[USMA:36575] Re: Chevrolet

[Michael Payne]

Newer cars just pick up revolutions somewhere on the transmission or drive shaft, and use that to send an electrical signal to the speedometer, which is programmed to convert the rpm pulse to distance traveled and hence to speed in either unit. I think the difference between the km and mile indications must be via some built in microchip. The rpm these days comes from a top dead center sensor that signals every revolution of the engine. The engine computer uses this to figure out when to inject fuel, etc. as well as to provide the tachometer reading, no mechanical connection these days in either. I remember there used to be a gear driven flexible drive from a wheel (in the VW beetle) or the transmission to the speedometer.  This particular Chevrolet Impala had a speedometer calibrated up to 140 in either unit. Fine in mph but easily pegged when I passed someone on a two lane road with it set to km/h.   Mike Payne ----- Original Message ----- From: Martin Vlietstra To: U.S. Metric Association Sent: Sunday, 16 April, 2006 18:49 Subject: [USMA:36574] Re: Chevrolet Odometers usually count wheel revolutions and have two sets of gears - one for miles and the other for kilometres. ----- Original Message ----- From: Mike Millet To: U.S. Metric Association Sent: Saturday, April 15, 2006 9:37 PM Subject: [USMA:36571] Re: Chevrolet Also I'm not sure if odometers calculate internally in km or if many of them are still in miles. Mike