instrument accuracy(was The Red Mark)

[treilley_at_BANKMARK@conseco.com (treilley)]

     I would think that the Audi(VDO) tachs are extremely accurate.  You 
     are comparing apples to oranges.  The main reason speedos are not 
     accurate is because of tire size.  There are formulas to figure out 
     how far off a speedo should be with a tire that is not the stock size. 
      Even a worn stock tire will give a slightly inaccurate reading.
     
     Your vw speedo was jumping around because the cable was beginning to 
     fail.
     
     Tim NJ 90CQ, 77Spitfire


______________________________ Reply Separator _________________________________
Subject: Re: The Red Mark
Author:  akowalsk@shrike.depaul.edu at Internet
Date:    5/24/96 12:57 AM


R Justin Andrews wrote:
> 
> >               >>>will going to the red mark hurt....<<<
     
> If you can get to the last red mark then your gauge is broke.
> Mine will only got to 7,500RPM when I try to push it with my finger
> it will not go any further (I did this when I was repairing the odometer) 
> HTH,
     
> Rich Andrew
> rjandrew@post.cis.smu.edu
     
     
I have a question.  What is the accuracy of Audi tachometers?  
Anybody ever heard of them been off severely?  Given that some 
speedometers I've owned and driven are off by five percent or more, I was 
wondering about the tachs...  if the tachometer was off by 10% 
(admittedly a large amount), you could be doing damage to the engine by 
revving it to the redline.  The next time I get my car serviced I'm going 
to ask my mechanic to hook the car up to the computer and read the true 
RPM (unless his computer's off, and then we'll have to hook that up to 
another computer and...) and compare with the tach.  I have no reason for 
asking this except that I remember my old VW Scirocco that had a 
speedometer that bounced all over the place, possibly measuring 
something, but speed wasn't it. 
     
Best Wishes,
     
Alex Kowalski
'84 4KQ
     
P.S. there are always those who ignore the tachometer anyway and shift by 
elapsed time from the end of the driveway ;-).