Natural Gas instead of petrol

[Robert Harris]

LPG (Propane), and CNG (Natural Gas) both boil at ridiculously low
temperatures - and are normally used as dry vapors and blended by
an additional mixer.  Kits are available cheap to convert just about
anything - except maybe your vintage Stanley Steamer - to either 
dual fuel or dedicated gas.  The conversions use outputs from the
existing EFI and EGO to feedback and optimize both mixture and
timing for the carb.  Both gas's run extremely clean - but in a dual
fuel, most states require you to pass emissions on both fuels. A 
friendly smog check station may allow you to switch fuels, but the
same station might just enter your numbers and stick the sensor
up the shop goat's tailpipe.

The main problems with conversions is that Propane has more 
energy per pound than gasoline, but less pounds per gallon, so 
mileage goes down.  Even more so with CNG.  Cost on propane
has skyrocketed recently so it is generally not as cost effective
as CNG which is being heavily promoted by your local gas 
company.

On the good side, both feature high octane - well above the best
pump gas - and make excellent hi-performance fuels.

Of course there is the matter of the extremely "crude" carburetor
("mixer") that seems to disgust most liquidphiles.  Before you run
your mouth ("Contempt before Investigation") based on liquid fuels
you should know that NO liquid device - not even EFI comes any
where close to being as efficient a mixer as a gas carb.

Simple physics.  If the liquid "boils" at minus ridiculous, then you are
always dealing with a dry, 100% homogenous mixture.

Cold starting and warm-up enrichment?  Not needed - waste of time -
complete proper mixture already.

Accelerator pump (transit circuit)?  Useless.  Dry homogenous fuel
does not "drop out' or refuse to vaporize under vacuum change"

Altitude and temperature compensation.  Useless.  Mixer meters 
dry vapor fuel with dry air by pressure thru carb.  Roughly right
thru all normal temp and altitudes.

Manifolds for "good" fuel/air distribution?  Anything your EFI can use,
so can propane or CNG - not a thang - and no heat EVER is needed
to "Vaporize" fuel.

Set up of a gas carb is knuckle dragging simple.  Set mixture screw 
and idle speed. done.  Kits available from MSD to optimize spark for
dual fuel applications.

Electronic feedback from the existing EFI is used to "optimize" the 
mixture so the frigging smog shit still works - primarily the cat's. On
non smog motors, can be combined with wide range exhaust sensor
and have adjustable mixture.  OBTW, propane in a well built engine,
runs just fine extremely lean - like 18 or 19 to one.  Lean mixtures
run cooler than rich mixtures, so it aint no thang.

Last, the major problem with injection is the fuel is stored in a liquid
form well above its free air boiling point controlled by pressure.  Any
metering device that lowers the pressure will flash vaporize the fuel.
Excess fuel (bypass) must then be pressurized to significantly 
higher pressure (and temp) before it can re-liquidify and be returned
to the storage tank.  A lot of work is going on in this area, but
IMHO it is simply turd polishing as you accomplish 99.9% of EFI
goals with a simple carb and feedback, but then, what the hell -
most of us (myself included) like to complicate shitting.

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


----------
> From: Dan <DanLlwln at ix.netcom.com>
> To: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Re: Natural Gas instead of petrol
> Date: Thursday, July 03, 1997 5:00 AM
> 
> How about the common forklift that uses propane.  Can the system be 
> adapted for your use?  I think the forklifts use the propane in its 
> liquid state.  If have wondered if a car having problems passing 
> emissions might be able to run dual purpose propane/natural gas
> or gasoline.  Just switch the fuel when needed.
> 
> Dan L
> 
> 
> > Hi all,
> > 
> > Could a EFI system be converted easily to Natural Gas by connecting
> > the fuel rail to a gas bottle with the appropriate pressure
> > regulator?
> > 
> > If the regulation pressure was set correctly then the fuel/air
> > mixture could be set to allow the use of existing mixture maps in the
> > EFI system.
> > 
> > Is this feasible or a wild dream ?
> > 
> > Mark Reed
> > Farnborough UK
> > 
> > mareed at dra.hmg.gb