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DIY propane injection, anyone have advice?

24K views 37 replies 16 participants last post by  stodg73 
#1 · (Edited)
I saw this post and will be searching for others:

http://www.cumminsforum.com/forum/alternative-fuels-additives-oils-lubricants/39896-who-else-using-propane.html#post389086

But am wondering does it give some MPG benefits misting 1-2psi of propane into the airbox?

Most importantly, is it safe? Is it safe compressing LPG through the turbo? What about the combustion chambers, can the head handle burning propane in small amounts with no extra wear?

I'm just looking for a simple diy kit to help with mileage. They say we might see $5/gal for regular gas this summer, diesel will be through the roof!

Also, it seems like a boost pressure switch of some kind would be the best way to turn on the propane. Something that activates the propane when there's 5psi of boost pressure. But it would be easier to put in an oil pressure switch that turned it on when the engine started. Would it be bad to idle the truck with propane? What about shutting it off with the propane going?

Any info would be appreciated.
 
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#2 ·
Don't forget to add in the cost of propane and the system when you figure your mileage and savings. Also, cummins don't really like propane. Not to say it hasn't been done successfully but I tend to shy away from adding an extra fuel to combust in my motor.
 
#3 ·
From the limited things I've read small amounts of propane acts as a catalyst to help burn unburnt fuel that is otherwise wasted out the exhaust.

I think the cost of the propane would be minimal compared to the efficiantcy of being able to burn a lot more of the diesel going in. Course I'm just going by what I read...

Why doesn't a Cummins like propane?

I'm just trying to get all the info I can. I definitely don't want to screw my engine up trying to save money on fuel.
 
#4 ·
It would act as a catalyst if you have a lot of unburnt fuel. From what I'm seeing in your sig your pretty stock so you shouldn't have a lot of unburnt fuel.

Don't quite know why our motors don't like propane but everything I've read and the people I've talked to say don't use it on a cummins. Ford's eat the stuff up like candy. Dunno bout the dmax's.

What's the current cost of propane? I'm not discouraging you cause by all means I'm one of the biggest advocates of thinking outside the box, just wanna make sure your aware of stuff.
 
#5 ·
I've also heard of guys running it in their trucks for 60K+ miles and not having any problems AND achieving 2 to up to 6 mpgs better. The best thing to do is to do a DIY kit with a switch to turn off the propane when you exit the highway, and only add it at a low PSI right into the turbo. That's IMO through research though. Good luck and play safe with it.
 
#6 ·
propane does not act as a catalyst, it is a separate fuel. there can be some benefits, but those figures of 2-6mpg do not include the propane fuel, just diesel.

propane has 90k btu per gallon, Diesel is about 150k. You need to get propane for almost half the cost to start saving anything.

Problem with too much propane is cylinder head pressure = head gasket. way too much propane can be catastrophic. 30-40hp is max without shead studs/ O-ring.

Timing from boxes does not stack well with propane either.
 
#12 ·
The BTUs produced by the propane are not the important part. The fact that the propane combusts JUST before the diesel is sprayed in is what makes the diesel completely combust as well as adding a little bit through its own explosion.
For safety reasons, the venturi is a very good idea.
 
#7 ·
Here is an article on a professional engineering website.
He states that there is some benefit, but lots of hype. Most people do not calculate the extra fuel used in their MPG.

It is not a good thing with extra timing or the extra compression on the HO motor. I get free propane. It is $200+ for a homemade vacuum based system if you already have the tank. I have not yet decided on doing it.

Diesel and Gaseous Fuels, DualFueling - Engine & fuel engineering FAQ - Eng-Tips
as follows:
Diesel and Gaseous Fuels, DualFueling - Engine & fuel engineering FAQ - Eng-Tips
__________________
 
#8 ·
Ok, thanks guys. It seems like if you did it at all the safest way would be the manual switch for just highway use ,and very low pressure. I'll keep reading up on it and looking for other contraptions I can hook up for better MPG. :lol3:
 
#9 ·
Oh, BTW, with the 4" exhaust, BHAF and a fuel cooler on the return line I'm getting about 22-23mpg freeway and probably about 17-18 in town hand calculated. I put in 20gal at a time. This last tank I did about 70% freeway and 30% in town. I got 20.5mpg. Before any mods I could only get 19 straight freeway. I don't know which one of those things helped more but I glad I'm seeing some improvement. And my truck is 2WD but has a ladder rack and two hi-side boxes that stick out a little and catch wind.
 
#10 ·
I used to run a powershot 2000 kit, It's definatly the simplest kit and cheapest out there, although not as cheap as DIY. if propane is used, I think it'd be best used on a stock truck I.E. no timing and or fueling boxes.
Shortly after starting to use propane, my headgasket started to leak coolant. coincidence? I dunno.
 
#11 ·
Ooh. Thanks for the post. Might have been related, don't think I want to take chances...

I think I might just put an Edge EZ on it and set it to the lowest setting. With that, my mods and pumpin' up the tire s a little I should see some good mpg. :lol3:
 
#14 ·
It really depends on how much you're pumping in. If you keep it at a low pressure, maybe 1.5-3 depending on how much boost you use then yes, it creates an environment that burns the diesel that would otherwise be ejected out in the exhaust. and of course, it being a combustible, the BTUs do help however, it's primarily diesel burning as it has 155K BTUs/gallon while propane only has 91.5K BTUs/gallon according to Diesel and Gaseous Fuels, DualFueling - Engine & fuel engineering FAQ - Eng-Tips
 
#16 ·
That is correct. The propane is ignited by the fuel, but spreads the flame. DI engines benefit from it more, as they are lower compression. I did a homebuilt propane injection on my skid steer with a petter air cooled twin with direct injection and 16.5:1 compression. The tricky part is the orifice for the gas. Even regulated down, the orifice must be nearly microscopic. I machined an adapter to fit a hand blowtorch tip to use the regulator and orifice, and used a relay controlled by the kill solenoid to operate a valve to turn it on/off. I didn't regulate the flow in regards to the throttle position/rpm. Way too complicated for me.

It worked. Mainly I was sick of breathing the smoke. It ran cleaner, burned slightly less fuel, even compensating for the propane cost. I ran the valve higher and lower, and the fuel efficiency seemed about the same, but it's really hard to tell in this kind of machine. The only way I figured it was by logging fuel use over hundreds of hours for an estimate.

The whole thing was a COMPLETE waste of time. I love to tinker and don't have better sense, and eventually just tossed a Perkins (same as a CAT) in it. Don't waste your time. It is not worth the hassle. Neither homebuilt or factory makes ANY sense whatsoever unless you are just looking for power and lower egt's. Now I DID consider putting in a h2o to hydrogen electrolysis system... See? don't listen to me!
 
#17 ·
I just installed a diy propane kit and love it! it adds power and hoping on mpg gain havent eaven run one tankof diesel yet but already hooked on the power!Thanks Zack!
 
#18 ·
FYI propane will combust under compression and it does so at pressures/temps close to diesel. But there needs to be a lot in there. Running too much propane can detonate on its own. Just like coal and sawdust are combustable at the right ratios in the air. Propane won't pre-ignite if the ratio is too high or too low. I do not remember the ratios where it combusts.
 
#20 ·
it is safe as long as ratios are low. it can't ignite
 
#21 ·
makes sense, that's why it can be so dangerous if you inject too much.
O man, i have a manual switch for my water/meth, and occasionally i will flip it on when i floor it, and forget to turn it off, come down to an idle and it'll spudded and blow tons of white smoke.
Ill have to remember that failing to shut off the propane like that will most likely result in blown up engine!!!!
 
#22 ·
make sure it is a vacuum controlled switch, or at least boost controlled with a solenoid and maybe another for fail safe operation. Most regulators (IMPCO model J) are not enough to run the engine on propane. But liquid propane expands like 200times in volume when it turns to a gas.
 
#24 ·
ok, got a an acetylene pressure regulater, that im going to run at 4lbs (though 1/4" line into the air box). the plan is to have a master "arm" switch in the cab, and wire it through a boost switch to open the solenoid valve at 5lbs of boost.

I know 4lbs is a little more than what most people say to run just for fuel economy, but propane is cheep and diesel isn't. On the other hand new diesel engines aren't cheep either. Anyone have any imput on the setup??
 
#26 ·
I am no expert. thanks for the correction and your information, I knew it was somewhere up around 200 times the expansion. My point was to be very careful about no letting liquid propane enter the engine. 270 times more propane would likely be a big problem.

I agree that 4psi is too much. I would start much lower like 1psi or less and bring it up slowly from there.

also those N/A trucks that see a large gain may not have their injection pumps/tuned/calibrated correctly.
 
#27 ·
just finished rigging up my propane today... I used an oxy/asy type regulater, ive got it mounted in the cab!! the line runs in the back of the cab, goes under the drivers seat, and is mounted right behind/beside the 4x4 shifter. I think it looks pretty dang cool and no one else is dumb enough to run propane through the cab, so enqueue also. Haven't tried it out yet, have a few finish touches.
here's my price list:
regulater (ebay)- $11 yep a steal
solenoid valve (ebay)- $20
New propane tank (ace hardware)- $41
Fuel lines, fittings, clamps, switch (ace hardware/shucks)- about $60
-------------
total $132
it was a little bit more expensive because i had to buy quite a bit more line to route it up to the cab. I also went with the best reinforced high pressure fuel line and highest grade clamps I could find since it seems slightly sketchy to be running 100-250+ psi of propane through the cab
 
#29 ·
This is the system I built for my 93...It worked great! Gave better MPG & more power.....
The system I built sets up so it injects the propane before the turbo. The ideal setup is a 1 to 4 ratio, the 1 being propane. You can purchase the Impco Cobra Regulator from any LP Dealer. They will most likely
have to order it for you. The Regulator can be used with Vapor or Liquid. That is one reason I used it. If the bottle should fall over or you go down a bumpy road and Liquid gets into the fuel line, the regulator will vaporize the liquid before it enters your air
intake. The regulator also ties into your heater water lines. Hot water needs to flow through the regulator to be able to vaporize the Propane if needed. The Regulator comes with a "BLUE" spring. I changed it out the Blue Spring & installed a "RED" spring. The spring determines how easy the regulator opens to release the propane. This system works on "NEG. PRESSURE" So it's more like supply & demand. The higher the engine rpm's the more propane is delivered.
It helps if you have a gauge (Water Manometer) that you can measure Neg. Pressure with. Having a gauge or meter really helps in designing your fuel tube. I ended up making 5 types of fuel tubes till I found the one that
had the best draw. Each tube I made I would install into the air intake and hook the gauge to it and the start the truck up. Then run the RPM's up and see which one had the best Neg. flow. If I remember right at high RPM my system is pulling a Neg. 7
I installed what is called a "LOAD BLOCK" into the air intake. The load block has a adjustable screw something like a over sized needle valve that you are able to adjust to control the amount of propane
being fed into the motor. Then inside the air intake I have a 3/8 copper tube mounted so the tip is seating right in the center of the air intake approx 4" inches from the turbo. I cut the end of the tube in what is called a "Draft Cut" Which is like cutting it into a point. Cutting a 45 degrees angle and have the front of the angle cut facing the turbo. As the turbo is sucking air in, the air passes around the Draft Cut causing a suction (Neg. Pressure) which pulls the Propane into the air intake. Then the turbo acts as a mixer, mixing the propane & air together.
Here is a link for you:
http://www.carbturbo.com/default.htm
Carburetion & Turbo Systems
(952) 445-3910 Speak with Eric.....This is where I ordered most of my parts from.
I ordered the Impco Cobra Regulator, 12 volt solenoid lock off, inline LP Fuel filter from the LP Gas company.
I have a 20# pound cylinder set in the bed of the truck. It works great. I have a switch inside the cab so I can turn the system on and off as I need it.
If you have any more questions let me know. It's an easy system to build. It not that easy to explain. I hope I didn't confuse you to bad.....
One key note: You want to mount the Regulator so you won't have to run more then about 18 to 20 inches of vapor line to the intake. The closer you can get it, the better off you will be.
After running the system for a while and I got a good feel for it. I removed the spring completely from my vaporizer & installed a Hobbs booster pressure switch. I set the boost switch so the system would come at a 7 pounds of boost.
If you would like to see some pictures send me your e-mail address and I'll e-mail you some pictures of the system
 
#30 ·
had to throw this in here.... Auto Propane (right now) costs about 1.82/gal in kansas city. So those who are saying that propane is expensive are quoting what you have to pay when you fill up on BBQ propane. Same gas, just different price points. I am switching over to Propane from CNG. for the same footprint in the truck bed i could only get 10 GGE of CNG, here real quick i'm going to be able to store 48 gal Propane.

while i was on CNG i was getting 45-50mpg (calculating diesel usage only) i'm anxious to see what i'm going to get with propane.
 
#32 ·
Powerslide

What would you like to hear?
 
#33 ·
You quoted getting 45-50 for diesel's running CNG. I would love to hear all about your setup to achieve that because it's double if not more than what most others are getting. I am assuming this is on a 24v 5.9 since that is the forum we are under. You mentioned switching to propane have you achieved the same MPG w/ propane as w/ CNG?
 
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