[s-cars] OBD GEEK question

[Paul Krasusky]

Gents-

All this OBD talk got me playing around these past few days.  Fun stuff, in
a cargeeknoid sort of way at least.  ANYway, was wondering this:

I (now) understand that the temp GAUGE reads from the M(m)FTS while the temp
OBD reads from the ECT read from the back of the head.  OK, good, two
different measuring devices measuring from 2 separate areas.

Now, <brace for stupidity>, when I'm in say, channel 17 reading RPM or 28
reading speed (may be vice versa, don't have list in front of me, whatever),
I'm sitting here all fat and happy that both seem to indicate that my
respective analog gauges are dead-on.  Right?  Or, Right????  Meaning, it
dawned on me, are each of these respective digital channels pulling their
info from the same sending units that power the analog gauges?

Basically, if my analog indicated speed is 182mph, er, 65, and the
corresponding digital value is also 65, this only tells me that the speedo
is READING right, not that it's indicative of true vehicle speed.  So if
speedo mph was changed due to tire size, etc., this is not a good test.
Same with RPMs, tach says 8,900, er, 4,000, and digital agrees...  if
they're both reading from same source, is that really of any value aside
from that the gauge is agreeing with the digital?

OK, too much time on my hands here apparently (I wish!), and I'm way over
thinking this I'm sure.

Begin laughter...

-Paulie Easily Amused
'95 //S6 OBD tracking lately...  because you can
'58 TR3A OBD?  Factory remote starter button mounted under bonnet should
scare you away immediately