Re: What's the CFM

CX500 & CX650 Turbo Forum

What's the CFM

Jason in PA 02-11-2007, 4:48 PM

Hello turbo folks! I was wondering what the CFM rating was on the 500 turbo? All I have figured out is a 500cc twin engine uses 88.176cfm at 10,000rpm (no turbo). Is there stats. on this somewhere I can check out? Any known info. would be great! Thanks!

82 GL500

Re: What's the CFM

RichNCT 02-12-2007, 10:05 AM

Turbo News newsletter, issues 1 & 2 from the 80s has IHI compressor maps and charts of info. I cannot understand it myself. But that's one place where you can find it.

Born to be relatively wild

Re: What's the CFM

Brian FORD 05-08-2008, 1:17 AM
You didn't say where that CFM rating of 88+ @ 10K rpm comes from. To my knowledge CFM is merely volume without regards to pressure. So what ever it is, should be the same for both normally aspirated and boosted operation, and determined solely by the engine displacement (nominally 500cc) X the number of cycles in which air is taken in (half the rpm on a 4 stroke engine) (5000 at 10K rpm) which for me yielded 25,000 liters or 883 cuft. in one minute.

If CFM refers to air at standard pressure (14.7 psi) then calculations can get quite complex. In a normally aspirated cycle, the air enters the cylinder at a slight vacuum as the piston drops to create the suction right up until the intake valves close. In a boosted cycle at a theoretical 10K rpm, (I think redline is 9K for both CXTs) and if the waste-gate is accurate (sure!) then you should be getting a max boost of 19 psi over standard pressure for a total air pressure reading of 33.7 psi which is 230% of standard pressure! So theoretically the corrected volume could vary as much as that between the two pressure extremes (880 CFM to 2017 CFM).

I know this weighs heavily on my mind as I'm holding on for dear life peering out through little squinted eye slits and pressing my fingerprints into my handgrips.

Re: What's the CFM

CXTURBOBOOST 05-08-2008, 5:04 AM
Can I ask why you want to know the CFM?

(The 500T runs up to 21 psi before the ECM shuts down)

Pete