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Thank you :) I see you also use a template. I have been using an aluminium template and hardened punches with high temperature gasket material. I was wondering about using the same methed to make some thin copper shims to adjust the compression pressure.

My experience has been that if you can ignite the atomised fuel with a small flame it will ignite in the engine. If it is too much of a jet it will not ignite. This is an extreme example with just a 0.35mm hole. All it would do was cover my lighter in oil.

I guess your Lotus sim is based on spark ignition and may be slightly misleading. In spark ignition engine the full charge is there ready to be ignited so the speed of combustion and hence pressure rise is based on the flame front speed. Diesel’s original design injected the fuel over time to...

Hi Minh, Looking good. How do you cut your gaskets?

It is interesting to think in the other directions and compare the dimensions of a big ship diesel engine (conventional not crosshead) or railway traction diesel engine with a 2L automotive diesel. The proportions are much the same.

This is the bronze big end bearing from my diesel. It’s 25mm bore and 40mm stroke so 20cc. The crankpin is 12mm diameter and the con rod is 12mm thick giving a bearing width of 14mm. There is a low pressure, low volume pumped oil system as it was originally designed as a two stroke. Compression...

Flame tests are fun :) How does the spray pattern match your combustion chamber?

There are plenty of design considerations here. The first is that this is an experimental engine that may or may not work. The critical parts have already been identified as the fuel injection system and the blower. Small size diesel combustion is also a consideration. The engine as I...

A plain bronze bearing will probably be fine unless you are intending to really use the engine. Schillings made a number of designs with roller bearings, but these used a built up crankshaft. Split roller bearings such as these are available...

Hi Minh, I think the difference in fuel tank heights is due to me using an inlet port and helix plunger rather than a ball valve for the inlet to the injection pump. It will work with a lower fuel tank but is more stable with the tank raised.

Hi Minh, I test the injectors using fuel with a test pump. As you say if they don't leak the engine will usually run. I am trying to improve the atomistion to get better and cleaner running. This is the spray pattern from the latest needle type injector used in the test run above which is part...

The effective swept volume of a two stoke is from when the ports close, typically 75% of the actual stroke. This will reduce your swept volume to ~3 cubic inches and your clearance volume to ~0.15 cubic inches. The piston area is around 2 square inches so if you allow 0.04 inch piston clearance...

My 20cc two stroke diesel was loosely based on the Petter Atomic with some Field Marshall ideas for the crankcase. This ran but not very well. I think it actually used the fuel that was atomized by blowing past the piston rather than the fuel that was injected. I confirmed this by converting it...

The intake reed valve is visible on the left hand side of the crankcase of this Petter Atomic diesel.

That description was obviously written at an earlier stage in construction as he has found the capillary tubing for the injection pipes and hopefully the important few microns in the injection pump. So with around 20cc per cylinder the fuel injection volume will be around 1 -2 mm3. That will...

Do you think it was sufficiently complete for the builder to have tried to run it? It looks very well made. The helix controlled injection pump with pneumatic governor looks excellent. It is hard to tell if the injectors are homemade or modified commercial units.

Plenty of fun there, a Roots blower and high pressure fuel injection :) It's a three cylinder opposed piston two stroke diesel.

This design was based on Ray Amsbury's twin choke SU carb for his 120cc V8 coupled with my road and competition experience with SUs. It is fitted to a 12cc twin which may be somewhat smaller than your engine. I am happy to share the DWG that I worked from, but I am not a designer. The build log...

Tracking across the spark plugs is a sign of a very weak mixture. As you have to have the choke full, jet in the lowest position, this is also indicative of a lack of fuel. Is there any simple way to check the fuel level in the float chamber? Can you attach a piece of clear pipe to the outlet?

I have made a fairly successful 6mm bore SU type carb. At this size an overflow tank was easier than a float chamber. The fuel level is quite critical, it should be a bit below the top of the jet. The orientation of the piston is also important so that the air connections to the top side of the...