How to Convert Your Engine to Propane
When I go wheelin' I
am always surprised at the first questions to come out of people's mouths
when they see my Jeep: "What are those tanks on the back?" I
don't know, I guess I expected them to ask about axles, suspension, or
something, not the fuel delivery. But the tanks do kind of stick out I
Anyway, when I tell them
that the tanks are propane tanks and that my truck runs on propane, people
become amazed ... they stare at me like I'm some sort of mad scientist and I
might have a nuclear reactor under the hood. I find this funny
because, to me, propane is easier to figure out than both a carb AND fuel injection. The next inevitable question to be asked is, "How does
that work?" In response, I write this article. I hope it will
educate those who want to know. The first section will be a Pros and
Cons section and the rest will be pics of my setup and explanations.
After reading, I hope people will see that propane is so simple that it is
LPG is the correct term
for liquid petroleum gas, also known as propane. In the world of
wheeling, there are numerous reasons to convert to propane and, as far as I
am concerned, only one NOT to. We'll start with the pros:
at any angle. Since propane is
in a gaseous state when it enters the engine, it is mixed homogenously
with incoming air. There is no float bowl to spill, no liquid
for gravity to pull down and, therefore, no way to choke your engine.
This is extremely useful on those really steep hill climbs and off-camber
reliable. Propane carbs,
also referred to as mixers, are simple. They vary depending
on model, but even the most complex models have only a few moving parts
and two diaphragms. So to start off with there is very little that
can go wrong with them. But if something SHOULD go wrong with them,
they're COMPLETELY rebuildable on the trail. My carb can be
completely disassembled, rebuilt, and reassembled with a simple flat-head
screw driver in a matter of minutes. There are no computers
controlling them, so your not out of luck like the EFI guys are if their computer
gets fried. There's also no wiring to screw up for the average
engine temps. My engine runs
cooler, and cools down faster since I converted to propane. I don't
know if this is due to the extra cooling effect from running my heater
hoses through the converter or just properties of propane burning, but
it's a fact, man!
engine. Propane has little to
no particulate matter in it. It leaves no carbon buildup in the
cylinders. Therefore, your oil stays cleaner longer. In fact,
the recommended oil change interval for propane-burning engines is
13,000 miles!!!! (And even then only due to viscosity
breakdown.) Even after 13,000 miles, most propane owners report that
the oil they remove from the engine is still golden-clear like it was when
it was put in! This leads to ...
engine life. Some people say
that the slow burn rate of propane as compared to gasoline wears down
valves and valve seats quicker and therefore lessens engine life. However, having
hardened valves, as most engines manufactured since the 70's have, is
reported to help, or even completely alleviate, this problem. Since
my engine is new, I can not attest to how many miles I have put on it.
However, I can attest to the fact that the man that I buy propane from
runs propane on his 350 Tahoe and has put 435,000 miles on his
engine without ever having had to turn a wrench. His valves have
never gone bad either.
usage. Propane is a liquid in
the tank. However, once exposed to atmospheric pressure, it expands
into a gas. Thus, even though the fuel pickup in a propane tank is
at the bottom, as the converter regulates the pressure down to 4psi for
engine consumption, liquid in the tank expands to fill the void left.
Therefore, when your tank gets low, it continues to suck fuel in through
the pickup. Even though the liquid may slosh around, it will not
result in your pickup running dry. Getting on a steep incline and
having your engine shut off because all the gasoline sloshes away from the
rating!!!! Propane is rated at
110 octane. Does your engine have pinging problems? Is your
high compression ratio causing you to have to run expensive 93 octane to
keep the pings away? No more worries there, buddy! Engines
built to run propane have been built with up to 16:1 CR! Mine is
10.25:1 and I have ZERO pinging. This also means you can advance your timing to get that extra power! It's as close to
racing fuel as you can get without running racing fuel!
tune. Propane is easy to tune. Once I got my timing right, my engine started up and idled
perfectly after over a year sitting. The nature of the mechanics of a propane carb
will not let too much or too little fuel enter the engine at idle.
Sure, the idle speed can be adjusted slightly with the carb, but for the
most part, if you have the correct carb for your engine CID, most of the
time the idle is within 250 rpm of where it should be before tuning even
begins. To tune it correctly, I just closed the fuel metering valve
in the carb as far as it would go and revved my engine to 6000 rpm.
It skipped a little, so I turned it up until it stopped. My engine
roars all the way up to 6000 rpm with ease now with the stock GM HEI!
find refill stations. This is
not 100% true, although I do have to admit that it is probably 70% true.
As a propane runner, I can not just borrow gasoline from someone on the
trail if I run out. I have to plan my fuel consumption and fills a
little more than gas users do. If I'm going somewhere for the
weekend, I have to know in advance if there is somewhere that I will be
able to fill my tanks. If there is not, I have to bring spares.
This problem could be solved either by just getting a big enough tank to
fuel my needs for an entire weekend or by not running fork-lift bottles.
Even though they hold less fuel, conventional grill tanks can be used and
exchanged out at most gas stations anywhere.
power. I did not find this to
be true at all. As compared to a perfectly tuned carb, converting to propane
will result in a small loss of horsepower at the top end of
your power spectrum. However, it has been true of the vast majority
of gasoline carbs that I have known to not have been tuned properly to
Tuning those things is not easy, much less getting them tuned perfectly.
Many people that convert to propane actually report a GAIN in seat of the
This is because propane carbs are simple to tune to max efficiency.
Once you get them tuned properly, there will be no way for your engine to
suck in too little, or too much fuel. That and the ability to
advance your timing will compensate for, if not completely eliminate, any
loss of power.
Recently, or to be more specific, a long time ago, a veteran of the LPG
industry contacted me to educate me on some topics that were discussed in
this article. My lack of free time has resulted in a severe delay in
getting the info here. Some additional things that I would like to
point out are:
While it is technically
possible to use 20# grille tanks with a system as outlined in this
article, it is not recommended. This is because they do not have a
special excess flow valve on them that will severely reduce the LPG flow
in the event of a line being severed. Certified motor vehicle tanks,
such as the forklift tanks used in this article do have the valves and are
Again, while a lock-out
valve is no a technical requirement, it is HIGHLY RECOMMENDED as a way to
stop fuel flow during an emergency.
My thanks go to Sandy
Kicliter both for reading my article and offering his years of experience
to me and my readers. I hope to someday wheel Moab with him.
chit-chat! On to the tech!