Spark ignition Diesel engine, AKA your car

[rmay635703]

Originally Posted by mechman600

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.

[mechman600]

[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.

[rmay635703]

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]

Originally Posted by rmay635703

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.

[naturalextraction]

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!

[mechman600]

Awesome! Thanks for that.

[ShadeTreeMech]

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.

[Phantom]

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.

[bandit86]

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

[Niftyjig]

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.