Spark ignition Diesel engine, AKA your car
 

I was thinking the other day: back in the 40's and 50's, many farm tractors could be run on gasoline, petroleum distillate, or kerosene, interchangably. Running on Kerosene was acheived by heating the intake manifold with a nearby exhaust manifold, heating the kerosone fuel before it entered the carburetor, and a slight ignition timing change.

Kerosene is sort of between gasoline and diesel fuel in a way, as their flash point (the lowest temperature at which a volitile liquid can vaporize to form an ignitable mixture in air) is almost identical at ~120-150F, depending on many things of course. As a comparison, the flash point of gasoline is -40F.

I am assuming that using Kerosene in an ICE works well with a carburetor with a fairly constant air/fuel ratio, as these aforementioned farm tractors used a carburetor. However, diesel fuel in an ICE does not like a constant air/fuel ratio. Restricting intake air flow effectively lowers compression pressure, resulting in too low of compression temperature at TDC for diesel to autoignite. Besides, the entire point of burning diesel fuel for efficiency sake (besides that fact that diesel fuel contains more energy per volume than gasoline) is to eliminate the throttle valve and its subsequent pumping losses.

In a diesel engine, intake air is compressed at a ratio of between 14:1 to 23:1, depending on the engine, to get a compression temperature of above 600F at TDC so that when finely atomized diesel fuel is injected, it starts burning, as diesel fuel's autoignition temperature is ~410F, depending of course on its cetane level. Now, a 10:1 compression gasoline engine will probably reach a compression temperature of ~300F if we use simple math, well above the flash point but below the autoignition temperature of diesel fuel. The ultimite question is: what will happen at this point if a gasoline style spark is introduced at this point? AKA...will it run?

The heating of kerosene was necessary in the farm tractors because of low compression ratios of 6:1 to 7:1. Those ratios would probably only yield compression temperatures of 200F (again, using ridiculously simple math) - sort of borderline with the flash point of kerosene (especially on a cold day), hence the extra heat required. Something tells me that a 10:1 engine may work, unless of course ambient temperatures fall too low. But that's what grid heaters are for.

My first guinea pig will be a 1978 Honda Hawk 400 twin motorcycle. If I break it, who cares. I will remove the carbs and fashion some sort of 1-into-2 intake manifold. I will fill my pneumatic spray bottle with diesel fuel, pump the snot out of it and screw the nozzle tight for a fine mist. Then I will hit the starter and start dosing the intake with fuel. Who knows what will happen....

If guinea pig #1 works, it will open up a new door of possibilities. I will then transfer my experiment to guinea pig #2, an '06 Matrix. I will disconnect both O2 sensors, MAF sensor, MAP sensor (if it has one - I'm not sure), and see if the ECU is smart enough to run on only the two inputs of engine position/speed and throttle position. If yes, I will remove the throttle butterly, keeping the actuator and throttle shaft intact so the ECU doesn't think that it's missing (fly by wire throttle). The next bit is completely dependent on whether gasoline fuel injectors do well with diesel fuel going through them, because the final step of this ridiculous scheme is to drain the gasoline from the tank and replace it with diesel fuel. The ECU will then use engine speed/timing and accelerator pedal position to vary injection.

Now for power estimates. Considering this would end up being a naturally aspirated diesel engine, power would definitely be low. First off, I know compression ratio affects BFSC in a gasoline fuelled engine. However, in a diesel engine, it really has little effect. Think of a "giant" 20:1 compression as a spring. The bigger the spring, the harder it is to compress, but the harder it will spring back - sort of self-cancelling. In a diesel engine, whether the compression is 20:1 or 14:1 has no effect on efficiency, as long as the fuel is burning completely. Pinching the wastegate line on a turbodiesel to raise the boost pressure and peak compression pressure does nothing for power unless fueling modifications are also made. Therefore, I don't believe a 10:1 diesel engine will be any less efficient than a 20:1 one, providing that all the fuel is burned completely.

So, for a simple example, let's take the 1978 VW Rabbit gasoline vs. diesel. Both engines were nearly identical in design, 1.5L diplacement and the same 5000 RPM or so redline. The gasoline version had 71 HP and the diesel had 48 HP. Again, using ridiculously simple math, my '06 Matrix has 126 HP, so a NA diesel version would produce 85 HP.

Ok, I realize that this experiment will not work. If it would work, there would be a million internet posts with instructions on how to do it. But, could it be that something has been overlooked? I give it a 5% chance.

I say go for it.
Like franklee says, just go out there and start wrenching on something.
At the worst you blow-up an old 400.
Current R&D is working on direct injection gasoline engines, diesels fed gasoline. Maybe that's backwards.
You mentioned a wye intake. How about warm up on gas, run on diesel setup?

The efficiency of heat engines is limited by the Carnot equation. Higher compression gives higher temperatures, and better efficiency.

Both diesel and kerosene have very low octane numbers. I think in order to run a spark-ignition without detonation you would need to lower the compression ratio down to the tractor level, reducing the efficiency down below the gasoline fueled version. You have things like exhaust valves and spark plug electrodes that get way hotter than just the temperature of compressed air and will pre-ignite and/or detonate and destroy your motor in short order.

I would put a small wager on it not working at all, and a side bet on it working slightly but not very well.

Firstly I don't think the spark will make the difference between not enough heat and enough heat. If its mixed with something that does burn then that may work but I don't think you can mix fuels so easily. Maybe a gas but then that adds all sorts of other issues with plumbing - in short dunno.

The compression in Diesels is there to generate the heat.

Plus you then have timing issues - remember diesel burns slower so you may not have enough heat generated to overcome compression unless you adjust it a lot.

Thirdly diesel engines inject fuel into the cylinders and not indirectly into the induction system like Petrol cars - no throttle. I'm not sure that thick fluid like Diesel will atomise like Petrol does using Petrol injectors. Diesel won't ruin the injectors like running petrol through a diesel system will - diesel is a lubricant whereas petrol isn't.

As for diesels having less power you have to remember that power doesn't really exist, it's just an equation - (lb/ft x rpm) / 5252

Mr Duckworth (the 'worth' bit in Cosworth) expressed it more simply as power = size of bang multiplied by the number of bangs. Diesel has more power in a fixed volume than petrol has but it burns slower so the engines can't spin as fast.

The result is much more torque but at a lower engine speed, so you get less power using the calculation above. My friend's tuned 1.9 TDI makes 180hp at but at only 4000 rpm, but the torque figure is over 300 lb/ft which is V8 petrol country.

If diesels didn't have enough power (as in strength) all those trains and trucks wouldn't work very well.

All true. Very true.

Here's the deal. I have a LOT of experience with diesels, and I understand them fully. I am a commercial truck mechanic on a dealership level (Peterbilt) who spends 99% of my time at work diagnosing/repairing engines, and these engines are basically giant versions of car diesels. Truck engines got into 100% computer management back in the early 90's, long before automobile diesels did. They have EGR, diesel oxidation catalysts, diesel particulate filters, variable valve timing, common rain injection, and now selective catalytic reduction as well. And all of these have been a "joy" during their various teething problems in the last number of years (read: nightmare).

There are my credentials, if needed.
Now to my preliminatry testing.

If you pour some diesel fuel on a table and try to light in on fire, it simply will not. Nothing will happen. Weird, but true. This is why diesel fuel is a much safer fuel. However, if you spray it as a mist, it will burn like crazy. Last night I loaded my spray bottle with diesel fuel, pumped 'er up, and sprayed a mist (not even that fine of a mist) through a flame, and voila, a massive fireball with very little smoke. And keep in mind the temp of our shop last night (I'm on evening shift this week) was only about 10C/50F, so pretty cold. So, misted diesel burns very well at pretty much any temperature. It doesn't require hot compressed air to burn; it only does to autoignite. And that's [maybe] what the spark plug will do.

Post 2007 Cummins engines have an injector on the outlet of the turbocharger, aptly named the "hydrocarbon doser," to provide raw HC for the catalyst for DPF regeneration. This doser works on pressures of only 200-300 PSI. I often do flow tests on these injectors by removing it, hooking up an extension supply line and harness, and enabling a test with the diagnostic software while the engine is idling so I can measure flow in a certain period of time. What I'm getting at is that this mist is a VERY fine mist of diesel fuel that lingers in the air for five minutes or more. So if done properly, I really don't think there will be an issue with atomization and making a combustable mixture in the cylinder. I just wonder if a single spark plug will be sufficient to light the whole thing on fire.

The mist from my spray bottle will not work for testing on my motorcycle. Too much fuel comes out. I'm thinking of turning a ball point pen into an injector. Hmmmmm.....

Um some very old books I have read mention spark lit 2 cycle diesels, very small motors usually.

Trouble is that type of motor was used because it was lighter, simpler and was mainly there just to be able to use cheap diesel for something.

It likely would not have any of the normal advantages of a true diesel engine and would run rather rough.

I've never worked on diesels. Driven them plenty, but never wrenched on them.

So you've ignited your diesel mist with an open flame - have you tried it with a spark?

As mechman said, diesel isn't terribly flammable. At the temperatures it would reach in an engine, it would likely ignite with the spark. However, I doubt it would burn well or completely, so it wouldn't be overly efficient and probably very dirty.

No, I haven't tried to light the mist with a spark yet. But I just thought of something.

The 2007-2009 Caterpillar truck engines use a system called an auxilliary regeneration device (ARD). Basically, it is a flame thrower on the outlet of the final turbocharger that shoots an actual flame into the exhaust stream, as opposed to other engines (including all diesel engines in cars) that rely on a hydrocarbon doser and oxidation catalyst. Regenerating a DPF (oxidizing the collected soot in the filter, turning it into "friendly" gasses, H20 and CO2) requires a minimum of 600F, and this device ensures that this temperature can be maintained for a length of time to keep the DPF from plugging up with soot. The temperatures actually reach more like 1100F at times during these "active" regenerations, as they are called. The ARD has a built in fuel injector, is fed bleed off boost air from the turbochargers, AND (wait for it.....) a spark plug. Yes, 2007-2009 Cat truck engines all have one spark plug, and this plug is what ignites a diesel fuel/air mixture to burn the DPF clean.

This still doesn't tell me if it will work in a very short "inside the cylinder" combustion event.

Just a suggestion.
If you're going to try this, maybe try it with varying mixtures of gasoline + diesel.
Start out with 25% diesel, then 50% diesel, etc.

I've thought of that too. The whole entire point, really, is ultra-lean burn. With gasoline, more than 16:1 is no good for economy, but with diesel, super lean works, obviously, as there is no throttle plate. It would be interesting to see how a diesel/gasoline mixture would react to ultra-lean.

...a LOT of people during WWII ran their cars on gasoline+kerosene (or used white-gas) due to war-time "rationing"

...my Dad told me about "wrapping" the fuel line (loosely) around the exhaust manifold to enable running on the gas+kerosene mixture AFTER the engine was fully warmed up; had to switch (valve) between two different tanks in the process: start on gas, warm-up on gas; then switch over to kerosene for driving. Of course, EPA didn't exist then!

mom filled her chevy astrovan with diesel once. she drove it home on the gas in the line and while it was warmed up. The next day we were able to get it to start and run very very badly. It would not drive we drained the tank and filled it with gas, after a while of cranking and barely running. We got it to run once the diesel was out of or diluted in the systems.

A jet engine running Jet A (diesel more or less) uses a spark plug to ignite the fuel charge in the hot section during starting.

My 1947 John Deere M can run on all three
 

never tried it though...

Nice. My dad had a 1947 John Deere G All Fuel. Gasolene, Distillate, or Kerosene. We tried it on Kerosene once, but I was too young to remember what happened....

Mechman-

Some people that know better than me or you insist that compression ratio DOES make a difference in the efficiency in the diesel cycle. See

The Diesel Engine

Even though the compression cycle is an "air spring" that regains it's energy in expansion, the expansion includes the added heat of the fuel burning... so they are not equal.

College was a long time ago, but I remember being sursprised that the diesel cycle is actually less efficient than the otto cycle also- the greater efficiencies of diesel engines come from their higher compression ratios, mainly, and secondarily from the higher heat content of the fuel.

I hate to tell you this, but it has already been done. There is nothing new under the sun – particularly in the way of engines.

Back before the First World War, the Germans built some kerosene (the Germans called it paraffin at the time) spark ignition engines for U-boats. Prior to that all of Mr. Holland’s submarines were gasoline-powered on the surface. Given the volatility of gasoline, early subs were unmitigated fire hazards which gave a lot of scope for reports of “…lost with all hands.” Kerosene and diesel (No. 1 and No. 2 middle distillate) have a much lower vapor pressure and as described are much less of a fire hazard. These engines did work, after a fashion. They ran and didn’t blow up (like gasoline subs) and in fact one paraffin-engine U-boat (the U-9) was quite successful.

The paraffin engines were nowhere near as powerful as either gasoline of diesel engines of the same size. The flame-front of kerosene is nowhere near as fast as that of a mixture of air and gasoline vapor. The paraffin boats were slow on the surface. The famous U-9 (and all paraffin boats) also had another characteristic they had to overcome: The paraffin engine smoked like a coal-fired battlecruiser. The plume could be seen for miles. She could only run of the surface at night or in an area where she could not be spotted.

But paraffin was abandoned when capable diesels came along (read after the invention of Herr Bosch’s fuel injector). The paraffin boats finished the war as training boats.

I’m not entirely sure what mechman600 is driving at. If he has a source of cheap kerosene, use it in a diesel instead. Diesels run just fine on kerosene. I’ve done it myself. If you have straight mechanical injection put a dollop of motor oil in the kerosene to reduce wear on the injector pump.

You might get that bike to run, but it will run poorly and smoke like a steam locomotive.

Also, from the lack of a throttle in the air intake.

You seem to see right through me! I have access to free diesel fuel. Like I said, I give this whole idea a 5% chance. If it doesn't work, at least I had fun trying. If it does, I'll be laughing my ass off.

It will work as I said and as Big Dave said there were spark fired diesel powered motors. If I can find the book it described quite plainly several small spark fired diesel motors and had breakouts showing their construction.

Also It would be strongly recommended that if you want the thing to have half a chance of working well enough to do something without breaking to do some modifications to the motor

Perhaps add glow plugs

And as suggested, add something flamable to coax ignition, cut with ether or gas perhaps.

I am uncertain on this regard but it would seem to me that diesel would be much more "lightable" if you increase the compression ratio of the engine just below the autoignition point, likely 12:1 but you also might get a lot of knocking so a cast iron piston would be needed.

As stated, probably will work if its warm enough around you but likely not very well.

And again, why not just get a cheap diesel engine?

They will run cleaner and better on the fuel.

[QUOTE=rmay635703;165224]....why not just get a cheap diesel engine?/QUOTE]

Because it's a motorcycle. The engine and transmission share the same case. You can't do an engine swap without swapping the transmission as well, and, there's no such thing as a diesel motorcycle engine with a transmission attached to replace mine with.

As for raising the compression, glow plugs, etc: I realize that these things will help. But I'm on a shoestring budget. This is all just to answer the "what if" question, nothing more.

If you get into it I remember several adding small amounts of welder poop among other things to the head to increase compression.

Also cutting the fuel with a bit of gas and ether would be a good idea to get it running from cold.

Cheers

[QUOTE=mechman600;165366]

Just cause this is right up my ally and I can talk about it a bit, I add a fairly carefully worded reply. The military has had many engines throughout history that ran on multiple fuels primarily diesel engines. Running on JP fuels and diesel are their main sources. Also better for transport as our armed forces do for obvious reasons. Gasoline being limited in many cases particularly in many other countries. There have been many engines through out it's history that have run on different fuels.
Without getting into much, our current prototype is a motorcycle, (the initial prototype was a car) an old 1981 air cooled 550 Yamaha that runs on any available (commercial) fuel. It runs at as lean as 22:1+ for cruise and 16:1 under boost. Any richer on any type of fuel creates detonation. Yes, running lean does not. Because we're an R&D company I wont get into specifics and there are a lot actually. Understanding hydrocarbon based fuels and their supplemental chemistry is a must. Understanding ICE, spark or compression, is secondary. Utilizing real science throughout the realm of application goes without saying. Knowing a butt load of math is priceless. The stock engine in the bike running with the designed system runs very clean and even NOx is significantly reduced. Which is a particular problem in ultra lean spark ignition engines.
The system extracts the internal chemical energy of the fuel, making more efficient use of the fuel first. (that was rather poorly said actually)The bike runs on a stock ignition module and timing is at it's set parameter for gasoline as it was originally designed for. This has taken about 5 years to get to this point. What took the longest was to have cold start utilizing heavy fuels like diesel. Yes temperatures are significant and everything is controlled via inputs from many areas referencing temperature. mechman600 you'll have fun in your experiments, gaining knowledge is fun!:thumbup:

Awesome! Thanks for that.

haven't read the whole thread yet, thought I would throw in my 2 cents.

I ran my 74 honda 400cc motorcycle on about 3 gallons diesel to half gallon petrol once. So long as I kept the engine hot (it was air cooled) and played with the throttle and choke it ran it--lacked power, but ran. (I was flat broke and could swipe diesel out of my uncle's tank for his skid loader) As soon as the engine cooled though, it wouldn't start.

I had to nearly choke it almost completely and blow a bit of smoke to get nearly to 65 mph. And high rpms? Forget about it, no chance in hades. But i did clock miles on it, and when it died, I added 2 gallons of petrol, cranked it forever from a jump from my car, and it sputtered back to life.

I've also ran diesel in my cars, but generally while being outnumbered by the gallons of petrol.

I have thought about doing this on a Buick 3800 but have no means of doing it. I think that you might need to run a hotter spark plug to help keep the temps up for autoignition. As for the fuel injectors if you cannot get it to work with a standard gas one try looking at one from the turbo Pontiac Solstice i believe they it is the one that had direct fuel injection if not one of the motors they used in that car did.

I know that some of the older generators and tractors that ran gas but could also run diesel could only do so when it was started with gas and once warm would manually switch to diesel. About the same set up as using SVO in place of diesel.

pour diesel in the tank and start it on gas first. once it's warm, then play with it

Done it
 

My data is polluted because the fuel was- I was desperate to get my machine to a fueling station, and I was angry and trapped. So, I grabbed anything I could find in a shed that looked flammable and poured it in.

This was about 2004.

The engine barely ran, and it turns out one of the small jugs had rust, water and other contaminants.

I did get it to run off and on, enough to go about 5 blocks (to a gas station), but each time it started was not enough to get any useful information.

After adding fuel, it was not much different until it ran for a short period, then it got interesting.

The heavy majority of the tank volume was kerosene (only had the ashtray coins). Once it started, I pressed the accelerator and it died. This is what heated it up, I believe, because it idled-- Rough, then cleared up. The second time, i was more careful. It didn't die until it was rolling down the road. After that, I played it safe. The engine would only operate in a narrow RPM band, and felt as if it had virtually unlimited torque. I wanted to make it home, though, so I didn't throw it into 5th, just to see what would happen in the name of science.

Fuel delivery was controlled by a mass air plate, with constant variable-flow injectors. This was a 79 rabbit, fitted with a GTI engine and a close ratio 5-speed box, closer than a convertible/GTi/GLi 9A. Possibly it was from a diesel. It is interesting to note that this engine and even the diesel version were based on a carbourated system which had the intake and exhaust manifolds on both sides, helping to atomize the fuel. My injectors went straight to the ports, but those ports in the head were even internally DIRECTLY adjacent to the hot exhaust.

The injectors are not designed to atomize that viscosity of fuel, though I suspect that due to their designed-in flexibility, they likely had better luck than duty-cycle varied, constant-delivery-rate injectors from a more modern digital proportional EFI system would have.

The fuel system setup meant I couldn't vary fuel delivery separate from air delivery. That would have been more useful data, and probly got me home faster.

After I parked, it would not start, a few hours later. I found ignition plugs covered in the viscous fuel, effectively fouling them and preventing any arcs. I cleaned them and it started rather easily, but was not drivable. I "determined" there was not available enough power to run on the road without garnering unwanted attention, which could result in massive fines if it was "determined" my tags were out of date and I carried no insurance.

It was likely this incident which led me to find fuel lines clogged, several years and a few fuel pumps later.

I got to this page trying to confirm a spark-ignition diesel existed, as the 1982 Audi 4000 diesel is listed as spark-ignited indirect-injection 1.5l (obviously a VW block) by automobile-catalog.com .I was there looking for gear ratios to help a smooth-shifting mod to an upcoming mogas conversion; we have found golf/4k/fox to be very strong, smooth and versatile boxes, avoiding the post-85/86 exploding diffs.

It's likely a typo, but I wouldn't swear to it. 4ks are rare enough I can't just go check a junkyard. Rabbits with the "comparable" engine were rated lower, the Audi 4k is listed as 52 on autocat.

The only really solid data I found was a military test, a230243.pdf found at dtic.mil .They outline achieving exactly what you proposed, with the caveat of fouling plugs (same issue I had). They used a "modified diesel engine", so likely were able to vary fuel input separately. They favored 12:1 compression ratios, for some reason, claiming it was somehow more efficient. The cold-climate instant-start and power benefits are clear, though. They also cited those. The document goes on to call for the design of an anti-fouler, but my interest stopped there. This is in 1990. Perhaps this is where those tubular anti-foul bushings on the rack at the auto parts store came out of, it was almost 30 years ago, now.

I have also seen designs similar to which you speak where the fuel was pre-atomized under extreme pressure. While normally used in power plants to run turbines on whatever they can get their hands on the cheapest, I have seen it done in a car. Then, you can take full advantage of the higher energy density in diesel, well beyond the normal 1/3 incidental higher MPGs vs. gasoline.

I got the idea to go to mogas (propane only, no butane from LPG) because the stock engine in a loved car had a high normal CO output (almost 1% total volumetric output). Since then, the NOx output, especially of diesels, has troubled me almost as much as the fact the issue doesn't get airplay. Incidentally, that same engine produces rather low NOx, I believe.

Either way, mo-gas will be far more economical and support an obscene amount of boost. Propane atomizes 100% into true vapor at any temperature on the globe, WITHOUT ingesting the extra air and heating it to burn nitrogen, like a diesel cycle does. I just have to pre-heat the fuel (familiar?) to atmo temp. If I want to add that high-pressure miracle stuff later, the gasoline-standard compression/ignition setup will still be ready-- I like the idea of being able to stock diesel on a site, it's not anywhere near as dangerous as the volatile or liquid-gas fuels.

There's another cycle that might be on the horizon that's compatible with diesel, though, so I'm not throwing out all those blocks.