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On 27 Nov 97, Toby Basiliko wrote:
> Didn't the octane ratings system change about the same time they went
> from engine horsepower to brake horsepower, i.e. sometime in the early
> seventies? I know little about this, other than that there are a
> bazillion ways to measure octane, and none of them give the same
> numbers...
Engine horsepower has always been measured by seeing how much power
can be put into a special kind of water turbine called a brake or
water brake. It is just a device to convert rotational energy to a
form that can be accurately measured.
What did change was the fact that in addition to driving the brake,
the engines are now expected to power their own oil pumps, cooling
systems, ignition systems, etc. I believe they are expect to drive
an exhaust system that is close to that on the auto
Before around 1970 the american automakers used to inflate their
numbers by providing the test benches with external sources for
cooling water, oil flow and electricity and using whatever exhaust
system they could come up with that produced the best numbers. I
think this was SAE hp (or bhp) and could be called Gross bhp.
The DIN system never allowed this and thus I would refer to it as a
Net system. I believe both systems are pretty much the same by now.
Jim
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Melissa Kepner Jim Adney
Laura Kepner-Adney
jadney@vwtype3.org
Madison, Wisconsin
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