Scott,
About all of the Triumph tachs I've seen (Spit and TR6) have been 3.55:1
ratio....
Has anyone else seen differently?
Jim
(putting his ignorance on the line :)
> -----Original Message-----
> From: Scott.Mackay@intl.sematech.org [SMTP:Scott.Mackay@intl.sematech.org]
> Sent: Wednesday, September 16, 1998 10:17 AM
> To: peb3@cornell.edu
> Cc: triumphs@autox.team.net
> Subject: RE: TR6 engine speeds
>
>
> Interesting Phil,
>
> Had a similar problem with a '6 I recently purchased. First, I'd check
> the
> speedo. At the bottom of the gauge face, there are a set of numbers. It
> should
> read something like 'S/N 6411/02.8 1120'. The last four numbers are the
> number
> of turns/mile for the unit, the first numbers are the Smith's part number.
> If
> you have a different set of numbers, I claim that you have the wrong
> speedo for
> you car. This was the case with my '6; I had a 1000 turns/mile unit and
> my
> odometer and speed was off by 15-20%. Since your odometer is accurate, I
> would
> lay odds that you have correct speedo and the incorrect tach. I assume
> that the
> tach has a similar set of numbers on the face, but don't know what they
> are.
> I'll check at home tonight and see what they say. If this is the case, the
> errors should be very linear.
>
> Scott Mackay
> Austin, TX
>
> -----Original Message-----
> From: Philip E. Barnes [mailto:peb3@cornell.edu]
> Sent: Wednesday, September 16, 1998 10:01 AM
> To: Scott.Mackay@intl.sematech.org; triumphs@autox.team.net;
> paradise@icx.net
> Subject: Re: TR6 engine speeds
>
>
> "I would suggest double checking your numbers. If the needles still
> indicate what you said, line up next to the family grocery getter to
> verify
> you speedo is accurate. If you speedo turns out to be accurate, your tach
> must be way out. These cars are notorious for having the incorrect
> speedo/tack unit installed."
>
> I have gone through the calcs myself in an effort to come up with a mental
> calibration for my speedo. I know that it's way off, but I find that my
> seat-of-the-pants feel for speed and moving with traffic tell me that the
> tach must also be wrong. Here's what I have found: The odometer is spot on
> for general use (+/-1% and only a ralliest would be concerned with that).
> I
> found this by measuring on the interstate over 10 miles or so. Knowing
> this, one could hold a steady speed for a good distance and time over that
> distance. You now have an average speed to compare to the speedo reading
> and could work backward through the equation to come up with an actual
> engine speed. It might be too much to ask that the error in the tach and
> speedo are linear, but it's a start.
>
> Phil Barnes (peb3@cornell.edu)
> Cortland, NY (nowhere near New York City)
> '71 TR6 CC61193L (21 year owner)
>
> Illiterate? Write for free help...
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