Simple 2-Stroke Diesel Injection Controller

New member, actually don’t even own any arduino whatsoever yet, came here to ask about a project I have in mind.

I have an old 50cc 2-stroke engine laying around that doesn’t currently run, and I’d really like to try to convert it to a 2-stroke diesel. I’m aware I’d need to dramatically increase the compression ratio and possibly add some sort of low-boost turbo/supercharger for scavenging, but my question is about the fuel system. For you car guys out there, is a simple fuel injection setup using an ebike 0-5V throttle (as a TPS), an intake pressure sensor, and a hall-effect sensor (as a crankshaft position sensor) feasible? Basically I’d like a setup that will inject fuel a variable amount of fuel (based on the throttle position and supercharger pressure) every time the piston reaches TDC. Would this be possible, and would an arduino-based controller be the right option for it?

I’ve also looked at products like Microsquirt and Speeduino, but they’re quite complex and I’d rather keep this project relatively cheap if possible (i’m already going to be buying high-pressure fuel system components lol).

Not asking if a 50cc 2-stroke diesel will work, simply asking what I’d need to control the fuel system for it.
:slight_smile:

Diesel fuel injection is entirely different from petrol (gasoline) fuel injection. Diesel injection works at incredibly high pressures directly into the compressed air in the cylinder and it is squirted through an incredibly fine hole so that it atomizes into very fine droplets that can ignite spontaneously in the hot air. I suspect for most diesel engines the injection equipment costs nearly as much to make as the rest of the engine.

You will need to find a ready-made diesel injection system that can be adapted to your needs.

The other critical thing is that petrol engines are not built with sufficient strength for the much higher forces that exist in diesel engines. I suspect that the machine would quickly destroy itself if you could make adjustments to get the required compression ratio.

...R

Control requirements are low. The outlined sensors are sufficient for supply of the relevant information. Not so easy may be the determination of the time and duration of the fuel injection, but I think that a standard Arduino (Uno, Pro Mini, Micro...) will do.

Robin outlined already the mechanical part of your project. I second that it won't be possible to convert an Otto engine into a Diesel engine, so that you may be better off with a motor simulation and visualization on a PC.

Robin2:
Diesel fuel injection is entirely different from petrol (gasoline) fuel injection. Diesel injection works at incredibly high pressures directly into the compressed air in the cylinder and it is squirted through an incredibly fine hole so that it atomizes into very fine droplets that can ignite spontaneously in the hot air. I suspect for most diesel engines the injection equipment costs nearly as much to make as the rest of the engine.

You will need to find a ready-made diesel injection system that can be adapted to your needs.

The other critical thing is that petrol engines are not built with sufficient strength for the much higher forces that exist in diesel engines. I suspect that the machine would quickly destroy itself if you could make adjustments to get the required compression ratio.

…R

I’ve sourced some diesel fuel system parts I’m planning to use, that should be up to the task. I do worry about the rest of my engine, particularly the connecting rod. I am planning on buying a billet rod and crank, but even then…

DrDiettrich:
Control requirements are low. The outlined sensors are sufficient for supply of the relevant information. Not so easy may be the determination of the time and duration of the fuel injection, but I think that a standard Arduino (Uno, Pro Mini, Micro…) will do.

Robin outlined already the mechanical part of your project. I second that it won’t be possible to convert an Otto engine into a Diesel engine, so that you may be better off with a motor simulation and visualization on a PC.

Are there any existing projects you can point out, to help me see how I’d go about this process? Complete noob here.

Which “process” do you mean?

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .

Can you tell us your electronics, programming, arduino, hardware experience?

If you have never programmed before, then you will find you will at least have to learn the basics before actually testing and programming for your diesel engine controller.
Your project is a big ask and will involve sensors and driving circuits suitable for high pressure injectors.

Have you googled

arduino diesel engine control

Thanks.. Tom.. :slight_smile:

SebastianZ:
New member, actually don't even own any arduino whatsoever yet, came here to ask about a project I have in mind.

I have an old 50cc 2-stroke engine laying around that doesn't currently run, and I'd really like to try to convert it to a 2-stroke diesel. I'm aware I'd need to dramatically increase the compression ratio and possibly add some sort of low-boost turbo/supercharger for scavenging, but my question is about the fuel system. For you car guys out there, is a simple fuel injection setup using an ebike 0-5V throttle (as a TPS), an intake pressure sensor, and a hall-effect sensor (as a crankshaft position sensor) feasible? Basically I'd like a setup that will inject fuel a variable amount of fuel (based on the throttle position and supercharger pressure) every time the piston reaches TDC. Would this be possible, and would an arduino-based controller be the right option for it?

I've also looked at products like Microsquirt and Speeduino, but they're quite complex and I'd rather keep this project relatively cheap if possible (i'm already going to be buying high-pressure fuel system components lol).

Not asking if a 50cc 2-stroke diesel will work, simply asking what I'd need to control the fuel system for it.
:slight_smile:

The reality is you are over thinking the project. You do not need injection or high compression for a Diesel. Once running and hot, a gasoline engine will run on #2 Diesel fuel. The carburetor may need to run a bit richer.

The real life engineering problem for you is not the injection or anything related. The problem is just getting the engine running!

Older Diesels were carbureted and had spark plugs. They started life with gasoline and when the engine was warm, switched over to Diesel fuel.

Newer, injected Diesel engines could not use gasoline, so had to have a different starting mechanism and this is where glow plugs came into use. My Kubota uses this method and the vehicles I used to own used this method.

Newer vehicles, like my Dodge truck and VW Jetta TDI use a small chamber with a heated screen to super heat the air immediately before it goes into the cylinders. The heat is shut off when the engine starts.

So, start with the basics, the starting cycle and figure out how you want that to operate.

Paul

Paul_KD7HB:
Older Diesels were carbureted and had spark plugs. They started life with gasoline and when the engine was warm, switched over to Diesel fuel.

Are you sure you're not mixing that up with paraffin (kerosene) - which used to be referred to (when I was small) as TVO or Tractor Vaporizing Oil. AFAIK those engines continued to need a spark when running on paraffin. I have never come across the phrase "diesel engine" to mean anything other than a compression ignition engine. It is probably possible to run a spark ignition engine with diesel fuel but it would not be a compression ignition engine. And AFAIK it is not possible to run a CI engine on petrol as it will not ignite spontaneously the way that the heavier diesel fuel does.

Rudolf Diesel's original engine used high pressure air blast injection.

...R

Robin2:
Are you sure you're not mixing that up with paraffin (kerosene) - which used to be referred to (when I was small) as TVO or Tractor Vaporizing Oil. AFAIK those engines continued to need a spark when running on paraffin. I have never come across the phrase "diesel engine" to mean anything other than a compression ignition engine. It is probably possible to run a spark ignition engine with diesel fuel but it would not be a compression ignition engine. And AFAIK it is not possible to run a CI engine on petrol as it will not ignite spontaneously the way that the heavier diesel fuel does.

Rudolf Diesel's original engine used high pressure air blast injection.

...R

Quite right, Robin.

I was thinking of our old John Deer tractor. It always used spark to fire the Diesel fuel. One hell-of-a-spark from a magneto. If the engine was hot it would start directly burning Diesel oil, but not if cold.

On the other hand, my father-in-law had several International Harvester tractors the started on gasoline and had compression release to stop the autoignition. Then when warmed a bit, you moved a big lever that stopped the ignition and the compression release and ran full auto ignition Diesel.

Then there was the Oliver tractors that were full Diesel, but were started by ether from a spray can. The air/ether mixture would auto-ignite at a log temperature and spin the engine fast enough to start, sometimes!

I wonder how the OP intends to supply the engine bearings with lubrication?

Paul

Paul_KD7HB:
Quite right, Robin.

I was thinking of our old John Deer tractor. It always used spark to fire the Diesel fuel. One hell-of-a-spark from a magneto. If the engine was hot it would start directly burning Diesel oil, but not if cold.

On the other hand, my father-in-law had several International Harvester tractors the started on gasoline and had compression release to stop the autoignition. Then when warmed a bit, you moved a big lever that stopped the ignition and the compression release and ran full auto ignition Diesel.

Then there was the Oliver tractors that were full Diesel, but were started by ether from a spray can. The air/ether mixture would auto-ignite at a log temperature and spin the engine fast enough to start, sometimes!

I wonder how the OP intends to supply the engine bearings with lubrication?

Paul

The bearings are lubricated via a small transfer hole directed towards the bearing, that oil travels through and keeps things moving nicely. A simple setup, hopefully adequate for this application? Lots of people drill out the hole even larger when installing performance kits that would up the demands for proper lubing. I'm also planning to pre-mix, but I suppose with a DI setup, it wouldn't make much of a difference to the rest of the engine. The crank-case does hold oil though, having gears inside that need to be kept nice and slippery and frictionless.

Paul_KD7HB:
The reality is you are over thinking the project. You do not need injection or high compression for a Diesel. Once running and hot, a gasoline engine will run on #2 Diesel fuel. The carburetor may need to run a bit richer.

The real life engineering problem for you is not the injection or anything related. The problem is just getting the engine running!

Older Diesels were carbureted and had spark plugs. They started life with gasoline and when the engine was warm, switched over to Diesel fuel.

Newer, injected Diesel engines could not use gasoline, so had to have a different starting mechanism and this is where glow plugs came into use. My Kubota uses this method and the vehicles I used to own used this method.

Newer vehicles, like my Dodge truck and VW Jetta TDI use a small chamber with a heated screen to super heat the air immediately before it goes into the cylinders. The heat is shut off when the engine starts.

So, start with the basics, the starting cycle and figure out how you want that to operate.

Paul

My plan is not to simply run my 2-stroke on diesel; I'd like a proper direct-injection system that can actually cold start using diesel (and a glow plug). I've always been a fan of Detroit's 2T engines, and I'd like something similar. I'm aware that it will be sort of ghetto-rigged and not amazing quality, but a good 2T diesel can reach efficiency numbers around 50%! I hope to gain torque and efficiency from the conversion, even if it isn't fully optimized in the beginning. You can always tinker with something to make it better, especially something you made yourself (more sensors and more coding to make use of them at least)

Perhaps rather than consulting and Arduino group, you should consult with people from Cuba. They are masters of doing what you are planning.

Paul

Paul_KD7HB:
On the other hand, my father-in-law had several International Harvester tractors the started on gasoline and had compression release to stop the autoignition. Then when warmed a bit, you moved a big lever that stopped the ignition and the compression release and ran full auto ignition Diesel.

Very interesting. I wonder of the "compression release" closed a valve to a small chamber which effectively reduced the volume and increased the compression ratio to that needed for compression ignition.

I have also come across systems for hand-cranked engines which had a lever that removed all compression to make them possible to crank. When the flywheel was spinning nicely you dropped the lever and hoped it would start. If not, it was time for another breakfast :slight_smile:

Then there was the Oliver tractors that were full Diesel, but were started by ether from a spray can. The air/ether mixture would auto-ignite at a log temperature and spin the engine fast enough to start, sometimes!

I had heard of that also, but had forgotten it. I believe you can use WD40.

...R

I believe you can use WD40.

Ha, Ha! That is because the propellant in the spray can is propane!!!!

Paul

The reality is you are over thinking the project. You do not need injection or high compression for a Diesel. Once running and hot, a gasoline engine will run on #2 Diesel fuel. The carburettor may need to run a bit richer.

When I was a boy I had an old Lambretta motor scooter I used to ride around the (large) garden we had. Petrol was expensive (on pocket money), paraffin was cheap, red diesel was free (thanks to my dad's business). I had it running on paraffin easily once it was hot. It sort of ran OK on diesel, not brilliantly but it ran. I had a pre heater (copper pipe wrapped around the cooling fins) for the fuel. I was probably lucky the thing didn't catch fire.

Eventually stopped running, I took it apart, it was clogged solid with carbon.