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Old 04-20-2014, 10:49 AM
v8volvo v8volvo is offline
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Join Date: Jun 2009
Location: Montana, USA
Vehicle: '86 745, '83 764
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Unfortunately 200 series 80mm diesel tachs are pretty rare, so may be hard to find one to refer to. You might have to do some experimentation.

I don't know whether the pulley ratio is the same on the D24 vs the VW motor, but I suspect it is not. From recollection, the crankshaft drive pulley on a 4cyl VW is significantly smaller in radius than the dampener on a D24 is, and the Volvo does not have an especially large alternator pulley -- I don't recall the VW alternator pulley being any smaller. Don't know what you would have to do to the tacho circuit in order to get the calibration right if there turns out to be a difference.

I have a spare 1.5L VW and probably have an alternator for a VW somewhere too so if you're in a bind I could make some measurements next weekend...

I know I did one time plug a 760TD tach into a running VW alternator (in order to determine which of two identical and unlabeled terminals was W and which was D+) and remember that the tach showed a generally plausible value for engine speed with the VW motor idling, so if the ratio is off it is at least not very far off.

You probably are already aware of this other alternative, which costs some money but works well:

http://www.dakotadigital.com/index.c...rod/prd128.htm

I have used these on a few different diesel conversions to get gasser tachs to work and have been generally pleased with their ease of use and performance.

Keep us posted on what you find out.
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