Caterpillar D2 engine fault update

Pete, interestingly some diesels run with a really low compression ratio. My father has a Lister CS 6-1 which starts on 17.5 and then once running is as low as 14.5. Worn, they'd have to be even less than that. Some gas engines are up in that range which kind of amazes me that they can run that high.
The Listers "always" go though. Youtube it or Listeroid, which are Indian or Chinese-made clones. Great engines for low power, slow-running, long-running applications. My father's one was a lighting plant, putting out 32V direct current to a set of alkaline batteries. Ran that for a few years before mains power came to the farm. This engine is like Dad's - the late model Chinese generator isn't…
http://www.youtube.com/watch?v=KSwhDSY8LHQ

Most of that hard starting is due to the fact that the engines are flat worn out. That means rings are worn, ring lands are out of spec, ring end gap is to large, cylinder bores are worn and have excess taper and for those "recovered" stuck engines the rings may not be functioning at all. If it wasn't for the pony exhaust heat they probably wouldn't start at all.

These old engines that we are dealing with are all about 17:1 compression ratio. They need a compression temperature of 750 deg. F or so to obtain auto ignition, 1000 deg. F or better to run efficiently. That's not to say that pistons and liners live in that temperature, probably about half of that when heat transfer/cooling is considered.

Every material has its own coefficient of expansion/contraction, cast iron about half that of aluminum. Yes, I guess foundry folks like to express shrinkage as a %. Still has to calculated from the materials properties.

I'm working with diesel engines here that run with around 14:1 compression ratio, this is enough to put cylinder pressure above 300 PSI at cranking speeds and they fire up straight away without any starting aids.

Pete, I read your initial reply yesterday, laughing so hard I almost fell out of my chair!
OM's reply is pretty much spot on, slight variations but the facts are there!
Catsilver---your a CAT mechanic? True the Turbo engines are 14-1 compression and yes they will start easy as long as they are above 65 degrees F (at least on the Gensets). As they go to rated and need to start right now, typically they have Block Heaters on them.

Yes I was a Cat master mechanic, I did 45 years with a Cat dealer, 13 years on the spanners before going to staff engineer, warranty supervisor, PSSR, service manager etc for the remaining 32 years, I am now past retirement but still work selling someone else's marine engines, we have a 22 litre V12 which runs at 14.3:1 CR and even in our coldest UK winter weather they will always start, usually before they have turned a full 360 degrees. The only start aids we have ever fitted have been block heaters for use in the Arctic circle.
The Cat 3208 always started very well without aids, the last 435HP marine engine was 15.5:1 CR, but tended to smoke until warmed up as most low compression turbo/aftercooler engines do.
The old Cats were not wonderful starters because they were relatively low compression, indirect injection, low injector pressure and just can't compare with more modern units which have at least double the injector opening pressure for far more efficient fuel atomisation.

I'd like to see the calcs on how they achieve auto ignition at 14:1 compression, 300psi and ambient temperatures.