Do it Yourself Diesel Propane Injection.... DON'T TRY THIS AT HOME!

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Do it Yourself Diesel Propane Injection.... DON'T TRY THIS AT HOME!

Post by WTF on Sat Jan 31, 2015 9:36 pm

Liquid Propane Gas (LPG) is both a primary and supplemental fuel in diesel engines almost since their inception a century ago for good reason.
Although LPG has less energy potential by volume, it releases its energy in a slightly different way than diesel, making it a cheap and convenient way to increase horsepower and fuel economy at the flick of a switch

The Plan

   Understand a few basics before introducing propane into your engine. First, propane is a fuel (not an oxidizer like nitrous oxide) and will explode sooner in the combustion chamber than diesel will. Mixing excess amounts of propane with diesel fuel will cause your engine to work against itself and blow up.

   Secondly, propane's primary benefit is that it rapidly cools the incoming air and acts as a sort of chemical intercooler. Be careful about how much you inject; around 70 horsepower you'll reach a point of diminishing returns and risk blowing the motor.

What You'll Need

   It really matters little whether you're working on a Powerstroke, Cummins, Duramax or an L-series Rover diesel; installation will be almost identical for any engine. A propane injection set-up won't be foreign territory for anyone familiar with home propane set-ups, as you'll find the same basic parts on any LPG stove or water heater. You'll need a propane tank, hose, regulator and pressure gauge (all of which are available at your local RV store, welding supply shop or franchise hardware store). Use a 12-volt normally closed solenoid valve (available online) and the wiring and a toggle switch to trigger the system. The entire project should set you back less than 150 smackers, not including the cost of propane, but the following system uses what is referred to as a BLOS Venturi Carb specifically for LPG - though commonly used on petrol engines - and that is around €120 on it's own.

We decided to conduct this installation of a fairly well used Rover 420 SDI...

And we are definitely going to lose the spare wheel on this one!

Now time to run the tank solenoid power feed and and the gas pipes.

So after much messing about trying not to put any kinks in the copper pipe, and to feed it neatly, safely (no chafing, rubbing or possible short circuits) and securing it to the chassis - Cutting a hole in the bumper and fitting the filler -  It was time to start at the business end...

Wires must now be run to the under hood solenoid and mixer.  This will be governed overall by a pedal switch ...

So the Mixer is now installed with wire fed via relay to the solenoid, the Gas feed pipe is attached to it, and the output now goes into the Blos, with a significantly reduced internal diameter. (a sleeved 1 mm Copper pipe)...  

Successfully modified a PSF 109 Vacuum switch by taking out the internal spring. It now runs as a pressure switch on the bleed side of a boost valve. Not ideal for adjustment as it is very sensitive, but it was what I had lying around. And it cost zero dollar.  Ideal activation pressure would be 7-10psi.  I run at 4psi for a kick in the pants, but the switch itself will only receive power from the (yet to be fitted) pedal switch when I floor it Smile

Voila - My DIY Pressure switch controlling the LPG fuel into the mixer.

It also lights up an led when the switch is activated so I know when the system is live and at what pressure. Great for trial runs before gas introduction
I will also be attaching a standard gas solenoid on the BLOS, because the pipe diameter vs flow rate with the injection mixer is nothing like a traditional diaphragm regulator, it will allow me to revert back to small diameter gas pipe. This means when I get to a predetermined pedal position, the fuel can be cut off of or activated. Once activated it will only kick in at the predetermined boost level (currently 4psi) and open the LPG feed. The overun boost that is encountered from the introduction of fuel after lifting off can also be controlled by dump valve or wast-gate solenoid, but the initial solenoid will prevent over bleed from the LPG that would still be in the mixer pipes.

Below is the boost activated led.  This will light up when the system is active.
It will be used for tuning the pressure switch and also allowing me to see when the gas is feeding and at what pressure. I will tidy it up later. Incidentally the same system can be similarly rigged as a Shift Light. Not as accurate as using your timing to activate the light, but very cheap and will achieve good results if your boost / vacuum pressures remain constant for the RPM you wish to program, in the specific condition's you would wish to use it.

Now to fit my chosen switch for pedal activation / deactivation.
It will control any solenoid mods that I choose to attribute to it. Mainly to be used as a lift off - shut off switch for the LPG, but it's secondary activation stage will again be via the boost pressure switch.

Now for some groveling in the drivers footwell.  This is where the activation switch will be fitted directly coming into contact with the throttle pedal.  Only one hole and a tight screw - as the actress said to the bishop....

Now run the cables back to the power source for the pressure switch - and job DONE!

Results were indeed profound and impressive, but before full data logging was complete, the rusty bonnet gave way to a smashed windshield, and this project soon became beyond economical repair - considering of course this was a cheap or free project and finances or investment capitol were non existent - however, it was much fun and we learned alot in the process -  until the final nail was hammered into the coffin.

The achivement from backyard junk was comparable to this $800 CNG conversion  - though my estimation for the Rover in it's limited state of tune would be around 80 - 90 mpg - not the 120 mpg stated in the video - although my aim was 100 mpg


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