[Diy_efi] LPG injection

[Derek]

>>Give me some real world results, not "quite likely."

> Somebody else already quoted it for you. About -20° F  MAT with liquid propane
injection.

Propane absorbs 193 Btu/lb during vaporization, and we can be sure of total
vaporization with propane. The stoich ratio of propane is 15.7:1. Let's run it
richer, 13:1 for power. So we have 13 lbs of air for every 1 lb of propane. So
we have 193 BTUs of cooling for every 13 lbs of air. That's 14.85 BTUs of
cooling per pound of air. The specific heat of air is .242 Btu/lb.

14.85/.242=61.35F. That's the intake air temp drop you will get if you have
liquid injection, and are using pure LPG (no gasoline for fueling). I know the
expansion will add some cooling, but not too much more. If you can, please share
how to calculate the cooling from just the expansion, I'd like to see how to do
that.

So I guess if this was a pure LPG gas, NA car on a cold day with 40F inlet temps
before the propane, I can believe the -20F claim.

Also curious to see how much power is lost to the space taken up by the propane
gas, vs gained by the charge air temp drop.


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