Fabricating a diesel engine

I’m looking into fabricating a diesel engine for a high school science project. I want to get something with a fairly small bore size to keep the cost down.

1. would i be able to get away with using a gasoline piston?

2. if not what would be a good piston to get?(such as a diesel generator piston)and where could I get this piston

Not to discourage you, but diesel engines run at extremely high pressures, and require fuel (diesel) to be injected at those pressures. How do you plan to accomplish this? How will you construct the cylinder and injector?

Find a new project. It will not be possible for you to construct, from raw materials and of your own design, a functional diesel engine.

I’m planning to use an existing injector and to have the cylinder cnc machined

Google “cast vs forged piston” and then decide. The site that I read said that forged pistons are better at tolerating detonation than cast pistons. A diesel sounds like continuous detonation to my ears. You might want to contact a piston maker such as Wiseco or JP Engineering. (found with Google)

Just curious, but exactly what are you using as far as the engine block, cylinder head, injection pump, etc. goes?

OK, and what will you use for the pump? And how will you time the injection? And what will you use for the glow plug?

If you are going to do this, then your best bet is to reverse engineer the entire engine.
Look on craigslist, and find the smallest diesel engine you can find, buy it, and take it apart.

Then use your trust CNC machine to start building parts.
Your target is to make EVERYTHING interchangeable with the engine you bought.

It shouldn’t cost you too much to find a cheap motor.


You might look into making a 2-stroke diesel if you’re dead set on this. It will probably be somewhat easier to do the valve system at least. (Think model airplane engine)

I have a plan that initaly sounds pretty simple, but you will learn alot. Show how difficult (or perhaps how easy) it is to make a screw,using only simple hand tools.

This is kind of like having ‘remove my brother’s appendix’ as your science project. Simple in concept, pretty hard in execution!

What about turning a gas engine into a diesel? That ought to be plenty complex for a HS project.

You’d need to come up with a fuel injection system, bump up compression, and add a glowplug. The glowplug could probably be sourced from RC engines and the compression could be bumped up by shaving the head/block.

Not sure how you’d work the FI, but by designing the engine for just one RPM/power output, you could probably devise a fairly simple system.

The best part is that a non-running lawnmower engine can be had cheaply (or free, if you get lucky on trash night). That way, you’re not out too much if this becomes too ambitious.

Your best shot may be building a homogenous mixture compression ignition engine similar to model airplane diesel engines. These use carburettors just like gasoline engines and have an adjustable compression ratio by moving an adjustable counter piston in the cylinder head. Fuel for these engines is a mix of kerosene, diethyl ether, castor oil for lube, and a dash of amyl nitrate for better ignition qualities. These ingredients can be hard to buy in the US without getting attention from the DEA but you can buy model diesel fuel already mixed from some model fuel distributers. Model diesels are not very popular in the US so don’t expect to find this fuel at your local hobby shop.

I’m not sure what i’ll use for the pump, but i’m planning on using indirect injection to keep the costs down. I’m not 100% sure on how i’ll time the injection, but i’m sure that will be the least of my concerns until i make Have all of the moving components figured out.