Hi Alan,
The reason the GTech seems to read high on lateral acceleration is body
roll. Higher end devices like the Valentine G-Analyst and Byron Shorts
GEEZ! software take this into account. Basically, as the accelerometer is
rolled out of the level plane, the acceleration component from cornering
goes down as the cosine of the roll angle, but the acceleration component
from gravity (1G) is going up by the sine of the roll angle. Near 0
degrees, sine increases much faster than cosine decreases.
For reasons of both a longer platform and (usually) lower G numbers, this
effect is not nearly as significant in acceleration runs.
Hope that helps,
Brent DeWitt
> -----Original Message-----
> From: owner-autox@autox.team.net [mailto:owner-autox@autox.team.net]On
> Behalf Of Alan Pozner
> Sent: Saturday, January 02, 1999 4:17 PM
> To: Jeff Winchell
> Cc: autox@autox.team.net
> Subject: Re: GTech Performance Meter?
>
> I think the g-Force numbers are a little optimistic but again they are
> very consistent. My A4 with Eibachs Bilstiens and 38psi Michelin Pilot
> SX GT pulled 0.92 in continuous mode clockwise around a 100 ft circle.
> Around the same circle my Honda delSol pulled -
> .84 with 185/60-14 Pirelli P600 at 1/2 tread depth
> .91 with 205/40-16 Nitto 450
> .99 with 205/55-14 BFG g-Force R-1
> All the CCW numbers were about .07g lower.
>
> While I think all these numbers are high (I would guess the Audi really
> pulls .85 - .88 as I have it equipped) what is important is that the
> differences are exactly what you would expect. As a tire comparo these
> numbers mimic the delSol write up that appeared recently in
> GrassRootsMotorsports.
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