I will check for slippage, but if there is a method to calibrate it, I'd bet
my money on the old cable was slipping and the tach is that far off. The old
cable was really, really old. Probably original and the casing was pulling
apart and the connector at the dist. end was detaching from the sheath. The
reading was noticeably erratic, but not in as big a range as the jump in
readings following replacement. It would wiggle about 200 rpm at 60 mph,
but now it has jumped 500-700 rpm. Unfortunately, I chucked the old cable.
Thanks again for your reply, and for all the other replies posted to the
list.
Jim Altman jaltman@altlaw.com Illigitimi non Carborundum
http://www.altlaw.com/ 69-TR6#CC28754L W4UCK
-----Original Message-----
From: Peter Zaborski [mailto:peterz@merak.com]
Sent: Friday, February 20, 1998 7:11 PM
To: 'Jim Altman'
Cc: 'TR6 List'
Subject: RE: Tach Question
> -----Original Message-----
> From: jaltman@altlaw.com [SMTP:jaltman@altlaw.com]
> Sent: Friday, February 20, 1998 4:54 PM
> To: 'Peter Zaborski'
> Subject: RE: Tach Question
>
> Thank you. I was reading about 3200 until I replaced the tach cable
> and now
> it reads about 3600. I wonder why a new cable would cause that?
>
It is indeed strange...
For the record, my car does show the ratio of rpm to roadspeed Bob
indicated in the message I quoted below.
Now back to your problem. We know the dist spins at a speed which is
directly related to the crankshaft speed (this is via solid gears). The
cable is attached to the dist and the other end to the tach.
Here are two more things to consider...
1. Why did you change the cable in the first place? If you put it back
in does the engine speed go back to where it was (ie. from 3600 back to
3200)? If so, perhaps the old cable was rounded and therefore slipping
in the square drive part of the dist (where the cable plugs in).
Alternately, maybe the dist end of the cable is rounded and the slippage
was causing a lower speed than actual to be displayed on the tach.
2. If the new cable is actually transmitting the correct (ie. full,
non-slipping) rotation to the tach and the old cable was rounded and
causing slippage somewhere in the linkage, then perhaps the tach is out
of spec and needs to be recalibrated?
If everything was fine with the old cable (ie no slipping) then I cannot
see how a new cable would cause the tach to speed up. There is no
gearing in the cable it is just a solid piece of steel.
These are my thoughts...
Peter Zaborski
76 TR6 (CF58310 UO)
Calgary AB Canada
> Jim Altman jaltman@altlaw.com Illigitimi non Carborundum
> http://www.altlaw.com/ 69-TR6#CC28754L W4UCK
>
>
> -----Original Message-----
> From: Peter Zaborski [mailto:peterz@merak.com]
> Sent: Friday, February 20, 1998 6:50 PM
> To: 'jaltman@altlaw.com'
> Subject: RE: Tach Question
>
>
> Jim this may not be exactly what you want but I saved it from a much
> earlier post by Bob Lang...
>
> RPM's Gear Speed
> 2000 1 10 MPH
> 2000 2 20 MPH
> 2000 3 30 MPH
> 2000 4 40 MPH
>
> All speeds are very good first order approximations.
>
>
>
> Extrapolation would suggest that 60mph results in ~3000rpm.
>
> HTH,
>
> Peter Zaborski
> 76 TR6 (CF58310 UO)
> Calgary AB Canada
>
>
> > -----Original Message-----
> > From: jaltman@altlaw.com [SMTP:jaltman@altlaw.com]
> > Sent: Friday, February 20, 1998 4:33 PM
> > To: 'Triumph List'
> > Subject: Tach Question
> >
> >
> > Lets try this again. Would one of you 6 drivers please note your
> tach
> > reading at 60 MPH and let me know what it is? Please. No OD.
> >
> >
> >
> >
> > Jim Altman jaltman@altlaw.com Illigitimi non Carborundum
> > http://www.altlaw.com/ 69-TR6#CC28754L W4UCK
> >
|