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That the engine will fire without fuel pressure is
a matter of record.
That's why we don't hand turn the prop with hot
ignition.
Mark Ravinski
----- Original Message -----
Sent: Monday, March 15, 2004 11:28
AM
Subject: [LML] Re: Hot Start Technique
THE WAY THAT WORKED
Responses:
George Shattuck: I
think what is going on in your case is that you are cranking until the fuel
pressure comes up to give the system the correct mixture. Then the
engine will fire. The open throttle is probably not improtant because
the airflow is determined by cranking speed on start. But it works
so it is the right way to do it.
Bob Smiley: I have thought about
adding the purge valve but decided to see if I could come up with a technique
that would give consistant results. It looks like what I have come up
with will work but time will tell. It is an ace in the hole if I need it
but it will add complexity.
Gary Casey: Again I think the amount of air
that the engine gets on start is a function of cranking speed and very little
on throttle position as long as it is open a little bit. Just watch the
manifold pressure when you crank. Mine hardly changes at all until the
engine fires. Without fuel pressure I don't think you will get a start.
If your system holds pressure on shudown you will get an easier start.
If not you have to crank longer until the vapor is gone and you have liquid
fuel. My boost pump is on the firewall and gets heat soaked also.
It will not pump fuel vapors. The engine pump will and will bring fuel
in until the pressure builds and things cool down. The boost pump will
then help but I usally don't even use it on hot starts.
Scott
Krueger: If I was flying behind the engine in my Honda Civic there would
be no problem. Return lines give cool fuel and pumps like to pump cool
(liquid) rather than hot (vapor). Some boost pumps like mine will not
pump vapor. Fuel pressure equals start, and because it is an
experimental you have to experment to see what works best. There are no
2 Lancairs that are the same. The engine driven diaphram pump will
always pump, it is a positive displacement pump. If it gets hot
enough you will start pumping vapor and loose fuel pressure. It will
still pump the vapor but the engine will not run without the right
mixtue.
Thanks again to all for the great
discussion.
Ray
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