downpipe. basically u want a "hot" mani and a cold dp or one that conducts heat away quickly. flow or velocity after the turbine doesnt really make a difference as it does in a NA car since the turbine has used up most of the energy in the exhaust flow already. u want high pressure before the turbine and lower pressure in the dp.

its easy to optimize all three and gain performance if u use a big dp, but sometimes cost is a factor and 2.5 bends either stainless or mild are cheaper than 3.0. the other factor is how much room do u actually have for a 3.0 inch system.

facts:

mild steel dp's
-a mild steel dp will conduct more heat than a stainless dp
-it wont last as long as a stainless dp
-doesnt have the "bling" factor that stainless does

stainless dp's
-conduct less heat (usually considered more of an insulator) than a mild steel dp
-lasts longer due to its greater corrosion resistance
-can be polished...then turns golden after a couple of heat cycles...bling yo

only wrap the exhaust system if ur worried about melting nearby parts/underhood temps. wrapping the exhaust insulates it and shortens the life of the material.

IMO, i would run a open dp or an e-cutout......but its * loud * and it *stinks*


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## themudboy (Sep 5, 2002)

*piping*

i allready had 2.5 and then dropped down to 2. and when i had 2.5, that piping hung from the bottom of my car. i scraped that damn thing when i went over any thing. and having 3" piping, oh hell no. but if worse comes to worse, i will just go back to 2.5. and im running 227 with 7psi. by the time the motor is in and shit, i can run up to 18psi. she's gonna be a sleeper


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## anthony jackson (Jul 16, 2002)

agreed with the tech lesson, but in themudboy's case, his clearance is the issue. so the 2.5 would be better in his unique case. And hell yea on the sleeper path dude. When my car is turbo'd im goin sleeper all the way!


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## javierb14 (Jul 9, 2002)

really, i just put a 2.5 in. cat back on my brothers 97 200sx....fits fine with room to spare.....


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## themudboy (Sep 5, 2002)

did u custom make the piping or did u buy it? if u baught it, from where?


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## javierb14 (Jul 9, 2002)

the straight is just some Rath 18gauge 304 stainless with a 90deg welded on. the pipe that bends over the rear beam is actually from a maxima. its also 18 gauge 304 stainless mandrel bent. fwiw, the A32(95-99) maxima rear beam exhaust section fits on the b14. i'll post some more pics later.


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## bizzy b (Apr 13, 2003)

it all depends on the size of the turbo and the amount of power you want to put out. with a small turbo only putting down 200-250hp max 2.5" piping is better. remember, its the speed of the gasses exiting the turbo that matters. if you use too small of a pipe it won't be able to get out quick enough, but if you use too large of a pipe it will just sit in the exhaust pipe moving too slow to be useful. if you're running a huge or even relatively large turbo you will need 3" piping but only if you're running upwards of 15-18psi. with less than that the exhaust gasses will just stagnate and take their merry ol' time getting out you exhaust.


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## javierb14 (Jul 9, 2002)

exhaust velocity after the turbine doesnt matter. you will make more torque from the boost arriving sooner than u will from any sort of scavenging effect after the turbine.


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## 1fastser (Sep 30, 2002)

FYI, 3" fits fine if it's made correctly. My 3" fits better than my 2.5" because it's made a little different. Just my .02


























laterz...Jody


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## 1fastser (Sep 30, 2002)

Also, it doesn't hang down as low as the 2nd pic is indicating. That's due to not having it on the hangers. Nothing is tight in the pics either, I was just checking clearance....*IT'S ALL GOOD!*

laterz...Jody


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## holy200sx (Jan 8, 2003)

anthony jackson said:


> *Henry8866 is right, i mean why would you want to but two and a half in. pipe on a stock civic, when it is only putting out about 120bhp. Its the same thing with the turo. if your only gonna hit about 200hp, your sill gonna need a little bit o back pressure for that little 4 banger. in my opinion 2.5 is enough. that is unless you plan on going T3 or higher with your turbo set up. *


You. Sir, Are an idiot. (j/k) no no

backpressure is bad

let me repeat

bACkpressure is Terrible

one more time for the visually challenged

BACKPRESSURE IS BAD 

the reason big pipes/wrong pipe diameter causes Backpressure is because its too big.. you want the ideal size, so that your exhuast flows perfectly.. for example.. if you iddnt give a rats ass abuot noise, or pollution. unbolt your header, and drive.. and you will feel No backpressure.. but while your exhaust trys to flow out.. its called exhuast velocity.. kinda like when you put water in a drain and it swirls.. thats the perfect velocity.. instead of bubbling.. Now, when you have 4" pipes. "air" bubble occour.. actually.. just.. 1.6.. even 2.0L wont make enough exhaust to fill 3..4.. inch pipes.. 
it will be pushing too little exhaust out.. adn wont be filling the pipes.. 

ending here

NA 2.0 is perfect

turbo 2.5 is ideal. 3.0 is good for HIgh HP apps.. 

BACKPRESSURE IS BAD ALWAYS END OF STORY


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## 1fastser (Sep 30, 2002)

I would say 3" is ideal. I noticed 12-15hp gains when I switched from 2.5" to 3" on my t25 BB setup. 

*ANY* backpressure (for turbo applications) is not desirable. Backpressure fights *against* the thrust bearing in the turbo, making it work against itself, and WILL eventually lead to turbo failure!!!

READ THIS AGAIN.

laterz...Jody


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## anthony jackson (Jul 16, 2002)

i wish that was my car i was looking at.!


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## javierb14 (Jul 9, 2002)

> turbo 2.5 is ideal. 3.0 is good for HIgh HP apps..


the biggest (usually most expensive) exhaust setup u can use on a turbo car is ideal, no matter what the hp level. not only does backpressure effect power output, it also effects response time or lag of the system. remember, turbines are pressure dependent. the larger differential u have between the exhaust manifold and the dp/exhaust system....the better the performance!

* best setup*
-high pressure in exhaust/turbo manifold
-lowest possible pressure in dp/exhaust system

an example of low pressure in the dp/exhaust is an open dp. with an open dp u r basically venting to atmosphere.....its hard to get much lower pressure than that unless u stick a Hoover in ur exhaust system 


1fastser,
nice setup  do u have any dynoplots of ur setup? from what i see, ur running a bb T3/T4, a log mani, and a 3.0" dp.


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## 1fastser (Sep 30, 2002)

> _Originally posted by javierb14 _*
> 1fastser,
> nice setup  do u have any dynoplots of ur setup? from what i see, ur running a bb T3/T4, a log mani, and a 3.0" dp. *


bb? That's an fmax stage II. Click the beast link for more pics. The car isn't running with the fmax setup yet...but it's damn close! I just have some little things left...i.e. vacuum lines, fuel lines, fluids, ect...

I should be putting down over 400fwhp. We shall see...

laterz...Jody


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## themudboy (Sep 5, 2002)

No one knows the answer. I heard from so MANY people to have backpressure. Then I heard from some people not to have back pressure. So what I'm getting from holy200sx is that there should be not backpressure. Are you 100% sure on that?


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## ForsakenRX7 (Mar 14, 2003)

Turbo cars do not need backpressure. If you could run A/C ducts for exhaust on a turbo car that would be great. Naturally aspirated cars on the other hand are differant. they need backpressure. you can actually hurt performance on a N/A car by having too large of an exhaust. I cant remember the technical explantion for this so I'm sorry I cant be all technical about it.


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## 1fastser (Sep 30, 2002)

Correct...turbo'd cars *DO NOT* need backpressure. It fights against the thrust bearing in the turbo and will eventually lead to turbo failure.

Jody


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## Hotshotnissan (May 10, 2003)

what so good about a t28 than a t3/t4? and what be the choice?


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## go4broke44 (Jan 14, 2003)

with N/A cars, backpressure is needed to have a scavenging affect, and with the right flow, pull the exhaust gases out of the manifold. now with a turbo application, your putting a turbine in the way of the exhaust gases. so therefore, all your backpressure is between the manifold and the turbo, as the engine has to push on the turbine to get it spinning, before it does any good. thus, anything after the turbo doesnt matter. in a way, this is like biology class, talking about equilibrium. you have an area of high pressure (exhaust pre-turbo) and an area of low pressure (exhaust post-turbo). therefore, you would want to have as little pressure post-turbo as possible, so that the exhaust gases move from the high pressure area to the low pressure area quicker, ie, more efficiency in your turbo system. this is why 3" is ideal for exhaust on a turbo application, to get the lowest post-turbo pressure possible, so that you get optimum flow across the turbine. hope this clears things up


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## holy200sx (Jan 8, 2003)

exhaust velocity.. technical def.


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