LPG on a air cooled engine(Porsche 911S)
LPG on a air cooled engine(Porsche 911S)
(OP)
I was asked about this and I found 3 problems:
1)How to make the vaporizer work(there's no heat water)
2)Where to place the LPG tank(the engine is at the back and is forbiden to install it at the front)
3)How to stop gasoline injection, because it is mechanical(Bosch K-Jetronic)
(you can see it here http://www.auto-solve.com/mech_inj.htm)
1)I'm thinking in using exhaust to heat water to make vaporizer work
2)May be under the seat
3)The big one. How can I stop gasoline injection without damaging the mechanical pump. I can't just stop fuel pump or the mechanical pump will run dry...may be cutting fuel supply just before the injectors.
Suggestions welcomed
Thank you...
1)How to make the vaporizer work(there's no heat water)
2)Where to place the LPG tank(the engine is at the back and is forbiden to install it at the front)
3)How to stop gasoline injection, because it is mechanical(Bosch K-Jetronic)
(you can see it here http://www.auto-solve.com/mech_inj.htm)
1)I'm thinking in using exhaust to heat water to make vaporizer work
2)May be under the seat
3)The big one. How can I stop gasoline injection without damaging the mechanical pump. I can't just stop fuel pump or the mechanical pump will run dry...may be cutting fuel supply just before the injectors.
Suggestions welcomed
Thank you...





RE: LPG on a air cooled engine(Porsche 911S)
Do not use exhaust heat to vaporize the LPG, even with water as the medium, the heat is not controllable. You should consider a type of electrically heated unit with thermal limits on temp and pressure.
European LPG cylinder manufacturers offer torodial LPG tanks that fit in the spare tire location, you will need to carry a can of "fix-a-flat".
There is no mechanical fuel pump, not sure what you are trying to describe. Just open the power lead on the electric fuel pump.
Your largest hurdle will be finding a fuel system which will work on your 911, with dual carbs etc.
Franz
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RE: LPG on a air cooled engine(Porsche 911S)
If you need the cold start injector then just plug the running injector line and the control unit's pressure regulator will return excess (in this case all) fuel back to the tank.
You should be able to add your LPG injector to the existing air box or possibly replace the petrol injector with a LPG one.
Your heater system will need one way valves to keep heated LPG from feeding back into the tank causing over pressure and to keep air from entering from the delivery end that might cause an explosion.
There is no room under the rear seats. They sit directly on the body sheetmetal.
How do you intend to regulate the LPG injection? One possibility is the MegaSquirt DIY EFI. This is a pulsed system set up for petrol but probably can be adapted.
Franz - the spare on a 911 is in the front boot so that location for the tank is unacceptable (sic). The K-Jet has a single large air box covering all the intakes. Otherwise he will have to go back to the '72/'73 mechanical injection to get separate intake throttle bodies and add separate injectors.
RE: LPG on a air cooled engine(Porsche 911S)
I will be using a continuous flow gaseous injection LPG system, based on two steeper-motors for flow control and a distributor. The steeper-motors are controlled by an ECU, with inputs such as revs, engine temperature, MAP(it has to be added one sensor), lambda sensor(one will be added), etc. You can see it here:ht
Heating systems for vaporizers on air-cooled cars based on exhaust heat are well proven too, but on VW Beatles and Citroen 2cv. You can see it here:http:
RE: LPG on a air cooled engine(Porsche 911S)
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RE: LPG on a air cooled engine(Porsche 911S)
I doubt this pump will work with LPG. I thought you were using the Jetronic continuous injection system.
Are you sure your stepper motors will have enough bandwith to keep up with the inputs?
RE: LPG on a air cooled engine(Porsche 911S)
RE: LPG on a air cooled engine(Porsche 911S)
Regardless, modifying that pump to not inject fuel without putting a clutch on the drive pulley would be a problem. It has an oil feed/return but also uses the fuel to lubricate the pump pistons. As far as I recall, they cannot be adjusted to zero fuel output. You have six pumps and injectors so valves to divert the fuel back to the tank would be expensive and a plumbing nightmare. You could fit the K system or use an electronic FI off a Saab 900 that uses an air mass flow meter. Not perfect but it is only for starting, right? Otherwise look into the MegaSquirt DIY EFI system.
The '72/'73 has a central airbox/filter with velocity stacks over each cylinder. Are you going to have an injector over each stack? Injecting from the center of the airbox will be injecting before the air filter (unless you remove it). You may not get a good fuel distribution either.