Propane Conversion
#31
04-26-2006, 11:45 AM
Although liquid propane injection systems do exist, none are commercially available in North America. All North American systems meter propane into the engine as a vapor. Modern systems meeting EPA/CARB requirements rely on a feedback system that uses the exhaust O2 sensor to ensure that the fuel mixture is correct. The only practical way to meet current EPA requirements is to use injection systems that deliver propane vapor to the intake port exactly like the way Keltic has shown with his truck. However, I do not believe that BRC makes EPA-compliant systems.
The (exhaust) valve problems that people have experienced have nothing to do with the fuel and everything to do with not knowing how to use it. Propane is very similar to gasoline in the fact that neither has any lubricating properties for the exhaust valve seats. In the old days, tetraethyl lead residues would form a protective layer on the valve seats. When unleaded gasoline was introduced in the 1970s, manufacturers had to use hardened valve seats to cope with the lack of lubrication.
The main reason that people run into exhaust valve problems with propane fuel is that they think they need to enrich the fuel mixture to keep the combustion temperatures low. The problem is the propane responds opposite to rich fuel mixtures. With gasoline, rich mixtures tend to lower combustion temperatures due to the evaporative cooling effect of the atomized liquid fuel. Because propane is already a vapor, no such evaporative cooling effect can occur.
In addition, rich propane fuel mixtures burn hotter and slower than a stoichiometric (ideal - not rich or lean) mixture so that it is entirely possible for a rich fuel mixture to still be burning when the exhaust valve opens. For open-loop (Impco & OHG) systems, the fuel mixture should be set to produce 1.0% to 3.0% CO at wide open throttle. I would be willing to bet good money that none of people with burnt valves have properly set up their fuel mixture. Modern EPA-compliant systems would generally not have this problem because their fuel mixtures are computer controlled.
The lead substitute injector that F150Europe has shown is completely unnecessary for properly converted propane engines. A propane conversion is a significant investment and should only be done on an engine in freshly-built condition. That means that the exhaust valve guides, seats, and faces must be in good condition. Since almost all engines today either have induction-hardened or stellite (or similar) valve seats, this isn't usually a problem. The cooling system must also be clean and scale-free. If the full-throttle fuel mixture is properly set up, engines last a very long time on propane. A purpose-built propane engine would have higher compression (10.5 to 11:1 would be good) to take advantage of propane's 104 octane rating. For best power and economy, the distributor must be recurved for propane as well.
It makes no difference whether the heads are cast iron or aluminum as long as it has hardened valve seats and the water jackets in the heads are clean. Different combustion chamber shapes might affect the ignition advance required but, with modern EFI conversions, the advance curve is generally whatever the OEM has programmed. The only difference is that the engine will usually get maximum advance because of propane's high octane rating. Since propane engines don't run any hotter than gasoline engines and since there is no way to add heat to port-EFI intake manifolds, intake manifold materials are not an issue either.
To answer grb912's question, there is fleet conversion list that includes conversions for your vehicle. Generally, propane conversions are done by licensed installers both in the USA and in Canada. Technocarb's product for your vehicle is PN DP-FO46PU-99-02. Most conversion kit manufacturers don't seem to be very forthcoming with information to the consumer so I don't have part numbers for other manufacturers.
Whether a conversion is a good idea is purely economic. If you do enough driving annually and there is a large enough price difference between gasoline and propane, you will have a reasonable payback. Propane prices vary greatly across the continent and often the best way to find out is to ask a taxi driver. Chances are if his cab is running on propane, it is reasonably plentiful and he will also know where the best places in town are to fill up.
Frank
The (exhaust) valve problems that people have experienced have nothing to do with the fuel and everything to do with not knowing how to use it. Propane is very similar to gasoline in the fact that neither has any lubricating properties for the exhaust valve seats. In the old days, tetraethyl lead residues would form a protective layer on the valve seats. When unleaded gasoline was introduced in the 1970s, manufacturers had to use hardened valve seats to cope with the lack of lubrication.
The main reason that people run into exhaust valve problems with propane fuel is that they think they need to enrich the fuel mixture to keep the combustion temperatures low. The problem is the propane responds opposite to rich fuel mixtures. With gasoline, rich mixtures tend to lower combustion temperatures due to the evaporative cooling effect of the atomized liquid fuel. Because propane is already a vapor, no such evaporative cooling effect can occur.
In addition, rich propane fuel mixtures burn hotter and slower than a stoichiometric (ideal - not rich or lean) mixture so that it is entirely possible for a rich fuel mixture to still be burning when the exhaust valve opens. For open-loop (Impco & OHG) systems, the fuel mixture should be set to produce 1.0% to 3.0% CO at wide open throttle. I would be willing to bet good money that none of people with burnt valves have properly set up their fuel mixture. Modern EPA-compliant systems would generally not have this problem because their fuel mixtures are computer controlled.
The lead substitute injector that F150Europe has shown is completely unnecessary for properly converted propane engines. A propane conversion is a significant investment and should only be done on an engine in freshly-built condition. That means that the exhaust valve guides, seats, and faces must be in good condition. Since almost all engines today either have induction-hardened or stellite (or similar) valve seats, this isn't usually a problem. The cooling system must also be clean and scale-free. If the full-throttle fuel mixture is properly set up, engines last a very long time on propane. A purpose-built propane engine would have higher compression (10.5 to 11:1 would be good) to take advantage of propane's 104 octane rating. For best power and economy, the distributor must be recurved for propane as well.
It makes no difference whether the heads are cast iron or aluminum as long as it has hardened valve seats and the water jackets in the heads are clean. Different combustion chamber shapes might affect the ignition advance required but, with modern EFI conversions, the advance curve is generally whatever the OEM has programmed. The only difference is that the engine will usually get maximum advance because of propane's high octane rating. Since propane engines don't run any hotter than gasoline engines and since there is no way to add heat to port-EFI intake manifolds, intake manifold materials are not an issue either.
To answer grb912's question, there is fleet conversion list that includes conversions for your vehicle. Generally, propane conversions are done by licensed installers both in the USA and in Canada. Technocarb's product for your vehicle is PN DP-FO46PU-99-02. Most conversion kit manufacturers don't seem to be very forthcoming with information to the consumer so I don't have part numbers for other manufacturers.
Whether a conversion is a good idea is purely economic. If you do enough driving annually and there is a large enough price difference between gasoline and propane, you will have a reasonable payback. Propane prices vary greatly across the continent and often the best way to find out is to ask a taxi driver. Chances are if his cab is running on propane, it is reasonably plentiful and he will also know where the best places in town are to fill up.
Frank
Last edited by fraso; 01-14-2017 at 05:04 PM. Reason: link update
#32
04-27-2006, 11:09 AM
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#33
01-27-2008, 09:49 PM
QRB912,
I talked (TODAY) to a guy (IN ENGLAND) who has exactly what You are looking for, unfortunately there's this little issue called (THE ATLANTIC OCEAN) Between us & him, however he was very nice, replied promptly, doesn't have steel heads, it was a "BRC"(they're in Italy) installed setup, and 35mpg is what You'll get (w/a camper shell on a 4x4 150 w/a 4.6L engine)...check out the link to his truck, I stumbled on this searching for mini's, lo & behold, this was almost as good as our WVO powered (most of the time...driving for virtually for Free only starting & shutting down the 7.3 powerstroke on real "diesel") & the emissions are well, close to nil? Don't let the naysayers get You down, technology is running faster than GM, & Ford, & Chrysler combined...IF the kit is out there, & based on the former postings I'm sure it is...go for it. I'm digging & seaching to find them for our Mercedes C230 to make the wife happy too. Heck, she wants to save $$, & Help the environment too, go figure. BTW, I read earlier today on somebody who was doing maint. on a truck that was dualfuel (propane/gas) & they couldn't beleive, ZERO Carbon buildup anywhere during engine teardown...198k miles, probably 180k mi. on the propane. They were doing the rebuild, JUST because of the miles & after the fact kicking themselves...thoroughly convinced it would have gone as far again w/o a rebuild after the fact...go for it & keep us posted please? (tank on the 1 below in the link takes the place of spare under the bed in rear)
http://www.pistonheads.com/sales/317228.htm
Hoping I helped...
-Snoop
I talked (TODAY) to a guy (IN ENGLAND) who has exactly what You are looking for, unfortunately there's this little issue called (THE ATLANTIC OCEAN) Between us & him, however he was very nice, replied promptly, doesn't have steel heads, it was a "BRC"(they're in Italy) installed setup, and 35mpg is what You'll get (w/a camper shell on a 4x4 150 w/a 4.6L engine)...check out the link to his truck, I stumbled on this searching for mini's, lo & behold, this was almost as good as our WVO powered (most of the time...driving for virtually for Free only starting & shutting down the 7.3 powerstroke on real "diesel") & the emissions are well, close to nil? Don't let the naysayers get You down, technology is running faster than GM, & Ford, & Chrysler combined...IF the kit is out there, & based on the former postings I'm sure it is...go for it. I'm digging & seaching to find them for our Mercedes C230 to make the wife happy too. Heck, she wants to save $$, & Help the environment too, go figure. BTW, I read earlier today on somebody who was doing maint. on a truck that was dualfuel (propane/gas) & they couldn't beleive, ZERO Carbon buildup anywhere during engine teardown...198k miles, probably 180k mi. on the propane. They were doing the rebuild, JUST because of the miles & after the fact kicking themselves...thoroughly convinced it would have gone as far again w/o a rebuild after the fact...go for it & keep us posted please? (tank on the 1 below in the link takes the place of spare under the bed in rear)
http://www.pistonheads.com/sales/317228.htm
Hoping I helped...
-Snoop