b18-c-rx

b18c, looking at about 300 bhp max power output

people running b18cs usually use 3" exhaust, but I'm led to believe (by corky bell) that I should run about 2.25". any input on this?

CivicEJ1

Go run open down pipe and then come back and talk to us.....for turboing, bigger is better...or you can say less restriction and less back pressure is better....

b18-c-rx

I am not sure, if it's too free-flowing, can it damage like my cat or the muffler or soemthing? i doubt it, but i'm just wondering, then, why everyone doesnt just buy 5" exhaust.

Evanmb44

5 in would be really hard to fit, not to mention nearly scrapin the ground (especially if the car is lowered) and it is just much simpler to run open downpipe or use a cutout if you want less restriction.

b18-c-rx

yeah that was half-sarcastic
but I have a GReddy SP2 Exhaust which is about 2.25" right now, and I don't want to sell it (I just bought it, but at the time I was not thinking about setting myself up with turbo). so do you think that 2.25" is actually too small, or is it just too far on the restrictive side to be safe if you're unsure?

I also don't really know where to get a 3" exhaust. If I have to get one, I want it cheap - any suggestions here?
thanks for your time

CivicEJ1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18-c-rx &raquo;</TD></TR><TR><TD CLASS="quote">yeah that was half-sarcastic
but I have a GReddy SP2 Exhaust which is about 2.25" right now, and I don't want to sell it (I just bought it, but at the time I was not thinking about setting myself up with turbo). so do you think that 2.25" is actually too small, or is it just too far on the restrictive side to be safe if you're unsure?

I also don't really know where to get a 3" exhaust. If I have to get one, I want it cheap - any suggestions here?
thanks for your time</TD></TR></TABLE>

Get yourself a free flowing cat and you'll be fine with what you got...

b18-c-rx

i already have 2.25" brand new magnaflow installed and running, works great, passes smog by a mile

so you think thatll work.. any other opins before i get too happy?

CivicEJ1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18-c-rx &raquo;</TD></TR><TR><TD CLASS="quote">i already have 2.25" brand new magnaflow installed and running, works great, passes smog by a mile

so you think thatll work.. any other opins before i get too happy?</TD></TR></TABLE>

Your good to go....

Don't get too boosted happy and go off driving with a lead foot....or kaboom...

b18-c-rx

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CivicEJ1 &raquo;</TD></TR><TR><TD CLASS="quote">

Your good to go....

Don't get too boosted happy and go off driving with a lead foot....or kaboom...</TD></TR></TABLE>
whats "too boosted" ??
if things are endangered, i'm going bigger diameter no matter what

b18-c-rx

bump

toolowsol

I have a 2" downpipe and stock cat on my b18c turbo right now, at 7psi it still makes impressive power, your 2.25 and hiflow cat will be fine. Next week I'm makin my 2.5" downpipe, installing a 2.5" high flow cat, 2.5" high flow resonator, so I'll let you know what kind of gains I see.

dasher

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18-c-rx &raquo;</TD></TR><TR><TD CLASS="quote">b18c, looking at about 300 bhp max power output

people running b18cs usually use 3" exhaust, but I'm led to believe (by corky bell) that I should run about 2.25". any input on this?
</TD></TR></TABLE>
Corky bell is wrong ... his chart in maximum boost says that a 500 bhp turbo charged car should run a 2.5" exhaust pipe. A 3" exhaust and downpipe will allow your turbo to spool up faster and will make you more power everywhere under the curve.

The exhaust velocity rules for NA no longer apply for turbocharged cars because the more important variable is now having a large pressure differentiation between the turbine housing and the downpipe.

I run a 3" exhaust and personally going to weld myself a 4" exhaust when I have some time .

Finland

I'm surprised to see the Corky Bell stuff, I don't recall that. I recall Corky saying the bigger the exhaust on a turbo car, the better...

I will have to re-read, it seems to contradict Bell's opinion on turbo exhaust..

RyanEJ8

You need to understand how a turbo works before you go saying that a large exhaust might be too free flowing. Turbos work on a pressure differential. Basically the idea is that the greater the pressure pre-turbine and the less the pressure post-turbine the more work can be created.

What does hot exhaust gas want to do right away? Expand. Therefore the greater area the exhaust gas has to expand (i.e. 3" exhaust), the more work can be created, the more horsepower made. No matter what size the turbo or power goals, 3" is not oversized.

DIRep972

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RyanCivic2000 &raquo;</TD></TR><TR><TD CLASS="quote">You need to understand how a turbo works before you go saying that a large exhaust might be too free flowing. Turbos work on a pressure differential. Basically the idea is that the greater the pressure pre-turbine and the less the pressure post-turbine the more work can be created.

What does hot exhaust gas want to do right away? Expand. Therefore the greater area the exhaust gas has to expand (i.e. 3" exhaust), the more work can be created, the more horsepower made. No matter what size the turbo or power goals, 3" is not oversized.</TD></TR></TABLE>



I also don't recall corky bell saying to use 2.25" for 300hp. I just remember him saying, "bigger is better." which is true.

totsie7944

first of all a 3" is going to show much better power than a 2.25". Turbos like to breath and a 2.25" is going to be very restrictive on it. I actually would be surprised to see you hit 300 wheel without cranking the psi up dangerously high.

Secondly, you DO need some back pressure even for turbos. A 3" is def NOT oversized and WILL NOT allow it to be "too" free flowing.

Thirdly, that 2.25" cat isn't going to help you at all. You should of at least gotten a 2.5" maybe a carsound, and hollowed it out and ran a 2.5" pipe through it soo it looks like that cat is still in place. Unless of course you have a concious for the environment.


Lastly, the more area the exhaust can expand, the more power can be created by the turbo, and it will allow for a quicker spool. I know of many turbo shops who swear by turbo gains on a 3" over a 2.5" exhuast with some proper tuning.

tegon-gsr

Im having the same problemnot sure what size to get im going for 300-350 hp but not sure if i should go with the 2.5 or 3 inch exhaust can 2.5 be ok for 300-350 on a b18c1 i will be building the motor in the next couple of weeks so i would like to up grade my exhaust as i turn up the boost.

RyanEJ8

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tegon-gsr &raquo;</TD></TR><TR><TD CLASS="quote">Im having the same problemnot sure what size to get im going for 300-350 hp but not sure if i should go with the 2.5 or 3 inch exhaust can 2.5 be ok for 300-350 on a b18c1 i will be building the motor in the next couple of weeks so i would like to up grade my exhaust as i turn up the boost.</TD></TR></TABLE>

Did you read the entire thread? My post in particular?

dasher

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">



I also don't recall corky bell saying to use 2.25" for 300hp. I just remember him saying, "bigger is better." which is true. </TD></TR></TABLE>

I took that figure straight from his chart from "Maximum Boost." He actually says that the phrase "bigger is better" is not true when it comes to Turbo. Go re-read it.

He is also wrong.

dasher

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by totsie7944 &raquo;</TD></TR><TR><TD CLASS="quote">
Secondly, you DO need some back pressure even for turbos.</TD></TR></TABLE>

This is not true for any exhaust system; NA, or Turbocharged. PLease stop refering to the term "backpressure" when talking about using ideal sized tubing.

What is true is that you want to have a properly sized exhaust tubing to maintain a certain ideal exhaust gas velocity for efficient exhaust elimination. With turbocharged cars pressure differentiation plays a more important role however.

jmal1919

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18-c-rx &raquo;</TD></TR><TR><TD CLASS="quote">b18c, looking at about 300 bhp max power output

people running b18cs usually use 3" exhaust, but I'm led to believe (by corky bell) that I should run about 2.25". any input on this?
</TD></TR></TABLE>

all has been said/debated before. In your case, you will be fine. I also believe/read that you want the least amount of restriction immediately following the turbine. Thus a 3" dp, to a 2.5" cat to your existing 2.25" exhaust would be a better compromise for your goals. That way, you can keep your existing catback exhaust, and still not choke exhaust flow too much to the point of concern.

DIRep972

iTrader: (1)

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

I took that figure straight from his chart from "Maximum Boost." He actually says that the phrase "bigger is better" is not true when it comes to Turbo. Go re-read it.

He is also wrong. </TD></TR></TABLE>

bleh, he says, "the best exhaust for turbo is no exhaust."

hypa

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">

bleh, he says, "the best exhaust for turbo is no exhaust." </TD></TR></TABLE>

He also added that silly chart that says 2" is sufficient for 200+whp, 3" for 500whp, and so on. I just read it again last night for other reasons, funny that it's a thread today.

dasher

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 &raquo;</TD></TR><TR><TD CLASS="quote">

bleh, he says, "the best exhaust for turbo is no exhaust." </TD></TR></TABLE>

I agree, he does contradict himself in that chapter.

nonvtecD

What this kid needs to know is no matter what size the exhaust is it isn't going to <U> hurt</U> anything (like he was worried about ) . It will just effect power and spool time. I know people running 4 inch exhausts.