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Propane powered Honda?

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Old 08-31-2004, 09:00 AM   #1
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Default Propane powered Honda?

I was in Norfolk, VA this past weekend at the final SEDiv SoloII race and came across a guy who races a propane fueled Morgan. My friend and I started talking to him about the setup and it really caught our attention. He basically has a 14 gallon (pretty big since it's a street driven car) propane tank he keeps on board. He says it's 108 octane all the time and burns 2 or 3 times more efficiently than gasoline, effectively doubling the lifespan of his engine. I've done some basic research online and found quite a few tidbits of information that support his claims, but only found resources that covered the conversion on carbureted vehicles.

They do this a lot across the pond since fuel prices are so high over there. Based on information I've gotten from some of the British websites, it seems that there's usually a 15% power loss associated with the conversion. Also, your "gas" mileage is decreased a little as well, but I think this is offset by the lower cost of LPG.

My question is, does anyone have any links and/or information that pertains to converting a fuel injected vehicle over to run on propane? I've run a search on HT but only came up with information for propane injection, which isn't what I'm looking for. I know there are some other people out there who've thought about this before. I'm hoping we can exchange information and ideas and see where things take us.

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Old 08-31-2004, 10:09 AM   #2
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Default Re: Propane powered Honda? (kappa12)

dam josh. this is new to me. I would love to see what people com up wtih.

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Old 08-31-2004, 10:42 AM   #3
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Default Re: Propane powered Honda? (kappa12)

ive heard of propane injection for F/I apllications but not the complete changeover.
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Old 08-31-2004, 10:44 AM   #4
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Default Re: Propane powered Honda? (kappa12)

I don't see how it would double the lifespan of the engine. I always thought it's just wear that determines how long it'll last, not how the gas burns. From talking to people that have done it, I understood that if anything it'll decrease the life slightly, but I also don't see how that would be. But yeah, they have lots of them over there, I guess it costs about a grand for the conversion, but it'll pay for itself quickly in gas savings.

Which brings me to my final point, that's the only reason you might want to do it for.... money savings on gasoline, but that's in countries where gas costs four times as much and people make eight times less. It's kind of useless here...
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Old 08-31-2004, 10:52 AM   #5
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Default Re: Propane powered Honda? (Lsos)

From what I've been told, it's a much cleaner burn, leaving next to no (if any) carbon deposits in the engine. People who have cars like this have said that when they change their oil, where it would normally be black or at least a little dirty, it's now nearly as new as when they put it in. I have nothing to verify that though, simply internet posts from owners. Maybe engine longevity is increased b/c oil is kept cleaner and can lubricate better? Just a guess...

The guy who drove the propane powered Morgan mentioned that the main benefit (besides being a cleaner burn) is the fact that it's 108 octane all the time. I just recently supercharged my civic, and it's a little bit of a hassle to find high octane, unleaded gas around here. Having 108 octane all the time from such a readily available source would have its benefits.
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Old 09-01-2004, 08:45 AM   #6
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Default Re: Propane powered Honda? (kappa12)

up for more info
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Old 09-01-2004, 09:20 AM   #7
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Default Re: Propane powered Honda? (kappa12)

interested to see what people come up with here
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Old 09-01-2004, 09:51 AM   #8
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Default Re: Propane powered Honda? (hybridvteceg)

i have seen taxis that use propane. most taxis around the new york area i think.
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Old 09-01-2004, 10:20 AM   #9
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they produced propane hondas in cali to cut down on smog
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Old 09-01-2004, 10:30 AM   #10
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Default Re: Propane powered Honda? (b20turbojason)

Pros & cons. I'm sorta guessing with some of this, but here goes...

Wt.% of carbon is a little lower for propane, but not enough to matter. Like 82% vs. 84%. So it's not about the actual amount of carbon contained in the fuel.

More likely it's because gasoline is a liquid, propane is a gas. Gasoline has to be atomized, then the droplets have to evaporate. That never happens perfectly, so there's always some liquid gasoline. It washes down the cylinder walls & gets into the oil.

Gasoline is a petroleum distillate, so it's not all isooctane. There's a bunch of heavier components like tars & varnish. They're even harder to vaporize, making more soot.

They've got pretty similar energy content (LHV) per pound, but gasoline is a lot more compact. You don't need a pressurized bottle to carry it & it takes up less space.
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Old 09-02-2004, 11:28 AM   #11
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Default Re: Propane powered Honda? (JimBlake)

Anybody have any links to sites with info on conversions for US fuel injected vehicles?
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Old 09-03-2004, 11:02 PM   #12
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Default Re: Propane powered Honda? (kappa12)

this sounds like a company you need to give a call to( i love google )

(scroll down to "company description")
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Old 05-10-2005, 05:01 AM   #13
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Default Re: Propane powered Honda? (clarkekent13)

Anything every come of this? I've also kicked around the idea.
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Old 05-10-2005, 05:41 AM   #14
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Default Re: Propane powered Honda? (DaX)

yea we have fix a few where in nyc .we have a contract with some company, so there sent them to us for small repairs. but theirs one we had for about 3 months. it dont wanna start but if u hold the gas all the way down and crank it for about min. it the propane fire with some light gas for the mixture and the engine just go BOOM and no little boom talking about the can see the hood flex up and then go down each time it go BOOM. this car is not a honda its a Chevy the honda ones seem to dont really give any probables. i think that if it would happen to one of the propane honda civic the block would crack just off the first BOOM
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Old 05-10-2005, 07:00 AM   #15
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How are you metering the propane into the engine? Is there a special type of gas injector as opposed to a liquid [fuel] injector?

Since the fuel is already in a gaseous state, do you just use one injection point for the entire engine?
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Old 05-12-2005, 10:47 AM   #16
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Default Re: (DaX)

GX civics (Fleet vehicles used by big companies or government) are LPG from the factory.

Also in Europe, quite a few cars are converted to LPG as it costs less. In fact, when I go to Belgium, I've noticed that that many of the big American suvs are converted to LPG. The inconveniece is that they can't park in underground garages, or got in certain tunnels. The power is also lower by about 15% on converted engines, but LPG is 1/2 the price of gas...
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Old 05-13-2005, 03:55 PM   #17
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Default Re: (GPNY)

I heard that CNG (compressed natural gas) car can run much higher compression like 12:1, then it won't make that big of a power drop, the problem seems to be finding fuel if you go for a long trip.

The good thing is CNG is not taxed as heavily as gas so you pay less, but converting a gas engine to CNG (tank, pump/regulator, etc, injector and spark can be the same) will net you a chunk of change. If you don't run it all the time like fleet cars it is not worthed.
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Old 05-13-2005, 08:15 PM   #18
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I'm talking LPG and running it all the time...CNG is just not as easy to find.
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Old 03-06-2007, 08:37 PM   #19
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found this link during my 3 hour surfing for info on pane conversions so i can build my kit

you can use this info to build your own kit for CHEAP!!!!!!
do the research and you will see

Whether for straight (dedicated or propane-only) or dual fuel (propane or gasoline operation selectable by the operator) use, Impco propane carburetion systems consist of four major components:

* Fuel tank
* Fuel lock off
* Regulator/Converter
* Carburetor

Fuel Tanks

For road-going vehicles, ASME tanks are required. Lift-truck and other off-road industrial vehicles commonly use DOT tanks, which are portable tanks designed for liquid withdrawal. Barbecue tanks and other tanks for heating purposes, which are designed for vapor withdrawal, are not made automotive use and are dangerous when used for this purpose.

Propane is a liquefied petroleum gas because it is stored under a high enough pressure to condense propane and the other constituent gases into a liquid. The pressure inside the tank varies with temperature from 0 psig at -42?C (-44?F) to 239 psig at 52?C (125?F).

Impco does not make propane fuel tanks. Major fuel tank manufacturers are Manchester Tank and Sleegers.

Fuel Lock Offs

These devices are designed to shut off the flow of fuel to the engine when the engine is not running or is shut off. Impco makes both vacuum-operated and an electric solenoid-operated shut-off devices, which they call Fuelocks. Fuelocks, with their integral fuel filters, receive liquid propane from the tank and filter it before allowing it to continue on to the regulator/converter. Straight conversions commonly use the vacuum Fuelocks, whereas dual fuel systems use the solenoid lockoff.

Impco's vacuum Fuelock is their VFF30 and has an integral filter. It is operated by a vacuum supplied from a nozzle on the mixer body. For dual fuel applications, the vacuum supply to the Fuelock should be interrupted.

For dual fuel applications on carbureted vehicles, Impco has a gasoline solenoid valve (GSV-3) to shut off gasoline flow to the carburetor.


Impco makes 3 regulator/converters, which we will call converters for short. Converters receive filtered liquid propane from the Fuelock at tank pressure and converts it to gaseous propane. It then reduces the pressure in two stages to one slightly below atmospheric. The fuel expands 270 times as it changes from a liquid to a gas. The reduction of pressure produces a refrigeration effect and heat must be added to prevent the converter from freezing up. Impco converters use hot water from the engine's cooling system to compensate for the loss of temperature and to aid in vaporization.

The smallest Impco converter is the Model J, which is rated for 100 HP, and is typically installed on the small engines used in lift trucks. The other two converters, the Model E and the Model L, are both rated at 325 HP. The practical difference between the two is in the locations of the inlet and outlet nozzles. The Model L was designed to be a lower cost alternative to the Model E. The Model E reportedly works better at higher power outputs.


The difference between a mixer and a carburetor is simply that a carburetor is mixer with an attached throttle body. A throttle body is the part of the carburetor that contains the butterfly valves. With the appropriate adapters, a given mixer can become the carburetor of several different engines.

All Impco mixers use an air valve design to meter the flow of fuel into the engine's air stream. The air valve design utilizes a relatively constant pressure drop (vacuum) to draw fuel into into the mixer from cranking to full load. The air valve incorporates an integral gas valve that controls the fuel flow relative to the air flow.

Mixtures between idle and full-load are controlled by the gas metering valve's shape. The gas metering valve is shaped to produce a lean mixtures at light loads and increasingly rich mixtures at heavier loads and higher engine speeds. The shape of the gas valve is designed for the optimum mixtures for the mid-size engine between the largest and smallest cubic inch displacement upon which the carburetor will be installed.

For dual fuel applications, a vacuum control solenoid (VCS) is sometimes added to some mixers to lift the air valve to its maximum opening. This minimizes the restriction in the induction system when operating on gasoline.

Selecting the Correct Carburetor Size

The following information has been transcribed (and edited) from Impco Service Bulletin 0100-01.

Air-Flow Capacities. It is important to size correctly the air-flow capacity of the IMPCO conversion carburetor to the engine air-flow requirement. Specifying the correct IMPCO carburetor is vital because a carburetor too small for a given engine limits horsepower. Up to a specific RPM, normal torque is obtained. Beyond that point, as air-flow is limited by the carburetor, torque falls off, with consequent diminishing of performance.

A carburetor excessively large for an engine may cause starting troubles. Idle will not be stable, and fuel mixture will not be consistent. As a general rule, the air-flow capacity of the carburetor should be reasonably close to the air-flow requirement of the engine being converted. However, the type of service the engine performs is a necessary consideration in selecting the appropriate carburetor (or mixer). Keep in mind the following:
bullet Engines which are never operated at wide open throttle give the best performance and service with under carburetion. Services typical of this situation include lift trucks and passenger car applications.
bullet Engines with a degree of under carburetion are easier to start and will develop the low end torque required in these types of service.
bullet Engines in over-the-road applications can safely be equipped with carburetors delivering somewhat over the air-flow capacity dictated by the engine's air-flow requirement. The larger capacity carburetor will be able to respond to maximum air-flow requirements.

Systems incorporating an IMPCO ADP device built into the vaporizer-regulator are less critical as far as carburetion mixture control is concerned. With the device, the fuel mixture richens and leans automatically when the throttle is opened and closed. In a system not using the ADP, the "step" configuration of the air-gas valve determines the mixture. No mid-range adjustment is possible.

Calculating Engine Air-Flow Requirements
Determining the specific air-flow requirement for any four-stroke cycle engine requires the application for the following formula:

CFM Required = CID x RPM / 1728 / 2 x VE

* CID is the cubic inch displacement of the engine
* RPM is the maximum engine speed
* VE is the volumetric efficiency (0.85 or 1.00)

1. Determine the cubic inch displacement of the engine from the identification plate or the user's manual. If the displacement is known in cubic centimeters (CCs), convert to cubic inches by multiplying cubic centimeters by 0.06102. If in liters, convert to cubic inches by multiplying liters by 61.02 (e.g., 2.0L x 61.02 = 122.04 CID).
2. Multiply the figure by the RPM figure corresponding to the maximum engine speed at wide open throttle (WOT). Use the point at which the tachometer is red lined. If the engine is not equipped with a tachometer, refer to the user's manual supplied with the vehicle or engine.
3. Divide this CIM (cubic inches per minute) by 1728 to obtain cubic feet per minute.
4. Divide the result by 2 (for 4-stroke engines).
5. Multiply the figure you obtain by the engines volumetric efficiency. Use 85% (0.85) for carbureted engines. Due to improved intake manifold design, use 100% (1.00) for fuel injected engines.

For example, a 351 CID engine with a 4000 RPM redline:

Carbureted: CFM = 351 x 4000 / 1728 / 2 * 0.85 = 345.31

Fuel Injected: CFM = 351 x 4000 / 1728 / 2 * 1.00 = 406.25

Turbocharged Engines (with mixer upstream of turbocharger)

CFM Required = CID x RPM / 1728 / 2 x Boost

* CID is the cubic inch displacement of the engine
* RPM is the maximum engine speed
* Boost is % boost pressure + 1

Normal air inlet pressure to the engine is 14.7 psia (one atmosphere). Adding a turbocharger merely serves to increase the inlet pressure. For example, 6 psig of boost equates to 14.7 psia plus 6 psig, or a combined inlet pressure of 20.7 psia (or 140% of one atmosphere) at sea level. Here is how this works starting at the above formula:

1. One atmosphere equals 14.7 psia.
2. 6 psig equals 40% of one atmosphere.
3. Thus, you must multiply the normal CFM by 1.40 to establish the requirement for 6 pounds of boost pressure.

For example, a 351 CID engine with a 4000 RPM red line:

Turbocharged: CFM = 351 x 4000 / 1728 / 2 * 1.40 = 568.75

In selecting the correct carburetor or mixer from the listing, bear in mind that whether the conversion is straight propane or dual fuel (propane and gasoline), all models listed are available for straight fuel or dual fuel applications.

Vehicle Engine Applications
(Wide Open Throttle 1-1/2" Hg Manifold Depression)
Model...........Hp ...........CFM ........... CF per Hour
50 ...........56 ........... 91 ........... 5,460
50-500 ...........67 ........... 108 ........... 6,480
100 ...........106 ........... 170 ........... 10,200
125 ........... 126 ...........202 ........... 12,120
175 ........... 130 ........... 210 ........... 12,360
200 ........... 172........... 276 ........... 16,560
225 ........... 205........... 329 ........... 19,740
300A small ........... 217 ........... 348 ........... 20,880
300A large ........... 270 ........... 432 ........... 25,920
425 ........... 287........... 460 ........... 27,600

Industrial Engine Applications
(Wide Open Throttle 2" Hg Manifold Depression)
Model ........Rated Horsepower ....... Cubic Feet / Minute .....Cubic Feet / Hour
50 ........... ........... 73 ........... ........... 118 ........... ...........7,080
50-500 ......................77 ........... ........... 124 ........... 7,440
100 ........... ........... 123 ........... ........... 197 ........... 11,820
125 ........... ........... 146 ........... ........... 235 ........... 14,100
200 ...................... 215 ...................... 345 ...................... 20,700
225 ...................... 237 ...................... 380 ...................... 22,800
200D ...................... 292 ...................... 468 ...................... 28,080
425 ...................... 333 ...................... 533 ...................... 31,980
200T ...................... 425 ...................... 680 ...................... 40,980
600 ......................600 ......................960 ......................57,800
600T...................... 1000 ...................... 1600...................... 96,000

Application Examples

Mini Pickup Carbureted 97 CID (1600 cc) turning 5600 RPM at WOT. The formula yields an air-flow requirement of 133.6 CFM. Relating this to the Vehicle Engine Applications listing, you will find that it falls between the Model 50-500 and the Model 100. Keeping in mind that vehicle conversions are more satisfactory with carburetion having over, rather than under, air-flow capacity, the choice should be for the Model 100 with its rating of 170 CFM.

Standard Pickup Carbureted 351 CID turning at 4000 RPM at WOT. The formula yields an air-flow requirement of 345.3 CFM. From the Vehicle Engine Applications listing, this would indicate the use of the 300A-1 or the 300A-20 for a dual fuel conversion. (Or for a vehicle operated at high altitudes or under hard working conditions, consider the 300A-50 or 300A-70 which are normally used for a larger displacement dual fuel conversion.) For a straight propane conversion, there arises the question of selection. Is the Model 225, with an air-flow capacity of 329 CFM sufficient, or will it be better to specify the 460 CFM of the Model 425? Since it is wiser for a vehicle conversion to have over capacity, specify the Model 425.

Industrial Gas Engine Naturally aspirated 817 CID turning at 2000 RPM at WOT. As gas engine of this size is often used in industrial service and may be fueled with natural gas or propane. The formula yields 401.9 CFM. Be aware that slightly under carburetion is satisfactory for this type of service. From the Industrial Engine Applications listing, select the Model 225 to provide sufficient capacity.
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