[Vwdiesel] 1980 Rabbit running the treadmill tonight!

[Val Christian]

> I did some 'speriments today with my VW 1.5D running at 1200 RPM.  I was
> able to make 1.5 kW electrical load at this speed with winter diesel as fuel
> using 0.9 litres/hour.  That means the engine will run doing this power
> delivery for 4.2 hours on a US gallon.  There was not much heat generated
> but the engine coolant did stabilize at about 185 F, the thermostat temp, so
> there was enough heat to keep the engine happy.  The engine sounded very
> quiet and relaxed like it could do this for years.  The efficiency was close
> to the same as running at 1800 RPM and 3 kW load with a throttle governor.
> I  measured  0.57 litres/kWh doing that and today at 1200 RPM slow speed and
> 1.5kW load got 0.60 litres/kWh.

	The fuel burn you mention here is nearly identical to what I get 
	with a 3.5 to 4.0 kW/hr load on my slightly more than 10 hp
	air cooled diesel.  The system rated capacity is 6.5 kW, and 
	I've been able to get 7.5 kW peak out of it.  

	A rough  ball park on efficiency is something like this:

	1 USgal #2 summer fuel 140,000 BTU

	BTU * 0.293 = watts

	so one gal is about 41 kW/hr



	I realize that there are many design decisions and trades, 
	but in general, a powerplant which runs at 75% plus or minus,
	will end up being most efficient.  50% probably works OK, and
	nearly 100% is probably OK.  And it's understood that the power
	output rating can be traded against engine life.


	Val