12-09-2020, 11:23 AM
(This post was last modified: 13-09-2020, 04:42 AM by Bob Culver.
Edit Reason: Altered to reflect weight of modern passengers!
)
Presumably rolling resistance includes all driveline and tyre and idle axle drag losses. With a streamlined heavy modern with wide tyres at 50 mph, rolling resistance presumably dominates. An early fwd Ford Escort at 50 mph was reckoned to need 8 hp "'at wheels." I suppose this means as a rolling road and not at hub so most of would be to counter wind. I presume a laden unstreamlined Seven saloon would need at least as much, so with about 12 flywheel bhp at 50 mph wind loss possibly about matches or somewhat exceeds rolling losses, and increases dramatically with more speed.
One passenger adds about 10% weight absorbing about 10% of rolling resistance power. But a 10% loss of speed would release 30% of power formerly absorbed by the wind, As the two commencing powers around 50 mph are probably vaguely equal speed reduces far less than 7%. I am too senile to solve the exact reduction.
Nevertheless it is surprising how little degradation will reduce a stock lc saloon to about 45 mph as per many original road tests. My RP when running the lc head used to recover about 4 mph from just removing carbon, a considerable gain in bhp.
Back to the original question, a fair idea of engine freedom is available from the crank handle, esp with plugs out.
Altered to ereflect weight of modern passenger
One passenger adds about 10% weight absorbing about 10% of rolling resistance power. But a 10% loss of speed would release 30% of power formerly absorbed by the wind, As the two commencing powers around 50 mph are probably vaguely equal speed reduces far less than 7%. I am too senile to solve the exact reduction.
Nevertheless it is surprising how little degradation will reduce a stock lc saloon to about 45 mph as per many original road tests. My RP when running the lc head used to recover about 4 mph from just removing carbon, a considerable gain in bhp.
Back to the original question, a fair idea of engine freedom is available from the crank handle, esp with plugs out.
Altered to ereflect weight of modern passenger