[Diy_efi] Liquid Phase Propane Injectors

[Greg Hermann]

At 8:34 PM 6/1/02, Mazda Ebrahimi wrote:
>Greg, can you explain further? Here's an example.
>
>You fuel up the first time... assume 95% propane, 5% butane.
>I don't know which would have a higher vapor pressure... let's assume
>butane.
>So, let's say the liquid is 96% propane, 4% butane, and vapor is 94% and
>6% respectively.
>Since we use liquid (and I agree even the carb systems use the liquid
>draw), we continue to use 96% propane and 4% butane.
>
>Next time we refuel, we add 95% propane, 5% butane.  But butane
>concentration of existing fuel in the tank is higher.  Therefore, when
>equilibrium is achieved, the overall butane concentration is increased.
>
>I agree this is fairly minor in terms of overall fuel composition; well
>within the ability of adaptive learning.  Even open loop carbs don't
>have a problem with multiple refuels.
>
>I experienced a problem with this when I converted a truck to LNG.  The
>composition of fuel sample in our tank didn't match the fueling reports
>we had from the supply.
>
>Thanks
>Mazda

What I was trying to say is that if you were using a gas draw tank, the
liquid in the tank would tend to getehighly biased toward butane over time.
With a liquid draw tank, the relative concentration of the components
varies, but does not tend to concentratee the higher boiling component as
would happen in a gas draw tank.

Similar to the way the dissolved solids tend to concentrate in a boiler or
cooling tower which does not have any blowdown water removed periodically.

With a gas draw tank, you could end up with a REALLY high butane
concentration (30%?????) in the liquid phase, over time, particularly at
lower fuel levels in the tank, even if just adding 4-6% butane fuel!

Greg



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