Can Propane and Gas be combined?

[steensn]

Anyone have a current cost calculation for vehicles they used this on?

[Impulse]

Up here we sell alot of these to diesel trucks, they are made by Bully Dog and cost around $900 doallars canadian, but I have seen complete kits elsewhere for alot less. One thing I noticed about the Bully Dog injection kits is that they turn the gas to a vapour right after it leaves the tank and has two regulators in the system.

[Isaac Zackary]

After some thoughts, good and bad, mostly bad, about HHO I've been interested in propane/gasoline mix in my 1972 VW Super Beetle. First of all, cold starts. I'd get rid of the choke and use propane to help start it.

But the second idea would be to try to get into a lean burn mode that will hopefully increase fuel mileage, but also reduce emissions. The idea is that when the AFR of gasoline is getting lean enough to reduce NOx emissions, usually around 18:1, most any engine will start to misfire and then HC (unburned fuel) emissions go up. Propane, on the other hand, can run at least as lean as 30:1.

Now I could try to go all propane. But that might not increase fuel economy due to the lower energy of propane and it's higher price. And even if it did, I'd be limited in where I could fuel up. So the idea of mixing propane and gasoline has caught my attention.

So here's the basic idea. I have an EGR port on the intake manifold I'm currently not using so I'd drill it out a bit bigger and hook up the system to there. There would lots of plumbing and solenoid valves and a restriction valve hooked up between the air cleaner, a small engine propane carburetor with it's regulated propane supply and all, and the EGR port on the intake manifold.

How it operates: There would be three modes of operation. Cold starting, gasoline running, and lean mixed running.

During cold starts the gasoline choke would be held open and not closed as usual. I might just make it a manual choke for this purpose. Valves on the propane side would admit a restricted amount or rich-as-necessary propane and air mix to the intake manifold. With the choke open the carb could not go into high idle mode, but the entering propane and air would create a high idle controllable by how much is let in. If I wanted to the system could be automated and the restriction could be controlled to step up or down, depending on engine temps, or even on load, since the open choke could cause the engine to die if the throttle opened and changed the fuel bias to gasoline. Once warmed up, however, this mode would change to one of the two other modes.

In gasoline mode the propane system would be completely shut off and the valve to the EGR por closed. In this mode the engine would run on gasoline as normal. During part loads the mix would be jetted close to stoichiometric or leaner if need be. But during higher loads the mix would have to become rich to protect the engine from detonation as is the case in all gasoline engines.

Lean mixed mode would only happen at part load. It would either have to be automated or I'd have to flip switches to solenoid valves only when cruising along at a fairly constant load. During this mode the valves would open in such a way that a 30:1 or so AFR mix of propane and air would be let into the intake manifold with little restriction. In a way it would kind of be like a big vacuum leak. Now this would likely not be enough fuel to keep speeds up in the little 1600cc engine, so I'd have to open the throttle some too. By varying the throttle, I'd get AFRs and mixes between pretty much just propane and air at a 30:1 to something in between, like a 20:1 AFR of air and propane and gasoline.

To top off all three modes I have a fully adjustable digital programable distributor already installed that can hold up to 4 32x32 spark tables. You can switch between spark tables by means of dip switches in the distributor, but I think I can carefully solder some wires so that the switches can be switched outside of the distributor. That way I can set up a spark table for each mode and switch between them as I switch between modes.

If my theory is right the engine would be able to run very lean due to the flame propagation of the propane and still run on mostly gasoline. This should result in lower emissions across the board as well as lower engine temperatures.

[oil pan 4]

One thing I have considered using propane in a gasoline engine for is a fuel trim adjustment.

How it would work is set the carb on the leaner side, use engine vacuum and throttle position to automatically detect the proper conditions for enrichment, maybe I could even find a wide band O2 meter with an output that energizes when certain air fuel ratios are met as a control.
Use a needle valve or possibly a hvac stepper valve to meter propane into the carb.

This would also aid in cold starting a carb with a good lean tune since they tend to run really bad at first.