first off, i copied this from the magnaflow website :

"As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4 to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque."

Horsepower ---- MUFFLE INLET -------- / OUTLET
------------------- Single exhaust ---- / Dual exhaust
100 to 150 ----- 2" to 2-1/4" ----------- 2"

100 to 200 ----- 2-1/4" to 2-1/2"-------- 2" to 2-1/4"

150 to 250 ----- 2-1/2" to 3" ----------- 2" to 2-1/2"

200 to 350 ----- 2-1/2" to 3" ----------- 2-1/4" to 2-1/2"


so, i was going to get an exhaust system pieced together at the muffler shop, and i wanted to know what pipe size to get, and i have a zc and its a 90 crxsi, but i do want as much lowend torque as i can get, cause i do a lot of stop and go city driving, so if it says to go one size up from OEM, then what is the OEM piping size on a CRX SI ? or on an 89 Integra since its a ZC ? cause i had an old aftermarket exhaust system on it so i don't know the OEM size. also i wanted to have two tailpipes out and one inlet, and it looks like on the chart above that the outlet tailpipes are smaller size than the inlet? which is strange?, but thats what i'm going to go by.

anyone know what size would be best ? thanks for any info

also i was wondering how to measure the piping size of an exhaust system on a car, would i put measuring tape around the outside of the pipe? cause when i did this, it did'nt look right, it seemed to be pretty big in size? thanks


Modified by crxaddikt at 8:23 AM 9/2/2004


Modified by crxaddikt at 8:24 AM 9/2/2004


Modified by crxaddikt at 8:24 AM 9/2/2004

 

I have one with the 2 inch and one with 2.25 inch. The difference is the noise level. I cannot tel much difference. I would go with the 2 inch if low end torque is desired. Be sure to have a resonator put in line just behind the cat or it will sound very raspy. The resonator helps to make the tone lower and sound less irritating

 

I don't know if that guide is very accurate. Pipe diameter isnt really decided by the horsepower output but more by a combination of your displacement and the horsepower it creates. There is a thread somewhere in the general forum (Maybe?) that went over this and will help you get a good idea of what you're looking for.

 

My opinion:

Get it out of your head right now that any engine needs 3" piping. Anything short of a 6+ liter diesel producing over 400 ft.lbs should not use anything at or above 3". Yes, companies like Banks use 4" and Greddy uses 3.1" blah blah blah... but they are selling it to the masses who have no experience in anything car related and have the "bigger is better" mindset.

If you're dealing with turbo's and are above 200HP, then I'd go with a 2.5"
NA cars with less than 190HP would do best buy using a 2.25" for all around drivability. But this is also the catch 22 with Hondas. Since they rev so high, a bigger exhaust would be benefical at high RPM's, but lag in the low RPM's.

This is a choice to be made by the person who is getting an exhaust. If someone makes you an exhaust, make sure its mandrel bent (if no, why are you making it?).

Point being: Unless you have an altered engine (+CR, valvetrain, etc) I would not see the point in using a tube larger than 2.25"....maybe maybe 2.5"

Rich

 

i knew i would never get 3" or bigger, i was wondering more of peoples opinions on which is better as far as 2", 2.25", or 2.5" and which is best for having good balance between lowend and highend rpm power.

after seeing peoples opinions and reading around, i am going with 2.25" piping, maybe in stainless mandrel bent from kteller http://www.Kteller.com
then see how much it is to weld the pieces together at a muffler shop, with a magnaflow 5"X8" oval muffler thats 18" wide (horizontally) and have two tailpipes exit out the bumper kind of like stock, it would'nt look too much like aftermarket since it wouldnt be all shiny, and would'nt get attention and still have good power over stock.

only reason i am forced to get a new exhaust is my stromung catback which i have had since 1998 has a broken weld around one of the pipes and is about to disconnect, but is still driveable right now, but its not going to last, and unfortunately they don't make them anymore as i understand, and i don't like any of the cat back systems i see around, since they are all like a single 4" tip, and i personally like dual tips 2.25 or 2.5".

 

Not always true. Like I said it depends on your displacement. Also, if you're boosted. Turbos need the exhaust to have as few restrictions as possible to move air out as fast as possible. I could see using 2.5 or even 2.75 pipe on a boosted Honda. Maybe even a 3" pipe on real built boosted motors.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revolver &raquo;</TD></TR><TR><TD CLASS="quote">Not always true. Like I said it depends on your displacement. Also, if you're boosted. Turbos need the exhaust to have as few restrictions as possible to move air out as fast as possible. I could see using 2.5 or even 2.75 pipe on a boosted Honda. Maybe even a 3" pipe on real built boosted motors.</TD></TR></TABLE>

Not even boosted engines need 3". Unlike current thought/rumor turbo's need backpressure to work, and supplying it is crucial to proper spool and effieciency.

I've had dozens of rides in WRX's with 3", but alwas come home to my 2.5" and am happy.

2.5" or smaller...

Rich

 

(Pardon me for reviving a old post but....)<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SJcivic &raquo;</TD></TR><TR><TD CLASS="quote">

Not even boosted engines need 3". Unlike current thought/rumor turbo's need backpressure to work, and supplying it is crucial to proper spool and effieciency.

I've had dozens of rides in WRX's with 3", but alwas come home to my 2.5" and am happy.

2.5" or smaller...

Rich</TD></TR></TABLE>

You sir are incorrect. Sorry.

 

I've been trying to make this decision too for my upcoming turbo upgrade. I bought a greddy TD04 and the downpipe is only 1.9" ID. Would it be worth while to go from that to 3" mandrel bent the rest of the way out? I was figuring the kit came with that size downpipe for a reason, so if the exhaust is choked down there, is it going to be benificial to have 3" the rest of the way?

Hope you don't mind me tagging on to your post.

 

The td04 isnt very big at all but that is a tiny down pipe! If you're not doing anything other than street driving then leave it alone. I would personally make it bigger though, that is just way too small.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revolver &raquo;</TD></TR><TR><TD CLASS="quote">(Pardon me for reviving a old post but....)

You sir are incorrect. Sorry.</TD></TR></TABLE>

Leaving it at that is making myself think that you haven't had too much actual experience with turbo exhausts. Can you give some references, examples of how/why your opinion is as you stated before.

Rich

 

You dont exactly have any evidence either. Just a load of bullshit that sounds like you copy/paste it on here. It wouldnt make sense to me why a turbo would need back pressure because the exhaust gas needs to escape as quickly as possible. A tiny pipe would prevent that. Back pressure is needed in the manifold to help suck out remaining exhaust from the combustion chamber upon the exhaust stroke. However not all setups use this method. Post some "evidence, quotes or references" to prove otherwise, and I will rebuddle(sp?) with my own.

 

i'd have to side with revolver on this one. i'd hate to think of running 22psi on a 2''-2.25'' exhaust.

 

Stay in the 2 1/4 - 2 1/2 area for your ZC needs, larger is not required. After that, your biggest restrictions will be the number of bends, catalytic converter and muffler.

Back pressure in any engine application will cause power loss, get your back pressure to be neutral with the right exhaust setup and you'll be fine.

 

Just use 2 1/4 pipe or get a greddy

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revolver &raquo;</TD></TR><TR><TD CLASS="quote">...sounds like you copy/paste it on here. It wouldnt make sense to me why a turbo would need back pressure because the exhaust gas needs to escape as quickly as possible.</TD></TR></TABLE>

Oh, why thank you. But infact a turbo does need backpressure to function at the turbine. (Lots of time has gone into this discussion on the Subi boards), with even sources from Garrett themselves through one of the local WRX, Evo, Z, shops in the Bay Area (thanks to Shiz @ Vishnu) and Clark from Innovative Automotive.

Yeah, you do want the gas to flow out the exhaust as quickly as possible, but there are a lot of other variables that come up in this. Idealy (with what your saying), is that a turboback setup would be beneficial if it was as short as possible without any backpressure. MattSpec did this (straight turbo, no exhaust) and found a couple extra horsepoer, but lost about 3-5 ftlbs Tq. Some people read that as "GREAT, extra horsepower" But it never sits right with me about losing the actual power, and just gaining effiency.

Oh well, I have my opinions and you have yours, and in this world we're equal. But if I was to advise anyone on turbobacks, I HIGHLY suggest to be moderate and go with 2.5".

Rich

 

There is no need for exhaust, just run a down pipe or straight header.

 

For a non turbo ZC 2.1/4 and be done with it. You need low end torque for daily use. This diameter will provide you with the correct amount of back pressure for real world driving. Any bigger and you'll have to rev it out more for the car to pull off the bottom.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Snapshift &raquo;</TD></TR><TR><TD CLASS="quote">For a non turbo ZC 2.1/4 and be done with it. You need low end torque for daily use. This diameter will provide you with the correct amount of back pressure for real world driving. Any bigger and you'll have to rev it out more for the car to pull off the bottom.</TD></TR></TABLE>



-Jon

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SJcivic &raquo;</TD></TR><TR><TD CLASS="quote">

Oh, why thank you. But infact a turbo does need backpressure to function at the turbine. (Lots of time has gone into this discussion on the Subi boards), with even sources from Garrett themselves through one of the local WRX, Evo, Z, shops in the Bay Area (thanks to Shiz @ Vishnu) and Clark from Innovative Automotive.

Yeah, you do want the gas to flow out the exhaust as quickly as possible, but there are a lot of other variables that come up in this. Idealy (with what your saying), is that a turboback setup would be beneficial if it was as short as possible without any backpressure. MattSpec did this (straight turbo, no exhaust) and found a couple extra horsepoer, but lost about 3-5 ftlbs Tq. Some people read that as "GREAT, extra horsepower"

But it never sits right with me about losing the actual power, and just gaining effiency.

Oh well, I have my opinions and you have yours, and in this world we're equal. But if I was to advise anyone on turbobacks, I HIGHLY suggest to be moderate and go with 2.5".

Rich</TD></TR></TABLE>

OK, thats more along the lines of something I can agree with.

 

taken out of a honda performance book:

d15, d16: 2'
B16, ZC, LS: 2.25'
GSR, R, H22, B20: 2.5'

These are good sizes to start with if you have an intake and exhaust. If you throw more stuff into the mix such as headwork or cams, you may want to add another 1/4' inch to the formula.

** don't forget that all the 4g's: CRX, hatchie, 4 dr. and the old school tegs all have 2 more bends than most every other honda. On a 92-95 civic the exhaust comes straight back, bends to the right and then comes out on the right rear.
On a crx, hatch, and old school tegs, it comes straight back, to the right, down, to the left, and then back down out of the left rear. That's four bends! That might be reason enough for most people to go ahead and get the next larger size.

I'm running a B20 right now with 2.5 muffler, 2.5 piping, 2.5 catco cat, and with an ITR header with 2.5' collecter. it is loud and raspy as fu&lt;k. But it has awesome power from 4k up. I also got this size knowing i'm adding some 404's later.