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With
winter storms approaching, we are responding to visitor requests for information
on converting engines for use with Propane.
Safety
notes:
Engine conversions must be carried out by qualified
technicians and/or persons who will follow all safety guidelines as contained
in pamphlets NFPA 54, 58, 38 or any other publication or guidelines stipulated
by local, state or federal agencies and the authority having jurisdiction.
As a starting point, contact your local fire department, propane supplier
and insurance company for guidance. They will be able to direct you
to the correct local governmental department for additional state and local
requirements.
The manufacturer of these kits reminds us that they are NOT approved for use indoors use!
For information on propane safety, publications may be ordered through The National Fire Protection Association at http://www.nfpa.org.
A partial list of applicable publications are
shown below:
Tecumseh
Horizontal and Vertical shaft engines:
Both
engines used the same Carburetor, so the discussion below applies to both
the Horizontal and Vertical engines.
Typical conversion kits require modification to the
carburetor, and once modified, the carburetor can not be used for gasoline.
So, if you plan to install a propane kit, you might want to also purchase
a replacement carburetor so you can swap back to a gas powered configuration
if needed.
This Tip of the Week Episode is under construction!
If you would like to be notified when additional information is available, please fill out the following form. We will notify you when additional details are finalized and are available. Just fill in your E-mail address, and push the button!
Why
use Propane?
Propane is easy to store in large containers,
and doesn't require special treatment for it to last a long time.
It is commonly used for outdoor barbecues, but also for cooking and
heating in homes and trailers. Propane is sometimes used to power
refrigerator units in portable applications. It can be stored in
refillable containers that can be refilled at many locations friendly to
motor homes, travel trailers and such. Many folks in rural areas
have propane delivered to large stationary tanks on their own property.
Since propane can be used for so many applications (cooking, heating ect), it's an ideal fuel for a generator as well. I like the idea of having one type of fuel source stored that I can use in a variety of ways.
The
existing carburetor on the engine must be modified to deliver propane into
the combustion chamber. It sound simple, and it really is.
Basically, instead of delivering vaporized gasoline as the engine sucks in the air/fuel mixture during the "intake" cycle, the carburator delivers a propane/air mixture. The engine itself is not modified in any way. It still sucks in the air/fuel mixture, compresses it, ignites it and converts the resulting explosion (internal combustion) into rotary energy during the power stroke. Thus delivering work energy to the item which requires power (to rotate a generator armature for example).
The waste products are still expelled in the exhaust stroke, and the process continues, over and over. It's like using little controlled explosions to rotate the output shaft. Suck it in, compress it until it's explosive, blow it up, and use the explosive energy to rotate the output shaft. That's the way an engine works!
OK, enough said... A propane conversion just swaps one kind of fuel for another, and the other principals are the same.
So
how does a conversion kit work?This conversion kit works because the air/fuel mixture is automatically adjusted as load changes are made. This automatic adjustment is only possible because this special flow regulator is linked by a vacuum hose to the carburetor itself.
This allows the flow regulator to automatically sense
changes in engine intake vacuum which is directly related to engine load
changes. So, if more load is added, the carburetor throttle changes,
which causes an increase in intake manifold vacuum. And this vacuum
causes the flow regulator in the propane conversion kit to increase fuel
flow to keep the air/fuel mixture ideal. Without this feedback, it's
impossible to keep the fuel/air mixture ideal and the motor running!
At
the heart of the conversion is the modification of a carburetor to deliver
the alternative fuel, and to provide a feedback method (a port to the vacuum
inside the carburetor) to an external propane fuel delivery flow regulator,
which is designed to accept the vacuum feedback and adjust the fuel delivery
flow rate. This special vacuum flow regulator is like having an extra
hand automatically adjusting the regulator output knob, keeping the air/fuel
mixture ideal!
As with all of the Tip of the Week episodes here
at TheEpicenter.com, we have tried to be technically correct in our discussion.
As always, I'm sure we will be corrected here or there, but what I'm trying
to get across is that the conversion is fairly straight forward.
The most difficult part of the conversion is drilling one hole in the carburetor.
The
main task in modifying the carburetor is to replace the existing gasoline
fuel delivery tube (the red plastic tube) with a brass propane delivery
tube.
To do this will require drilling out the opening in the carburetor where the old jet was located. The new brass jet (and some other fittings and a valve assembly) will take the place of the gasoline delivery jet.
Another brass fitting (the slow running fitting) will be replaced with a larger (hollow) fitting, which will serve as a vacuum feedback port to the vacuum controlled flow regulator.
Unused air passages which are only required for gasoline fuel use will be sealed with RTV silicone.
Step
One.
Step
Two.
Step
Three.
Step
Four.
Step
Five.
Toss
the extra parts.
What
does it look like when things are hooked up?The modified carburetor is connected via two hoses to the vacuum controlled flow regulator. The hose connected to the bottom of the carburetor delivers propane or natural gas to the new jet.
The second, smaller hose is connected to the side of the carburetor where the vacuum fitting has been installed. The other end connects to the vacuum control feedback port on the flow regulator.
The third hose connected to the vacuum flow regulator could either be connected to the low pressure household feed for natural gas use; or, with the a portability tank kit, it can be connected to a portable propane tank using the special 12 PSI regulator included with the portability kit.
Shown here is the motor and flow regulator mounted on a pressure washer
cart, and a close up of the flow regulator connected to the carburetor.
The next shot is of the completed project.
In this project we used our direct drive alternator bracket and couplers
to connect a 93 amp GM alternator and charging cables to the propane powered
motor.
Q. Where
can I buy a kit like this?
A. We don't
sell kits, but there are many companies that do.
The best thing to do is use our search tool and enter "propane
conversion" and the brand of your motor. Like this: Briggs & Stratton
propane conversion kit
A. The kit we used was custom designed to include every gizmo needed for the Tecumseh engine. It included all the little stuff that would have taken time at the hardware store to round up.
A. About the
same amount of propane as your motor uses in Gasoline. Propane has
about 10% fewer British Thermal Units (BTU's) than Gasoline does.
But the estimate for your engine running on gasoline in terms of hours
per gallon will be very close to that for propane.
Q.
What is the "portability kit" you mentioned and do I need that too?
A. Yes in most applications. The basic kit is designed to tie into the output of a regulator on a bulk propane tank. Small portable propane tanks (like barbecue tanks) do not have a regulator. The "portability kit" contains the required 12 PSI regulator, and a 12 foot hose. This kit is only required for use with portable tanks. It then feeds the vacuum controlled flow regulator that connects with the modified carburetor.
A. The kit took about 2 hours to complete the instillation. But we couldn't try it out for 24 hours until the RTV had set up. Also, you will need some common tools like screw drivers, socket set and such, and a 17/64th drill bit and power drill.
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This site address is http://TheEpicenter.com
Epicenter
384 Wallis #2
Eugene, OR 97402
(541) 684-0717 Voice
(541) 684-338-9050 Fax
E-mail: bjnelson@TheEpicenter.com