[Diy_efi] Liquid Phase Propane Injectors

[Phil Lamovie]

Hi Bill,

One thing that I should point out is that Liquid Phase
LPG injection is an order of magnitude more complex
than petrol EFI.

This is the short list.

Fuel varies in propane / butane mix from day to day.
Therefore energy per ms has no meaning
Fuel pressure varies between zero and 350 psi static.
Injector current requirements change with  pressure.
Injector flows are not linear in respect to pressure.
Fuel vaporization area will be at sub zero temp and will
cause icing. may block 50 mm wide duct with ice
Fuel pressure regulator subject to 350 psi variation in static
system pressure.
Pulse width resolution and span are a real pain.
If you use 3 ms at idle at 300 psi you will need 75 ms at
25 psi. Or if you use 10 ms at peak power 6000 rpm and
300 psi you will need 100 ms at 35 psi.
All these things will choose to change at the same time
if that is going to make it difficult for you.
Engine exhaust will be about 100 deg C hotter than the same
engine on petrol. Turbos need to be sized accordingly.

Of course the 30 % increase in torque generated by cooling
the inlet air to the region of -25 deg C is nothing to spit at.
as well as the knock mitigation of cool charge plus very
high RON/MON

And yes it's cheap, clean and really good Otto fuel.

So pick your project wisely.

Phil


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