how big of a difference will 2.5 give me over 2.25 exhaust piping with a stock engine? Im debating on wether to get the comptech exhaust or hytech.

 

Exhaust diameter performance is dependant on how much HP you are making.

You go too big or too small and your performance will suffer.

You need about 1 square inch of cross sectional area per 60hp to the flywheel.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
2-1/4" up to 210HP @ the flywheel (about 180-185 whp)

2-3/8" (60mm) up to 235HP @ the flywheel (about 200-207 whp)

2-1/2" up to 265HP @ the flywheel (about 225-235 whp)

2-3/4" up to 325HP @ the flywheel (about 275-285 whp)

3" big for big HP (Forced Induction: &gt; 275 whp)
</TD></TR></TABLE>

A stock B18C1 puts out about 150whp.. so if you ONLY want bolt ons, 2.25" is perfect. But you should plan the size of your exhaust based on how much HP you hope to have when you are all set and done modifiying your car.

 

so when i get my jdm 4-1 header(2.5)...
should i modify my stock cat to mate up with my rs-r exhaust(2.36)?

 

Does the comptech muffler or any other type of piece for the comptech exhaust rust? b/c i thought i saw a kid selling his and it had rust on the back part of the muffler?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by skunkintegra &raquo;</TD></TR><TR><TD CLASS="quote">so when i get my jdm 4-1 header(2.5)...
should i modify my stock cat to mate up with my rs-r exhaust(2.36)?
</TD></TR></TABLE>

Your stock cat won't bolt up to a 2.5" collector, and you don't want to go from 2.5" to 2.36" , its backpressure city which is one of the things you are trying to remove with an aftermarket exhaust system.

 

wtf do i do then...
i already bought the 2.36 rs-r ex mag???
whats a good 2.25 header???

F***

edit-- but since i dont have over 200 hp...dont i want a little backpressure???


Modified by skunkintegra at 9:37 AM 7/13/2003

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by skunkintegra &raquo;</TD></TR><TR><TD CLASS="quote">well ****....wtf do i do then...
i already bought the 2.36 rs-r ex mag???
whats a good 2.25 header???

F***

edit-- but since i dont have over 200 hp...dont i want a little backpressure???</TD></TR></TABLE>

do what i did.... USDM 4-1 DC SS header + 2.25 carsound + comptech axle back

 

to try and answer the other question...
did ur comptech rust??

thanks guys!!


Modified by skunkintegra at 9:38 AM 7/13/2003

 

You could always use a stepped design in your exhaust. From the cat(buy a carsound 2.5") have a muffler shop weld a flange that transitions from 2.5-2.36. It's not ideal but it's still better than stock. Plus if you ever decide to upgrade you could always get a new flange and piping.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by skunkintegra &raquo;</TD></TR><TR><TD CLASS="quote">well ****....wtf do i do then...
i already bought the 2.36 rs-r ex mag???
whats a good 2.25 header???

edit-- but since i dont have over 200 hp...dont i want a little backpressure???</TD></TR></TABLE>

Nope, you never want backpressure.. thats a myth. The key is exhaust velocity, which is why diameter has such a huge impact.

Depending on what you want to do, it may be better to get a new exhaust than a smaller header at this point.

If I had to recommend a 2" header for mild NA (note: There are no 2.25" collector headers for integras. All the non 2.5" collectors are designed to matte up to the stock cat which has a 2" inlet) it would be the comptech 4-2-1 (not the race header). If you look at the great header test, it kept its ground with the 2.5" collectors.

 

man...i just dont know what to think...
everyone keeps telling me i'll be okay...

i asked my local shop guy...
maybe u've heard of him... joey keyman....
http://www.excessiveautosports.com
(note paragraph on the right - "other news")
he seems to think i'll be all right too...

soo, once again....i'm confused

 

You will be ok if you do a step down in exhaust size.. its just not going to be a well setup exhaust system, which is a very important area of your engine. So your gains for all of our modifications are going to be effected by it.

The only situation you want where the exhaust diameter is not consistant, is a slight increase in size as you get further away from the engine, which is called stepping and prevents exhaust reversion.

 

FYI, the OD of a JDM ITR 4-1 header is 2.5". but the ID (what actually counts, the diameter of where the exhaust actually flows) is around 2.36" or so.

 

Yes, but catbacks are also measured OD, so they also have a smaller ID.

The only component of an exhaust that is commonly measured in ID are cats/test pipes. This is because most of them are universal and muffler shops/etc need to know the exact inner size to fit them with stock exhaust components.