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#1: 01-10-2013, 12:53 PM
propane conversion thread
frank_ster's Avatar
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Location: Knuckastan
Car: 05 lgt 5EAT 3.8, buell 1125cr ,79 camaro
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so some people have been starting to ask questions on propane so might as well start a thread.

first question :

excuse my dumb?, but how does that work exactly? i am very interested in that if its an option for my 05 gt

a propane tank is installed in your car. Different tanks can be installed they have simple rectangular tanks, round tanks and spare tire location tanks.

there are two types of propane systems. vapor injection and liquid injection.

the tank sends propane to vaporizer that lowers the pressure to about 15 psi above manifold pressure. the vaporizer is heated with coolant from the heater core to prevent it from freezing and yes it can freeze in the middle of summer if your driving fast!

the propane is then sent to an array of injectors. the injectors are simply mounted near the stock injectors, then hoses run down to nozels that are tapped into the intake manifold.

the systems comes with a ecm to control the fuel and when it begins working after warmup. the engine needs to be warmed up on gas when below certain outside temperatures. inside the car there is a small switch that also has 4 led lights indicating the level of propane in your tank. so pressing this switch will switch from gas to propane while you drive. you may feel a light jerk.

Lpi liquid propane injections is pretty much like regular fuel injection
you have a tank pump injectors and pressure regulator.

lpi you can cold start on propane and even in -20 deg temperatures.
lpi the fuel is injected as a liquid that will vaporize in miliseconds that will freeze to about -40 deg. this will cool the intake charge. so expect more hp on propane than gas when using lpi.

lpi there are no kits as far as i have seen on ebay yet. and would be for dedicated change to propane or have two injector fuel rails.
the lpi system uses stock like injectors on the stock like fuel rail. i say stock like because i'm testing the compatibility, i have seen photos of lpi systems ( new your city garbage truck and other city trucks using lpi that the injectors appear stock.
so i tried it.
so in the 1 hour i ran it its fine. the orings and seals on a gasoline engine are perfectly compatible to propane also.
the key that i didn't have in the video is a circulation pump. the circulation pump is for when the fuel rail gets warm or hot the propane has a tendancy to "vaporize" this pushes the liquid back into the tank. and when your try to restart its injecting propane in a gaseous form which is much less dense, so a fuel pump is used to circulate the fuel in the rail to push new liquid propane into the rail. the vapor will return to the tank to cool some of witch will turn into a liquid again.
the pump i plan to use is a gerotor type and have a 5 psi regulator back into the tank.

costs: the ebay kits are about 1700$ with the tank. 1000$ for the injection components and 700$ tank give or take.
cost of propane is typically half the cost of gas. but it can vary. to estimate your fuel consumption you can figure 1 gallon of propane will get you 90% as far as gas. so if your getting 22 mpg figure about 20 mpg after.
depending on how much you drive the kit will pay for its self in 3 months to a year.

the liquid propane will likely be cheaper. if the stock injectors and fuel rail can actually be reused, circulation pump is about 100-150$ and the return regulator is 8$. i would run new steel lines or stainless braided hoses to the fuel rail.
the tune may be altered by 10% , cranking pulse widths change is still unknown, the wot full rich can be made even richer 9.5-10.5 to 1 afr you can run much richer using propane with out the black smoke, which is the key to the increased power levels.

on the kit ( vapor system ) you may have less power on the propane, and in the case of you wanting more power you can hit the switch and in half a second your back to gas ( may feel the engine stumble depending on the tuning) and your exactly where you were before the conversion.
Now that's thinking out of the boxer!
fyi all 05 + legacy's have built in code reader

Last edited by frank_ster; 01-10-2013 at 06:20 PM.. Reason: to add some information
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