2000Accord5sp

Just because I did this for a 240sx using a '02 WRX turbo and it would seem that the turbo won't work, I tried to see how efficient it was with running on the car it comes with:


Using a couple posts I found, here is what the engine flow rate would be at 8psi (stock wastegate on WRX turbo is set to):
RPM * Displacement (L) / 12964 * (boost psi + 14.6)
6000 * 2.0 / 12964 * (8psi + 14.6) = 20.92 lb/min

(Since (CFM * 0.078125) = LB/MIN, divide by that to get engine flow in CFM for this compressor map case)
or divide that by 0.078125 (48 degrees) = 268 CFM

At 8psi, Pressure ratio will be:
(14.7 + amount of boost) / 14.7 = PR
so to figure out the PR for 8 PSI
(14.7 + 8) / 14.7 = 1.54 PR

So this puts the WRX Turbo on a WRX engine at 68% efficiency? Does that sound right? Or am I just completely not understanding any of these posts?

If I do this with a 240sx engine, it's barely even on the graph.

2000Accord5sp

Any suggestions? Like "You're a retard, you did it all wrong" or anything? Just want to figure this stuff out. Thanks. (and whether the turbo I bought is crap for my engine)

jmal1919

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2000Accord5sp &raquo;</TD></TR><TR><TD CLASS="quote">Just because I did this for a 240sx using a '02 WRX turbo and it would seem that the turbo won't work, I tried to see how efficient it was with running on the car it comes with:


Using a couple posts I found, here is what the engine flow rate would be at 8psi (stock wastegate on WRX turbo is set to):
RPM * Displacement (L) / 12964 * (boost psi + 14.6)
6000 * 2.0 / 12964 * (8psi + 14.6) = 20.92 lb/min

(Since (CFM * 0.078125) = LB/MIN, divide by that to get engine flow in CFM for this compressor map case)
or divide that by 0.078125 (48 degrees) = 268 CFM

At 8psi, Pressure ratio will be:
(14.7 + amount of boost) / 14.7 = PR
so to figure out the PR for 8 PSI
(14.7 + 8) / 14.7 = 1.54 PR

So this puts the WRX Turbo on a WRX engine at 68% efficiency? Does that sound right? Or am I just completely not understanding any of these posts?

If I do this with a 240sx engine, it's barely even on the graph.</TD></TR></TABLE>

I always wanted to know how to determine a engine's CFM, and if your right, thanks!

Sorry if it doesn't help you, but from probably the same posts you read and a few others I read using google, it looks right, but I am not an expert.

kpt4321

Looks fine. Keep in mind that estimating the airflow like IS only an estimate.

dgonzals

thats rocket science to me....

kpt4321

If you want to learn, search around here, on the net, and try buying a turbo book. Learning is good, and there are plenty of people who will help.

EFb18b

I think you forgot to solve for corrected mass air flow and if I'm right you would probably see that the turbo is probably closer to being around 70-72% efficent. Also, don't forget that the rpm level you are setting is the MAX rpm you are looking to create power in. RPM in the equation can also be used to determine somewhat what the effectiveness of the turbo's powerband might be like.

EX: how effiecent might the turbo be at 6000rpm?

DaX

iTrader: (1)

I wrote an excel program that calculates and plots the engine's flow vs. pressure ratio at certain RPM's. You can then compare these plots against a compressor map. I can email it to you if you want.

2000Accord5sp

I never read anything about corrected mass air flow. How is that figured out?

Also i figured since the WRX engine makes peak power at 6000, i would use that for the equation. Is that not what you want to do?

631 Teggy

Get your hands on Turbo magazines vol. 19 (April 2003)... They have a few pages on how to read a compressor map...

They look at the T04E '57' trim compressor map and the airflow numbers they use are a bit different. They actually represent airflow in pounds per minute, which makes it alot easier to understand. They said and I quote:

"As a general rule, each pound of air generated represents 10hp(to the flywheel)"

I dunno if that helps...

PS: to me this seams a bit hard to believe being that every application will make different power per pound of air, but hey they sounded to know more then I do...

EFb18b

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaX &raquo;</TD></TR><TR><TD CLASS="quote">I wrote an excel program that calculates and plots the engine's flow vs. pressure ratio at certain RPM's. You can then compare these plots against a compressor map. I can email it to you if you want.</TD></TR></TABLE>

Thats funny I did the samething....

IM me with your email address if you want the program. I've given the samething to several people already it seems to help them out when they can get their hands on an existing compressor map. It also incorporates all of the formulas used in the issue that 631 Teggy was talking about to explain how the numbers arrive. The only formula it doesn't incorporate is flow converted to cfm.