Chillinit

I have my 3" exhaust from my turbo setup and I'm wondering if I can use it on my n/a setup.

Setup details.

-b18c1 plant...81.5mm bore
-12.0: 1 compression
-buddy spec 3+ cams
-upgraded valvetrain

Will I lose too much torque?

null.

you're not pushing in alot of air compared to having turbo. 3" is too big for n/a, you will lose back pressure. may want to cut it down to 2.5" or 2.25"

AllMotorMark

i bet you make more power on the 3 inch, don't listen to all these back pressure "miths" its not about back pressure its about scavanging, you will not loose hp running the 3 inch, go for it

1allmotordc2

you are going to lose a lot of back pressure

AllMotorMark

yes you are LOL
, less back pressure = equals more power

GOLDBERG

yeah i doubt youd lose that much..people make more power usually open header right?so why would 3 inch make u lose power??i'd say just use your current exhaust

98itr0448

less backpressure= more power but loud as hell on n/a.

Ti3d in

Backpressure is bad, but it helps keep exhaust velocity up, which creates more torque to an extent.

Chillinit

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GOLDBERG &raquo;</TD></TR><TR><TD CLASS="quote">yeah i doubt youd lose that much..people make more power usually open header right?so why would 3 inch make u lose power??i'd say just use your current exhaust</TD></TR></TABLE>

This was one of my reasons for posting this. People run open header at the track all the time and clock better times. Is it because they are actually making more power or the fact that the runs are being made minus the weight of the exhuast?

How much louder will the 3" be?

rice4life

iTrader: (3)

3" exhaust on NA car is going to be loud as hell, i did it before. for some unknown reason, my 3" exhaust was even louder than an open header car. i guess the exhaust pipe just amplify the sound like a trumpet. you will loose some low to mid rpm torque but will gain hp on top end.

zz10xx

i have 3" on and its the loudest exhaust ive ever heard.

98 coupedelux

i have a b16a in my coupe and before i did the swap i had a boosted y8. keept all the piping which is 3" kept my apexi dunk on there and it isnt loud at all i idle realy quiet and the vtec over sounds the exhaust

Sr20 B12

A 3" on N/A is prefect for it your running huge cams. Anything other than that is not good.

hype r 555

if you didn't have the cams i would say no go 2.5 but with those cams and your setup you shold be just fine .. you notice a little bit of low end loss , but you will make up for it in top end gains ... jmo

S@nt0s

i plan on steppin up to a 3" on my 2.0L
but for a 1.8 i think 2.5" is enough.....but having less backpressure will take a bit of torque away, i say is so so since your only a 81.5 bore maybe if you had at least a 84 then go for it but let us knwo how it goes!

All Motor EH2

I'd say stay with your 3"

codeh22a4

question,i have a 99 prelude base manual with 11:1:0 high compression pistons type s cams(jdm lude type s)dc sport header,if i put a 2.5 custom made without cat. and resonator just plain 2.5 all the way from header to muffler will i lose backpressure?

Sr20 B12

Whats all this worry about backpressure? You want as little back pressure as possible, espically on a high reving engine. 2.5" is ok for your Prelude engine. 3" is also ok. But don't expect hugh power gains from either one (unless you have an exhaust cam with huge over lap or spraying).

BlackRocket

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ti3d in &raquo;</TD></TR><TR><TD CLASS="quote">Backpressure is bad, but it helps keep exhaust velocity up, which creates more torque to an extent.</TD></TR></TABLE>

with a 3 inch and no back pressure your air is just slowly flowing out instead of smooth and fastly being forst out, if anyone can kinda understand that.

GOLDBERG

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

This was one of my reasons for posting this. People run open header at the track all the time and clock better times. Is it because they are actually making more power or the fact that the runs are being made minus the weight of the exhuast?

How much louder will the 3" be?</TD></TR></TABLE>

they "usually" make more power..but not always

specie

No backpressure NO back pressure. You do not want back pressure, back pressure does not increase the exhaust velocity, back pressure does NOTHING to help your power output. It just hinders the scavengering effect. You get more torque or better low/midrange with smaller exahaust diameter because gas velocity is faster in a smaller pipe vs one that has larger diameter. It has nothing to do with backpressure.

I had a 3" thermal exhaust with a rather large magnaflow resonator and it didn't sound too loud, but it was louder than a 2.25" exhaust setup. I didn't notice much of a difference because I switched to a jdm dc 4-1 header when I switched to the 2.25" thermal.

I ran open header at the track and ran the same time as I did when I had the exhaust on.

Are people making more power with open header?

DA6righthand

i found this link somehwere, i think it ws off of tt.net. it might help ya decide http://www.nsxprime.com/FAQ/Mi...y.htm

thanx
justin

Sour Diesel

Well since you have the 3 inch piping already, take it off and put on 2.5, go to the track or have it dynoed. If you get more power keep the 2.5, if you get less put the 3.0 back on.

rev limiter

great article but why are there na people with 220-250 whp running open header at the strip ??? According the article you will make more power with exhaust

codeh22a4

well i got a 99 lude 2.2vtec with a custom made 2 1/4 exhaust without cat or resonaitor,should i get a 2.5 custom exhaust without cat and resonator?