Hello,

I'm wondering (also for my exhaust choice) how much (in CFM) a stock blacktop head flows. Only mod i did to the head i have is a very light polish on the exhaust side, but nothing serious.

thanks.

That's kinda like asking how much a garden hose flows.
It totally depends on the water pressure of the water source, the size of the piping leading to the valve, whether there are any restrictions after the hose and so on.
We could guess with some degree of accuracy.
The 20v is pretty efficient in the higher RPM so let's guess a VE of 95%. .8L/rev x 8000 RPM = 6400 L/M x .95 = 6080 L/M.

I'm more looking for the flow in cfm. I thought that's a value that isn't depended on anything, it's just a fact about how much it could flow. I thought it was around 170cfm but don't know for sure.

onnaj wrote:I'm more looking for the flow in cfm. I thought that's a value that isn't depended on anything, it's just a fact about how much it could flow. I thought it was around 170cfm but don't know for sure.

No there are no such absolutes like that. CFM is cubic feet per minute. My calculation of 6080 L/M comes out to about 215 CFM.
Although that is just a guess the moral of the story is that there are plenty of variables that could change it even with the stock ECU and internals. Intake and exhaust will change the VE and that will change how much air your particular motor flows. A dirty air filter or clogged cat will limit how much the the motor can flow.
What exactly are you trying to figure out?

I wanted to know to be sure if my custom exhaust would flow enough, but if i look over here: http://www.exhaustvideos.com/faq/how-to ... e-diameter then my setup will be sufficient for the stock flow.

I'm using only an OEM AE111 Apexi intake and have no other mods.

I believe I said something along these lines in your last thread. If I remember right you are going with 2".
On a dyno you might be able to notice some loss in the low end and some gain in the high end going up to 2.25 or 2.5 however I think you would be lucky to notice it on a dyno. I definitely don't think it's worthy enough to fret over.
I don't know any forumlas off the top of my head but this comes from seeing various peoples experiences, reading and being involved in many discussions over the years. I think 2 or 2.25 would work great for your goals.

onnaj wrote:How much does a stock 20V blacktop head flows?

all of them

there was a graph here, but it was the wrong graph.
sorry.

yoshimitsuspeed wrote:I believe I said something along these lines in your last thread. If I remember right you are going with 2".
On a dyno you might be able to notice some loss in the low end and some gain in the high end going up to 2.25 or 2.5 however I think you would be lucky to notice it on a dyno. I definitely don't think it's worthy enough to fret over.
I don't know any forumlas off the top of my head but this comes from seeing various peoples experiences, reading and being involved in many discussions over the years. I think 2 or 2.25 would work great for your goals.

Thanks! I've read this ofcourse but i was just curious about the estimated flow so i could check it with the charts on exhaustvideos.com

@burdickjp: thanks for the graph!

onnaj wrote:I'm more looking for the flow in cfm. I thought that's a value that isn't depended on anything, it's just a fact about how much it could flow. I thought it was around 170cfm but don't know for sure.

@ 28" probably closer to 160 cfm then 170

oldeskewltoy wrote:

onnaj wrote:I'm more looking for the flow in cfm. I thought that's a value that isn't depended on anything, it's just a fact about how much it could flow. I thought it was around 170cfm but don't know for sure.

@ 28" probably closer to 160 cfm then 170

At what lift and with what intake configuration? I haven't seen one top out under 170CFM.

At what valve lift though? Anyone with a spare blacktop head and access to a flowbench will be able to tell you.