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But what was the actual technical reason for not liking rapid throttle changes? Frankly I find those usual remarks in general literature dubious until someone produces a credible technical reason for such problems. I wonder if the experience with the Leyland engine (of 2-stroke opposed piston design) in the Chieftain tank would be of use...
Why would a diesel powered heavy bomber have shorter overhaul times? Normally they cruise to and from the target at a slow and steady speed. Not much different then a Do-18 hauling mail to South America.
They were heavy. Because of the high cylinder pressures a diesel operates at they require heavier construction than a gas engine. The better fuel economy doesn't equal the combined engine+fuel weight of the gas engine until long flights are required. There was a lot of interest in diesels during the 20s and 30s but gasoline kept getting better allowing higher compression to be used in gas engines for better economy so the goal post kept moving. The diesels that were built needed careful maintenance and didn't like the frequent throttle changes that combat required.
Do-18
Do-26
Bv-138
Bv-139
Bv-222
Blohm Voss and Dornier built quite a few seaplanes powered by Jumo 205 diesel engines.
1930s Dornier was probably the most experienced seaplane builder in the world. They must have had good reason to power the state of the art Do-26 with 4 Jumo 205 diesel engines rather then 2 Jumo 211 V12s.
We are in 2012, not in the 1920-1930s; Think of the 24 hr LeMans compression ignition (diesel) racing at 700-800+ [SHP] for 550 [lb] 5.5 liter (335 cu in) installed (0.7 [lb/SHP]) using lightweight materials/manufacturing technologies, common rail injection (chamber pressure control, startability, SFC, etc.), liquid cooled (i.e. higher power densities, stability, TBO reliability) dual channel FADEC, Jet A/A-1 fuels, etc.. For 2500+ hr TBO with this technology think of ~1.25/1.50 [lb/SHP] installed which favorably compares with the current AVGAS installations that are at equal or higher figures. Think also of the installed weight + total mission fuel advantage that is most of the time positive.
In this respect, it could be interesting to note that two Isotta Fraschini gasoline-fed aero engines of the '30s are still wit us, under the form of diesel marine engine. The W18 Isotta Fraschini Asso 1000 / L.181 became the CRM W18 (same bore, stroke, crankshaft assembly, ignition sequence, connecting rods, even the details of the valve train), probably establishing a record of an engine in production since 1927. The V12 Asso XI / L121 became the CRM Asso 1500 / Asso 2000 (bore and stroke are now those of the Asso 1000, but the rest remained pratically the same).We are in 2012, not in the 1920-1930s;
Another factor may be the limited RPM range of a diesel. Not familiar with aero diesels, but a 3406 Cat, for instance, has a power band from 1500-2100 RPM. A similar power gas engine will have a band much wider, like up to 3300 RPM for a Griffon-like engine. That's one reason why gas engines remained common in tanks, the wider power band required less gear shifting. A diesel aero engine would require a much more sensitive CSU (governor) to adapt to throttle settings.