coasTTal

I am interested in knowing the amount of air flow passing from intake, going through Turbo, back up and around through the hot pipe, through the intercooler, and then through the intake to the engine.

Somewhere there should be some specific data on air passing through the intake.

TTschwing

from the MAF sensor would be the only readily available Data John.. Figure around 180-200 g/sec at full chat. More on modded cars.

GorTT

through, and - natch - since colder air is more dense than warm, more is better, but I'm surprised the range is so narrow (or is it?). I've forgotten my Avrogadro's...

TTschwing

To Lbs and CFM. There is also a multiplier (forget) which gets you close to a HP estimate based on G/Sec. If you do a BAMM you can throw those numbers out the window though as the MAF reads 10% lower..

gesTTalt

Here's an example (Run using DBR chip, Audi MAF, Airetek/LLTEK intake):

226.42 g/s @ 6160 RPM, manifold pressure 2250, temp reading 39*C (ambient temp of 84*F)

scfm = standard cubic feet per minute

There are as more "scfm" definitions than there are standardizing committees. I'm using the metric conversion of one commonly used in US (atmospheric pressure 1013 mbars, temperature 19°C, weight of cubic foot at this temperature and pressure 34 grams).

(226.42 g/s) / (34 g/cf) * (60 sec/min) = 400 scfm

So flow volume would be 400 cubic feet if air were open in the room. However air is being crushed into manifold by turbo, so we need to correct for temperature and pressure there.

Pressure correction:
(400 cfm) * (1013 mbar / 2250 mbar) = 180 cfm

Now we need to correct for temperature. At 0°C air will have considerable volume so you need to use the proper scale as was done for pressure (1013 mbars is 0 gage pressure), an absolute scale - Kelvin (273 K is 0°C)

(180 cfm) * (273 + 39)K/(273 + 19)K = 192 cfm

GorTT

The reason I'm asking is the common-sense test says 400 (or 180) scfm doesn't seem like that very much, particularly when you consider the total displacement and the engine speed (1.8L x 6160).

GorTT

so my only question left is related to the compression factor.

TTschwing

Gary had that in his response /\

GorTT

just to convince myself of the correctness of his numbers. But I still don't understand the compression differential - why the figure isn't larger, rather than smaller, than the total potential (since we're compressing before we get to the cylinders).

GorTT

In fact, why doesn't 2 bar boost equal at least twice the "tpv"?