So . . . in the case of a 1.9L with a coil to feed the tach, does it
matter which of these two gauges one uses?
--
Rocky J Squirrel

On Sun, 2011-05-01 at 10:46 -0700, mark drillock wrote:

> Only diesel engines use the W lead driven tachs, AFAIK. Until somewhat
> recently diesel engines had no pulsing signal that represented engine
> speed other than from an internal connection point in the alternator.
> Alternators meant to provide this signal have an extra lead that you can
> connect to. Bosch and VW call this a W lead and Vanagon alternators have
> a marked spot on the back of the case for the W lead which may or may
> not be actually present. Since gas engine Vanagons don't need the W
> signal only some replacement alternators have it installed in the
> alternator. This so fewer alternators need to be stocked because the
> same alternator works across more applications and the cost of the
> rebuilder adding the lead is nearly nil. Since the alternator is belt
> driven and often by a compound pulley system there is not any known
> exact frequency that means an exact engine speed until the tach is
> calibrated for a given pulley setup.
>
> Mark
>
>
> Rocket J Squirrel wrote:
> > I've settled on the VDO "Cockpit Black" series of meters for Mellow
> > Yellow's upcoming gauging project.
> >
> > Looking at eguages's offerings in the 2-1/6'' diameter size, 4000 rpm
> > range, I find two very similar gauges.
> >
> > One is the 333 365, the other is the 333 369. They have very similar
> > prices and seemingly the exact same specifications:
> >
> > For use on 4,5,6,8 cylinder application engines with standard
> > coil ignitions, most square wave electronic control ignitions
> > with tachometer output terminal, and alternators with "w"
> > tachometer terminal.
> >
> > Eguauges does not know what difference there is between them. After some
> > searching, I found this:
> >
> > 333 365 is 4,000 RPM (400–1300Hz)*
> > 333 369 is 4,000 RPM (800–2400Hz)*
> >
> > where * = For Alternator use only
> >
> > Can someone help me figure out which gauge will read correctly when
> > connected to the coil? Maybe they both will, but this difference of 2:1
> > in the frequency spec gives me pause.
> >
> > --
> > Rocky J Squirrel
> > '84 Westfalia: Mellow Yellow ("The Electrical Banana")
> > '74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
> > Bend, OR
> > KG6RCR
> >