imported_magicguy

for a B18C motor
1. how much power am I looking to lose if going 2.25 exhaust instead of 2.5"?

approx.?

2. and with cams definitly go for 2.5 right?
once again, what is the power difference between 2.25"and 2.5" after cams installed?

3. if 2.25" header then 2.5" cat-back, is it just the same as 2.25 all the way back?

zeeman

iTrader: (1)

i felt a big difference when i went with a 4-2-1 header w/2.5" collector and 2.5" exhaust compared to the crappy DC 4-1 header and 2.25" exhaust on my built b16 (higher CR, stage 2 cams and valve train, p'n'p and all of the bolt-ons)
If internal mods are in the future definately go with 2.5".

armash

just the exhaust it self wont do much difference

chris_si98

on a semi-built motor it will

zeeman

iTrader: (1)

I totally agree with that...on mine 2.5" over the 2.25" made a big difference, but i changed to a header w/2.5" collector at the same time.

92extremehatch

a 2.5" exhaust is the way to go

imported_torscot

is the apexi ws2 a 2.5 exhaust?

Sassafrass

Unless your motor has some work done to it, I really dont agree you need a 2.5" system.

However honestly ask yourself this question, am I going to add more engine components in the future? So in other words SERIOUSLY are you gonna increase the hp? If your answer is yes then maybe you should go for the 2.5" exhuast now so you dont have to change it later. Do it once, do it right kinda deal.

But....... If your car is daily driven I would stick with 2.25" exhaust. Your gas mileage wont suck as bad and you wont loose the torque.

But again the difference is marginal on stock motors.



And also no one can just tell you want the difference is between: 2. and with cams definitly go for 2.5 right?
once again, what is the power difference between 2.25"and 2.5" after cams installed?

You know how many different kinds of cams and exhausts there are out there, not to mention no one motor puts out the same power.

EL_CIVIC

2.25..any bigger u lose backpressure and you lose torque..

2.5+ is for the turbo guys...

zeeman

iTrader: (1)

gunna have to disagree from my first hand experiences with N/A cars that have 2.5" exhaust there's definately no loss in torque.
If you doubt this, come for a ride in my car, i'll tell you what engine is in there after you go for a ride.

EL_CIVIC

well.. it wont be consistent unless there are dyno numbers to show an increase or decrease in power...

zeeman

iTrader: (1)

so why would so many people run 2.5" exhaust?
http://www.honda-tech.com/zerothread?id=1457951

I guarantee you IF there is a loss in low end its very minimal and the gains through out the rest of the rpm range out weight the minimal loss in low end.
Just out of curiosity, EL_CIVIC have you had 2.25" then switched to 2.5"?

EL_CIVIC

i belive such an exhuast is good for only really high compression motors.. ie. 11.5:1-13:1.. etc..

as for me..i'm boosted... im running a full 2.25 mandrel bent system.. its all i need..

zeeman

iTrader: (1)

you said yourself that 2.5"+ is for turbo guys. Why would you only use 2.25"? Thats gunna hold you back big time....unless you're only boostin 8psi or so.
Magicguy is obviously planing on some internal mods, so he should go with 2.5" for sure.

8.5K

Z already said it, you will not lose tq. even b16's benefit through the entire powerband with 2.5" vs. 2.25". actually, it was me that convinced Z to go up to 2.5" after i noticed the increase on my b16. and, gas milage will not be affeted from a larger exhaust. getting on the throttle more beacuse the 2.5" makes more power is why gas mileage will suffer....with that said, i'm staying 2.25". i'm willing to sacrafice a few ponies to reduce exhasut tone. but, 2.5" ideal. there a itb'd 230whp K24's running 3" right now, and losing no pwer across the range vs. 2.5". strictly gains.

zeeman

iTrader: (1)

thank you C.
i was waiting for you to chime in on this one.
2.5" is definately louder, quite a bit actually.

ADR3NLYN_EK

i have a ek with a jdm b16 motor and 2.25" custom piping, i ordered a 2.25" magnaflow muffler but they accidentaly sent me a 2.5". I guess this really makes no difference, being only .25" bigger, however it almost feels like i lost a bit of power (torque) under 4k...uh its probably just me...

USDMSIG

Just like others have said, you loose a bit in the lowser end, but gain up top, just decide what u want, Peak HP isnt always everything.

zeeman

iTrader: (1)

maybe on a stock engine. But when i switched to 2.5" i didn't loose any bottom end.