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post #1 of 69 (permalink) Old 11-18-2012, 01:29 PM Thread Starter
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Cool DIY Propane Injection.

I've been approached by several folks to do a little talk on Propane Injection. OK, I'll do that, but first I want ya'll to hear something.

Propane Injection is nothing new! I first experienced it from a Diesel Mechanic that worked on a farm and plantation in the south back in the 70's.
He was a good friend, his Employer had seveal tractors that were getting too small for his place. He was overworking them.
His Mechanic, my friend had talked to his dad, had told him how he did it years earlier in a construction co. that had a big, D9 Dozer that needed a little help from time to time.
Back then, they just mounted a bottle by the drivers seat, hooked a small regulator to keep the pressure under control, ran a hose up to the intake just ahead of the turbo, and installed a hose there to spray a fog into the intake tube.
When power was needed, you just cracked the valve open just a little, then turned it off. You only add this when your motor is reved up and you need power. Some folks used it to cut down of fuel consumption and to add a little pep....the regulator was just cranked down lower.

Diesel only burns 70 to 75% in the motor, wasted fuel is passed out the exhaust. POWER ADDERS like propane injection and Nitrious just help burn the little extra thats left over in the combustion chambers. This is not rocket science, nor is it VooDoo, it just simply works.
In this day and age of high fuel prices and parts, we can all benefit from this! All you have to do is choose your system, hook it up, and HAVE IT TURNED DOWN AT FIRST, then gradually increase your pressure. A little bit will go a long way. And don't just add this to a running motor! Your rpm has to be up above idle.
I'm not condoning the use of this by idiots or morons, USE THIS AT YOUR OWN RISK! I WILL NOT BE HELD RESPONSIBLE FOR YOUR STUPIDITY! This is completely safe if hooked up correctly! Thousands of poeple have done it!

Theres 2 systems, and I have the latter, because I wanted the adjustability. The first on is the most safe, and is highly suggested for the first timer.
I will refer to this one as the BBQ Method. The parts list is simple.
I'm gonna tell you how to do it, I will supply my knowledge, you must look up the parts yourself. This is not hard people! It does not take a Genius to do this!

The BBQ Method is just as it sounds, you use a BBQ setup. This injects propane at less that 1 psi, and this wil increase mileage and add some pep. The bottle, the regulator (2 Stage) and the hose. Mount your bottle in your bed, I use a 30# bottle with a fryer/BBQ regulator. You can pick these up at Tractor Supply, Lowes, etc., for about $44 and up. Get a hose to run up to your intake, hook it into your intake tube just behind your air cleaner. You need a good, tight connection. Tap the inside of your fitting, screw in a small piece of copper tubing and insert a furnace or burner jet. Put your jet toward the center of the tube. I use a # 60. OK, a carb jet can work too....just make sure everything is tight and secure or your turbo will eat it and throw shrapnel into your intercooler and/or motor. I'm paranoid, so, I have a piece of screenwire over my turbo intake to keep things like that from happening.
Now, we need to add the electrical part of our system.
I install a Hobbs switch the is in a Tee with the oil pressure sensor. The Hobbs switch has a switched 12 Volt accessory wire, going to it. I pick up this wire at the Fusible link section there on the Drivers fender. Put a heavy Duty 12 volt Toggle switch right on the dash wired into there....this will be your Emergency Kill Switch! I use a heavy duty switch from Cole Hersee, they're about 10 bucks, and I have a red flip up cover on that switch, so, you know what it does! After the Hobbs switch senses oil pressure, it feeds its current to a universal 12 volt relay. That relay energizes a small fuse block on the inner fender on the drivers side.
Now then, right behind the pressure regulator on your bottle, you have to cut your new line and install a 12 volt Pressure solenoid. You can find these thru your camper supply folks, or your Auto parts place if they are good parts folks. I used Impeco's. And You Will Need 2 of these!!!! You can get them from Google or on Ebay. The Universals they sell on Ebay and Amazon are about $20 but the Impeco's are rated for Propane....
Hook the Pressure solenoid up to another toggle switch in your cab on your dash. Now run this back to your small fuseblock thats hooked to your relay thats hooked to your Hobbs switch. (Now, I actually use a relay for each Pressure solenoid, but thats just me. These draw some current, I just wanted to be safe.)

Now for a small recap! When your bottle is turned on, theres no pressure flooding into your intake. Its stopped at the 12 volt pressure solenoid. You start your motor, now the Hobbs switch is energized, energizing the small fuse block, allowing the relay to activate, BUT only if the switch inside on your dash is on. This is your emergency kill switch. Turn this switch off, it kills everything, because it shuts down your small fuse block.
We're almost there!

Now, go to Radioshack, or your automove parts store, get a roller arm micro switch, much like is used to activate a nitrious system, mount this were the throttle cable is hooked to your injector pump, and adust it so its activated a bit above idle. Hook this up to your fuse block.
Now, Remember thet OTHER 12 volts pressure solenoid you purchased???? Now, find a good spot up on your pass, fender, mount it close to your air cleaner. Cut your line and hook in inline there. Run a wire from your micro switch to your 3rd Toggle switch on your dash, then from your dash to your fuse block. Run the wire from the other side of your micro switch, to your 12 volt solenoid by your air cleaner.
Your system is now complete. I didn't supply part #'s because you might not be able to get what I used, so, you can substitute whats needed.
All thats needed now is adjustment. ROUGHLY set you regulator on your bottle to 10 PSI, if your using the "Serious" System. Set your other regulator by your aircleaner to 1 PSI or to where it just barely reads. Don't go any higher than 1 until you've driven it some. The BBQ is Non-adjustable....will increase your milage and add a little pep. The More pressure you add, the less MPG and more power you'll have.

By each switch, inline, on the dash, I mounted a LED for each switch so I could see which is active. I have them labeled....the E-Stop has a red LED to let you know everything is active at the fuse block. The 1st solenoid is a green LED so is the 2nd Solenoid....The last green LED thats wired into the microswitch will go on and off, as you step on the accelerator. I find this quite handy adjusting the switch....
Let me also add, this system, I've redone it several, its safety first with this system. Now, I also used universal 12 volt relays to activate these 2 pressure solenoids, just to be safe.

The 2nd System I call the "Serious" system does not use the universal low pressure regulator from a BBQ, but uses a 2 stage welding regulator, regulated down to 10 PSI. Then, just before the 2nd pressure solenoid, I have another regulator where THAT regulates the line pressure down to 1 PSI.I have a pressure gauge there right after that regulator! At less than 1 PSI, you get good fuel milage, its only injected when that microswitch on the throttle is energized. Above 1 PSI, its less mileage and more power. I have known forks to use up to 5 or 6 PSI, but do this at your own can melt your pistons!!!! BIG POWER CAN BE HAD, AT THE DANGER OF SERIOUS ENGINE DAMAGE!!!!!

I use that latter system because I can adjust things myself. Every truck is different! A non-Turbo truck will be more sensitive to adjustments.... I did use the BBQ system for years, raising my fuel milage by 4 to 6 MPG's. That was while I was using 215-75-R16's.
With the Serious System I run 235-75-R16's, and I'm lite on the throttle to get good fuel milage. The reason for 2 regulateors on my "Serious" System, is also, every truck is different. so you might want to add a little, or take a little away.
Also, during the summer months when its hot as hell, with the welding regulator on the bottle,(theres a adaptor for that), the pressure fluctuates somewhat, so, thats the reason for the 2nd regulator. 1st one is for rough adjustments, the 2nd one is for fine tuning!

Now, for the Parts list:
1. (3) Heavy Duty Cole Hursee toggle switches, 1 with a red flipup cover, about $12 each
2. (3)-1/8" 12 volt LED's, 1-red, 2-green ($5 ea. with holder)
3. (3)-Universal 12 Volt relays (about $6 from O'Reillys)
4. 100' roll of 14 Ga. wire.
5. 10' of #8 or #6 wire to feed fuse block.
6. (2)-pressure solenoids, 3/8's or 1/4" ports ( As low as $20 ea. to as high as about $100 ea.)
7. (1)-HeavyDuty Microswitch ($8 at RadioShack, $6 at Wholesale Elect. Supplier)
8. 15' Propane hose ($20 from Lowes or Tractor Supply for Fryer or Propane heating torch, or get one made up by welding shop for 1/2 that!)
9. A pressure gauge to install right after the 2nd regulator if your using the "Serious " System. Usually theres a 1/4" NPT port on the regulator, but if not, use a T there for your pressure gauge to screw into. ($8 for the gauge from Tractor Supply or Industrial Supplier, $3 for the T)
10. (1)-30 Pound tank from Tractor Supply, but the one from Lowes is DOT certified....(I use 2, one to fill as a spare and one on my truck)
11. Assorted hardware like Spade terminals, male and females for your wiring, hooling up stuff. Pipe sealant. Use HeatShrink tubing! Fuse for safety....don't burn your truck down!
12. A universal 2 stage non-adjustable regulater from Tractor Supply or Lowes, From $45 to $65. This is for the BBQ Setup. The "Serious" Setup uses 2 stage welding regulator that screws directly to the bottle. (About $85 on up) The low pressure regulator will usually run about $25 to $45 bucks, can pick these up most anyplace that sells propane or compressed gas equipment.

Last but not least, if you smell propane while the truck is parked, DON"T START IT! You left a switch on/something stuck/ or a line is broken! CHECK IT OUT!
I have mine adjusted, and I leave all 3 toggle switches on! The other 2 just for the solenoids are mostly for troubleshooting purposing, and so you can control them should a malfunction happen. It helps divide the system up should there be a propane leak somewhere.
I leave my bottle on, the solenoid shuts everything down when the motor isn't on....REASON FOR HOBBS SWITCH!

PS- Let just add that Propane, while it is a fuel, is quite safe! To be conbustionable, or explosive, you have to have a certain amount of air to a certain amount of propane. I did work around this stuff alot welding. Below that threshhold, nothing happens, anything above that threshold, it might go 'POOF' and scare the hell outta you and burn your eyebrows and hair off, but won't explode. It will only explode if contained inside of a enclosed space, and under the right amount of air or oxygen.
Don't enclose your bottle in a toolbox. I have mine mounted under a trapdoor on the bed of my truck and its nestled in a small cradle, upright. Air can circulate around it and its not enclosed.
Its out of view of the cops and Troopers....outta sight, outta mind. If a DOT person sees you with a non tied down bottle in your bed, be prepared for a Big Ticket! Mount it where it can't be seen, or Put a cover over it!
It helps keep the sun from shining directly on your bottle, keeps your pressure even.....also, those puppies have a burst cap on them should the pressure get too high, it'll vent to the atmosphere!

"----If it ain't loud, lowered, long, and ain't belchin' black don't have at least 1 ain't about S***!"-SCREAMIN' METAL

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post #2 of 69 (permalink) Old 11-18-2012, 01:40 PM
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Just so it's been asked: if this is the fix for all that fuel being dumped out the exhaust (25 ~ 30% ), how come everybody isn't doing it?

While you cover the assembly of the system, how does one go about tuning the regulators so as to arrive at the right mix for the best mpg or that extra power? Perhaps I missed it above.

Do you have any before and after results that we can consider? How does the cost of the propane affect the implied diesel fuel savings?

So that I understand the mechanical side of things better, how is adding an additional fuel gonna make use the that wasted fuel?

Since propane is a fuel, adding it to the mix, what does the EGT gauge think of it?

How long can one expect the 30# cylinder of propane to last?

Original owner of a plain'ol VE fueled '93 W250 ClubCab. Green

Last edited by BC847; 11-18-2012 at 01:49 PM.
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post #3 of 69 (permalink) Old 11-18-2012, 02:45 PM Thread Starter
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Set your high pressure regulator to 10, low pressure regulator to 1 psi. Turn up your low pressure up or down to suite your needs. The BBQ systen is non adjustable and is strictly for fuel mileage.
My '91 Dodge Cummins Turbo Diesel with a DIY cool air intake, stock motor, with 215-75-R162 got about 18 mpg with a flatbed, small toolbox. I added a small welder, bottles, droped to 16 mpg.
I added the BBQ System, I got back up to the 21 to 22 MPG range. This was being light on the throttle.
I started using 10% WMO, as per Cummins Guidelines, I increased to 23 to 24.5 mpg's. I did this over a period of 3 1/2 years, writting down my milage and figuring it up.
Next. I went my "Serious" System, I started adjusting my low pressure side. I run right at 1 PSI. I got roughly 27 MPG, thats with my truck weighing #8500! Thats 1 PSI, and with 3 gallons of Waste Motor Oil pouring into my diesel tank every 3rd tank. I don't run my truck completely out. That was at the end of 2010. I had been running the "Serious" System for 5 years.
I changed now to 235-75-R16's and am now getting almost 29 MPG's with light throttle. Drive it aggressively and it drops to 24 to 26 mpg's.
A #30 tank lasts me almost 1000 miles, which is about 2 months....

Check this out!

"----If it ain't loud, lowered, long, and ain't belchin' black don't have at least 1 ain't about S***!"-SCREAMIN' METAL

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post #4 of 69 (permalink) Old 11-18-2012, 02:48 PM Thread Starter
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Heres some more into I just happened to look up for my friend that did his truck....
This is from EHow....

Do it Yourself Diesel Propane Injection
By Richard Rowe, eHow Contributor, last updated May 05, 2012
Do it Yourself Diesel Propane Injection
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.
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1. 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.
2. What You'll Need
It really matters little whether you're working on a Powerstroke, Cummins or Duramax 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, not including the cost of propane.
The first thing you'll need to mount is the propane tank, then (in this order) the pressure gauge, pressure regulator and solenoid valve. Run a line from the solenoid valve to the air filter box, connect your on/off switch to the valve and you're almost done.
Although this basic setup will indeed introduce propane into your engine, you're far from finished. You might seriously want to consider mounting a servo to your pressure regulator, which should be connected to a cab-mounted dimmer-style switch. This will give you some much-needed real-time control over the amount of propane being injected, a setting vital to preventing engine destruction while introducing enough to make power.
Tuning and Triggering
Don't trigger the propane injection if your engine is idling, decelerating or the turbo is producing less than 5 psi of boost. In other words, flip the switch only when your engine is under load and boosting. When tuning the amount of propane injected, start with the valve just open and continue to increase the amount of pressure until you start to hear pinging, then back it off by about 5 psi.
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"----If it ain't loud, lowered, long, and ain't belchin' black don't have at least 1 ain't about S***!"-SCREAMIN' METAL

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And here's another one....from one of the other sites by another Propaner.....

LPG Fumigation
Page One

Lately, I've been getting quite a lot of e-mail from folks who are interested in the LPG Fumigation system that I have installed on the Pusher, so it makes some sense to have a page dedicated to that subject, with at least as much as I know about it, and some links to other resources.
What it is...and why:
Simply stated, Propane (LPG) Fumigation is the introduction of gaseous propane into the air intake of a diesel engine for the purposes of attaining more power, economy, or both. The parallel is often made between fumigation and using Nitrous Oxide on gasoline vehicles to achieve a power increase. This analogy is similar, although the properly implemented use of LPG on a diesel engine will actually result in a better-running engine without the possible damaging effects that N2O has on gas motors.
Exhaust emissions are reduced as a result, with lower quantities of unburned hydrocarbons and fewer particulates (smoke). LPG fumigation will even clean up the odor of diesel fuel in the exhaust, making the smell from the tailpipe of an engine utilizing it much less objectionable.
How it works:
Introducing LPG gas into the combustion air intake of a diesel engine acts as an accelerant, promoting the even burning of the diesel fuel, and more complete combustion, resulting in more power being produced. Many web pages and forum posts will call LPG a "catalyst" but this is not correct, as LPG creates no change in the molecular makeup of either the air or the diesel fuel.
Propane by itself resists self-ignition inside a diesel-fuel compression-ignition engine due to it's high flash point and narrow fuel-to-air ratio. During the compression stroke, the air/LPG mixture is compressed and the temperature is raised to about 400C, not enough to ignite the LPG, which has an ignition temperature of about 500C. In the small concentrations that LPG fumigation uses, the LPG mixture is not rich enough to be overly flammable and is more difficult to ignite. When the diesel fuel is atomized into the cylinder under high pressure, it immediately self-ignites (diesel ignites at about 385C.), and causes the LPG to burn as well. Since the LPG is in mixture with the air, the flame front from the diesel spreads more quickly, and more completely, including igniting the air/fuel mixture which is in contact with the cylinder walls, which are cool in comparison to the super-heated air inside the combustion chamber. Much of the cleaner burning of the fuel is attributed to this ignition against the "cooler" components of the engine, and accounts for raising the percentage of combustion from a typical 75% for a well-tuned diesel engine running on pure diesel fuel alone, to 85-90% with the addition of LPG. Obviously, this more complete combustion also gives a nice boost in power, with an accompanying increase in fuel economy and reduction of pollutants.
What to Expect:
OK, here's where we have to draw a distinction between engine types. Normally-aspirated engines require different systems to introduce the gas than do turbocharged engines. The results are different as well.
Normally-aspirated (N/A) engines will realize only a modest gain in power by the use of LPG gas. Displacing 0.5% of the intake air with LPG will result in a small power increase, perhaps 5-8%. Nearly no increase in power will be noted at full throttle, assuming that your injection pump is correctly adjusted already. Attempting to provide more gas to the engine will not increase performance, and will in fact lead to a condition not unlike pre-ignition in a gasoline engine. This has been attributed to excessive peak pressure inside the combustion chamber, and may have a lot to do with the fact that most N/A engines are also IDI (Indirect Injection), which means that the diesel fuel is not injected directly into the combustion cylinder, but instead enters a "swirl chamber" where ignition takes place. The flame front then shoots out of the swirl chamber into the combustion chamber, where it combines with the air (and LPG) to force the piston down in a power stroke. Apparently, these engines have a problem in that the flame front exiting the swirl chamber ignites the LPG/air mixture, all of which burns instantly instead of in a metered, controlled manner as it would during the normal diesel injection window.
I have had satisfactory results on my VW 1.6 N/A engine when adding LPG at a rate of 8-10% of the BTU rating of the diesel the engine is using. It may be possible to turn the fuel up, but I do know for sure that too much fuel does not increase power, and causes the engine to make very unhappy noises.
It's worth noting that if you experience a big increase in power on a naturally-aspirated diesel engine after installing an LPG fumigation system, then you should go back and check to see that your injection pump was adjusted to provide a nearly stoicheometric air-to-fuel ratio at maximum throttle without the LPG turned on. It's possible that the significant power boost you are seeing is due to the engine now being adequately fueled for the first time. The additional BTU content of the LPG is simply being substituted for the diesel fuel that you haven't been injecting all along.
Turbocharged diesel engines are able to realize a significant increase in power by using LPG fumigation. While the usual suggested increase is considered to be approximately 20%, by careful management of the gas introduction, power gains of up to 40% are possible. My understanding is that it is a very fine line between lots of extra power and a dose of LPG that will render an engine scrap metal in a hurry, so consider carefully before you decide to "turn it up".
Turbo engines are by design blessed with a lean air-to-fuel ratio, and can be fed concentrations of LPG up to about 6-8% of the intake air volume. TDI (Turbo Direct Injection) engines have shown dramatic power increases when properly fumigated with LPG, combined with an "Upsolute" chip, or computer engine management upgrade. (Of course, these modifications will void any manufacturers warranties...)
Types of systems:
I am aware of two basic fumigation systems.
The first, I call the "dump" system, which means that you pick a value of propane to feed to the engine, either by calculation, or by trial-and-error, and you simply "dump" it into the air intake. Little provision is possible for correcting gas flow depending on engine load, so the system is probably only optimized for one type of load demand. The advantage is that this type of system can be cobbled to together by backyard experimenters like myself at a low cost. The disadvantages are that you will probably need to error on the side of caution to make sure that you aren't overloading your engine with too much gas, and that the system doesn't compensate for variations in engine speed, load, etc.
The second system is much more sophisticated, and uses a variety of sensors and controls to monitor engine performance and load, and adjust the gas flow to suit the need at the moment. Most commercially available systems will be of this type.
Levels of fumigation are best utilized in the mid to high power ranges. Determining when the engine is operating in these ranges is problematic. Accelerator (fuel lever) position sensing is not a reliable indicator for load on the engine due to most diesel engines being governed. Additionally, diesel injection pumps have internal fuel adjustment and regulation devices which make fuel lever position inaccurate in relation to engine load. On modern diesel engines using management computers may mean that the accelerator position means very little to the actual engine load, the injection system being "fly-by-wire". The vehicle operator may have the accelerator to the floor, while the computer is waiting for boost to build, or limiting fueling due to engine RPMs, etc.
Intake air volume is not a particularly good indicator of load for naturally-aspirated engines. Since diesel engines are "throttleless", they operate without a butterfly plate restriction in the intake air flow. As a result, the flow of air through the engine is mostly constant for any given engine RPM, independent of load. On turbocharged engines, air flow can be regarded as a reliable indicator of load while running "on boost".
There are systems that have been designed around intake volume to regulate LPG gas flow to the engine. Since diesel engines have no natural intake manifold vacuum, a venturi must be placed in the air intake. A sample of the vacuum produced by the venturi is fed to a metering system, either electronic or mechanical, which adjusts the gas flow to suit the circumstances.

The installation consists of a specially designed, branched duct fitted to the fresh air inlet of the existing
air filter. The branch is connected by hose to a standard automotive demand-type LPG mixer.
(Photo and text courtesy of the Society of Automotive Engineers)

Turbo engines have a great indicator of load built in. It's a fairly simple process to take a sample of the boost pressure developed by the turbocharger and use that to control the metering system. Most commercially made systems are designed for turbo engines, both for this reason, and because of the greater power gain that the turbo realizes from fumigation. Since boost is such a reliable indicator of engine load, higher values of fumigation can be realized, with tighter control over the results. Remember that turbochargers are not simple volume-driven compressors, but actually use some of the heat contained in the exhaust gasses, converting it into mechanical energy to produce boost. More load means more heat, which means more boost, which means more fueling, which means more heat, well, you get the idea, it's an upward-spiralling chain of events.
Mechanically supercharged engines aren't going to provide the accuracy of turbo boost, due to the boost pressure being a product of engine RPM rather than load.
The best and most reliable indicator of engine load is fuel flow, but this is difficult to measure accurately. Diesel fuel injection systems pass a greater flow of fuel through the pump than the engine is consuming, the excess being returned to the fuel tank. A differential fuel monitor must be designed and installed which can measure fuel arriving to the injection system and returning to the tank, the difference in the flows being the fuel the engine is consuming. Obviously, this is beyond the the scope of this document, although modern electronic engine management systems may have this fuel flow information available in the engine data stream. Megasquirt, anyone?

Next, we explore theconstruction of a basic LPG system.

"----If it ain't loud, lowered, long, and ain't belchin' black don't have at least 1 ain't about S***!"-SCREAMIN' METAL

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LPG Fumigation
Page Two

Construction of My System:
This page describes the components of a basic fumigation system

But first, a word from the Shark legal department:


LP gas, like any combustible fuel can be dangerous. If you are going to attempt to construct your own fumigation system, be aware of the hazards present when you use this fuel. Use proper fittings and fixtures, and be aware of the high pressure present at the output of an LPG storage tank. Gaseous propane is heavier than air, and can collect in enclosed places. Any containment of a tank must be properly vented. Never check for gas leaks using a flame. ETC, ETC, ETC. This isnotintended to be a complete tutorial on good engineering practice for flammable gas systems. You should be familiar with the tools and techniques of gas plumbing systems before attempting construction of such a system.
Additionally, while adding fumigation equipment to a diesel engine is becoming a commonly accepted practice, keep in mind that doing so may void your warranty, negate any emissions certifications your engine has and/or violate local or state vehicle codes. It is not impossible that done incorrectly, adding LPG to your diesel engine will cause damage to it's operation or construction.
The information contained here is believed to be accurate, but like anything else, is not necessarily 100% infallible. Use your own judgement, applied to your own circumstances.
All of this is meant to say: "YOUare ultimately responsible for any and all actions thatYOUmay take after reading this web page. In no event, will I be responsible for any damage to your property or person, or that of any others as a result of anything you do with the information contained here".

Mr. Sharkey's is a litigation-free zone!

OK, now that that's out of the way (can't be too careful these days), we can get down to business.
The Tank and Regulator:
What type of tank you use may depend a lot of what type of vehicle you intend to use it on. If you are adding a system to a large truck or a motor home, you will probably have plenty of room for a frame-mounted horizontal tank. If it's a motor home, you may not need to add a tank at all, just use the existing one, although an additional regulator may be necessary, depending on the type of system you install. The smaller the vehicle, the more difficult the job of finding a suitable location to mount the tank, and the more difficult it will be to find a tank the right size and shape.
Should you be tempted to mount the tank in the enclosed trunk of your car, remember that DOT (Department of Transportation) rules forbid such installations unless the enclosure (your trunk) is well ventilated to allow any seepage or leakage of gas to readily escape. If you want to know how well ventilated it needs to be, go visit a motor home or travel trailer dealership and see how propane cylinders on recreational vehicles are mounted. Unless you plan on wearing a racing fire suit while driving, forget mounting the gas cylinder inside the passenger compartment.
The size of the tank will also depend on your usage. If this is a long-haul truck or RV tow rig, you will probably want the gas on full-time, in which case you will need a sizeable cylinder. For occasional hill climbing or passing on the road, you might be able to get by with a capacity of only a few gallons. Installations in cars meant for racing or speed exhibition will need only a small reservoir of fuel, perhaps with several tanks that can be interchanged when emptied.
During my initial trials, I used a Coleman camping fuel bottle as a source for gas.This picture is posted elsewhere on the site, and has been picked up by several discussion forums as an example of how not to do it (like I always drive around with a propane cylinder balanced on the drive train hump...). The small cylinder was good for about 60 miles of continuous use, but has been replaced by a 1 gallon cylinder with a proper shut-off valve. This image also shows the BBQ regulator and 12 volt solenoid valve that I used to test the system. These components will be discussed in greater detail later in this page.
This does bring up an important point. Any containment vessel you choose for your system should be properly and securely mounted to avoid damage to the equipment during driving. Any wiring or plumbing from the tank or associated components should likewise be properly secured out of harm's way.
The regulator you use will depend on how much pressure and flow is needed. The BBQ regulator shown above was perfectly adequate for my purposes on the VW N/A engine, operating at 25,000 BTU per hour. It cost me $2.00 at a salvage yard, and produces 11 inches of water on a manometer (.397 PSI). If your fumigation system will be for a turbocharged engine, or if your engine is of a high displacement, you may want to purchase a regulator that has an adjustable output pressure. Turbo'd engines generally require pressures of 4-6 PSI, at greater flow rates than a household low-pressure regulator can provide.

The 1 gallon LPG cylinder is securely mounted via a steel ring
encircling the base and a wing nut through the protective top collar
mounts it to a custom bracket. In this photo, I'm trying out an
acetylene regulator. Note the proximity of a fire extinguisher!

A regulator of the type use on oxy-acetylene welding equipment is one type suitable for an LPG system. Just make sure that any regulator you use is rated for the pressure of a propane cylinder (approximately 250 PSI) and is rated for flammable gas duty. Two-stage regulators will be less affected by changes in altitude, barometric pressure and temperature.
Note that systems which demand a lot of vapor will need a regulator which can supply the specified flow without freezing up. At some point, large gas flows will require you to install an evaporator system like those used on LPG fueled spark-ignition engines, and the tank will need to feed liquid LPG to the evaporator/regulator.
The Solenoid Valve:
This piece of gear seems to be the sticking point in many of the LPG systems that I hear about. Essentially a solenoid valve is an electrically actuated valve that is used to control the flow of gas into the engine. It needs to be rated for the pressure that it is being asked to control, and be safe for flammable gases. The electrical rating needs to be 12 volts DC, continuous duty. I was lucky enough to find a valve being offered by a surplus equipment supplier for $5, but their stock in that part ran out. Some research into substitute valves reveals that there are several choices available.
The most common supplier of solenoid valves isAsco. Their general purpose "Red Hat" low pressure valve is catalog # 8262G002. Thespecifications sheetincludes the information that the 12 VDC coil number is 238310-004-D. Presumably, this coil could be ordered separately as a replacement part and installed on any compatible valve body.
W.W. Grainger company also lists some 12 volt DC solenoid valves.This valveis apparently still stocked and available for purchase.
Be aware that these specific valves may not be rated for LPG gas duty. If I were doing it over, I think that I would try to find a purpose-built LPG or natural gas valve from Asco, then purchase the 12 volt DC solenoid coil and fit it to the valve body. Such valve bodies should be easy to find from a gas appliance repair shop or even in a salvage yard. Most likely they will have 120 or 24 volt AC coils, as this is the most common voltage for machine controls. Fitting the 12VDC coil should be fairly trivial.
If anyone comes up with a better source for 12 volt solenoid valves, please drop me a line so that I can update this page with additional information.
Orifice Action:
Metering systems for gas pressure devices generally include an orifice, or jet to control flow. The size of the orifice can be fixed, or adjustable. Fixed orifices must be drilled out to increase the flow for a given pressure, while adjustable units can be manipulated with a wrench or similar tool to change the quantity of gas that passes. Note that adjusting the gas pressure will also effect flow rates. Since my "dump" system utilizes low pressure and salvaged components, I opted to simply reuse the orifices that came with the second-hand gas BBQ grille, and drill the hole for best results.

Here you see two additional jets that I drilled to try out high rates of fumigation. The installed orifice (left) has a #53 drill hole, while the two others have 1/16" and 3/32", respectively (They suppliedwaytoo much gas for my engine!).

Supplying Gas to the Intake:
While it is possible to connect the orifice(s) directly to the intake of the engine, I chose instead to locate the jet at the solenoid and supply the metered gas to the engine via a length of LPG-rated rubber hose. The hose is terminated at the intake manifold end by three "T" fittings which distribute the gas evenly to four ports drilled into the air box after the engine's air filter. These ports are nothing more than 1/8" male pipe thread to " hose barb 90 fittings. The intake manifold was drilled and tapped to accept the pipe thread ends of the fittings. The aperture of each port is directly above each of the runners in the intake manifold that supplies air to the cylinders. The ports are visible as the brass fittings at the top of the aluminum manifold air box. Also visible is the 3" air duct which supplies intake air from a cowl scoop mounted on the hood. We will discuss the importance of free-breathing on a later page.

Here's a very simple way to get gas into your engine, but it suffers from the drawback that eventually, your air filter will become coated with an oily film from the LPG.
Note that the stock air horn is of a small diameter, and is picking up warm air from behind the car's radiator. See following pages for advice about modifying this intake.

Fumigation introduction on a turbocharged engine usually takes place before the air intake to the turbine, allowing the turbo to help mix the propane with the intake air. Please note, however, that this will mean that your turbo, intake piping, and intercooler (if you have one) will contain a flammable and potentially explosive mixture of LPG gas and air under pressure. Adding the gas after the turbine output is possible, but you will need to account for the boost pressure, raising the LPG regulator to a value greater than the turbo output, typically by 3-6 PSI.
Liquid LPG Systems:
Occasionally, I get messages from people who are interested in knowing if it's possible to supply liquid LPG to the intake of the engine, both for the purposes of fumigating the charge air, and because the evaporating liquid would further decrease the temperature of the charge air.
In response, I can only say that I have not experimented with such a system. The control and metering of liquid propane gas is much more difficult, and requires specialized equipment to which I do not have access. Additionally, the safety aspects of handling liquid LPG are much more strenuous, and any fire/explosion hazard associated with a vaporizing flammable liquid are enough to scare me off!
If this type of system is of interest to you, consider doing some research on methanol injection, it accomplishes the same results with much less complexity and risk!

Next up, learn someself-control!

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LPG Fumigation
Page Three

Control Systems:
For any installed LPG system, you will need at least a basic electrical control system to activate the solenoid valve, as well as protection and interlocking circuits to make sure that the propane is turned off when the engine is not running. Here's a description of how my system is wired:
1. First and most important, the 12 volt power to run the solenoid valve is supplied from the switched side of the ignition system. This insures that the gas is always off when the ignition switch is off. The supply wiring to the rest of the circuit is protected by a fuse.

In this photo, the LPG switch is mounted in a plastic box along with the other Pusher
controls, but you could just as easily put it in a hole drilled into the dash.

2. On/Off switch on the dashboard. On my system, I use the gas for a boost during passing and hill climbing mostly, so I need to be able to control the LPG "on the fly". It's a good idea to have one on any system, so that you can defeat the gas when the engine is cold, or in case a problem requires shutting down the gas.
3. A throttle-mounted switch to prevent gas from entering the engine during idle conditions. You don't need additional power while sitting stopped at a signal, and from experience, I can tell you that you probably won't remember to shut it off manually. Adding gas during idle will also result in a fast idle, which isn't necessary either.

I lucked out and the injection pump for the Pusher already had a switch mounted,
although I did easily fabricate one for my other BioDiesel Rabbit.

4. An interlock that prevents gas from entering the engine when it isn't running. "Oh, isn't that the ignition switch"? you ask. No, it's not. What happens if the engine dies, or you turn on the ignition to listen to the radio, or you're having trouble getting it started and are holding the throttle open while your crank it, or any of 19 other "impossible" scenarios that can dump gas into the motor while it's not running and consuming the fuel? Forget it, install an interlock tied to the engine oil pressure and you're done. No oil pressure means that the engine isn't running (or won't be for very long) and the gas should stay off.
There are two ways to sense oil pressure. One way is to install a "Hobbs switch", which is a normally-open contact device that closes the circuit and supplies power to the gas solenoid when it senses oil pressure in the engine. This type of switch must be installed on the engine oil gallery, either by using a "T" fitting, or by attaching it to a spare oil port on the engine, if one exists.
The other method, which I used, is to use the existing oil pressure "idiot light" switch to supply logic to the interlock circuit. Unfortunately, oil pressure indicator lights are the exact opposite logic from what is needed, so an interface circuit is needed to turn the normally-closed oil pressure switch into a normally-open one. This simple circuit monitors the indicator logic and simply reverses it for the interlock without affecting the operation of the oil pressure indicator on the instrument panel of the car:

The Darlington transistor should be a power type and be properly
heat-sunk. If you use a Hobbs switch, put it in place of the
Darlington transistor, on the negative side of the LPG solenoid,
and ignore the connection to the oil pressure indicator light.

5. [Optional for turbo engines] Many installations on turbocharged engines utilize a pressure switch on the intake manifold that detects boost pressure and turns on the gas when the pressure reaches a preset level. Generally, this level corresponds to increased load on the engine encountered during passing or hill climbing. The "Hobbs" switch described above would be one choice to control the solenoid.
Multiple-Stage Control:
An additional thought would be to use multiple pressure switches connected to multiple solenoid valves, each with it's own orifice supplying gas to the engine. In this manner, the quantity of gas could be increased as boost pressure increases, giving an approximation of commercial systems that use a boost-adjusted regulator. My vision might be for a three solenoid system, with three differing orifices. By building a controller that integrates boost pressure switch operation to allow any single or combination of solenoids to be open depending on boost pressure at the time, seven levels of gas quantity could be supplied, which should be enough to give good overall tracking response.

Boost Pressure
Solenoid valve(s) open
Orifice Size
Gas flow
#1 & #2
small + medium
10 PSI
#1 & #3
small + large
12 PSI
#2 & #3
medium + large
14 PSI and above
#1 & #2 & #3
small + medium + large

Of course the boost pressures cited in this table are only an example. With experimentation it might be possible to adjust pressure switch settings to utilize a wider range of pressures, or to be non-linear in response, for example to be optimized for boost pressures encountered normally when the vehicles is cruising at freeway speeds, or to allow more accurate quantities of gas to be delivered under heavy loads, etc. Such a system would have many variables, but would also allow the greatest amount of "tuning" to be undertaken. Addition of a fourth solenoid and orifice would make the system more complex, but introduce even greater control of the quantity of gas delivered.
Commercial Variable-Rate Systems:
The commercially available systems which I have knowledge of use a controller to determine the rate of gas necessary, sending control signals to variable valves which meter the gas to be sent into the engine. They are of several types, the most common being stepper motor valves, and needle valves.
Stepper motor systems work fairly well, but due to the delay in the reaction of the motor to the control signal, they tend to lag a bit in response. This can mean lack of power when it's needed, and worse, too much gas at the wrong times as the valve closes slowly in response to the controller.
Needle valve systems have nearly instant reaction times to control signals, but of course, the increased performance comes at a monetary price.
Any sophisticated LPG system would by necessity tap into the engine management computer to sense EGT, load, RPM, and critical engine conditions. Properly integrated LKPG control systems would have software written to read and react to the engine management computer, or even replace it in extreme installations.

Up Next:Figuring it Out

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LPG Fumigation
Page Four

Calculating the amount of gas to apply:
For the simple dump system on the Pusher, I calculated gas flow in BTU's, since this was about the only way that I could understand how to correlate diesel-vs.-LPG. Here's what I started with:
The Pusher, using a 1.6 liter diesel engine gets around 30 MPG of diesel fuel. A gallon of diesel contains 128,000 BTU's of thermal power. Assuming 60 MPH, the consumption would be 2 gallons per hour, or 256,000 BTU/hr. I was aiming at 10% LPG for a start, so I simply divided 256,000 by 10 = 25,000 BTU of LPG.
Consulting the chart at in the appendix of this section, we see that in order to get 25,000 BTU/hr from the regulator that I planned on using (11" WC), I'd need an orifice of 1.5mm diameter, or a # 53 number drill bit.
Calculating for an ordinary VW Rabbit, which gets 50 MPG, we see that fuel consumption is 1.2 gallons per hour at 60 MPH = 153,600 BTU. 10% would be 15,400 BTU, or about 1.2mm/#56 bit. Using the larger orifice from the Pusher would yield about 16% LPG.
Determining gas rates for turbocharged engines is a bit more troublesome, as there is a lot more air available to add fuel and gas to. What I have been told is that gas pressures can run in the 6 PSI range, with orifices of to 3/8 of one inch. This is a *lot* of gas, and will require a regulator capable of the increased flow, as well as a much larger storage tank for the gas. See the gas flow calculator in the appendix of this page.
Tuning it up:
Adjusting the orifice and/or gas flow for optimum performance could be tricky. Basically, increase the LPG flow incrementally until you see/hear detrimental effects. The first, and most noticeable is hard knocking, or pinging from the engine. If it sounds like someone threw a handful of ball bearings inside your motor when your turn on the gas, by all means TURN IT DOWN!!! The rattling you are hearing is the excessive peak pressure, and is also the sound of your pistons being turned into molten aluminum. If anything, adding LPG to a diesel engine's intake air should make the engine quieter.
Adding too much LPG can result in your diesel engine's timing being thrown for a loop. The normal injection window of fuel delivery of a diesel engine is that the fuel is metered into the combustion cylinder (or the pre-chamber if it's indirectly injected) in a controlled manner, which is calculated either mechanically or electronically to correspond to the position of the piston during the power stroke. A excess of LPG will upset this fuel-to-piston timing. A combustible air-to-fuel ratio of LPG will be ignited by the very first introduction of diesel to the superheated combustion charge. (Remember, LPG/air mixtures should not normally be ignited by compression temperatures alone. The first atomization of diesel into the cylinder will act as a "spark", setting off the LPG/air mixture.) The flame front of the LPG will contribute to cylinder pressures, and the remaining diesel injected during the injection window will cause the peak pressures inside the cylinder to be overly high, resulting in the "pinging" you hear. This should be avoided at all costs!
Another thing to watch for if your engine has a pyrometer (exhaust gas temperature gauge), is EGT's dropping. LPG promotes more complete combustion, so some of the heat that used to escape through the exhaust pipe is now being converted into mechanical power and transferred to the wheels.
Diesel engines do not react well to LPG fumigation when they are cold. Turning on the gas before the engine has warmed properly will result in rough idle and bogging, or lack of pulling power. Let the engine come up to something near operating temperature before turning on the gas. Another reason to have a dash-mounted control switch.
Exhaust Gas Temperatures:
Before you begin fooling around with any aspect of diesel performance, you should already know the design limits of EGT's for your engine, and have a method of measuring them accurately. This is usually accomplished by the addition of a pyrometer to the exhaust manifold so that the temperature of the exhaust gas can be monitored. EGT's are the best and most accurate method of monitoring the load on a diesel engine, and can be used along with observation of exhaust opacity to determine effects of changes to fueling, timing, breathing, LPG quantities, and other performance modifications to your engine.
The best place for the thermocouple that detects the exhaust temperature on a TD engine is pre-turbo. This will give the fastest response and the most accurate reading. In some cases, it may not be possible to put the thermocouple before the turbine, in which case the reading on the gauge must be corrected by a small factor to allow for the cooling effects of the turbo. Adding 300-400 degrees Fahrenheit to the reading should get you back to the actual temperature of the exhaust.
There are many suppliers of EGT gauges, as well as many manufacturers such as Isspro. Also don't neglect that pyrometers are common in aviation, and gauges used on airplanes are likely to be more rugged and accurate than those used in automotive applications. A good source for used EGT gauges might be your local heavy truck wrecking yard.
What to Expect:
If my experiences using LPG fumigation on a normally-aspirated VW diesel engine are any indication, don't expect a lot, and you won't be disappointed. I don't get any huge surge in power, in fact, it's unnoticeable for the most part. If I'm holding a steady speed and turn on the gas at, say, 60 MPH, I see a gradual increase in speed of about 4 MPH. Someone with better math skills than me calculated that accounting for wind and rolling resistance, the increase in power was about 21%. Since my EV and Pusher are heavy (4,500 pounds, together), and the diesel engine puts out a paltry 52 horsepower, even a 20% increase in power is welcome for passing and climbing mountain passes.
Turbocharged engines will realize a dramatic increase in power when fed an adequate quantity of gas. I've heard stories of long-haul trucks using fumigation burning up transmissions and melting tires after storming up a long steep grade, the rest of the truck's drive train wasn't adequate to handle the power boost the LPG provided. Of course, tweaking the boost pressure, installing a modified engine control management computer chip, and providing intake and exhaust flow enhancements are all a part of race-prep for diesel engines. If you have a turbocharged vehicle, you are probably going to want to look into a commercially manufactured fumigation system to make sure that you get the most from your engine, with the least likelihood of engine damage.
Notes about air flow
Probably the single most important thing you can do for a diesel is to improve the air flow into and out of the engine. This is particularly important in a N/A engine.
Intake Air:
First and foremost, remove any and all possible flow restrictions. Several low-restriction air filters are available, such as the K&N brand filters. Increasing the diameter of the intake ducting is also important. On the VW diesel engines, the "snorkel" which leads into the air filter box is designed to minimize intake noise ~not~ maximize flow. Converting to a larger pipe will mean that the engine has less pulling loss, resulting in more air per piston intake stroke, which means you can stuff more fuel (and/or LPG) into the engine, resulting in more power. Check out the 3" ducting on my engine in the photo above in the "Supplying gas to the Intake" paragraph above. This ducting is fed by a cowl scoop at the back of the hood. I like to think that it at least decreases intake air restriction by allowing the outside air to be a positive pressure.
Temperature of the air is also important. Cooler is better. Cool air is more dense, more oxygen to aid in combustion. The intake end of the pipe leading into the air filter should be supplied with the coolest air possible. Usually, this means from either the grille, a hood scoop or under the front bumper of the car. What you don't want is air that has been warmed after coming through the radiator, in other words, engine compartment temperature air.
Turbo engines benefit from installation of an intercooler, which is essentially an air-to-air heat exchanger that removes the heat produced when the intake air is compressed by the turbine. Cooler boost air will allow greater gains in power through increased fueling, either through adjustment of the injection pump, by fumigation, or both.
Exhaust Gases:
Getting rid of exhaust gases quickly is also very important. Diesel engines do not benefit from controlled back pressure like gasoline engine do. In all cases, larger diameter exhaust pipes are better. Low restriction exhaust manifolds, down pipes and mufflers all add to power and performance, in dramatic ways. Less exhaust restriction is also beneficial to keeping exhaust gas temperatures lower.
If you are trying for ultimate power, a good old fashioned cylinder head port-n-polish of the intake and exhaust ports works wonders.
Other Mods:
Most anything you do to enhance performance will result in the engine running outside of it's design parameters. It may be necessary to compensate for this by adding high performance parts such as racing head bolts/studs, ceramic-coated pistons, additional cooling system enhancements, larger clutch disc and pressure plate, and even a locking differential transaxle to minimize wheel spin. It all depends on how far you intend to go in your diesel power quest. Like anything, the only limit is what your wallet can support!

Appendix: Charts and Calculators

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LPG Fumigation

Eventually, I'll have some links to fumigation resources here. For now, what's available is the orifice chart , BTU calculator, and fuel specifications chart.
Guide to Orifice Flow Capacities:
Caution: Orifice flow capacities are dependant on a variety of factors that cannot be included in a simple table. Capacities vary with the composition of the gas, specific gravity, orifice configuration, back pressure etc. This data is approximate.

DRILL size
BTU/hr at 11" WC
DRILL size
BTU/hr at 11" WC
DRILL size
BTU/hr at 11" WC
DRILL size
BTU/hr at 11" WG





Calculate Heat output in BTUs:
NOTE:This JavaScript Calculator was produced by Anthony Clarke from the data and formulae in the Excel spreadsheet version prepared by Thomas Vincent, featured on Ron Reil's burner page. All units are in the Imperial/US units used in the USA.
WARNING!:This calculator is provided as theoretical information only. Use of the information in a practical application is at your own risk.
Top of Form
Orifice Diam d=

Enter Gas Orifice Diameter in inches as a decimal. See Note 1:
Gas Pressure p=

Enter Gas Pressure in pounds per square inch (psi). See Note 2:
Efficiency e=

Change the Efficiency value only if known. See Note 3:
Click button to calculate

Output Data

BTU Output ==

Air needed to support combustion ==

Consumption of Gas ==

Theoretical gas supply time using given gas tank (from full)
Enter any tank size in pounds prior to running the calculation.
Tank size=

lbs (A one gallon tank has a net weight of 4.24 pounds)
should last about

Note: "infinity" or "NaN" in the output indicates that you have entered invalid data.
Bottom of Form

Base Data for PROPANE Gas

BTUs per Cu ft.
BTUs / cu. ft.
Air to propane ratio for (1 cu ft of propane)
cu ft per min.(CFM)
BTUs per Lb of propane
BTUs / Lb.
Propane weight per (US) gal.
Lbs / gal.

Notes on Gas Calculator Details
Note 1:Enter orifice size in inches- . Use a machinist drill size chart to convert decimal drill sizes to a decimal value in inches. If you are using fractional drills calculate the decimal equivalent. Divide the upper number by the lower number. Again, this number must be in inches.
- Example: a #51 decimal drill has a diameter of .067". A 1/16" fractional drill has a decimal equivalent diameter of .0625 inches.
Note 2:Enter the propane pressure in pounds per square inch. (from the pressure gauge) The pressure gauge should be reasonably close to the orifice, no more than 6' away to avoid pressure drop.
Note 3:Efficiency Factor - This number is an average orifice coefficient (efficiency) factor. Use .75 as a default, unless you know your orifice coefficient factor. Depending on the orifice size, shape and design, this number may vary from .5 to .98 . Coefficient of discharge range for (5-25 psi) will be around 0.65 to 0.70 for Sharp edge or Re-entrant type orifice.

Fuel Comparison Table:

C8 H18
Research Octane Number
Motor Octane Number
Cetane Number
Density of Liquid Fuel(kg/lt)
Density of Gas (kg/m3)


Boiling Point (C)


Lower Heating Value(kj/kg)
Energy Content (Volume)(kj/lt)
Energy Compared to Gasoline
Energy Compared to Diesel

Stoichometric A/F Ratio (mass)
Heat of Vaporization (kj/kg)
Energy of Stoich. Mixture (Mj/m3)


Wobbe Number (Mj/m3)

Auto ignition Temperature (C)

Peak Flame Temperature (C)

Spark Ignition Energy (mj)

Flammability Limits (vol %)


Detonation Limits (vol %)


Flame Spread Rate (m/s)

Max. Burning Velocity in NTP air (cm/s)

Specific Gravity at NTP (kg/m3)

Reid Vapor Pressure (psi)


Diffusion Velocity in NTP air (cm/s)


Diffusion Coefficients in NTP air (cm2/s)


Quenching gap in TNP Air (mm)


Flame Visibility, relative

Flash Point (F)


* @ 3500 PSI

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Sorry for that last post being all outta get the idea. Hope one of the Moderators can straighten it up for me. Thanks Guys! I got a ton of other stuff but when I go to post it, it says I'm I just cut and pasted....
Everyone!, Just do a search of DIY Diesel Propane System! Its easy! There's alot of info out there, use it!
And ALOT of folks are doing it!

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Originally Posted by BC847 View Post
Just so it's been asked: if this is the fix for all that fuel being dumped out the exhaust (25 ~ 30% ), how come everybody isn't doing it?

While you cover the assembly of the system, how does one go about tuning the regulators so as to arrive at the right mix for the best mpg or that extra power? Perhaps I missed it above.

Do you have any before and after results that we can consider? How does the cost of the propane affect the implied diesel fuel savings?

So that I understand the mechanical side of things better, how is adding an additional fuel gonna make use the that wasted fuel?

Since propane is a fuel, adding it to the mix, what does the EGT gauge think of it?

How long can one expect the 30# cylinder of propane to last?
ALot of folks are, they're not running the DIY systems....Lookup what BullyDog wants for theirs....I built mine for less than $200.... That extra $ I did upgrades to my truck.
My new truck is a 91 W350 dually with a flatbed....a "Serious" system on it....I'm averaging 28 mpg and its needing a rebuild.

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Well done, since you want at least 5 lbs of boost before injecting propane then you should be able to use a boost pressure switch to turn on the solenoid at a preset boost pressure. Is that correct, instead of the micro switch at the throttle?

It wouldn't be much different than injecting W/M at a certain boost pressure.

92 D250 parted out

97 2500 4X4 auto, 8 fuel plate, BD converter

96 F250 4x4 with 92 Cummins zf5
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