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To give an idea of the size of my injectors: ( I didn't have any matches ;) )

To get a small diesel to run the fuel pump, the injector and the combustion chamber are all important. Sufficiently atomized fuel must be injected into high temperature and pressure air in such a way that combustion takes place rapidly but in a controlled way. As Minh says control of volume and...

Maybe it's a big match :)

Depending on the details of the design Bellville washers may block the fuel flow wheras it will flow through a coil spring. They will also require a fine adjustment of the closed length to set the load correctly. Do you have a source of small Bellville washers ~1.5mm bore, 3mm OD?

Find Hansen’s design is similar to that used in the GM 5.7 Litre diesel engine. It has the benefit of only one critical sealing point and no requirement for a fuel leak off. The problem is accurately controlling the angle of the cone. If it is too acute it jams and too obtuse will bring a spray...

Were you ever a member of MEM, if so what is your user name? We have had problems with a number of Email hosts blocking messages. Have you tried registering with a different email address and user name? Minh was unable to get onto MEM for a while, then we got him on again. He was then unable...

The semi diesel tractors had a compression ratio around 5-1. The Lanz Bulldog I have mentioned had a 10 litre single cylinder and developed 55 HP so around 5 HP per Litre. My VW T Cross develops more than 100 HP per litre.

Here are a few that I have made. The poppet injector works and is the basis of Minh's design. The open injector with a 0.2 mm nozzle wouldn't run and the latest needle injector runs quite well. There are significant detail points. The angle of the cone on the poppet injector is critical but...

I am very much an experimenter and don't produce real drawings like Minh. There is a lot of technique and feel in producing miniature injectors without a full toolroom and metrology lab available. I will share the drawings the I have however all the manufacturing detains are on...

This is my current design, I have been experimenting with diesel fuel injection for more that 10 years so everything is a development. All the details and techniques are posted on MEM: https://www.modelenginemaker.com/index.php You need to sign up to see the pictures but all I have done is...

I use Acrolaps: https://www.acrolaps.com/ The needle laps with 1 micron diamond paste for the injector components and the barrel laps with 40 micron diamond paste for cylinder liners.

The 5 cylinder swash plate Hulsebos Hesselman engine is on my build last for when I have finished the Junkers CLM and the Saurer Doppelphaeton engines. I will probably never get round to it :rolleyes: I have attached a PDF of a Hesselman brochure.

A bit more information on hot bulb engines. The adjustable spray nozzle was fitted to the Lanz Bulldog and as rolphill says it was used to adjust the combustion conditions between light loads when a narrow spray was injected into the hot bulb and heavy loads when a wider spray was spread around...

The hot bulb engine had several disadvantages: The low compression ratio, typically around 5-1 gave a low thermal efficiency compared to the Diesel engine and to the spark ignition engine as higher octane fuels became available. There is a significant time required to heat up the hot bulb...

An excellent summary :) 👍 I initially chose a loop scavenged two stroke as I wanted to keep the combustion chamber as small as possible to minimize heat loss so I could compress the air to ignition temperature. The design was loosely based on the Petter Atomic diesel engine. This had a...

This is my latest needle style injector. The actual seal/orifice is between the tapered end of the needle and the edge of the 0.2mm bore. The seating angle at the end of the nozzle is greater than the angle of the needle in an attempt to get as close to a line seal as possible. Keeping...

Glad you found the problem 👍

Hello Minh, I think that is due to the pump not always refilling. In engine use the stroke is a few tenths of a millimeter wheras the test pump has a stroke of over 2 mm. When the plunger returns there is a vacuum in the pump until the inlet port opens (not a problem with an inlet valve) and...

I have drilled nozzles down to 0.2mm in brass and stainless steel. Brass is easier :) . A 0.2mm open backed by a one way valve did not produce sufficient atomisation for my 20cc diesel to run. It will run with a needle or poppet type injector so the fuel is being atomised by the gap between the...

I agree.