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BMC 1.5 - What is this connection for?


jhodgski

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Thanks for the replies.

 

Tony, did you mean the W terminal is to drive a tachometer?

 

Roger, Yes I would prefer an electrical solution if it isn't too expensive. Does this mean I need to buy a new alternator, though?

Not if you've got Tony's W terminal as it is a single phase output specifically to drive a tacho. There are various ones available but I believe that you will still need access to an optical tacho to calibrate the tacho output because pulley ratios vary from engine to engine.

 

ASAP Supplies do Faria ones that can be driven from a tacho sender that connects to your mechanical output if you haven't got a W terminal on the alternator but this can start to get expensive having to buy both the sender and matching tacho. You would also need to speak to them to see if the linking nut adaptor sleeve for the sender would fit the threads on your mechanical output.

 

Many tachos are more designed for high speed petrol engines rather than marine diesels so often give up to 8000 rpm rather than a more suitable 3 or 4000 top end. One of the Farias on ASAP's site goes up to 3000 rpm.

Roger

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Seeing the petrol B series (and the A series come to that) have the pushrods on the same side as the 1.5 diesel I very much doubt the camshaft is on the other side on the petrol version. I think (almost know) the distributor drive was a long one running across the block.

 

This link (scroll down a bit) http://www.classicbuses.co.uk/+Morris.html shows the block of a 1600cc B series petrol engine. You will see the timing cover has its larger diameter offset to the left of the engine (looking from the back) and its the larger diameter that houses the cam shaft sprocket. Thus the camshaft is on the left of the block so the distributor drive must run right across the engine, just like the diesel version.

 

Also on all BMC & Austin engines of this age the fuel pump was on the left and these drive directly off the camshaft so again the shaft has to be on that side of the engine.

 

 

The B series petrol cam is on the same side as the diesel. The skew gear on the cam droves the oil pump and also the distributor which is on the alternator side of the engine. It was standard Austin practice to put the electrics on one side of the engine and the fuel, inlet and exhaust on the other. The A, B, & C series are all like this. It does mean that you have siamesed ports on the head so they don't breathe that well. You can buy a 7 port cross flow head for the 1800 petrol but they're £££.

 

I know and weren't they a B,,, nuisance Well they are on my MGB.

 

L

 

SU do a transistorised version that is more reliable. I fitted a Facet cube on my MGB GT. (nearly back on road after 17 years hybernation....)

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Cheers, Roger. I'm pretty sure my alternator doesn't have a W terminal. If that's the case, then I'd need...

http://www.asap-supplies.com/search/mechanical+tachometer/faria-generator-tachometer-sender-kit-90901

...with one of the "magnetic flywheel" tachometers?

 

Or get a phase tap soldered into your alternator.

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When I first got my boat I wanted to fit a rev counter, thinking it would be useful to know what speed the engine is running at. However, other things have always been more important so budget hasn't allowed. Two years on and one year being a cc'er I've covered about 230 miles, I can honestly say not knowing the engine speed has never been an issue. It's pretty obvious whether the engine is running at a comfortable speed by the noise and smoke it makes. Water depth and flow make using a rev counter to set your speed largely irrelevant and given that, to set an alternator driven rev counter accurately needs additional specialist equipment, it's a lot of expense and effort for very little reward.

 

Of course, it's up to you if you want to proceed though.

 

If any forum member wants to borrow it, I have a signal generator that converts the pulse from a diesel fuel pipe into a signal which can drive a timing light or rev counter to help set your w+ or mechanical driven rev counter accurately.

 

Sealey TL95 You'd need your own timing light though.

 

Rob

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When I first got my boat I wanted to fit a rev counter, thinking it would be useful to know what speed the engine is running at. However, other things have always been more important so budget hasn't allowed. Two years on and one year being a cc'er I've covered about 230 miles, I can honestly say not knowing the engine speed has never been an issue. It's pretty obvious whether the engine is running at a comfortable speed by the noise and smoke it makes.

 

 

Exactly that. I do have a rev counter, but I have no idea how accurate it is, and I don't use it to govern my behaviour with the throttle, there is a "sweet spot" at which the engine has perfect pitch and the boat travels at just the right speed, a fraction above or below this and the engine sounds totally wrong and the boat vibrates so much that things fall off of shelves. If my rev counter packed up tomorrow I wouldn't bother replacing it.

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My Father had one of these to estimate machinery speeds.

 

17969.jpg

 

You hold it against the engine, turn the dial which pushes/pulls the wire out or in until you get the maximum resonance, then just read the frequency off the scale. Not 100% accurate , but more than good enough for a quick estimate.

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My Father had one of these to estimate machinery speeds.

 

17969.jpg

 

You hold it against the engine, turn the dial which pushes/pulls the wire out or in until you get the maximum resonance, then just read the frequency off the scale. Not 100% accurate , but more than good enough for a quick estimate.

But a bug**er to use when cruising I would imagine :)

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  • 2 years later...

My Father had one of these to estimate machinery speeds.

 

17969.jpg

 

You hold it against the engine, turn the dial which pushes/pulls the wire out or in until you get the maximum resonance, then just read the frequency off the scale. Not 100% accurate , but more than good enough for a quick estimate.

They say - Many considerable engine manufacturers around the world belong to our costumers for years.

 

Do they keep it in the 'dressing up' box or what :-)

Edited by Dual Rectifier
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Agreed. There are many ways to a solution of providing a tacho. Only the OP can decide which is right for him with the knowledge now gained and the budget that he has available.

Roger

True though that drive take off is very similar in looks and position to the 'rev counter' take off on a Nuffield tractor engine. Might be worth sniffing around vintage tractor websites. The instrument had multi band calibration to give some idea of road speed for any given gear too. Not much use on a boat but could puzzle some folk.

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