Anybody know of an inexpensive way to build a propane injection system rather than buying a $600-700 system? And what kind of mpg increase, power increase can I expect. Thanks

 

http://www.members.shaw.ca/k2pilot/P...20article.html

 

Building a DIY propane system is fairly easy.

Building an effective DIY propane system is not easy.

Most simple propane systems use a single constant flow jet to meter propane into the intake air. The result is to much propane at times of low demand and not enough at times of high demand (when you really need it).
Some sort of variable flow system, complete with control mechanism, is the only way to ensure that available propane matches demand.
Many variable systems use multiple (usually 3) jets to control the amount of propane injected into the intake air. Opening and closing the supply line to each jet when certain trigger points are passed, during increasing or decreasing demand, controls the amount of available propane. This system only partially addresses the problem, since each individual jet is constant flow and the pressure of the propane is constant the supply increases in stair-step fashion leaving the leading edge of each step oversupplied and the trasiling edge undersupplied.
The only way to optimize available propane at all demand levels is by using a constantly variable pressure regulator and therein liers two problems first is expense and second is how to control it.

There are also safety concerns to consider, if a single drop of liquid propane enters the intake air stream it could cost you an engine.

I did a lot of research before adding Propane injection to my truck. My conclusion -- the Powershot 2000 offered the best solution. It comes with a constantly variable regulator that is controlled by boost and it is a vapor phase system which almost eliminates the possibility of liquid propane entering the distribution system, the only way that could happen would be turn the tank upside down.

 

I've been running my home-built system for about 2.5 years now and it works great. The original system was 2-stage but the power was too choppy. I have upgraded it to 4-stages and it works much better. With four stages I was able to decrease the supply pressure which took care of the "leading edge of each step oversupplied and the trailing edge undersupplied" problem that Phy mentioned above. <O></O>

All four stages use 12 VDC 1/4" NPT solenoids. The solenoids are controlled differently for each stage. The first stage is very low flow controlled by a limit switch on my gas pedal to activate the solenoid. Basically, anytime I hit the gas, the propane is on. The 2nd and 3rd stages are medium flow controlled by 2 standard auto pressure switches at 4 and 8 psi, respectively (boost pressure of course). The 4th solenoid is high flow controlled by a pressure switch set at 14 psi. <O></O>

I have to say, the info given above is very basic and the system was quite challenging to build even with my engineering background. I had to take in account safety, size and location of the system under the hood, C3 flow rates, C3 pressures, 12 VDC power supply, activation points, and lots of "back to the drawing board." <O></O>

As far as price - ~$300. However, I was able to use some stainless steel fitting that I have acquired over the years. This saved me a little bit of $.<O></O>

Anyway, I only recommend building it if you know what you’re doing.

I don't post to often, in fact, I lost my original account name and this is my new one. Anyway, if your serious about building it, I can see if I can find my parts list.

 

Pokerface5,
Welcome to FTE, again.
I built a single stage system for my 6.9 turbo.
I will agree that just using a single stage system or one that is activated by the throttle position alone is sad at best.
Just because you are at WOT does not indicate you are up in RPM or boost and the over applied propane does nothing good for you.
For a while I went to total manual control, but that was such a pain I finally removed the system from my truck.

I have been considering a system like yours, but have not taken the time to find pressure switches like you used to control stage two thru four.

Did you use seperate nozzles for each of your stages?
That is the best way to my way of thinking.
I would be interested in seeing what you used for pressure switches.