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There was an 18cc carburetted compression ignition moped made some years ago: https://onlinebicyclemuseum.co.uk/1951-lohmann-18cc-diesel-engine-new-old-stock-unused/

The Hvid design is similar: https://www.gasenginemagazine.com/gas-engines/Hvid-Engine-Combustion/

Describing how to make an injector or injection pump is quite difficult so I don’t think Find Hansen is being difficult. At an amateur level it is not possible to measure and tolerance the various dimensions. I think I am achieving clearances of a few microns on a 2mm bore but can’t confirm...

Some interesting and useful points in this thread. On that seems to have been missed is the problem of ignition delay and controlled rate of combustion. This is affected by the fuel itself, the atomisation from the injector and the air swirl/turbulence. Diesels first trial with the injection of...

I would remove the centre pillar from the second option and just support from the sides. This would give you more space if you have to modify the injector design (which my experience suggests will be the case).

Are you planning to make a compression tester? There is quite a difference between what feels like a lot of compression and enough to reach ignition temperature ~30 bar plus.

A lot of the design and complexity of the carburettor design depends on it’s intended purpose. As has been said on here if the engine just has to idle at an exhibition for a few hours/days it can be quite simple. If the engine is coupled to a load it becomes more difficult. There have been many...

I have not had a problem with bent silver steel (drill rod) but I did have a piece that was not round, trilobar, which measures correctly with a micrometer but won't fit through a hole of the specified diameter. After that I moved to using pin gauges to make my injection pump plungers from. They...

Small diesels are interesting. There are many different possibilities starting with the model aircraft type using compression ignition of a carburetted mixture of kerosene (paraffin), oil and ether. There was the Lohmann commercial moped engine that used an 18 cc carburetted compression ignition...

Did you heat treat them to get the 'spring'?

Using a rack to rotate the sleeve is quite feasible. I have made a helix pump using a MOD 0.4 rack with a 20 tooth pinion.

I would suggest that you look at a suitable drive dog or free wheel so you can turn it over with an electric drill, especially in the early stages. This allows you to adjust settings whilst the engine is turning.

Pump diesel will not be a problem, many common rail engines circulate the fuel through the injectors. Plant oil based fuels can be a problem as they break down at high temperatures. Using cooking oil as a fuel for a conventional jerk pump system is ok, for common rail expect problems.

0.2mm in brass is ok, in stainless steel it is more difficult. Getting adequate compression pressure and temperature in small engines is difficult. The cam timing, specifically the closing of the inlet valve, can significantly effect the compression at low/cranking speeds. Gardener used a...

I think that this maybe the early Vickers common rail fuel injection system. There is a separate engine driven pressure pump delivering 100-200 bar. The injector is held closed by the spring right at the top and is opened by a cam and rocker. There is a brief reference on Wikapedia dating this...

Thank you for starting this thread 👍 A few comments/thoughts. Ball inlet valves are a problem with fuel volumes that are less than the volume of the ball. The ball has to move and as it returns to it's seating it effectively increases the volume of the pump chamber. This is why I have chosen...

My compression gauge fits in place of the injector. It has a non-return valve as close to where the injector nozzle would be as possible so as not to affect the combustion chamber volume. The valve currently doesn’t seal as well as I would like. In the video clip the pressure is reaching more...

Excellent 👍 👍 👍

20-1 compression ratio will work with a compact combustion chamber with minimal heat loss. My diesel has, I think, a higher ratio. The compression pressure is around 30-35 bar when cranked at 2000 rpm with the drill. For volatile fuels you will need a feed pump for the injection pump. For...

I have used that material on several engines without problems. The compression pressure on my 25mm bore four stroke diesel is around 40 bar and the cylinder head is fixed with 5 M4 studs.