Major Brainstorm - Diesel Conversion

[rustyATV]

I've been doing a lot of wondering about diesel conversions for two stroke engines.

Now, I know there are two stroke diesels out there, but those are normally a totally different design with a sealed crankcase, lower compression rings on the pistons, and roots blowers for scavenging.

I was wondering about what would be involved to make a diesel conversion for cycle engines along the same or similar lines as those for radio controlled car/plane engines.

http://www.davisdieseldevelopment.com/home.php

They've been around for years, just never got really popular.

All I can figure out that's involved in the RC conversions is that you put a head on the motor with so much compression that it will run diesel. But since cycle engines are far more sophisticated that RC engines, I'm guessing that in order to get good performance, I'd have to work a diesel injector into the head, or something, and what a chore that would be to figure out an engine management system.

Any thoughts, though?

[Aceman]

Originally posted by rustyATV
Any thoughts, though?

Why? Is the first thing that popped in my head.

Just an FYI, Detroit made a lot of 2 stroke diesels. My dad has one in his loader.

[LONG-ROD]

well like an rc car they dont have any rings.. just a very tight clearance and they have to keep a certain temp or the plug gets cold and they flame out.. a plus would be you could eliminate the stator. but you would have to have an electric starter and battery for starter and plug igniter. I guess if you could get a 250 plus cc motor to spin 30-40,000 rpms on 30% nitro it would be stupid fast.

[LONG-ROD]

well like an rc car they dont have any rings.. just a very tight clearance and they have to keep a certain temp or the plug gets cold and they flame out.. a plus would be you could eliminate the stator. but you would have to have an electric starter and battery for starter and plug igniter. I guess if you could get a 250 plus cc motor to spin 30-40,000 rpms on 30% nitro it would be stupid fast. and you could just use a pressurized fuel system off the pipe.

[rustyATV]

Just an FYI, Detroit made a lot of 2 stroke diesels. My dad has one in his loader. [/B]


[i]Originally posted by rustyATV
Now, I know there are two stroke diesels out there, but those are normally a totally different design with a sealed crankcase, lower compression rings on the pistons, and roots blowers for scavenging.

Because diesels have come a long way since your Dad's loader was made.

http://www.youtube.com/watch?v=iiRhoLQvb1I

[rustyATV]

Originally posted by LONG-ROD
well like an rc car they dont have any rings.. just a very tight clearance and they have to keep a certain temp or the plug gets cold and they flame out.. a plus would be you could eliminate the stator. but you would have to have an electric starter and battery for starter and plug igniter. I guess if you could get a 250 plus cc motor to spin 30-40,000 rpms on 30% nitro it would be stupid fast. and you could just use a pressurized fuel system off the pipe.

You're looking at this wrong; I'm not trying to get a cycle motor to run like an RC car motor, that's physically impossible. My thoughts are to combine advantages of two stroke cycle engines (simplicity, light weight, high power density) with those of a diesel (excellent low rpm power, high torque density, fuel economy).

I came up with this idea because I believe that for two strokes to have any potential at surpassing four strokes, they would have to evolve from what they are now and make up for their shortcomings.

[atvmxr]

well there have been turbos and electric powered supercharged 250rs from time to time over the years...
i think once you got it going it could work. the problem i see is start up, and the extra torque destroying clutches and yukons.. :)

[bill wright]

Originally posted by LONG-ROD
well like an rc car they dont have any rings.. just a very tight clearance and they have to keep a certain temp or the plug gets cold and they flame out.. a plus would be you could eliminate the stator. but you would have to have an electric starter and battery for starter and plug igniter. I guess if you could get a 250 plus cc motor to spin 30-40,000 rpms on 30% nitro it would be stupid fast. wait a minute, back up; deisels do not run spark plugs. glow plugs only .also, i have never seen that type of motor run those RPM'S. i dont understand what you are saying. please explain

[rustyATV]

Originally posted by bill wright
wait a minute, back up; deisels do not run spark plugs. glow plugs only .also, i have never seen that type of motor run those RPM'S. i dont understand what you are saying. please explain



http://www.davisdieseldevelopment.com/

[fearlessfred]

cool idea but as u allready mentioned u would have to seal up the crankcase to run motor oil in it .but the crank case is to small of an area to put much oil in it. the compression ratio on a diesel is around 18 to 1 to 22 to 1 the bottom end wouldnt hold up . u would need fuel injection and a blower detroit diesels run below 3000 rpm and have pour fuel economy or at least the ones i have run in heavy equip. did

[Burns310r]

Im only going to start the debate of this. It will go far deeper than this into why it wont work.


First off. diesels run on a much much higher compression ratio than gas engines. hence the reason they done need spark plugs.... the immense pressure is what ignites the fuel. some where around 17-20 to 1 compression. When even the highest 2 strokes on gas achieve maybe 14(guess cause im not willing to do the math right now for 250psi)

second problem you state is the scavenge. It has nothing to do with the boost into the cylinder, but actually the exhaust out of.... The pressure waves of each stroke out of the engine creates a vacuum behind it to pull the exhaust out of the next combustion cycle. Where this happens and under what force dictates the so called power band..

Just a few points to add to your discovery.


best of luck none the less. im sure others will help in this discussions.

[zedicus00]

Originally posted by rustyATV

I came up with this idea because I believe that for two strokes to have any potential at surpassing four strokes, they would have to evolve from what they are now and make up for their shortcomings.


stick a 450cc 20 year old 2 stroke motor in a new trx450R chassis. take it and a stock one out on the MX track. then you come back in here and tell me which one you think is more technologically advanced.

AND if 2-strokes were still being produced that had that extra 20 years of R&D money poured into them we would all have 100hp clean running,fuel injected, 2-stroke ATV's.

[troybilt]

The Diesel 2 stroke quad is interesting, but there is ALOT of major challenges, you'd be better off building a motor from scratch. If you've got the coin, I'd say go for it. I honestly think we'll see high performance EV ATV's or Compressed Air ATV's before 2 strokes come back, unfortunately.

[troybilt]

Another issue with diesels is you have to have to control the rpms, so that they can't go too fast. A diesel can "runaway" lose control by drawing "fuel" from its own wet crank case oil. I've personally seen this happen.

[86Rrider]

troybilt points out a very important fact as to why the 2-stroke diesel went the way-side of the 4-stroke diesel. I too have seen many Detroit diesels "run-away" in the shop after a injector service and the control rails were not adjusted properly. Closing the air supply-off is the only way to stop them.

I'm sorry that I don't have better information on this, but I'm sure a web search should produce it; back about 1998, Chrysler had a working prototype hybrid electric vehicle that used a small displacement, 2 cylinder, 2-stroke diesel engine to run a generator to keep a battery pack charged for the electric drive motors. This was prior to the whole lithium-ion batteries, so the concept was to use a small, efficient engine to run a charging system for the battery pack to increase the range of the vehicle. This might be a engine design to look into for ideas......

[All250R]

Originally posted by rustyATV
because I believe that for two strokes to have any potential at surpassing four strokes, they would have to evolve from what they are now and make up for their shortcomings.
I'm going to hijack the thread for a moment for my favorite soap box around here. Like you stated, 2strokes already surpass 4strokes, and have been for years.

I made an analogy that I like; making a 4stroke larger doesn't mean it's more powerful than a 2stroke, any more than making a 2stroke smaller doesn't mean it's more fuel efficient, or less pollutant than a 4stroke.

Rusty, you're the type of guy who could make something like a cycle engine work as a diesel. When you're filthy rich, expand your business into manufacturing better ATV's! :)

[LONG-ROD]

Originally posted by bill wright
wait a minute, back up; deisels do not run spark plugs. glow plugs only .also, i have never seen that type of motor run those RPM'S. i dont understand what you are saying. please explain


nitro rc engines run 30,000 rmps all day long some turn as much as 50,000, like the new ninja motors, also like I said they have to keep a certain temp or they flame out cause they use a glow plug, just like a diesel engine.

[fearlessfred]

no offence to you mr, long rod ,but a diesel only uses a glow plug for starting and is not used once the motor is running and as far as rpms go the larger and heavyer the piston the less rpms it can turn without tearing itself apart. im hoping your just messin with us

[2-330s]

i don't think gitting the compression would be hard.what comp rato do you think one of these motors is when you squeeze 265 psi out of it? 20-22 to 1???

[rustyATV]

Ok, there's a lot here and it's late, so I'm just going to touch on things.

First, let me just say that there is about a snowball's chance of me even getting anything drawn up in CAD, let alone a viable design made, developed, and running reliably enough in any kind of cycle. I have a CAD program I can model this in, but no computer powerful enough to run it (yet), no practical knowledge of engine component design, and not nearly enough time to spend on it. This isn't nearly the only idea I have, and well after about three entire quad designs I'd want to do first. So this is meant to just think of how it could be done.

When I started thinking about lubricating the bottom end, I very quickly realized that there'd have to be more than a conversion. At first I thought you could just let the lubricating oil drift off into the combustion chamber, but recalled a redneck friend's colorful story of wrestling a runaway diesel with a shop manual. Perhaps the lubricating oil can be metered electronically to also control the idle? Electronics are rather capable these days.

I know of a way to seal off the crank; there is a guy who patented a Planetary Crankshaft (http://www.memagazine.org/backissues/membersonly/apr03/departments/input_output/input_out.html) design based on the old Spirograph kids toy that produced a pure linear rod motion, which would allow for sealing at the rod, but this still leaves the piston to be lubricated.

Patent: http://www.freepatentsonline.com/6510831.html

Actually, I could see this alone being put into a two stroke for a power/rideability benefit.

As for strength of the bottom end; I'm not entirely sold on it needing to be exceedingly heavy. Two strokes are easier on parts because of how the power is delivered; parts are nearly unidirectionally loaded, whereas a four stroke constantly reverses the loads on components thanks to its intake stroke.

I wouldn't think compression would be an issue. I'm sure with a heavier piston the peak RPM's would drop, so a tighter maximum squish could be achieved. If nothing else, then perhaps the piston diameter would have to be larger?

Did a quick search on the Chrysler engine but didn't dig very deep. Looks like they were close to a two stroke gas engine until emissions jumped in the late 90's.


Originally posted by zedicus00
stick a 450cc 20 year old 2 stroke motor in a new trx450R chassis blah, blah, blah.

Yes! The die-hards never disappoint! About a dozen years ago over a discussion on camless engines, guys like you would snidely remark that a four stroke could never be faster than a two stroke, they'll never be more than the low revving air cooled junk at the time, yet here we are!

Really, misplaced as claims against two strokes may be, the fact is they have perceived faults, and if those faults can be overcome, then the case for their re-adoption would be stronger.

Besides, look at the history of motorcycling and you'll see two-strokes and four-strokes have been sort of "leapfrogging" each other. First four strokes were the only things capable of making power until someone decided to put an expansion chamber on a two stroke, then four strokes were put on a diet. To think that two-strokes will just jump back up top without any kind of changes is a bit naive.

[LONG-ROD]

Originally posted by fearlessfred
no offence to you mr, long rod ,but a diesel only uses a glow plug for starting and is not used once the motor is running and as far as rpms go the larger and heavyer the piston the less rpms it can turn without tearing itself apart. im hoping your just messin with us

lol.. i said it would haul if you get it turn those rpm's,, never said it could be done,, and I m well aware of how a glow plug works.. and Im talking about an rc glow engine turning those rpm's nothing more.. don't look to deep into it man, lol..

[LONG-ROD]

someone correct me if I am wrong but a glow plug is used way beyond just starting the engine.. the coil in the plug stays hot, due to combustion, and ignites the mixture.

[fearlessfred]

no. plenty of diesel motors dont even have glow plugs the fuel is ignited by being injected into highly compressed air, that is super heated from being compressed the glow plug is used to heat the air to make it easier to start but are not needed to stay running all passanger trucks due have glow plugs ,but plenty of constuction equip. does not

[troybilt]

http://en.wikipedia.org/wiki/Glowplug

diesel can also ingnite by being compressed itself, such as in a the case of a large pile driver... etc...

[LONG-ROD]

thanks, learn something new everyday.

[RyanWsly]

2 stroke diesel has the same short comings of a 2 stroke gas, lack of a large power band, lack of low end power, not really that fuel efficient. 71 series and 92 series Detroits both fall on there faces just like gas 2 strokes under a certain RPM, and have less than desirable fuel economy. Having said all that, try it out and see what happens, it's what this country was founded on, just don't be disappointed with the results is all. Glow plugs are used for initial ignition of fuel for start up, they have used many different methods for that, that is just the most common one. A spark plug will ignite diesel, check out the emissions on a Ford truck or a 07 and newer Cat C15, or search CRS or ARD systems. Troy that's a bit out of your area, but I'm sure you have a lot of access to the info, check out "operation readiness" through Cat.

[rustyATV]

Hmmm. How about a kind-of-but-not-really diesel?

http://www.youtube.com/watch?v=fIoB0zTeUAY

I've got to look into the advantages of a "heavy fuel" spark engine.

[rustyATV]

I wonder how far this concept went

http://www.yamaha-motor.co.jp/global/news/1999/03/23/super-diesel.html

[rooster300ex]

I was blow away by how much compression my ol chevy 6.2L diesel had. It was 22 to 1 :eek2: Thats why the starters can be burned up so easy. Alot of people don't know how to prime the fuel filters when they change em and burn it up.

[KM250R-BDTM]

Not to throw cold water on a very good discussion, 2 stroke diesels, in particular a 2 stroke diesel 250r engine conversion had been done and tried with success back in 85-86 at Honda R&D facilities in Japan. I can share it is a lot easier to convert than most think and have stated on this thread. A successful running 250r was converted to full diesel operation with only an adjustable head compression counter piston, dome and fuel changes including oil lubrication. No need for sealed crankcase, lower compression rings or a roots blower. The conversion was very simple and functional. The overall results proved it could be done easily with an existing engine designed for 2 stroke gasoline fuel. Power was increased bottom end torque with reduce top end performance and excellent fuel economy.