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Re: [TR] high engine rpm

To: Triumph Sports car discussion <triumphs@autox.team.net>
Subject: Re: [TR] high engine rpm
From: <jimmuller@rcn.com>
Date: Fri, 20 Jul 2007 17:45:49 -0400 (EDT)
Terry Geiger wrote:

> The speedo and tach were design to track with each other in
> top gear so 2krpm should get you 40mph, 3k rpm 60 mph and
> so on.

Through the clever use of advance technology before the development of 
microprocessors, Triumph engineers were able to make the engine speed and road 
speed track linearly with each other no matter what gear you were in!  And of 
course, if he fixes his mal-adjusted tach so that it reports rpms correctly 
that will also cure his overheating on the highway.

But all seriousness aside though, when I read that original posting I was 
struck by the tire size issue.  (Did the TR6 really come with 205/70's?)  I 
wondered if maybe a PO had tweaked the tires and/or diff to get better torque 
to the wheels at the cost of higher rpms.  A PO might have changed both.  Of 
course, we are smart enough to know that tweaking the tire size is equivalent 
to tweaking the diff ratio as far as road speed vs. rpms is concerned, so if 
his new correct tires restored the accuracy of the spedoometer then the diff 
must be correct too (unless the spedoometer was wrong, except that he checked 
it against another vehicle).  So the only possibilities are either that the 
gearing was changed or that the tach is inaccurate and the overheating is a 
different problem completely.  The latter seems more likely.

Jim Muller, who once owned an immobile TR6
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