Hello Dave,

Twelve individual injectors will dominate the engine, you just cannot make them small enough for them to disappear from sight.

I had a thought, that you could maybe consider reducing the number to four injectors, if we treat the 917 injection system as four, three cylinder engines. Each injector firing sideways into a single plenum chamber and throttle body, with three inlet trumpets above, then feeding down into a group of three cylinders. The injector pumps being based loosely on the Hunzinger and the "Schilling" solutions.

I went further and used Google Ai to do some calculations:

First, the air to fuel ratio (AFR) for methanol glow plug engines from max lean to max rich and max power. The wide FAR range of methanol fuel is amazing.
Then, the actual flow rate (quantity) of methanol fuel that needed to be delivered (at full speed) to the single injector feeding the group of three cylinders. Now have a good handle of the required ml/min.
Then, I asked about the fuel rail pressure needed to flow that quantity of fuel through 0.1mm, 0.15mm, and 0.2mm spray nozzles I mentioned in an earlier post. The smallest available 0.1mm nozzle shows a lot of promise.
Finally, I asked about the  ideal air intake throat diameter for each of the three individual inlet trumpets. the suggested 5.0mm choke diameter does not seem unreasonable for a single 6.5cc cylinder.

I am still analysing the responses; There is a lot of detailed calculations and information to check; however the use of a 0.1mm spray nozzle at about 2.0 bar fuel rail pressure looks promising at full speed and also at a fast tick-over at a reduced pressure.

The problem I now have is I cannot simply cut and paste the full Google Ai responses due to formatting issues. I may be able to summarise the findings, if there is sufficient interest on the forum ( fuel injection is not a popular flavour with our steam engine brethren).

We all know by now, how careful you need to be in phrasing the correct question to an Ai bot, I have made a first attempt.

Cheers

Mike

Ha Ha!!     but don't forget the ring of bolts securing that engine to the transmission which itself is well attached to the tube chassis.

Mike

OK   Last weekend, I spent some time trying to nail down center distance and size.   Not in the lathe, but with 1/4 plate and the mill.    What I was really after was as made center distance.   It was an eye opener!  I was also trying to work on how I will be measuring the bores which I also think I was successful doing.

Theoretical center distance is 1.09375.  ( 27.78 mm)   Great!   But here's what I found.  They clashed badly there, like not go together clash badly.  I made 3 more test plates with the mill, opening out the center distance each time by .005" and checking again....   The best "mesh" of the center drive gears, which include the crankshaft, output shaft and fan/ignition shaft was more like 1.105" (28.06mm)    0.011" difference!

Errors in the gears?   Probably   These are shop cut gears, and pitch diameter will vary, but I was surprised by how much!

Now that's the bad news.   The good news is there more than enough material in the bores that I can shift the position that much and get the mesh where I want it without too much bother   At that point they mesh well, so I'm happy with that.

i purchased 2 bore gages and 2 bore standards for this project ( used on ebay) and I can report that the big one works wonderfully!   I love being able to measure size to .0001" compared to a standard ring gage.   It's nice to check against my mikes as well.

I may have an ideal candidate for the cylinder oiler/lubricator (see photo) if u compare it to the one fitted to the actual green engine; good to reuse these old parts

Thanks chaps, to be continued….

Andy