All in all I was content with
the power output that the dyno indicated. I know that the published
power output of the Sprite engine was 43hp, probably at the flywheel,
and the engine in my car is a good 40 years old, and virtually
stock. I'm told that a 20% drop from flywheel to rear wheels
is the rule of thumb. That would suggest a flywheel output of
After I posted my hp figures
to the Lotus email list, Mike Ostrov sent me a report from the
test of his Lotus Seven America:
I examined my Seven America rolling
road results, when the car had 17,248 original miles, just a
few years ago. All stock, except I removed the original 4.55
diff, as offered for all BMC and 997 Ford Sevens and replaced
it with the 4.11 ratio, as fitted to the Super Seven. Helps reduce
the revs a bit, at the top end of 78 MPH !!
2500 rpm 18.4 hp 10.2 CO
3000 rpm 24.0 hp 9.8 CO
4000 rpm 28.9 hp 9.9 CO
5000 rpm 31.2 hp 9.8 CO
5500 rpm 30.7 hp 9.6 CO
6000 rpm 30.2 hp 9.7 CO
Did a number of runs, changing
the ignition advance, colder range spark plugs and adjusting
the air/fuel mixture. The figures above are the final results.
So Mike's relatively low mileage
Seven America topped out at 31.2 hp at 5,000 rpm. There is certainly
the chance that I might have seen a slight increase at 5000 as
well. Particularly considering I was running on last year's plugs
with dubious carb settings and last fall's fuel in the tank!
Okay, I did install some neat little velocity stacks that may
or may not have had much effect, but they look cool!
All in all, at the end of the
day I was not disappointed.