"Stewart Hargrave" wrote in message
...
Because there's more to the internet than hits alone, Biker_Bry
wrote:


Some of you were looking at the ins and outs of Liquid Injecting
Propane.
I'm a Yank, so sory my measurments are in English.

The difficulties to overcome LPEFI are as follows...
1. Propane cannot hold a liquid state at underhood temps (207deg F)

= about 97 deg C. Actually, I doubt thet it gets that hot under the
hood, though there may be hot spots where the local surface
temperature reaches that. The cooling system on my car operates at
around 80 deg C (which doesn't appear to leave much margin).

Any temperature increase under the hood in relation to the injector, rails
and fuel lines
will create pressure in the lines, and will continue to collect heat until
the fuel goes critical,
or overcomes the fuel pump and sends the liquid back to the tank.


In a common fuel rail system, where the fuel is continually cycling
back to the tank, then the problem may be largely mitigated by a
sufficiently high flow rate.

2. Liquid must stay at the injector at all times while running (fuel
pump
nessisary)

A common rail would achieve this.

3. Vehicle must complete a purge cycle before starting similar to a
diesel
waiting on glow plugs.
(to rid the fuel lines of vapor).

Not sure about a pre-starting purge, but it occurs to me that the fuel
would need to keep cycling for a while after switch-off if the
under-bonnet heat is a problem.

4. Fuel Pump must be inside the tank, so how do you pass wires through a
fuel tank and have it safe?

I've often wondered about getting wires into the tank in order to make
an effective fuel guage sender a possibility. But in fact I don't
really think it would be an insurmountable problem. Probably quite
easy, in fact - a solid connector embedded in enough vitreous sealant
that passes through the multivalve.

Tank must still meet all safty regulations... Would this still be possible
with a passthrough?
Tank guages for propane are internal, and turn a magnetic dial on the
outside
of the tank with no *phisical* passthrough.


But why must the pump be in the tank, anyway? To prevent cavitation?

Yes, the pump must go into the tank to keep submerged in propane.


BTW
Mixing air/fuel *before* the cylinder breeds backfires and they will
cause
serious problems.
Ask anyone tha has used an old Impco system.

Do you mean specifically in the case of *liquid* fuel injection? Why
would this be? ATM all LPG systems mix the fuel and air before the
cylinder.

Newer intake manifulds are plastic, and can contain as much as 2.0 Cubic
Meters of
air fuel mixture ( with a vapor fogging type system).
One backfire with the hood (bonnet) up and you will be picking shards of
plastic out of your
face :-) (ouch)!




--

Stewart Hargrave

Finally visible on www.hargrave.me.uk

I run on beans - laser beans


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