My experience is that the normal loss between an engine Dyno pull and a
chassis dyno pull is 5 - 10% using a standard transmission and
non-quickchange rear end in high gear . The loss increases in lower
transmission gears.
With a quickchange the loss may be as high as 20%, depending on ring &
pinnion ratio and final drive ratio. The fewer gears, the better.
Quickchange's give flexibility, but rob horsepower.
Bruce
From: drmayf <drmayf@mayfco.com>
Subject: [Land-speed] Chassis Dyno Operations
To: "LSR" <land-speed@autox.team.net>
Date: Saturday, June 12, 2010, 7:46 AM
More fun dumb questions from me. Why do we use high gear during a chassis
dyno pull? The dyno does not know what gear the car is in, does it? Is
there
a general limit on the acceleration rate of the rollers? If high gear
(1:1 in
the gear box) is better than a lower gear, then would overdrive be better
that
the 1:1 gear? Is there some final drive ratio that is best? Or is top
speed
the consideration? And why does shifting during the pull matter? Are
there
other considerations in how the pull is accomplished? Isn't the desire to
get
tuning data for the enitre rpm range? Or should it be for reliability at
peak
rpm?
anyhoo, just fun stuff before breakfast...
comments? thoughts? flames?
mayf
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