All the non-DYI-EFI crap I've put up here

[Robert Harris]

> From: Joe Chiasson <chiasson at hutchtel.net>
> To: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Re: All the non-DYI-EFI crap I've put up here
> Date: Saturday, September 13, 1997 8:35 PM
> 
> Bi-fuel dual fuel, I'm always getting those mixed up, don't think I will
> ever get it right.
> Anyway thanyou for your reply, it sounds like a very interesting system, I
> really hope it works.  I have been considering more of a dual fuel system
> myself (gasoline and propane with propane being the primary and gasoline
> being a back-up, main reason some places its hard to find establishments
> which are licensed to fill motor vehicles.) Your bi-fuel system, as I said,
> seems really interesting, perhaps out of my ball park (not a wiz with
> controllers yet), but reading about your system may push me to go ahead and
> work on a dual fuel system.

Vehicle is a 34 foot long converted Immigration Bus - Basically a Ford C-600
tilt cab with a 27 foot passenger bus body placed where the flat bed would be. 
Engine is a 429, 5 speed with granny and 2 speed rear end.

The control scheme is to take ANY off the shelf EFI system and by replacing the
gasoline injectors with vapor injectors - let it do its thing without any big
deal. The piggy back liquid system merely extends the control range without
getting crazy on the injectors.  Making the vapor injectors flow about the same
as the gasoline injectors means that simply by "flipping a switch" I'm burning
both gasoline and propane and the EFI controller doesn' t even need to know it
happened!!  Remember - simplify and steal.

First - vapor phase.  Tank is a 60 gallon US tank - mounted right front under
body, just behind engine - typical truck style.  The vapor is used only for
starting, warm-up and when gasoline not available.  Basically as control fluid.
 The bulk of the fuel under load will be liquid propane.  Assume 10 MPG, 60
miles per hour, that means 6 gallons x ~5 or 30 lbs. an hour of propane vapor
to be pulled from the tank if no liquid gasoline or propane being used.  Not
much for the size of the tank and the fact its hanging out in the open, subject
to heat and vibration. Speaking of heat, since leaving South Dakota as a kid, I
consider solid water to be an un-natural and unlivable condition, I avoid those
climates at all costs.  Fall back if heat is actually needed is to run black
heater hose from engine cooling about twice the length of the tank - with a
on/off valve for coolant controlled by pressure.
But using your scenario - I would be taking one third the fuel over an hour. 
I'll try it but at the low actual rate, I don't think it will be a problem. 
Smaller tanks and higher rates of fuel flow it would rapidly become a problem.

Next to liquid propane.  The model is NOS bottle kits.  Safety valve at tank
liquid, one way line to engine.  (Remember - this is NOT a closed hood auto but
an open engine bay with about a 8 foot max spray bar to tank run).  NOS gas
solenoid valve (handles 1500+ PSI) opens line to spray bar - 3" max.  Selecting
which are on and off gives binary control.  The solenoid valve is much larger
than the spray bar. Only place for vapor to form is on output side of solenoid
valve as its dumped to the spray bar.  Any vapor forming in line from heat will
push liquid back into tank.  If line all vapor  at turn on, oh well it soon
won't be. Since the liquid propane is going to be just dumped unregulated into
the intake, using a small line will minimize the problem. Also remember, spray
bars are flowing constantly - and the valve serves only to turn off or on the
flow - not to regulate.  Thats controlled by the fixed orifices at the spray
bar.  

Since a stamp computer can readily convert pressure to flows thru the binary
jets, it is far simpler to eliminate all the pumps, injectors etc and use three
nozzles sized 1 - 2 - 4 to get 8 major steps  and then just accept them and
reduce the vapor side by the step amount.  Leave all the analog like stuff to
the main controller to smooth out.  With 7 equal steps, it does not really
matter where each kicks in - as long as the vapor system is still left in
control range.

"When some one gets something for nothing -
             some one else gets nothing for something "

If the first ingredient ain't Habanero, then the rest don't matter.
Robert Harris <bob at bobthecomputerguy.com>