the chargepipe going from my compressor housing all the way through both sides of the intercooler is 2.5", so i ordered an ebay CAI to make my upper chargepipe, but the problem is it comes in 3" (even though it clearly said 2.5" diatmeter on the ebay auction). i'm kind of stuck with it. i guess the quesiton is will i have any type of air flow problems if i mate the 2.5" charge pipe to the 3" charge pipe? i think i may have read somewhere that the volume of air is affected if the same diameter charge pipe is not used throughout the whole charge piping system.

 

wrong forum but 3'' piping may be a little big for you app.

 

ahh ****..can a moderator move it for me? i didn't even notice.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AzntaggeR &raquo;</TD></TR><TR><TD CLASS="quote">ahh ****..can a moderator move it for me? i didn't even notice. </TD></TR></TABLE>

youll be alright. if anything, you might get slightly increased spool time.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AzntaggeR &raquo;</TD></TR><TR><TD CLASS="quote">i think i may have read somewhere that the volume of air is affected if the same diameter charge pipe is not used throughout the whole charge piping system. </TD></TR></TABLE>

It's actually the speed of the air that is affected. Since the air moves slower, it takes longer to pressurize the larger diameter pipe, and this translates into increased lag.

https://honda-tech.com/zero...02591

 

thanks for the link. i didn't even see that. but i have a question. how do i figure out which cfm to look at for each diameter piping?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AzntaggeR &raquo;</TD></TR><TR><TD CLASS="quote">thanks for the link. i didn't even see that. but i have a question. how do i figure out which cfm to look at for each diameter piping?</TD></TR></TABLE>

The CFM will depend on your turbo and how much CFM it will push at xx amount of psi. A good way to estimate is use the following following formulas:

(cid x rpm x .5 x VE%) / 1728 = CFM no boost

cid = cubic inches displacement (Liters x 61 = cid)

VE% = volumetric efficency, VTEC motors have peak VE at same rpm as peak HP. And peak VE is around 102-106% (112% for S2000). non-vtec motors have peak VE at peak torque rpm.

for rpm you wanna pick the rpm where peak VE% occurs

That formula gives you your basic engine CFM. Then if you multiply that by your pressure ratio you'll get your CFM under boost. To figure your pressure ratio use this formula:

(14.7 + desired PSI) / 14.7

So for a B18C:

(109.8 x 8000 x 0.5 x 1.04) / 1728 = 265 CFM for a B18C
at 10 psi or a pressure ratio of 1.68 your B18C will flow 445 CFM because 265 x 1.68 = 445

Now look at that other thread and look at the different airflow velocities for different pipe sizes. Look at just the speeds for 400 CFM, dont look at any other CFM's because 400 CFM is roughly how much you're flowing at 10 PSI on a B18C.