There has been talk about lowering the compression ration when adding a turbo. Seems that the 6.5 is around 19:1 ish and the 6.2 is 22:1 ish and that if you add a turbo to a 6.2 that one should look at lowering the compression ration to around that 19:1 mark. My questions be how does one lower the compression ratio? Put 6.5 heads on? Change the pistons? Change a ring? Take out spacers? I would like to know. Thanks
Joe
The 6.2 is 21.5 : 1 from the factory and the 6.5TD's were 21.3 : 1. They are pretty much identical in CR from the factory. The 6.5TD engines had a coated piston crowns, but the CR was pretty much the same. 6.2's will live long, heathly lives if you keep boost at 10 psi or below, water temp below 230, and EGT's below 1000 degrees if you drive them reasonably. If you beat it to death, drive it like a race car, or pull 15,000# trailers up grades, you can expect a premature death. I have logged several hundred thousand miles on turbo'd 6.2's over the years. A lot of people ignore the fact that these engines are light duty design, and were mainly developed for fuel mileage. They are lighter than any other pickup diesel by a considerable amount, and they just cannot compete wuth D Max's and Cummins without a lot of mods, and even then, a slighty modded D-Max or Cummins is still going to be better.
The most common ways to lower CR is pistons. Several manufacturers make them, but they are pricey, and require a rebuild which adds even more cost. The "cheap" way to do it is thicker head gaskets. Manufacturers like Cometic and others make thicker stainless gaskets, and they work well. As with any head job on these engines, they need at least new head bolts, but I used ARP studs when I built my 19 : 1 engine. The gaskets aren't cheap either at about $400, but you don't have to rebuild the engine and it can be done in the chassis. Lowering the CR will actually cost HP unless you add more fuel and boost than you would run with std CR 6.2. I was running 16 - 18 psi with mine with Holset HC-1 and running a turned up 4911 6.5TD injection pump. It was by far the strongest 6.2 I've ever had. I have all the stuff besides the turbo to build another one, and I plan to build one for my M1009 later on. For now, I'm going to use the Banks stuff off the engine below and run it that way for a while.
http://www.youtube.com/watch?v=eolZIk1f_PA
