Why does the Drag and Rev-Hard kit come with 2.25" piping when intakes for NA integras are 2.5"(AEM) or 3"(Injen)?

 

cause we're dealing with a turbo'ed car not NA...

going with a 3" IC piping would probably make the turbo LAG more noticeable.

 

I just thought that since the turbo is pushing more air into the engine than an NA car that it would at least have the same diameter piping.

 

but it's pushing air across a much greater length. from the compressor through the IC piping through an Intercooler and then through the last stretch of IC piping to the TB. Thats what about 2 to 3 times the length of a cold air intake?

 

I just looked in Maximum Boost, and it's a lot more complicated than I thought.

It also has to do with air velocity, air velocity drag, and piping diameter.

page 61-62 Maximum Boost by Corky Bell

 

what does it break down to?

 

What does it say?

 

well it goes into speed of sound (MACH), CFM, and calculating the max airflow.


I quote page 61-62 of the book Maximum Boost by Corky Bell.
the calculation seems simple enough but there are a lot of fractions that need to be divided by other fractions. and after the whole formula is drawn out it looks kinda complicated, the formula is:

Velocity = airflow divided by area
(It's a lot more complicated than it seems)


I dont know of any other way to put that in laymans terms so I just copied it word for word. I can also sketch out the formula in JPEG format if someone can host it for everyone else to see.

but basically the "book" says a large tube is bad, so who am I to argue?


[Modified by BlueShadow, 11:58 AM 3/31/2002]

 

quite true, but even If I cant figure out the formula out of the book here is how it came out.

the formula was Velocity = airflow divided by area
the numbers used in the example are:
-400 BHP
-600 CFM (airflow)
-2.5" (area)

now the formula is supposed to tell us if 2.5" is going to be the right size for a goal of 400 BHP.

the velocity comes out to 293 ft per second (velocity) they took that and divided it by 1100. the speed of sound is 1100 feet per second (MACH).

293 / 1100 = 0.27

The book doesn't say why .27 is good or bad it just says based on that number that 2.5" is adequate.

or maybe it's cause the velocity in the 2.5" tube didn't go over 450 feet per second (0.4 MACH), which as stated in my previous post is the point after which the air starts to get increased drag and increased drag leads to flow losses.

 

Not trying to question the book because he is far more knowledgeable than I, but just trying to throw ideas out there.

If the problem is too much velocity then doesn't velocity increase with smaller and longer pipes but decrease with larger and shorter pipes. So if the pipes are longer like you said won't making them bigger cut down on velocity?

 

yes, and thats pretty much what I quoted out of the book. I'm not exactly sure how much the length of the IC piping has to do with the velocity. But the main thing is the IC piping diameter throughout the system.

 

Yeah I two have to work out the size of my intake also…

As many of you know, im doing the Max rev turbo thing.. but of course it did’t come with a intake tube, I was going to hack open my 3” CAI and make that my intake tube from the IC.

But that was one of my problems my IC pipes are 2.25” where as my CAI is 3”
I figured.. having a 3” intake pipe would be fine. .but now I wonder if I should make it all 2.25”

So drag intake pipe is 2.25’ ? to the tip of the throttle body ???

Also what size is the throttle body on engine intake? ( im 2 lazy to go outside and rip off my CAI and measure the size of the intake )


Regards James