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Old 12-26-2013, 05:33 PM   #11
City: Venice Louisiana
Country: United States
Join Date: Dec 2013
Posts: 1,097
And brake specific fuel consumption. Lower compression allows the input of more air from the turbo and allows the engine to utilize more fuel to make the requested power. Cylinder pressure needs to be controlled, to much and they go boom. The problem with this approach is that instead of 19 or 21 to 1 compression ratio the high output DDs are usually around 17 to 1. Thats ok on a new engine but with a little wear they get really hard to start because of it. You'll see lots of white smoke on startup and for longer periods of time, due to low cylinder temps, which is why it was hard to start. A lot of DDs were fitted with ether injection systems for this reason. Lower compression ratios are also one of the reasons these high output engines dont do so well at low speed and low loads. Being a 2 stroke they are basically aircooled at these loadings and cylinder temps are low, resulting in unburnt fuel.
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