[BiturboS4] SAE vs. DIN

[Noah Ward]

There are several specifications of horsepower and how it is to be measured
Engine manufacturers must base their claims of power upon the standard
selected by the country in which the claim is being made. In the US, the
standards body for engine power is the Society of Automotive Engineers
(SAE). So all power claims in the US are measured in SAE horsepower. Other
countries have their own standards bodies which create their own definitions
of power. As I recall, Japan uses JIS and the European Community uses ISO
(and I think Germany used to use DIN). Each standards body's specification
dictates what the designator is to be (e.g hp, BHP, etc.) as well as what
must be included in the measurement. For example, the SAE may specify that
water pump power losses must be included but not exhaust stream losses, and
the ISO may specify that it's measurement be in Watts instead of horsepower.

Also, specifications change: US "Brake" horsepower (abbreviated "Bhp") was
measured at the point of output, with no load from a chassis or
power-robbing accessories and with fuel and ignition operations under ideal
conditions. Often called "SAE gross" horsepower, this figure was often used
for advertising purposes prior to 1971.