Originally Posted by
superquag
Did you check that link ?
Some comments from the horses' mouth...
"...WALTER C. BAKER:—Why is an efficiency twice that of a gasoline car claimed?
ABNER DOBLE:—Everything depends upon what you mean by "efficiency." We know that 18 per cent thermal efficiency is obtainable from a gasoline engine running at full load. We also know that cars do not run at full rated load much more than 1 per cent of the time. .When running at 20 or 25 m.p.h. about 5 hp. is required to drive the car. Under such light load the ordinary engine will have a thermal efficiency of about 4.5 to 5.0 per cent.
The highest thermal efficiency we know of to-day with the steam powerplant is about 21.8 per cent at its full rated load. This is obtained by using a combustion system in which the air is preheated, at the risk of burning out the grate bars. The Doble steam generator has no grate bars, but uses a refractory material that we developed. It will stand about 3400 deg. F. before it fuses. The temperature attained in our fire box is about 2600 deg. F. The air is preheated to 200 deg. before it enters the carbureter, by utilizing about one-third the heat that would otherwise go out of the stack. The boiler efficiency without the economizer is about 82 per cent. This is equivalent to standard practice in boilers.
With our boiler we can increase the efficiency about 4 per cent by the economizer and by using a regenerator, which can be placed on the end of the stack, we can raise the boiler efficiency to about 92 per cent.
The best net thermal efficiency that we have been able to secure from our powerplant is about 16 per cent under full load. With the 5 hp. load imposed when a car is driven at 25 m.p.h., we realize 14 per cent net thermal efficiency.
My car, which was built three years ago, and is crude in some ways, has been driven almost 40,000 miles. It will run 15 miles to the gallon of kerosene under favorable conditions, and will average about 11.5 miles per gallon, although I drive through traffic and mud a part of the time. The old type of steam car never ran more than 7 miles per gallon...."
Hmmm, not that far removed from a LR V8. - and with HEAPS more torque..