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matchlesswdg3

Running 24 volts. Pros and cons?

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For example, running a 24V Land Rover, I understand that the 24V systems on FFRs and Wolfs is robust and better than the 12V, inherently (?), but what are the downsides?  Cost of components may be one....significant?  Availability of parts?  

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24v FFR is designed for radio fit so everything is screened. Coil, plugs, alternator, distributor etc etc. So you won't get bits in Halfords. Unless you want to fit radios why have to buy two batteries when they die? You see what I'm saying, unless you need the 24 volts stick with conventional bits and bobs and 12 volts.

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On the other hand, if it’s already 24V and everything works fine, why waste time and money converting it, and lose originality?

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2 minutes ago, sirhc said:

 and lose originality?

and lose value, people don't realise that chopping around the electrics might seem an expedient to them & may all be changed in what they believe is a logical fashion may turn out to be a nightmare for the next owner or anyone asked to sort out the bodgery!

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Posted (edited)

And as someone who has purchased a 24volt vehicle that has had a POST (previous owner stupid trick) performed on it and chased mickey moused wiring and jumpers and resistors around it isn't fun.

All the 24 volt stuff for the most part is available or re-buildable (perish the thought) and as others say it keep the value up for those of us who care.

It is a similar vein to why would you put WMIK kit onto a 1986 Land Rover 90 that has a 2.5 na diesel in it?

However, our veterans fought for your freedom to do what you wish, however your peers may give you funny looks

 

Edited by robin craig

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Far more robust system, water proof,  spark plugs are quality as is the whole system. Once you get thinking head on and instead of pulling the plug leads off by hand, its a spanner. Better starting as 24 volts are used and when running drops to 12volts.

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2 hours ago, Peakrec said:

Far more robust system, water proof,  spark plugs are quality as is the whole system. Once you get thinking head on and instead of pulling the plug leads off by hand, its a spanner. Better starting as 24 volts are used and when running drops to 12volts.

As I understand, Defender Wolf is 24V period, even the non FFR types.

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As far as British military vehicles go, although a 24v ignition system through a ballast resistor reduces the voltage to the ignition coil to 12v (or 10v in series Land Rovers) it has an advantage over a purely 12v system.

The rate at which the ignition coil can magnetise (when the CB closes) & demagnetise (when the CB open) determines the effectiveness of HT output, most importantly at high revs.

This is because the time constant of the primary circuit in a 24v system is determined the ratio of inductance of the primary winding to the resistance of the primary circuit (ie resistance of coil primary + resistance of ballast resistor).

Whereas the time constant in a purely 12v system will have a similar inductance but the resistance of the primary circuit will just be the resistance of the primary winding.

So the time constant of will be lower in a 24v ballasted system than a 12v unballasted system.

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16 hours ago, fv1609 said:

As far as British military vehicles go, although a 24v ignition system through a ballast resistor reduces the voltage to the ignition coil to 12v (or 10v in series Land Rovers) it has an advantage over a purely 12v system.

The rate at which the ignition coil can magnetise (when the CB closes) & demagnetise (when the CB open) determines the effectiveness of HT output, most importantly at high revs.

This is because the time constant of the primary circuit in a 24v system is determined the ratio of inductance of the primary winding to the resistance of the primary circuit (ie resistance of coil primary + resistance of ballast resistor).

Whereas the time constant in a purely 12v system will have a similar inductance but the resistance of the primary circuit will just be the resistance of the primary winding.

So the time constant of will be lower in a 24v ballasted system than a 12v unballasted system.

I understood all that up to "As far as British military vehicles go....".  Look, its just smoke in the wires and 24V has faster smoke than 12V so things happen.....betterer.  Right?

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17 hours ago, matchlesswdg3 said:

I understood all that up to "As far as British military vehicles go....".  Look, its just smoke in the wires and 24V has faster smoke than 12V so things happen.....betterer.  Right?

Think of it as water coming out of a tap.  24V has a higher pressure than 12V.

Andy

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Well here is that very 24V engine I had in mind.  It looks pretty busy to me, but all present and correct?  I would motnhave a clue on this stuff, althpugh Inguess the pancake air filter is not original!  Has what Inthink is a rebuild plate and owner reckons number has been ground off the onlong under the manifold.  The brass plate shows (not sure these numbers were read correctly) "524139/4" and "K11420010".  The first 5 may be an S for an exchange engine?  The "K" number may indicate workshop and 20 thou oversize pistons and 10 thou crank regrind?  Thats if its vaguely similar to other rebuild plates Inhave seen described.

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On 3/5/2020 at 10:41 PM, fv1609 said:

As far as British military vehicles go, although a 24v ignition system through a ballast resistor reduces the voltage to the ignition coil to 12v (or 10v in series Land Rovers) it has an advantage over a purely 12v system.

The rate at which the ignition coil can magnetise (when the CB closes) & demagnetise (when the CB open) determines the effectiveness of HT output, most importantly at high revs.

This is because the time constant of the primary circuit in a 24v system is determined the ratio of inductance of the primary winding to the resistance of the primary circuit (ie resistance of coil primary + resistance of ballast resistor).

Whereas the time constant in a purely 12v system will have a similar inductance but the resistance of the primary circuit will just be the resistance of the primary winding.

So the time constant of will be lower in a 24v ballasted system than a 12v unballasted system.

This is one of those occasions where I really wish I could understand what was written 😀  Sadly electrics are ike Alchemy to me I have as much chance of producing gold as I do fixing electrical gremlins...... 🤪

 

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This article covers general ignition principles as well a more detailed description of 24v ignition systems in Land Rovers & their advantages. Although I see only one person liked it :  (  

 

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Clive.....I know its not much to go on, but can you draw any conclusions as to the engine I illustrate above (not the photo with the arrow).......looks all there and relatively unmolested?  I am totally unfamiliar with the 24V engine.  Thank you.

 

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Ferg it is some years since I owned at LtWt but apart from air filter it does look pretty unmolested.

I notice the two relays look newish as they easily rust out given their position & the king lead (ie HT) from the coil to distributor looks newish which all suggest that there has been sympathetic electrical maintenance going on.

I notice the filter box (contains filter & ballast resistors) no longer has any of the original countersunk screw heads. In order to lose those, suggests the cover may have been off for a while. So it would important to ask if any modifications have been done inside. One of the ballast resistors has quite thin wire & can easily break, I have never seen a satisfactory owner repair with a substitute resistor.

I'm pleased to see that the ignition coil is mounted correctly as military replacement coils fitted with a bracket generally are 180 degrees round from where they should be for mounting on the rocker cover. Due to the SW lead being quite short it then gets incorrectly wired up resulting in a positive rather than negative spark. I can tell yours is ok as I cannot see the two tiny drain holes as these are underneath & not visible.

If the charging system has two ammeters on the dash, it would be important to observe the vehicle ammeter at switch on, start up & revving to see that it does in fact charge & that the ignition warning light goes out. If you have a single ammeter in a box (shunt box) between the two front seats, this ammeter only reads the rate of charge just to the radio batteries (if fitted) It does not measure discharge from the the radio batteries.

If radio batteries are not fitted it is important that the two battery leads are isolated from earth & each other as these become live when charging as a relay in the Generator Panel No.9 joins the radio & vehicle batteries in parallel.

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Nothing to do with 24V, but looking at the photos I'd be inclined to replace the missing/moved clips on the fuel line that's directly above the exhaust manifold!

Andy

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Very useful - thanks, Clive (and Andy).  These pics show a little of what remains from the internal FFR fitments.  Thats all the photos I have for now.12072106.thumb.jpg.ce8d9bed826f5ec15498d526c45059d8.jpg12072108.thumb.jpg.f5fe37fea9f9dd971bb7756289bba512.jpg

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Ferg inside looks quite reassuring. The various types of harness look nice, I suspect they have been painted as their connectors look less dazzling. But at least it shows someone has taken some interest & care to conserve the wiring in the back that so often is the first victim of bodgery.

When you go to see it, do check that it is charging along the lines of the basic tests I suggested. If you get stuck on anything here is bit more light reading for you : )

 

 

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Thanks, Clive!  I will arm myself.  It is amazing (depressing?) how many of us supposedly intelligent yoomans cannot get our heads round elektrickery!

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Yes it is curious how even mechanically minded people have an (ir)rational fear of electrical issues. What I like about electrical equipment is that when you apply appropriate test equipment you can measure what is happening in a give circuit. There is nothing discretionary in the diagnosis, apply logic to what the circuit should be doing & you can measure what is or is not happening, unlike some other automotive skills such as judging that an engine is pinking say, I'm at a complete loss on how to make such an observation with any certainty.

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