Propane enrichment for diesels
Propane enrichment for diesels
(OP)
I recently read about an after-market kit for electronic injection turbo-diesel automobiles which injected propane into the intake manifold. This proportedly improved emmissions (gaseous and particulate), power, torque, and fuel-economy. The system ran on a maximum 15% propane (15% of caloric imput I presume). Economy must have been computed as % ultimate efficencey of the combined fuels(?). The kit seemed to rely on the electronic diesel-fuel management system to lean out the charge to achieve appropriate exhaust O2 levels. Unfortunately, I've forgotten the name of the company and have had no success searching the internet...
I am interested in finding independant studies or documentation of this type of "dual-fuel" system and verifying its benefits. Does anyone know of application of this system?
I am interested in finding independant studies or documentation of this type of "dual-fuel" system and verifying its benefits. Does anyone know of application of this system?





RE: Propane enrichment for diesels
Propane has an octane level and fuel sensitivity levels that prohibits it from being used in CI engines with a static compression ratio much over 16.5 to 1.
Very small amounts (minor fraction) of propane can provide GREAT amounts of power, and is the reason for the great prolification of these kits being marketed today.
I have seen some inside notes from one of these kit makers, and the way they calculated the percentage of use is that they use 1 gallon propane per 6.5 gallons of diesel (HUH?).
Also, as of this posting, the EPA has not recognised the minor fraction fumigation as an alternative fuel, and no propane fumigation systems have EPA approval.
Several kit makers advertise a 30% gain in power with a 30% gain in fuel economy because the propane acts as a catalyst, increasing the efficiency of combustion, burning 90% of the diesel!
Something is missing, like my first class in Thermo 101.
The concept is a great idea, but the marketing folks are driving the engineers. Propane in the diesel engine is not new, and a little bit is fine, but with almost all things, if a little bit is good, a lot is better. One transmission manufacturer has declined warranty on some beta systems because of the power and torque load increases.
Regards.
RE: Propane enrichment for diesels
Somehow, when a driver becomes used to a particular vehicles performance criteria, they desire more. Liken this to a beginning hot-rodder; first the big tires, then the carburetor, then the manifold, cam, headers, transmission, suspension, etc.
Once the driver becomes accustomed to the lower levels of fumigation, they feel they want more power and increase the amount of propane. A driver adjustable system is probably the worst thing to happen here, since a little power is fine, but a lot of power can be damaging.
Regards.
RE: Propane enrichment for diesels
I am interested in quantified information about the moderate power boost and improved emmissions that could be available from minor fraction fumigation with LPG of CI deisel engines, as well as the possible minor benefit that cleaner operation might have on engine wear. I would like to know what levels of fumigation produce corresponding power output, and at what point this dual mixture begins to damage a "stock" engine. I am particularly interested in the potential emmissions improvement. Is this improvement in NOX and SO emissions and/or particulates? What and to what extent?
If these are indeed advantages of minor fraction fumigation, I'm suprised that they seem to be ignored by the EPA. If no propane systems are approved by the EPA, does this mean that these after-market kits are not street-legal?
If you can point me in teh direction of some existing, reputatable research, I would greatly appreciate it. And again, thanks for the response.
RE: Propane enrichment for diesels
when is it used- part power or full power conditions, or both?
since c-i engines always take a "full breath", the only time most of the air will get used (for burning fuel) is at full power. I don't know how much excess air is available at full power conditions in a typical c-i engine.
(more importantly, in "your" c-i engine.)
A c-i engine with turbo could be harder to evaluate- add more heat, the turbo will pump more air- limitations being the turbo performance, etc...
add propane to use some of the excess air, get more power, maybe help burn any of the (liquid)fuel that otherwise sneaks out unburned or partially burned (soot).
now- will the propane politely wait till the proper time, and not ignite/detonate early?
will it burn well/completely under part-power conditions?
will it steal some of the air that was needed to burn the liquid fuel, leading to more unburned/partially burned liquid fuel?
and, if you keep adding more fuel, will the turbo keep winding up, and overspeed/overload/frag your motor?
cheers
jay
RE: Propane enrichment for diesels
It appears the the "excess air" available varies wildly from one engine design to another...
RE: Propane enrichment for diesels
The EPA states that a minor fraction fuel is less than 50% of the primary fuel. Since it is difficult to get propane to operate in a CI engine at ratios above 15 to 20%, it is a minor fraction fuel. The higher the static compression ratio of the engine, the lower the fraction of propane. The higher the turbo boost, the lower the fraction. Also remember that propane has a critical compression ratio somewhere around 12:1, at which it may begin its combustion process by compression generated heat, usually quite a bit before the diesel injection process.
One reason the EPA has not addressed these applications is that most of them are not initialized during the normal FTP-75 driving cycle, or if they are, it is only for a finite period. Also, there is not established testing protocol since the engine is a dual fuel application (bi-fuel?).
Although the diesel engine only uses the amount of air needed to oxidize the fuel during the combustion process, (the excess air comment) when propane is metered in, the balance of the air is mixed with propane vapor, which also burns, but with the balance of the air. Propane burns quicker and has a higher pressure spike than diesel. You now have two distinctly different combustion processes taking place inside the combustion chamber, and a phenomenon called “colliding flame fronts”.
And lastly, the use of propane in a diesel engine can produce copious amounts of power, but also cause catastrophic engine damage. OEM dealerships are now instructing their diesel technicians to look for signs of a recently removed fumigation system, and if they are found, an engine warranty is voided, often along with the transmission warranty! Also, there is no significant amount of cost-per-mile savings when using a fumigated fuel, for reference: diesel has 150,000 btu’s per gallon, propane 91,500. Its hard to justify the savings at 15% substitution.
By the way, I am a very staunch advocate for alternative fuels, propane in specific, but want it used responsibly. I conduct research and training in gaseous fuels.
Best regards;
RE: Propane enrichment for diesels
RE: Propane enrichment for diesels
In the US with most diesel engines (used by medium duty service in the 5.9 to 7.4 L region), the marketers of the dual fuel systems claim a 25% increase in power with the same percentage reduction in fuel usage. Maybe with the diesel, but the LPG use increases. I have done the dyno work, seen the engines, read the emissions, and drawn my own conclusions. Locally, LPG fuel is about 15 cents higher per gallon than Diesel, at about 60% the energy value.
Diesel-LPG has its place, as a competent, quality installed system, without driver overrides, and minor fraction values, somewhere in the 10-12% range.
Very modern diesel engines with drive-by-wire and electronic injection, and aggressive computer controls, are hard to trick by dumping in another fuel.
Your comment about reducing greenhouse gasses is partially correct, the CO2 does drop, but the HC's, CO, and NOx increase.
Regards;
Franz
RE: Propane enrichment for diesels
I'm a bit puzzled why the CO2 should drop, unless the CO rises in direct proportion.
Is the actual combustion efficiency improved by this LPG injection?
Cheers
Greg Locock
RE: Propane enrichment for diesels
The last Diesel I tested emissions on showed about a 4% decrease in CO2 when about 5% lpg vapor was fed into the engine at 10% load (estimated to be a low load cruise). When the air balance is altered with a gaseous fuel (and displaced too), the CO2 ratio changes too. The lpg ignition point (CCR), pressure rise and drop, and flame travel speed are totally different than diesel. These colliding flame fronts cause very unusual exhaust readings that often skew an amateurs rational’s, and reasoning’s. Here in the US, NOx is the big bugger, and dumping fuel in raises the combustion temperature way past the Nox generation point.
The EPA has not authorized any emission testing protocols yet, mostly because any of the kits marketed here do not even energize at the levels offered on the FTP-75 or the new US-06, and I think on the Euro medium duty standard either. Since the kits do not energize, the readings are no different than the OEM certified, thus meeting the EPA’s mandate that any system installed do not “effectively increase emissions over the baseline engine”.
ARRRGGHH!
Diesels do not operate at the nice tight Stoich window that gasoline/petrol engines do, so any emission calculations based on chemistry are pretty well a guessing game.
Help any?
Still haven’t figured why the cruise liner had the “thump” at cruise yet, but I think it may have to do with two screws in synchopation. This ought to get the thread readers guessing!
Franz
RE: Propane enrichment for diesels
Are you suggesting that there was some sort of "beat" phenomena going on? And btw, where the heck did this topic come from?
RE: Propane enrichment for diesels
Franz
RE: Propane enrichment for diesels
Cheers
Greg Locock
RE: Propane enrichment for diesels
(Now for my pat on the back!)
Franz
RE: Propane enrichment for diesels
Plus, the rest of the members, myself included, have placed him on top as 'el numero uno' by voting for his posts in the automotive forums.
Try not to let this all go to your head, mate, but I do post this with sincerity.
Rod
RE: Propane enrichment for diesels
I have a Ford DIT diesel and I see some of the owners chatting about it on other sites. I don't see any need to add something like this. The added cost of fuel, the additional components, appears to be more trouble then it would be worth. Seems to me the best way to up power in a diesel would be to add an intercooler change to a smaller turbine housing to compensate for pressure drop and watch for excessive EGTs.
phasers
RE: Propane enrichment for diesels
It sounds like moderate fumigation (5-12%) offers some increased power and a linear increase in engine wear (is there a decreased production of particulates that might benifit engine wear? Straight propane engines don't pollute their oil).
Sounds like NOX production might be increased by Propane, but how significantly at low propane %? It seems to me that if you have carbon in your fuel you are going to get the corresponding amount of CO2 -- in fact, I would guess that the best way to exhaust Carbon would be at Maximum CO2 levels, else you get CO or soot, which is a big pollution factor in diesels; which brings me to third:
Emissions:
Their are two emissions issues with diesels: greenhouse/acid rain and human health.
I don't know what the CO2/CO/NOX/sulfur emissions for modern diesels are and what the U.S. and European requirements are for these (Reader: Please steer me to web-site, lay-digestible info on these topics). How do the emission of diesels compare to those of gasoline engines, underload, and after 100K miles? Its my impression that diesels are better on gaseous emissons and bad on particulates. I believe that damage to the humans lungs is less of a "sin" than damage to the larger ecosystem. Aren't particulates unburned carbon?
As far as why:
being able to use 10% of an alternative fuel gives one a different fuel-market to exploit, as noted about. Minor enrichment takes little modification and is there to take or leave. Propane is still not a fuel that it would be easy to drive accross country on; This dual-fuel option would promote and exploit the expansion of the automotive propane fuel-delivery infrastruction without being wedded to it. On-board propane could be used to great advantage in other ways on certain types of vehicles: Heaters, generators, refrigeration. Imagine that you had a small propane engine in your engine bay that could drive the engine mounted compressor and generator through clutch engagement or a couple of opposed freewheels (hell! If you wanted you could simply detach these place them elsewhere in your vehicle to solve other auto design issues.) small propane engines start, run and maintain more easily than liquid fuel models, and produce only H20 and CO2. Think of it as extended battery maintence and backup. You could also take the load of these parasitic devices in times when you wanted full HP to the drivetrain. Thirdly, as a further refinement of systems like VW's (euro-only!) Eco-diesel concept, you could shut the diesel down at idle and run you A/C and creep in bumper-to -bumper traffic in the propane engine alone. You could also use it as an alternate starter, a handy thing on a hard-cranking diesel. Am I sounding like a crank? Talk to me....
RE: Propane enrichment for diesels
Rod
RE: Propane enrichment for diesels
Great comments. The single biggest problem with a vehicle operating on two fuels is training the driver to fill with both, or either. For years, large manufacturers have discovered that starting an engine on a gaseous fuel is easier on the engine, less polluting, faster catalyst warm up, longer lasting engine since no liquid fuel wash down, etc. The problem was training the driver to find and fill two fuel systems, and the transition period when the gaseous fuel stopped, and the liquid fuel began.
Visualize this, the engine starts on propane and runs for about 1 minute. Total fuel consumed about ½ pint. But during this period, the driver would back out of a driveway and begin to accelerate on a city street, just about the time the engine switches fuel. How to make the transition smooth without bucking or backfiring is the problem. The advantage is that the engine is starting on a dry fuel, no cylinder washdown, good fuel distribution, a rich enough mixture to preheat the cat. The HC’s and CO are handled by the rapidly heating cat and since there is minimal particulate production with a rich gaseous fuel mixture, there is almost no contamination of the oil.
Also, running two fuels brings into play the engine management system, how do you optimize two different and separate fuel systems? OEM’s have had a difficult enough time with one, much less two.
Your comments on the diesel emissions are well placed. Consider this: Diesel engines are unthrottled and inherently produce more NOx because of excess air. The addition of propane decreases the air BUT increases the combustion temperature and pressure, resulting in increased NOx and HC’s, but at slightly decreased PM (more fuel, less diesel, higher temps, equal power at a lower throttle setting.)
There is a well-established propane distribution network in the US, and in most of the world too. Take all the other alternative fuels vehicles worldwide, then quadruple the amount, and propane vehicles are still more than that too! It IS possible to drive coast to coast on a pure propane vehicle, I have done so, with a little planning. Remember the Olds diesel produced in the late 1970’s? In the owners glovebox was a diesel distribution outlet guide showing car friendly diesel outlets. The same is possible with propane.
Final parting thought, remember that diesel fuel has a higher caloric value by weight than propane. It takes 1.6 times the amount of propane to produce the same power as diesel.
Regards;
Franz
RE: Propane enrichment for diesels
Diesel fumigation is newish here, and I have been playing with a 160 bhp cummins B series using vapouriser,power valve and simple 10mm pipe mixer in turbo intake, pressure switch bringing gas on at 3psi.Setting is finger in the air stuff, and suggestions would be appreciated.I have been adjusting the inline power valve on the move, while turning the gas on and off, and monitoring the sudden increase in boost pressure. A point is reached where the pressure rise peaks for increasing amounts of gas, eg 5psi at 70mph --- 9psi + acceleration.I am assuming this represents max. power but at what % lpg I have no idea. I would also have thought that the injection pumps boost enrichment should be reduced with gas applied,but not sure about main fuel adjustment Any thoughts? I know some outfits reduce main diesel adjustment to prevent engine and transmission going bang. I am monitoring transfer box temperatures, and they soon start to climb with gas on!
I have toyed with the idea of a motorised power valve ( lambda control type) but no clue as to what to monitor to control it, excess lpg in exhaust?, use electronics to continually maximise boost pressure?
The vehicle is a 6x6, 5 tonnes camper, I have built based on a Land Rover 101 ex mil. tractor unit, and power is what I am after. In the UK this engine is usuallly 130 or 160bhp and 210s are not that common
Now I am rambling,need to get out more! Must go
Regards
BigH
RE: Propane enrichment for diesels
RE: Propane enrichment for diesels
The problem is as I mentioned earlier, a little power is fine, but soon, the driver wants a LOT more, and its available often by a twist of the screw! This is dangerous and can lead to EXPENSIVE non-warrantable repairs. The TV shows and on-line advertisements do not disclose the possible side effect, only that a BUNCH of power is available.
Lastly, NONE of the web-advertised LPG-Diesel fumigation kits are EPA or CARB approved, therefore illegal to install or sell commercially. Treat it the same as an aftermarket camshaft or intake system on a gasoline (petrol) product. It was not emission tested or certified by the manufacturer, therefore, not permissable to install on over the road vehicles, your own or for a consumer.
Caveat Emptor (there have been more than a few dissatisfied owners so far!)
Franz
RE: Propane enrichment for diesels
Just thought I'd let you know that at last there is a viable concept to cheaply and easily measure shaft torque, from which of course you can get power by combining with RPM.
It's not hokey, it's not snake oil, it can be retrofitted without altering a drive shaft, and it has the potential of being inexpensive. It has been patented overseas and a U.S. patent applied for via the patent cooperation treaty.
If interested, let me know.
RE: Propane enrichment for diesels
RE: Propane enrichment for diesels
cheers mike michaeleve@bigpond.com.au
RE: Propane enrichment for diesels
I did LNG (natual gas) powered golf car conversions in a former life - the Major pain was finding room for the gas cylinders and the safety issues. I'm not sure I'd want to be cruising down the highway at 75 with a big propane tank strapped in the bed of the Dodge Ram.
Of course it would be handy at the Tailgate parties....
Keep the wheels on the ground
Bob
showshine@aol.com
RE: Propane enrichment for diesels
The propane tank in the bed of a truck is possibly the strongest item on the vehicle, excluding the engine block and possibly the frame members. The have an excellent safety history, far greater than either diesel or gasoline.
The propane tank is far stronger than the LNG dewar, and safer than 3600 psi NGV-2 cylinders.
In its place, propane can be excellent benefit to diesel engines, but with the proper use and ratios.
Franz
RE: Propane enrichment for diesels
I am wanting to assemble a toyota 22r engine to run on propane only..
does anyone know what compression ratio would be suitable???
thank you
bikejeremy
RE: Propane enrichment for diesels
A few years back The factories got into act with propane powered cars and trucks. Dodge built a liquid injected 360. They heated the injectors to prevent them from freezing. Man talk about throttle responds, it was unreal.
I've turbo charged, supercharged, added nitrous, etc Added it to diesels. What I've found is its hard on pistons lands and rings especially if you get to much compression, I prefer no more than 9-1 on heavy truck and no more than 11-1 on light cars. Although I have turboed trucks with 9 to 1 and 20 pounds boost. I've also done 13-1 N.A.
They were high dollar custom stuff. It just not worth the grief to push the compression ratio to 12-1
Anyway its hard on exhuast valves and seats, Prefers cams with smaller duration than gas, likes lots of timing on lower compression engines,it will lug down low like a diesel
When added to big diesels,if you get carried away it breaks drivetrains parts like transmissions, rear ends,etc from the increase in power. As a side benefit to propane the oil stays clean so the interanal parts don't wear.
RE: Propane enrichment for diesels
One item that seems to be overlooked is that when a gaseous fueled engine goes lean, the exhaust temps also LOWER, and when the mixture goes rich, the temps RAISE. There is no evaporative effect with the gaseous fuel. I ran one 6.0 liter engine to L=1.9 and the exhaust temps were around 800 deg F! This was at 3000 rpm, 30 psi turbo boost, and about 290 bhp. Bringing the L ratio closer to 1.0 raised the power levels, but also the exhaust temps, and the NOx went through the roof!
Lean burn and NOx control are also different with gaseous fuels. Going a tad rich (A/F .97) will lower NOx, but will also raise them again due to exhaust temps).
It takes a different mental picture of the combustion process when operating with gaseous fuels than with liquid fuels.
Its also kind of addicting! I am sure RacerRick will agree!
Regards
Franz
RE: Propane enrichment for diesels
Is it possible to have to much quench turbulance in the chamber?
It seems to decrease the octane of the fuel if you do. I've found you need some but not to much.
It seems like the reaction rate of propane increases at higher piston speeds due to increased turbulance within the chamber which can cause some high quench chambers to detonate even though they have the same CR as a more open style chamber.
In other words the more open the chamber to a point the less likely it will detonate at higher rpms. Is that generalization what you have found?
It reacts, kind of opposite to gasoline
RE: Propane enrichment for diesels
I have personally liked open chambers with unshrouded valves. Seems like the trend with gasoline is to small kidney shaped chambers to promote fast burning.
I tend to agree with all of your comments. One thing additional is that Propane tends to have low fuel sensitivity compared to Natural Gas, thus more critical as to compression and ignition timing.
Been a while since I have seen the high speed photography with a propane combustion front, but at some of the pistion travel speeds in the 6000 rpm range, the flame held together equally as well if not better than liquid fuel applications.
I would like to see a direct comparison on equal engines between open vs closed chambers, possible one engine with two different styles, one for each bank. This might shed some light. Research funding anyone?
Franz
RE: Propane enrichment for diesels
I just came across this thread. I'm doing some research on propane(lpg) fumigation of diesel engines. I intend fumigating a pair of normally aspirated Perkins 4-236c.i. direct injection diesel engines presently rated at 84bhp @2800rpm. These are on a marine installation and run almost exclusively on cruise and full throttle speeds.
To what extent would a fumigation system be beneficial on such an installation?
Look forward to comments from you all out there.
Thanks and regards
Autogasmarine
RE: Propane enrichment for diesels
Franz
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RE: Propane enrichment for diesels
I was introduced to the fumigation topic 20 or so years ago in the heavy duty trucking industry. There were several people pushing it. That was before the days of electronic engines and the fine control that they offer.
As a ME that had survived Thermo 101, I saw potential, but I also saw some of the drawbacks mentioned here. Since I had a passing interest in the topic, and an associate who had an industry connection, I inquired about the progress/status of the concept. The only answer I got was that fumigated HD diesel engines had suffered an inordinate amount of stretched head bolts, and that it was a no-go.
This would go to verification of some of the problems mentioned herein.
My contribution to a very old, but none the less interesting thread.
I think your third star is long overdue, Franz.
rmw
RE: Propane enrichment for diesels
There is an FAQ on propane, been there a couple of weeks now.
Ages ago, I heard of truckers using Cummins Big Cam engines, and others with Detroit 671's with a propane tank behind the cab, a hose and barbeque regulator, with a ball valve in the cab, dumping propane vapor directly in the air intake. Reportedly, it would allow for hill climbs without dropping into the low split box (old over the road trucks would have dual boxes with twin shifters). Stretched head bolts, cracked heads, blown pistons and sleeves, blown exhaust manifolds and early turbo's, burned underhood rubber parts from glowing exhaust manifolds, were all stories from old truckers I've heard.
Franz
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RE: Propane enrichment for diesels
Cheers
Greg Locock
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RE: Propane enrichment for diesels
The big rig systems I was mentioning were not just jury rigs, they were store bought systems. If I think long enough, I will remember the name of the company in the Los Angeles area that was a big promoter. I visited their place, but didn't have the $$ to do it to my pickup. Later I just added a turbo, and had that 6.9 Ford IDI diesel doing about it could anyway.
rmw
RE: Propane enrichment for diesels
Franz
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RE: Propane enrichment for diesels
Franz
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