Small Two-Stroke Diesel Engine

Hello ky

I'm sure you know how small 2-stroke petrol engines work - using the crankcase to transfer mixture tothe cylinder and force the exhaust out. It might be feasible to build a diesel on similar lines (obviously there would only be air in the crankcase, this would blow into the cylinder to provide exhaust, fuel injection normal). I believe model aircraft engines work like that, but while they are compression-ignition I don't think they have fuel injection.

Bigger 2-stroke diesels use a blower for exhaust. There's only an exhaust valve, air is blown in via a series of ports at bottom of cylinder, exposed when the piston is near BDC. How small this type of engine is made I don't know offhand.

Maybe that helps.....Codey

Thank you Codemaster

Air intake and injection are the only things that will change and not internally but with minimal adjustments outside the engine. As you will appreciate I can't give any more details and need some hands on experience just to satisfy my "tinker genes".

Thanks again, Ky.

Hi ky:

t may be possible to modify a small petrol engine. The injector would go in place of the spark plug, some surgery to raise compression to at least 18:1 (the smaller the diesel the higher the compression ratio needs to be).

If it has crankcase compression and reed valves, some alteration to porting will allow an air scavenge to flush exhaust out.

After much tearing out of hair and cursing, it should work.

Of course as you are making a different injector system, the need to supply that won't worry you.

Good luck.

If I can be of any help, either ring or email.

Thanks sceptic, good to hear from you.

When I posted this question I thought I'd have one up and running by now. There must be a small pre-manufactured two stroke diesel off the shelf some where. Well, maybe that is why I can't find them on the internet.

It is exactly the scavenging function that I am after. As I have mentioned I would like to keep the tearing out of hair and cursing at a minimum. Before the Eurika scream there will be plenty of that anyway.

I am not even sure yet if I have to change the injection system but maybe get away with some minor external changes leading to the injector. I have spoken to a professional but he is out in the mines and I don't want to bother him to much. Three weeks on two weeks off sort of situation. Once I get to a certain stage he is committed to help with the refining and has understood and seen a small prototype in action. No, not of the engine, but what comes before the injector. Just need and want to carry as much weight as I can for as long as I can and get a bit firmer on the subject without bothering third parties.

I think I will call you later today and give you a rundown on what I am proposing and after that maybe send you some schematics and some detailed explanations. (Draft paper)

No rush at all but I think it its about time I make that next step, Ky.

An interesting article:

http://engineeringtv.com/blogs/etv/archive/2008/07/01/opposed-piston-opposed-cylinder-engine.aspx

Yeah, great stuff. I am sure I could attach what I am thinking about to this engine and get it to run even on less fuel.

Thanks bwire, Ky.

Hope this will help you see where the problem with your idea is and hope that you can figure a way to do this in an economical way. The figure below shows the layout of a typical two-stroke diesel engine:

At the top of the cylinder are typically two or four exhaust valves that all open at the same time. There is also the diesel fuel injector (shown above in yellow). The piston is elongated, as in a gasoline two-stroke engine, so that it can act as the intake valve. At the bottom of the piston's travel, the piston uncovers the ports for air intake. The intake air is pressurized by a turbocharger or a supercharger (light blue). The crankcase is sealed and contains oil as in a four-stroke engine.

The two-stroke diesel cycle goes like this:

1. When the piston is at the top of its travel, the cylinder contains a charge of highly compressed air. Diesel fuel is sprayed into the cylinder by the injector and immediately ignites because of the heat and pressure inside the cylinder.
2. The pressure created by the combustion of the fuel drives the piston downward. This is the power stroke.
3. As the piston nears the bottom of its stroke, all of the exhaust valves open. Exhaust gases rush out of the cylinder, relieving the pressure.
4. As the piston bottoms out, it uncovers the air intake ports. Pressurized air fills the cylinder, forcing out the remainder of the exhaust gases.
5. The exhaust valves close and the piston starts traveling back upward, re-covering the intake ports and compressing the fresh charge of air. This is the compression stroke.
6. As the piston nears the top of the cylinder, the cycle repeats with step 1.

­

­From this description, you can see the big difference between a diesel two-stroke engine and a gasoline two-stroke engine: In the diesel version, only air fills the cylinder, rather than gas and air mixed together. This means that a diesel two-stroke engine suffers from none of the environmental problems that plague a gasoline two-stroke engine. On the other hand, a diesel two-stroke engine must have a turbocharger or a supercharger, and this means that you will never find a diesel two-stroke on a chain saw -- it would simply be too expensive.

Thanks Jim

I'll have to add the turbo to my shopping list, although that will be at a later stage, if at all. I am planing to run a diesel but not on diesel (or maybe partly). I am beyond the basics and the graph you supplied must have just missed the one I put up. Thanks anyway, Ky.

Back in the day, there were numerous diesel model aircraft engines. They had a second piston above the one connected to the cor rod/ crankshaft. You could adjust the compression by way of a wing nut on the cylinder head where the glow plug sits on a glow engine. Davis Diesel Conversions even sold kits to convert a glow engine to diesel. The diesels were more common in Europe than the US. They were less powerfull than the same displacement glow engine so went out of style. Davis Diesel engines is still around google it for more cool info. They may even have just what you are looking for.

Thank you Guest

Very interesting link but I will have problems concernig the space I need for attaching my gadgets and the altenator etc. Seems great for the model stuff but just to small for what I need. I hope some one interested will find Davis Diesels as an interesting alternative to what they are doing now.

Thanks again, Ky.

It used to be model airplane motors were considered diesels because aside from the glow plug giving initial heat they ran on compression ignition of the fuel, albeit with a carburetor.

I believe that a 5hp two stroke injected diesel may be a tad complicated for the effort. Plenty of 4 stroke ones around. When you consider that the larger truck/industrial two stroke engines use some sort of super/turbo charging (or both) for efficiency/power.

Part of that is to get sufficient air into the combustion chambers as well as expel the exhaust gas when the piston is at BDC.

That said you could find a three cylinder Detroit 3-53 motor, that's water cooled, you could mount that on a stand with wheels to move it around. They weigh a bit though and produce around 60hp @ around 1850-2200rpm. If you feed the exhaust through a water scrubber it might shut it up. Have to be careful not to load the back pressure up too much. Most two stroke diesels are a tad noisey when their running.. You would want to put a water pump connected to a 44gallon drum of water, on the flywheel end to give the engine a load when its running, or else you'll glaze the bores, and it'll run bad afterwards. Diesels love to work hard.

Dunno if that helps, sounds like an interesting project....

Tobugrynbak

Interesting. I'm taking it all in. Seems that I was a bit naive at the beginning, but like diesels, I don't mind hard work. Might use it to get some well water onto my garden and have a good excuse for making noise.

Thanks for the information, Ky.

I think that you have put your finger on the problem, there are basically no small diesels around, (ignoring model aircraft motors of course, but they are not that efficient fuel wise).

I would like to have a diesel driven generator for camping, the economy that a well designed diesel would bring would be great.

I hope that a relatively well built petrol engine will help you in your endeavours.....

I personally suspect that the Diesel problems of building a small injector system are part of the reason that small diesels are not very prolific.....

Just a thought, have you looked around in India for a small diesel.....(Googling, not visiting!)

Good to see you Andy

I would like to have a diesel driven generator for camping, the economy that a well designed diesel would bring would be great.

That is what this engine is supposed to do. But not only that. Please find below a cut and paste of what I said on a long going HHO thread here on CR4.

Now to reinventing the wheel.

As you and others here know, I have always claimed, while sitting on the fence, that I have a different approach to using electrolysis in an IC engine. Even though I understand the ins and outs of what has been discussed here (he keeps saying), I see my "system" as feasible. It requires a more intricate hardware setup and I am not aiming at the automobile market at all but at decentralized power generation for households.

I don't need to produce thousands of units to prove the technology. I don't have to step up to some car maker and beg him or the Government for funds, which is the most depressing part of it all, and don't have to be concerned about weight and all other issues arising when putting such a "generator" into an existing car. I can put the first unit in my house and R&D would be not as cumbersome. Attaching new things to an existing governing system is a very restricting environment to work in/with and cutting that out can make things easier, I think.

As things stand the unit will be the size of an old fashioned TV set (for a Family of 6) and would have an estimated (+/- 10%) price tag of around $2500 when low numbers of units are produced. It would run virtually free of pollution and would be suitable for houses not on the main grid at first. Others to follow, once proven in the field.

I have a paper in progress and will publish this to some of (you know who) in the coming months. (That includes you Andy) To have the hardware in place will take some time out of my and lately some body else's life. It is also delayed by the tightness of funds all around. That is great, because it gives me more time to think. The next wave is mine.

This was not to long ago and now I am committed to doing it. Just need "that" engine to get started.

Now I'll go to India, although I am highly allergic to coriander.

Thanks for your help, Ky.

http://www.hatz-diesel.de/index.php?id=31&L=1

Gen sets and water pumps:

http://www.hatz-diesel.de/index.php?id=61&L=1

There are plenty of small four stroke diesel motors around, Hatz, Lombardini, Kohler to name some euro ones, there's also Robin(subaru), Tohatsu, Yanmar, japanese and China makes all sorts of small 4 stroke diesels.

I have a 8hp Lombardini running a 5.5Kw 240Vac 50hz generator, works well, a little heavy for overnight camping (bit noisey too) but good if your away for a week, runs 1litre an hour fuel consumption at 4 Kw draw which is pretty economical. especially when camping with modern women..LOL.

There are smaller gensets which run diesel motors, its best to have them well loaded (say 3/4 capacity) when they are running so they can perform at their best. If your only running light occasional loads then a small petrol generator is the go. Don't bother with any of the cheap chinese ones, they don't regulate engine speed/load at all well and certainly few have any altitude compensation. Which means they tend to damage equipment attached to them or they die quicker than you can ask "has the cheque cleared?".

Cheers

Perry

Thanks Perry

Things are clearing up but at this stage it seems that the scavenging part of the two stroke is very well suited to what I have in mind. Not that I am stuck with it but just for now it seems the best way to go. I have responded to Andy and that will give you a better understanding of what I am on about. Also see the link I provided in my opening post. It will make things a bit more transparent but will still leave plenty of questions to be answered. Only a matter of time and I will get what I am after.

Greetings to the modern women, what (were) would we be with out them?

Ky.

Hi, ky!

Dunno whether someone else recommended this route or not; but have you tried looking through the scrap and parts yards online?

Mark

Thanks Mark

No, but now I will. Would save some of that stuff we all ran out of, wouldn't it? See what they can come up with. I'll let you know, Ky.

take a look at aux. diesel engines used in moderate sized sail boats. Not sure just exactly where to tell you to begin a search except to begin with a search of sail boats with aux. power. A friend of mine had just such a boat, about 36 ft. long. The aux. engine was a two cylinder model, under 8 hp., water cooled.

Good luck,

'TooMuchFun'

Thanks TMF. The more choice the better. I'll have a search, not having Toomuchluck yet although one very good lead. Have fun, Ky.

Hi ky

Small diesels were often used to drive yachts. Unfortunately, most would be 4 strokes, but you might get lucky.

A browse around some of the boat yards in Townsville and on the Island may be worthwhile. (Always interesting even if no use).

Good luck

There is a russian built 2 stroke diesel motor that was used for Radio controlled airplanes. It was built back in the 50's, and used diesel fuel. I don't know much about it but it is a very simple design. If you really think about it the 2 stroke motors that we use everyday are a diesel since there is no spark plug, they just don't use diesel fuel. I wonder if you could use diesel fuel in a standard 2 stroke model airplane motor.

No, without additives Diesel won't burn in a model diesel engine......

Diesel needs to be injected under very high pressure and fully atomized.....of course one could possibly design a tiny "proper" diesel engine I expect.....I will have a look with Google...Sorry, nothing quickly apparent.....

I found a good web site for model diesel fuel mix, check here:-

http://www3.telus.net/dieselcombat/diesel_fuel.htm

Here are a few important lines from this site with regard to the mix:-

1. Kerosene, which is the base fuel and is the major power-producing ingredient
(equivalent to the gasoline in your weed whacker);

2. Oil, which performs the lubrication and sealing functions;

3. Ether, which has the function of reducing the temperature necessary in the cylinder for ignition to occur and also acts as a solvent to keep all the components in solution; and

4. an ignition improver, which further lowers the ignition temperature requirements and also reduces lag time for ignition to commence when the right temperature is reached.

Thanks fishpipes and Andy

It looks like I have to admit that finding exactly what I am after will not happen. No problem at the moment. I am setting up my "fuel system" and it should be ready soon. It will be rudimentary but will hopefully give some indication of combustibility with out an engine present. These results will more or less govern which diesel to choose. It will be possibly larger than expected to take advantage of the many possible variations and functions that a two stroke can deliver (others as well, but for a proof of concept two stroke would be the simplest to govern), if and when alterations have been made. There are always more questions than answers when trying something new and new it is, I (we, by now) think.

I thank all who have helped here and will keep you up to date.

Have a good one, Ky.

Very interesting topic Ky.

Be great to know how your system works out, I have also developed a keen interest in small two stroke diesels, especially opposed piston types. Also having great difficulty locating a small one to play with. There are a few new small (100HP) aero diesels emerging but VERY pricey, did you have any luck finding anything in the marine type, or anything else for that matter?

G'Day Hoppy

How time flies. Just a couple of months gone and there have been some encouraging developments. I have decided to take the theoretical route and have done some preliminarily tests with a demonstration setup which has confirmed that following up seems more than warranted.

I know more about the subject now and that is to the credit of CR4 and the participants of this thread. My next step will be the one were I shoot with "real bullets" and I can't wait. It (the fuel injection part) has made a huge leap forward.

The most amazing thing is that I have not come out of my workshop with dirty hands or busted ear drums, yet. I am working on drawings now so that the parts I require can be made by the appropriate people in two different industries. Once I have those and can put them together I will see. Once I have the quotes and the funds to keep them happy I will install it in any diesel that I can get my hands on.

I will be able to use existing governing systems to regulate what I have come up with. 'Not long now' I keep saying to my self. Am I there yet? No, but there are less obstacles in my path and things are improving by the day. Only in my head at the moment but that's were it all starts in the first place, whatever one does.

Welcome to CR4 and I hope you can contribute further and not only to this thread. Thanks for your reply, Ky.

Of the Tiapan model Aero motors made in Australia some were "2 stroke diesels". But not in the manner that we have become accustomed to. The fuel is premixed with the air and ignited by compression, there are no injectors. What segregates them from normal compression ignition 2 strokes is the decompression screw in the head and when running, the higher compression ratio and of course the fuel used. The working part of the fuel is kerosine, the ether is to cause ignition and the castor oil to lubricate. I recently read a good write up from the manufacturer but can't recall how I found it, (probably a model engineering archive) searching for Tiapan engines should help though.

As for 2 stroke diesels generally they are obsolete in sizes below ship drive systems. Last I checked Detroit Diesel only make the 92 and the 53 (cubic inches per cylinder) models with the 71 and 149 being discontinued some time ago. The reasons for obsolescence are emissions, fuel consumption, oil consumption, noise and increasingly cost. 2 Strokes once had a weight advantage that somewhat offset the disadvantages, that advantage has long gone. High horsepower high speed diesels are now all 4 stroke, the 16V149 being replaced by the 12V4000 DDC / MTU engine and smaller engines such as the 8V71 replaced by the 60 series Detroit 4 stroke. The 3 cylinder model mentioned in an earlier post is the 353 Detroit, once common as auxilliary engines on tugs and the like.

For really small engines the cost, weight, height, complexity, fuel consumption etc rules them out. The air must be forced into the engine to even start them. If a mechanical blower isn't used then an electric blower is used until the turbo charger takes over and honestly I've only seen that configuration on 30,000hp or bigger low speed marine engines. High speed diesels all use a mechanical blower and that is quite expensive to do on small engines.

If you wish to modify a petrol engine then electric blowers could be the way to go.

As for modern 2 strokes the Orbital Engine Company have done quite a bit of research in relatively recent times, their air shearing injection system is reputedly able to run a blowerless 2 stroke diesel engine. Even OEC though recommend using a mechanical blower when boosting a 2 stroke.

While my resaerch is definitely not exhaustive, I haven't even seen model makers take on miniature 2 stroke diesels.

Hi! I think you mentioned all those arguments needed to cloxe this thread. but i dont wont to give up this early. Why are two stroke not double as powerful as gazoline ones? okay the gasexchange isnt that good, but that cannot be the whole story, can it?

Greetz Jo

Hi, Jo!

Not sure what you mean by "double as powerful as gasoline ones". The power of the stroke and output power of an I.C. engine isn't dependent upon the type of aspiration process (although that can be limiting) or the kind of fuel being consumed by it. In order to answer your question satisfactorily for you, we would have to know what you mean when you use the term "powerful".

Mark

Hi!

With the term powerfull i mean an engine that fits into my motorcycle; isnt heavier than my fourstroke gasengine (48kg without gearbox) and has as many KWs (34). Diesel engines rpm are limited (4500) due the limied burning rate. A small engines like high rpm since the piston speeds stay equal. Small diesel engines cannot use this advantage, gasoline ones do. So a small diesel engine that fits into my motorcycle will be less powerfull is guess.

Greey Jo

Hi

In Germany we have a 500ccm 2-stroke diesel, built by Sachs in the 1950s (Sachs Diesel D 500 W). The Design is from Holder.

Some Details:

Bore x Stroke: 80mm x100mm (Displacement 503ccm)

Power: 10hp @ 2000rpm

Watercooled (thermosyphon), but aircooled versions and 400ccm to 600ccm versions later although available

Indirect injection (prechamber) with Bosch pump and injectors

Scavenging through crankcase, piston-controlled exhaust-port (like a conventional gasoline 2-stroke)

Dry-Weight: 88.5kg

Take a look at the manual (german language, but a lot of pics): http://www.einachser.org/holder/Sachs/D500W%20Rep.htm

Greetings

Tommi

(P.S.: From Detroit Diesel there is a one-cilinder version of the series 71, called 1-71 with similar power, but a few times heavier...)

Thanks Tommi

I tried the link but it leads me to no where. Could you check on that and send it again. My project needed other matters to be resolved first but I would be interested in getting all the information I can. It sounds good.

Never mind the German language, wir sprechen Deutsch.

Thanks for your effort, Ky.

Try this one Ky

http://www.einachser.org/holder/Sachs/D500W%20Rep.htm

This is I think what you are looking for, now where you're gonna get one is a different story

I just pulled out einachser.org/holder/Sachs/D500W & searched that when ever you get a failure for a link

Thanks Mate, I appreciate it, Ky.

Thank you for your effort. You are right my inquiries back then have given me some really good choices. I am not sure if all you mention were considered but I will have a look at them.

To modify any of them I will have to rearrange my workshop and have a machine shop nearby. That is not going to happen over night but it will happen. German it will be, Ky.

There is a misprint in my post. I mentioned Sachs, but I meant Stihl (Sachs has made two-stroke petrol engines). Also the Lanz D 2416 seems to be a four-stroke, even though some sources claim it to be a two-stroke. There is an interesting story behind the Ford AD 4 and AD 6 engines. They were initially made by Gräf & Stift (http://www.fomcc.de/graefford.htm). They were the engines that brought down the Ford truck production in Germany due to a lot of initial problems with the engines (http://www.fomcc.de/fk.htm last section).