Member - Glenn D (NSW) posted:

Hows it going Ingtar,

Are these type of Tacho's for petrol engines , where do they pick off, the coil ?

Guess it multiplies the amount of ignition pulses by 4 for correct RPM but depends on number of cylinders being pulsed.

Glenn.

Member - Roachie (SA) posted:

G'day Matt and all the others who have replied.....Thanks for the info.

The motor was installed by my mate, but it was prepared by Brunswicks. There was actually a hold up in it being shipped due to them having to wait for the tacho sender units to arrive (they'd run out of stock).

It isn't attached to the alternator, but there are 2 wires eminating from the front, passenger's side of the block, right near the large pulley on the crank shaft. This makes me think it runs off the timing gear, I guess.

Stupid part of this whole exercise is that he didn't get one word of instructions with the $15,000- "kit" he bought!!! After he installed it he had a lot of strife with the clutch.....couldn't get any clutch action happening. After several unfruitful phone calls to Brunswicks he eventually decided to phone Mark's Adaptors who supplied the adaptor kit to Brunswicks. They were dismayed that their instructions (at least) were not included......they always include comprehensive instructions with anything they sell. Once they faxed him the instructions for their part of the set-up he was able to see in a flash exactly where he'd gone wrong with the clutch.

I suppose what i'm now saying is that perhaps there is some sort of switch or adjustment that needs to be made that changes the Nissan's tacho from looking for a 6 cylinder motor's input, to a 8 cylinder.

The one thing that is irrefutable is that in 4th gear (straight through from motor to tail shaft), there should be no difference in the revs/speed ratio from what he experienced when the 4.2 was in it. That would also be true for the other gears too.

I like the idea of using a strobe light. That might tell him a bit about what is happening.

Thanks again.

Roachie

Member - Matt Mu (Perth-WA) posted:

No worries bit more info. These are just inductive pick-ups....so the sensor is just a coil of wire that as you pass a block of metal past you induce a voltage in the form of a sine wave(simplistically)....voltage builds as it approaches and droppes off as it moves away.

So you can imagine a crankshaft with a series of lugs spaced around it that pass the pick-up as it rotates.

The guage counts the pulses and can determine the rotating speed of the crank depending on its settings.

Now because we are matching an OEM tacho to a non OEM inductive pick-up...there could be a calibration that needs to be made to sync them properly and Brunswick should have this info in their 'extensive' kit!!!!!!

If there isnt any adjustments or matching boxes that need to be installed inline to sync the tacho then Im a little lost as to what else could be wrong. The are very simple and apart from an open circuit in the sensor or spaced too far away from the lugs...nothing else can be wrong with them.

I would be giving brunswicks a call since they supplied the kit for the correction process.

Otherwise you could always have a good look at your Roachie and see if there is anything else in yours that the other one doesnt.

Interesting to hear the outcome!

Matt.

Member - Roachie (SA) posted:

Cheers mate, I'm hoping he will be able to come over to Warraweena next weekend....Ironically, he may decide not to come because he doesn't want to drive all the way at @ 90k/h (which is doing 2600rpm according to his tacho!!!).

I still reckon that simply cannot be possible UNLESS the clutch was slipping really badly. (And it's not).

Cheers and I'll keep this post alive as the truth emerges....

Roachie

Member - Glenn D (NSW) posted:

Maybe I should have read a bit further before giving out theories !

Glenn.