First of all, thanks for teaching me about pre cups and energy cells. I have a new energy cell in an AGOCO box and one of them on my tractor is making a nasty johny popper sound. I tighened down the two bolts on the clamp structure and this seemed to fix most of the noise. Now it only pops when I put a little sweedish steam behind the throttle:)I have studied this pre cup and studied its location within the engine. It was puzzeling as to what it did and why it was there not having seen these on more modern engines. But it makes sense. The key to diesel ignition is simple. Effective destabilization of the flash point for the fuel. This is done by throughly mixing the fuel with air to form a fuel air mixture and then compressing it to force it to destablize and self ignite. Sounds simple but in practice, its more complex. The new engines have very very high injection pressures and very complex designs on the injector nozzles. Rocket science stuff here! How can a hole be so complex:) The idea is get a fuel air mix that is almost like a fuel molecule next to an oxygen molecule (O2). As I recall, didnt Honda have pre-ignition jets a few years back? I think the civic engines had this. The plug is actually inside a small shunt chamber and not the main ignition chamber. This ignited a portion of the fuel air mix which then turned into a fire jet that was injected into the main charge of the cumbustion chamber. A scheme to get more complete and uniform ignition. I would not be surprised if this is what is happening with the pre-cup. In studying the one new one I have, the outside is a very simple design. Then there is a hole about 1/8 inch bored through this structure. The cup itself has an almost hemi like bottom which feeds this hole. The hole then exits in sharp 60 degree flare out. This almost suggests that a pre ignition jet comes out of this thing and moves a flame front down the outer area of the cylinder resulting in even ignition and evenly distributed piston down pressure. I guess this would be one way to get even and complete combustion from a mix that is not automized well enough. In any event, it does not appear to be heat treated and looks like it may be made from either a chrome molly like 4140 preheat or from a 300 series stainless steel. But the design is straight forward. Right now, I am moving my metal shop and doing some rigging. My toolroom lathe is in the barn and will be moved back into my shop shortly. It is a hardinge HLV-EM toolroom lathe and can knock off these pre-cups with no effort at all. In fact, quite a few parts can be made in a simple shop. So I am not that concerned about what AGCO does with is D-17 parts lineup. Knowing how greedy corporate america is, I am not surprised that they have not trashed all support for the allis chalmers tractors years ago! One of the beaties of these old machines is that they are workable. In other words, many parts were made on relatively crude machine tools by machinists who could not spell the word computer or CNC. The modern stuff is often made on CNC machines costing hundreds of thosands of dollars or in dies that cost thousands of dollars to make. This makes the fabrication of replacement parts darn hard for modern AGCO machines and very straight forward for old iron such as my D-17. If any of you wish to see what a true hobby machine shop for old vintage gasoline engines looks like, check out my buddies shop at this URL... www.antique-engine.com And click over to current work or the shop buttom to see what Craig has. There are alternate solutions to finding parts. If you think finding parts for a D-17 engine is hard, how about finding a water pump connecting rod for a vintage hit and miss oil field engine with a fly wheel weighing many tons!
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