RT:

What's wrong with running 3500 rpm? I do it all the time in the 220D. The notion that high rpm and diesel power are incompatible is a result of US manufacture engines that wouldn't pull themselves below 1800 rpm and tossed a rod at 2400. Long gone now, but the mythology lingers -- 2000 rpm is the only speed that works. Never true for Benz (most Benz diesels have a redline between 4600 and 5500 rpm). Longer stroke may give more torque, but at the cost of flexibility, and believe it or not, most automotive engines don't drive gensets at fixed rpm.....!

I agree about lowering power output for warrenty purposes. As far as I know, no one has come up with an automatic that holds up under the torque load of a diesel, and many of the manual trannies are somewhat inadequate as well. Most heavy applications really need a split ratio rear end, too.

Another part of the problem is people, IMHO, using pickups for jobs that really require more truck -- I have a story about someone dragging a Sundowner horse trailer with a "fake dually" diesel pickup and tires -- that big Sundowner puts the combo over the GVW when you drop it, empty, on the fifth wheel hitch! Ain't a job for a pickup, not enough truck, not enough tires, and not enough brakes. Add that to a ladder frame with nowhere near enough rigidity and you got trouble!

I would imagine that chipped engines will also fail NOx and particulate tests, too. Power don't come free.

New engines certainly have much better technology, but ten years ago when I moved home, the norm was long stroke, low (16 or 18:1) compression ratio, fixed injection timing engines. Most of them even now are horribly noisy at idle, which can only mean poor combustion. CDI/TDI engines are better, but again, all new in the last few years.

I've also heard one should avoid whatever GM is using -- short IP life (ditto for some Fords), and cracked blocks and heads. Shades of the 603?

NC:

High compression is more efficient, period -- elemetary physics. The more expansion, the more heat is converted to work. Low compression diesels produce tons of soot, will blow unburned fuel out the exhaust cold, and use considerably more fuel. "Normal" compression for high output diesels is 21:1 or 23:1 in European practice (Benz, Volvo) and usually results in higher output per volume, with considerably less specific fuel consumption. My Volvo TD (late 70's early 80's vintage design) puts out 105 hp on 2.4L. Engines as built often exceed 26:1. MACK makes at least one engine with a 35:1 compression ratio (don't know the application). US manufacturers seem to have ring land problems at high compression, I have no idea why.

US built "low compression" engines all have much larger turbocharger systems (many multiple) running at considerably higher boost -- you get the same effective compression ratio under full boost either way, but complicated turbo systems aren't the way I would do it.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!