In a message dated 96-12-05 13:58:16 EST, lchillin@siu.edu (Lawrence
Schilling) writes:
> was driving around with a friend the other day in my Stag with the TR6
>engine and he looks over at the dash and says, your tach's not right. This
>friend has previously owned a TR4 and now a Porsche 356. I hadn't thought
>much about it since I don't drive my car very hard but since he mentioned it
>I ran it up through the gears and the tach never went over 3500.
>
>He says, and I'm sure he's right, that it should have read more like 4500.
>
>So now I'm wondering. Since the tach itself is a Stag tach and the engine
>is a TR6 what does this all mean?
Lawrence,
If the Stag has an electronic Tach then the tach is probably reading 3/4 of
the correct reading. The reason is simple: the tach was calibrated for an
8 cylinder engine. You have a TR6 motor which has 6 cylinders. The tach
reads the coil pulses and the 6 cylinder coil delivers 6 pulses per 2
revolutions where the 8 cylinder coil delivers 8 per 2 revolutions.
Another way to look at it is that when the tach reads 3000 RPM the engine is
running at 4000 RPM. When the tach reads 1500 RPM the engine is running at
2000. The easy thing to do is to mentally translate the readings the same
way you would if you set you watch 5 minutes fast. You know your watch is
fast and you know that even though your watch says you're 2 minutes late you
still know that you have 3 minutes. It never worked for me, either.
Dave, St. Louis, MO, USA
TR6Massey@aol.com
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