Just a note, that a 1.5-1.7L is going to probably use 1-2gallons of fuel per hour because it's oversized. Even a smaller powerhead wont improve things much because the gph of fuel used just to run the engine at idle is still substantial compared to a small 2.5kw diesel genset at full load.
The comment "it would take 94 ' # of torque at 1800 rpm or 153 ' # at 1200 rpm to run a 20 kw generator" is probably about right, remember you can gear it to run anything so you could run 700rpm on the engine or whatever idle is and drive any speed generator at say up to 7kw or so. It wouldn't be as efficient per kw made as a higher speed, but the dang engine would probably last near forever. Or maybe 10kw at high load at 1200rpm. Either of these options might lug the engine which it may not like, a smaller genset would stop the lugging but wouldn't improve fuel consumption much, and the lugging would only occur if youre using all that power anyways so i'd rather have the larger powerhead if available and just not tap all that power. A larger powerhead will of course cost more in most instances.
info from random searches:
- someone else already built one like this
"The problem with the NA VW diesels is the lack of power at low RPM. Ideally you want the genset to run at 1800 RPM, less noise, hopefully less fuel consumption. The HP torque curves for the NA VW diesels of the early 80's show around 20 HP at 1800 RPM. That would run a 10KW generator. Now these little diesels were rated at 52 HP but that is much higher at around 4500 PRM. There were 2 sizes the first engines introduced in '77 were 1500 CC and produced 48 HP they grew to 1600 CC about a year or so later and bumped up to 52 HP. Around '82 they introduced a turbo version which bumped the power up to about 70 HP. These engines had aluminum heads so they did not tolerate overheating. They also used a timing belt, which should be changed every 60K miles. I've also heard of the older M-B diesels being used, those older cars rusted out before the engines wore out in northern climates."
Another post i've seen reports they last around 6000hrs even if run fairly hard (3600rpm running pumps)