diesel tachometer question

aztec

aztec

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ok...

i know that you can buy tacho's for diesels... they run from either an engine driven sender or from the altanator.

so, where would i get a sender unit to fit a perkins prime, where would it bolt to, and if i did that could i use an ordinary coil sensed tacho?

OR...

can i modify (or have modified) a coil sensed tacho to "read" altanator output?

OR...

can i go to the scrappy and just buy a tacho from a scrap car/truck... or are some driven from the ECU?

if you're interested in the rest.... read on, but it might be dull!

i used to make dashboards, cut them out, put new gauges in... reasemble.. etc.

on the boat there are two options.

1) go for aftermarket gauges, fit them in a bit of ply, and get on with it.

2) make up a base dash, with scrap guages, (you know, the modern ones, with lighty up needles), fit it all into the base, then place an acrylic cover over the lot, and recess this into the helm, if nothing else it'd look posh, btu wouldn't suit the style of the boat.

ideally i need some older looking gauges, that will run from diesel altanators, and arn't too dear.

(any tips or recomendations here would be good)

but i'd still like to know, how the diesel ones actually work... and why ordinary ones wouldn't if connected to the altanator.

cheers, steve
 
Steve, I fitted DURITE Guages, for my perkins 4108's,but the oil pressure sender units keep packing up, i think it might have something to do with the vibration on the diesels.
my tacos are mecanical,
 
Bits I've learnt (the hard way /forums/images/graemlins/blush.gif): my tacho is driven by the alternator. Both bits came from scrap yards. They are not "matched" (if matched, the rpm on the tacho is corrected for the ratio between the crank and alternator pulleys), so my tacho reads 50% high - it is a linear error (1200 tacho = 800 rpm, etc): I bought a mechanical unit to check/calibrate. Some tachos can be adjusted with a hidden screw (mine can't /forums/images/graemlins/crazy.gif). You can't use a petrol unit which works on the impulses from the coil or modern equivalent (no spark on a diesel).
 
I think Mike Bellany at Lancing marine does some reasonable cheapo guages, I got some of mine from him, I do think setting then in a panel with a clear window over the top would be good.

on my perks the tacho's are driven from the alternator, btw, most guages have a adjustment screw on the back and you can use a optical tacho with silver tape on the crank pulley to calibr8.
 
FWIW modifying the alternator to provide Tacho pulses is dead easy.....open up the alternator and solder on an extra wire to where any two diodes are connected....before the voltage is rectified.....

This will drive the Electronic tacho....adjusting the speed may need different pulleys...

But it is really simple.....On a diesel Alternator the W winding is connected as above
 
thanks steve,

i don't have a problem with the altanators, they have the correct terminal.

just wondered if i could modify a standard car tacho to work..

doesn't matter iv'e found some faria gauges that will do the job

steve.
 
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