[AT] Engine power

[Dennis Johnson]

 Grant,
 
Today most engine manufacturers have different ratings for the same basic engine. An "Industrial" rating may be 400 HP, a "Vehicle" rating may be 600 HP, an Oil Field Intermetent rating might be 700 HP, and the "Fire Truck" rating might be 750 or 800 HP. The basis for these different ratings has a lot to do with the expected life and use of each type of engine. In general more air and more fuel can make more power, but will also cause more stress and wear. Drag race engines are on one extreeme - maybe 1 mile per overhaul, but very high on the power output.
 
Even many years ago the 2 cycle Detroit engines had similar ratings. Some changes required only larger injectors, and then going up a bit more required different pistons, etc.
 
Today the engine manufacturers are changing some of the basic assumptions I was taught in my IC engines class in college. The way they are doing this is to control when fuel is added which may also control cylinder pressures during the combustion process. They lower the peak pressures at TDC (top dead center) a bit, but have the pressures higher as the piston moves down. The result is that an engine with a lower compresison ration might have the same output as an older engine with a higher compresion ratio and most of the fuel put in a short time with the piston near TDC.
 
Back some years ago, I used one of the first CAT 3412 engines at 650 HP oilfield rating - the highest rating offered at that time. Today this same basic engine is available between 800 HP and  1500 HP for there "E" rating. Much of this is done with improved materials, turbos, etc. 
 
Generally farm equipment had one of the lower ratings because they wanted long life with long hours.
 
Regards,
Dennis
 
 
 
 Grant

    Most engines are well overbuilt for the designrd tasks. Engines may be 
built for basic tasks and years of service with basic systems such as 
mormally aspirated. These engines may be speced for many tasks by adding 
turbochargers, intercoolers, changing camshaft timing, duration and lift and 
injector size and type. Also varying engine speed for a certain application. 
Internal engine changes such as piston skirt oiling and cooling. Higher 
output engines may have stronger crankshafts and connecting rods. An engine 
designed for a constant speed application will have a lower horsepower 
rating than the same engine used for highway truck use where more speed is 
occasionally needed. RPM has a large influence on the rated horsepower. A 
Farmall 560 with a 281 cu. in. engine turning 2200 Rpm developes  58 
horsepower and a 660 with basically the same engine developes 84 horsepower 
at 2800 Rpm.

    Turbocharging and computer controls have had an impressive influence in 
modern diesel engine designs. High pressure, multi-stage fuel systems have 
greatly improved the fuel efficiency and at the same time reduced the shock 
loads on all engine components. Modern truck engines can be tuned by 
sattellite communication links depending on power required for any region of 
the country. Giving best fuel economy in the plains states and increasing 
the fuel and boost for the mountain west. The computer can control the fuel 
flow, ingine boost and available RPM.

    The main reason for different specifications is to eliminate the need 
for making a specific engine for each usage when an engine can be built to 
power requirement of aech task.

                            Gene