Propane Conversion On A GM 2.2 Engine

Below are pictures of the parts I cast and machined from aluminum on down to the finished product. Obtaining maximum efficiency is an ongoing project, I may have more advanced developments in the mixer as I go. The current setup is getting me about 20 MPG on propane which is now the primary fuel. You can click the images to enlarge.

Background:
Experiences with places that sell kits:
OK, if your're here reading this then you've probably already found a dozen websites or so that sell conversion kits for various engines and some of them even state if you have a fuel injected engine don't bother to contact them because they will not help or even sell you parts. In my experience with one website, I was just looking for a place to buy regulators, so I called them and told the guy I was looking for an Impco regulator to use with the mixer I built. Now this was supposed to be one of those custom kit places, but he just couldn't grasp the concept that I built a mixer from scratch. It kind of makes you wonder how limited their custom work is? Bottom line was, I knew exactly what I wanted, the guy wasn't all that friendly and wasn't interested in selling individual parts. He gave me the impression that if I wasn't going to buy a kit then he didn't want to talk to me. So much for customer service. I believe they put together the kits they sell, basically matched regulator and carburetor sets with fittings so they would've had parts. I wasn't about to spend $800.00 for a kit that I would only be able to use pieces from. You can get the parts for way less than the price of a kit anyway, that is if you're willing put put a little more effort into it. Now i'm not saying all of them are like that because they are not. I picked this particular one out because I believe it was a small company, maybe 4 employees at the most and usually they are more helpful. I will not mention the name but beware.

It used to be that propane was more expensive to run than gasoline, now it's almost cheaper to run propane if the system is setup right, at least in my area it is. The unique thing about propane is it is one of the most widely available alternative fuels in the US and is the 3rd option in motor fuels behind diesel and gasoline. It is also the next best alternative to gasoline in terms of how much power it can produce, and aproximately 88% of the propane we use is produced right here in the US from natural gas wells and oil refining. Although it's not so common to see a vehicle that runs on propane here in Ohio (except for propane delivery trucks & Swans) it can still be easily found at gas stations and truck stops. It is common to see propane powered forklifts around here but the majority of tanks being filled are grill & RV tanks. If you buy in larger amounts like a 100lb bottle you will get more fuel for the money, but this depends on your supplier of course. I currently run my backup generator and portable welder on propane and both work great. I don't have to worry about the gas going bad. I wanted to run my truck on propane. Since this has a fuel injected engine you just can't simply go buy a kit like you would with a carbureted engine, so I had to design and build the mixer myself. It took about a week to build the mixer from design to casting the parts from aluminum and doing the finish machining. I wasn't able to get any pics of the casting and machining process of the main part of the mixer. I didn't have the camera on hand, sorry. There were a few reasons why I wanted to run propane. 1- Propane is a cleaner burning fuel and is better for the environment. 2- Engines that run on propane typically last longer, it doesn't wash down the cylinder walls and you don't get that carbon buildup. 3- With $3.00 a gallon gas it may save some $$ on fuel and even if the prices were the same why not run the cleaner burning fuel. If you decide you're going to attempt a conversion on a fuel injected engine there are a few things you need to do. First you need to be familliar with engines in general, comfortable working on them and have some knowledge of the ignition, fuel and computer systems. All this is going to help determine wether or not it's going to work. Next if you don't have the technical service manual, go get one. It will have all the specs and wiring diagrams that will make things way easier on you.

The Details:
What we've done here is convert a GM 2.2 4 cylinder fuel injected engine to a dual fuel (propane/gasoline) engine. This engine has the throttle body with four individual injectors. Since they aren't in the way and will not affect the performance they can be left in place. This makes it ideal for a dual-fuel system. Since the injectors do not send any feedback to the computer it doesn't know when they're turned off. My truck is a 96 Isuzu. I suspect it could be a problem with some of the newer models of any vehicle which would make the conversion more dificult as the systems get more complex and components like injectors may send feedback data to the computer. In this case I was able to just simply turn the injectors off. This was done by adding a relay and switch which allows you to go from one to the other. The mixer we cast and machined from aluminum is 3" OD where the air cleaner and throttle body hoses are attatched and a little bigger diameter in it's center section. The inside is machined so it tapers in going toward the throttle body, and there's also an air regulator plate that goes in which helps regulate the air/gas ratio. Propane has a much narrower window of combustion in terms of the air/gas ratio than gasoline, and it also has a higher ignition temp. The throttle body air intake is actually larger than required so it therefore has to be reduced at the right place in the propane mixer to get the venturi effect or the engine won't throttle properly. The air regulator plate also helps with this as it's located on the taper side of the mixer. The regulator/converter I used is a typical regulator found on forklifts that takes liquid LPG converts it to a gas and also regulates the gas to the engine. You need to draw the liquid off the tank or it will freeze up after a while. The regulator is heated from the engines coolant. I simply re-routed the heater hose through the regulator and back to the heater core. Since the airflow is very minimal when the engine is idling it's unable to pull fuel from the regulator so I needed to add an idle line which comes out of the idle port on the regulator through a needle valve and this is your idle adjustment. I'm still testing and doing some fine tuning but so far the system works very well and the engine seems to run smoother on propane. The engine temperature is running exactly the same as it does on gasoline. You can be going down the road and all you have to do is flip the switch to run one fuel or the other and it does it instantly. Different engines will be setup differently although most of the parts like your regulator/converters are the same but mixer size and design will vary. Generally regulators have a HP range they will work on. I had to change the secondary spring in mine to make it work. I am very pleased with the results of my current mixer, but I will probably design a more complex mixer that will hopefully maximize efficiency and performance even more. I would probably recomend Impco's line of regulators and mixers for multi-cylinder engines even though I didn't use them on this project mainly because I built a custom mixer. For small single and twin cylinder engines I like Beams line of regulators. I think the model 202A secondary regulator is what I used on my generator and welder. Under most conditions it's really not necessary to use a liquid setup for small engines, but if you live somewhere where it gets really cold during the winter you might consider it. A regular 20lb or 100lb tank is all you need under normal conditions.