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diminished horespower in rebuilds
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Supercharger is not the right term for the blower on a Detroit Diesel, blower is the correct word, because the blower is geared to turn about one and a half times crnkshaft speed to provide a small amount of pressure for exhaust scavenging. <br /> <br />Supercharging weather by turbo or blower is when at the end of intake stroke, the cylinder air pressure is higher than atmospheric. A blower used in the capacity of supercharging can then be called a supercharger. I did not know that Detroits could use a larger blower as an option for supercharging. <br /> <br />In my own experience, I have seen 12v71's are in fact two 6v71's bolted together. 71 blocks and all Detroit blocks are machined with flush ends to which an adapter plate is bolted for accessories, etc.. This allowes an engine to be built in many diferent configurations, the "front" could be on either end of the block, regardless of direction of rotation, fuel pump, heat exchanger, and any other accessories can be mounted in a variety of places. Detroit is not the only manufacturer to do this. EMD blocks have a similar appearence, but the end plates are welded, and the block is a complete block for however many cylinders the engine has. <br /> <br />That said, there is no reason that I can see why a 20 cylinder block cannot be cut to any number of cylinders, because of its construction is of separate peices welded together, instead of a solid casting. Oil and coolant passages are also less of a problem, the block is "dry" with coolant jackets integral to the cylinder liners, and flowing directly to each cylinder head bolted directly to each liner. Coolant flowes from cylinder to cylinder via jumpers. If a block were to be cut, I imagine great care must be taken to maintain proper alignments. <br /> <br />The reason I know that EMD crankshafts and camshafts are modular, is because I used to have an EMD manual for 645 marine engines, it was quite a while ago though, about ten years ago, before my kidneys failed. I was borrowing it from a freind, but it got stolen from my truck because I was living in a bad neighborhood. If I remember, there was a chart showing the bolt pattern of the crank's and cam's ends and the correct holes to align when assembling a crankshaft or camshaft. If for some reason a journal was damaged beyond repair, the whole crank or cam does not need to be replaced, also, if an engine was to be decommissioned and the parts were still usable, they could be assembled in a different engine, but I don't remember any direct reference to modifying the number of cylinders in an engine. <br /> <br />That said, to me, it makes no sense to blank cylinders without changing the firing order, and assembling a shorter crank and cam means the block has to be cut. <br /> <br />I have read that EMD thought long and hard before deciding to build a 20 cylinder engine, because they knew it would break crankshafts. What promted them to explore was IIRC, a Japanese company had succesfully built a 20 cyl. marine engine, that proved to be reliable. About ten years ago Detroit built two 20 cyl. 71 engines as an experiment for an offshore cigarette boat, which was successfull. A twenty cylinder engine has an awfully long crankshaft, and the windup must be terrible, allowing tortional vibration to amplify. If it was hard enough to build one in the first place, why mess with it? <br /> <br />I know enough to know what I don't know, and developing a mathematical model of all the forces and vibrations in a crankshaft is WAY beyond my knowledge or experience. I once copied the equations describing a piston's motion relative to a crank's radius, and a given rod length - "rod ratio", it's three pages of trigonometry and calculus! And that's just figuring the motion let alone the forces or the vibrations. I know enough that I can look at it and point out the major parts and the general meanings, I suppose if I had to, I could take the time to learn more, but if you have ever took the first step of trying to design something, even if you know the equations, that doesn't tell you where to start !!! When all you have is variables and no constants, maybe you understand the relationship between the variables, but that doesn't help you !!! <br /> <br />Anyway, if you can see from the getgo that blanking cylinders is asking for trouble, a complicated mathamatical study is probably not a good idea either !!
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