Re: Two-stroke with oil crankcase
Detroit Diesels, as we knew them, were two stroke-supecharged-with a valve train (exhaust only) and fuel injection, as described. The block was pressurized by the supercharger (gear driven) and the air charge entered the cylinder via ports in the cylinder liner. They were also miserable oil leakers and the power bands were extremely narrow, not unlike 2-stroke outboards. <br /><br /> How does all this relate to outboards? The Detroit was an animal all it's own. However, the introduction of the air charge was similar two any 2-stroke. The exhaust side (valves) was somewhat unique to the Detroit. As we know, 2-stroke outboards do not have exhaust valves. The exhaust valves were needed to build the compression ratios high enough to ignite diesel fuel.<br /><br />Detroits required constant "fiddling" with the valve trains and unit injectors to keep them in a reasonable state of tune. They also were not particularly well known for their longevity compared to other diesels. They produced allot of HP for their size but suffered many malodies, as mentioned. Plus, they were extremely dirty regarding emissions.<br /><br />With all that said, they had their place. They were relatively cheap as compared to others.<br /><br />A little history.<br /><br />They (DD's) were versatile. They came, for the mostpart, in four types: 53, 71, 92 and 149 series. The numbers referred to the cubic inches of each cylinder. Each cylinder was an engine in itself. As an example: a "6-71" was a six cylinder with 71 cubes in each cylinder.<br /><br />Because of the design, the engineers could make the blocks in many variants: in lines, v-types and a combination of those bolted together. As an example: a "12V-92" was two 6V-92's bolted together.<br /><br />I have worked on many variants from 2-53's to 12V-92's. Once you know the basics of the design of the engine family, working on any variant was relatively simple. Later variants had 4-valve/cylinder heads and (DDEC) electronically controlled injection.<br /><br />There was just no way the 2-stroke Detroits could pass the first automotive wave of diesel emissions controls started in 1994. Thus, they were relegated to industrial/marine applications. However, there are millions of them out there dating back to the early 1940's. They were replaced by the "Series 60" which is a four stroke design.<br /><br /><br />The DFI outboards of today are still basically block scavanged designs with sophisticated fuel injection systems. The four strokes are not really any different than any other four stroke design whether it was automotive or industrial based. Whether it's carbed, fuel injected or Supercharged really makes little difference other than the potential power output of the engine.<br /><br />I suppose one could turbo or supercharge a DFI 2-stroke, but sealing the crankcase would be a major headache, just like the Detroit Diesel was.<br /><br />I think DFI 2-strokes definetely have a place in the marine world, because of their weight advantages. They are proving to be as efficient and robust as four strokes. Technology has made that possible.
Ya mean like a Merc Verado? 
