Installing aftermarket rev counter / tacho into a petrol T25

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bigbadbob76
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by bigbadbob76 »

Thanks for the link.
I'll have a poke around down there and see if it's fitted or blanked. :ok
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bigbadbob76
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Installing aftermarket rev counter / tacho into a petrol T25

Post by bigbadbob76 »

Hmmm......
Comparing the one on "the samba"

Image

With mine...

Image

It dosn't look like mine ever had a sender there, but it's a b suffix engine in a 1986 van, and has the yellow wire that someone has earthed.
I'm confussed dot com.

Unless someone stripped the thread and welded up the hole.
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937carrera
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by 937carrera »

Is it possible your van has had a replacement (early) engine / crancases, therefore there is no location for the second pressure sensor ?
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by itchyfeet »

937carrera wrote:Is it possible your van has had a replacement (early) engine / crancases, therefore there is no location for the second pressure sensor ?

B suffix case is a late case, clean off the oil and it will be clear if it has been welded up.

other than the part number moulded in you can check this...
Imageearly late case by Paul_Barr, on Flickr
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bigbadbob76
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by bigbadbob76 »

Mine's definately the wider casting which makes it a late engine.
I guess someone did weld up the hole. :roll:
Cheers guys. :ok
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by itchyfeet »

worth checking it closer to see, if its a weak point it could fail
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by The Hairy Camper »

Great post. I know it's old now, but has anyone done this mod for a diesel? Is it a similar process?

My van came with the clock instead of a tachometer. Would be nice to put one of these aftermarket tachometers on the dashboard.
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by Oldiebut goodie »

 Usually a signal is taken from one coil of the alternator on diesels.
You used to be able to get a sender on one injection pipe that worked by sensing the pulse and converting it into an electrical signal as well.

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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by The Hairy Camper »

I checked my alternator last night and it does have the W terminal. Does that mean I can attach an aftermarket tachometer and get an rpm reading?

There is another wire going to the W terminal though, any idea if/what it will be using it for at the moment?
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by Oldiebut goodie »

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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by Aidan »

if it's a late van it should have 'buzzer of doom' oil pressure monitoring, that would require rev signal
if not maybe split charge for leisure battery set up

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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by The Hairy Camper »

Interesting, it does indeed have the 'buzzer of doom'.
Can more than one device be connected to the W terminal? I.e. 'BOD' and tachometer?
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by Aidan »

The Hairy Camper wrote: 27 Feb 2024, 17:33 Interesting, it does indeed have the 'buzzer of doom'.
Can more than one device be connected to the W terminal? I.e. 'BOD' and tachometer?

yep that's how it is done in a factory rev counter set up, it's split on the foil board, once split the trace goes to the bod circuit and another trace goes to the rev counter
You could t into the wire before the 14 pin connector to supply your rev counter
You will need a rev counter that speaks w signal as opposed to the more common petrol ones that speak coil signal

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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by The Hairy Camper »

Cheers Aidan, I've just ordered a Diesel aftermarket tachometer. It would have been nice to have a factory tachometer instead, but I suppose the big clock will have to stay.
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Re: Installing aftermarket rev counter / tacho into a petrol T25

Post by AngeloEvs »

Slaughterhouse offer a Tachometer that is a copy of the VW type fitted to the T25. It’s designed to use the standard Temperature and Fuel gauges unlike the VW Tacho which requires different shaped gauges. Fitting an after market Diesel Tacho requires it to be calibrated to suit the engine as the pulse frequency varies due to different rotational speed of the Alternator. More expensive than a standard aftermarket model.
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