[s-cars] RE: [200q20v] intercooler

mlp mlped at qwest.net
Mon Dec 3 16:48:16 EST 2001

> -----Original Message-----
> From: Brian Link [mailto:brianl at starsys.com]
> Sent: Monday, December 03, 2001 1:16 PM
snips.... >

Brian Link wrote:
> I calculate approx 208 cfm at 5300 rpm, lets suppose that
> is equal to engine bhp of 230 that would be .9 cfm per bhp.  (?)

No, I don't think you've factored in the extra cfm's it takes to make
the +1 (over ambient pressure) to -> upwards of 24+ psi of boost one
can run;  or the @ 15 to 18 psi in "over boost" mode the stock UrS4 is
supposed to be running to get to its claimed 227 (or whatever) bhp
> CFM =3D rpm * (Engine displacement ft^3 )/2  (?)

+ boost cfms less temperature psi adjustments, ? @ 2x atmospheres.
The 1.6 cfm/bhp (some say a bit less, more like 1.4 or 1.5) used as a
"rule of thumb" gauge (& I suppose more accurately it should be rated
in "pounds of air", not cfm is, I think but wouldn't guarantee it
something derived from a rough estimate of how many BTU's there are in
a given measure of fuel & who much air it takes to effectively burn
that quantity of fuel.  But again, that's partly a guess as to how a
"x#lbs of air to bhp" correlation is arrived at.)

> Im using a peak flow 19.7 lbs/min (.85 VE) as the mass flow
> rate.

I think VE changes a bit with boost doesn't it?  If it does you would
have to be picking 85% as an average, and for some reason I think that
85% may be low vis-=E0-vis the 20v engine VE.  If you play with those
numbers in some of the engine dyno programs, it is very hard to get
2.2 liters of displacement to get you anywhere near a 227 bhp program
result without bumping the VE used up closer to 100%.

> I'm using an inlet air temperature of 130F (wag).  Up here in
> CO.  I'm spinning my k-24 at 140,000 at 20 psi????

At @ 20 - 24 psi & roughly an outside ambient in the mid 60's IIRC you
can/will see inlet temperature over 300 F going into the IC.  Maybe
Hap will chime in on what he's currently seeing for IC inlet temps on
his Davtron gage?  I don't know that anyone has posted any info on
stock UrS4 IC values.


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