Mike's question to K-PT engine series fuel injector types
Posted: Fri Jan 07, 2005 5:48 pm
It could even be made less cumbersome by using brake line of smaller OD, but at the date I built this engine only 12mm OD V2A pipe (because of the need of welding I had to take some small steel pipe) was available...so it was rather a fact of circumstances. Now the market also sells 10mm OD and 8mm OD V2A pipes.jmhdx wrote:Your cumbersome looking fuel injector is actually rather good, could you describe it again?
There is nothing really special about the injector. It is a derivate of Bruce's "fuel rail" (other names: "swizzle stick", "internal pipe fuel injector" or something like that).
For the K-PT 04c (60mm comb. chamber ID) the 12mm pipe was flattend a bit for reduction of drag and blast reflection.
I drilled holes of 1.8mm to 2.2mm diameter (don't know exactly, but I used a drill about 2mm in diameter, but there was no special scheme of [e.g. widening to the diameter to the centerline] used) into every of the two more or less flat sides, so that propane spilles out about 90degrees to the virtual center line.
The distance between the middle of two holes is about 9mm to 11mm.
Because of the fact the injector lies in cross-section plane and crosses the virtual center line of the comb. chamber, the holes were put from one side to the other, leaving a distance from a hole middle to the wall of about 6mm to 8mm (5 to 6 holes per side; about 10 to 12 all in all).
Having a pipe size of 12mm OD I welded a M12 connector nut onto the top of the piece of pipe looming out of the comb. chamber.
To the connector nut a steel pipe heat protection transition is attached, which then is connected to the propane hose via a homebuild thread transition (propane hose special thread - M12).
The other end of the injctor had been squeezed together and then been welded.
The main problems of this injector are the restriction at smaller engines, the prevention of starting without additional air - short: prevention of an air-induction effect - and addition of an internal Helmholtz resonator to the engine, what might cause disadvantages (but perhaps advantages when well opimized for a special engine) through frequenzy interferenzes.
The last problem could then become a real devil in the detail.
But as you can see I've been lucky by not getting real trouble with these injector type. But at following engines I'll rather use a mixture of SNECMA/Bill Hinote/Mike Everman/(assumption here:)Milisavljevic style injectors.
Under the "Small Lockwood - propane injection problems?" (much earlyer, about Jan./Feb. 2004) you'll find (a) drawing(s).
P.S.: Thanks for the flowers.