Propane Motor Fuel Injection

[Johnny]

At 02:41 PM 12/1/95 -0700, you wrote:

>This is a little off topic, but I have a question as to how much power 
>would be increased by increasing the cr from 9:1 to 12:1.
>
>I have a formula which states that the percentage increase would be:
>
>(1-new_cr^-.4     )
>(------------ - 1 ) * 100
>(1-old_cr^-.4     )
>
>Pluggin the numbers in shows a gain of 7.7%. This doesn't really seem like a
>whole bunch.

hmm, 590hp plus 7.7% = 631hp 
Which would you rather have?

>Why do people run 12:1 compression ratios, having to use avgas
>and/or octane booster, when they can run ~10:1 on pump gas and lose only a
>few hp. 

Your right, it is a little off topic, but at the risk of being rude I will
briefly comment that it is not only the gain in power from the compression
itself, which at 7.7% is subsantial (if that is indeed what it really is),
but the main reason is that the crazier the cam timing, the more compression
ratio is recomended for it to work right. If you put a cam with a duration
of 255 degrees @ .050 lift and a total valve lift of .690 with 102 degree
lobe center into a 9:1 engine, you will be sadly dissapointed in the way it
runs, if it runs at all. 

To extract the most power, you have to adjust your torque curve to as high
as your engine will bear. To do that you have to run the crazy roller cam.
To do that you have to run a compression ratio of 12:1 or more. To do that
you have to run race gas, alcohol, or propane... etc.

Now your starting to make some power.

Of course there's alway hope for that 9:1 engine if you add a blower to it.

The point of my earlier reply to the tax/fuel price/emissions issue was that
you can end up with a win win situation by going to propane... and while you
are doing that you might as well take advantage of being able to run the
highest compression ratio you can get away with, just like you do by running
swamp water in your 10:1 engine. If you design the thing for propane, you
would be lame to not design it for at least 12:1-13:1.

-j-