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J60 electronic ignition for B series ?


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I know about the Jolley Engineering conversions to put electronic switching on almost any points type ignition system but I have become interested in using the optical module from a J60 distributor to convert the closely related lucas distributor used on B series engines.

 

Obviously it is necessary to use the original B series advance and retard mechanism and for 4 or 8 cylinder engines a new disk with the right number of cutouts would have to be made but a more technical problem is the electronic rev limiter in the J60 setup. This is, I understand, set to 4750 rpm but most B series engines are limited to 3750 rpm (though safe to 4000).

 

One could simply use the original B series mechanical cut out rotor arm but this is rather crude and good ones are getting very hard to find. Using the J60 plain rotor arm would be a much better option but then the rev limiter is set too high to protect the engine. If the J60 limiter works by limiting the RATE of pulses it would actually limit an 8 cylinder engine to 6/8 of 4750rpm which is 3562.5 rpm which is a little low. Does anyone understand the electronics well enough to suggest how the rev limiter function could be modified? Ideally it might be possible to connect a resister or capacitor to one of the existing terminals on the module to change the rpm ?

 

There must be some electronics experts out there :cheesy:

 

David

 

Ps I do know that J60 distributors turn opposite to B series but the optical modile wouldn't care about that !

Edited by David Herbert
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David looking in some SEME lecture notes on electronic ignition on CVRs it says unfortunately "The manufacturers have not disclosed the circuit details" although it is assumed limiting is by a thyristor with the gate switched by a time delay circuit.

 

I did x-ray one once but never managed to figure out the circuit. I'll try & get this page scanned if I can get the scanner to go but its making grating noises at the moment.

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Thanks Clive.

One of the things that prompted my interest was your article "Ignition Matters" where you did in fact include some x rayed images of the module. Unfortunately I am not very into electronics so although I am quite happy to replace a component on a PCB, I do not readily understand what I am looking at.

 

Does anyone properly understand exactly how the speed limiter works? It must be reliant on the value of some part of its circuit to set the cut out speed and it may be possible to add a component to one of the accessible terminals that will alter the setting. Alternatively it is possible that the size of the 'windows' in the shutter disk (and thus the time that the receiver is illuminated at each pulse) is what is read by the speed limiter. It would then be possible to make a new shutter disk with the required number of windows but with windows of a different size to get the right speed setting.

 

Also, I believe the contact breaker version of the J60 distributor is a No2 Mk1 but what is the designation of the electronic version?

 

David

 

Clive, just seen your last post which crossed with mine. That I think suggests that changing the window size would alter the speed setting. I just have to put on my thinking hat to work out which way!

Edited by David Herbert
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Do we know if the spark happens when the optical sensor is first illuminated or when the light is cut off by the shutter disk?

 

If the speed limiter is timing the window in the shutter disk there will be a direct linear relationship between the size of the cutouts and the speed. It should be that 10% change in the cutout will change the speed 10%. But is it really that simple ? And which way will it change it ?

 

David

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Hi David,

I am no electronics expert, but worked a lot with J60 engined vehicles at REME workshops for many years. The CVR(T) and Fox were both introduced with conventional points set up, but due to the distributor rotating opposite to the B Range engines, there was a problem with wear of points cam heel, and the regular resetting of points, which entails a lot of work on both vehicles. A modification was introduced to convert the distributors to the new Lumenition system. The Fox had no speed limiter in the circuit, only CVR(T) had it. To be honest if driven with respect, a limiter is not necessary. I understand the speed limiter rotor arm was not satisfactory on the J60 and thus not used. I was told why many years ago, and think it could have been something to do with causing engine damage.

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David,

 

It looks like the timing circuit uses some sort of timer to set a diode to effect the ignition cut out. You won't be able to manually change it, but going to an 8 cyl. engine will affect it as you expect. At the end of the day though, I would strongly recommend that you just get a jolley kit. Pissing around with a J60 unit will not net you very good results and even if you can make it work. It will cost more than the jolly kit in the long run.

 

Cheers,

Terry

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Do we know if the spark happens when the optical sensor is first illuminated or when the light is cut off by the shutter disk?

 

If the speed limiter is timing the window in the shutter disk there will be a direct linear relationship between the size of the cutouts and the speed. It should be that 10% change in the cutout will change the speed 10%. But is it really that simple ? And which way will it change it ?

 

David

 

Hi David,

Here is a Lumenition rev limiter ; http://www.lumenition.com/images/pdfs/ERL-V-instructions.pdf This is not visually like the one fitted on CVR(T) engines, but worth enquiring with Autocar (who supply Lumenition) to see if it is compatible with the ones the MoD were supplied.

 

Richard

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Lumenition speed limiters and ignition modules are a phenomenal price. A possible alternative to the Jolley unit is advertised on ebay for Lucas distributors which retain the speed limiter of the original B series engine as does the Jolley Unit. The Jolley ignition module is easy to fit albeit priced well beyond what it should be.

 

There seems to be no purpose to reinventing the wheel by attempting to modify a J60 Lumenition module.

 

Diana

 

 

Hi David,

Here is a Lumenition rev limiter ; http://www.lumenition.com/images/pdfs/ERL-V-instructions.pdf This is not visually like the one fitted on CVR(T) engines, but worth enquiring with Autocar (who supply Lumenition) to see if it is compatible with the ones the MoD were supplied.

 

Richard

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Lumenition speed limiters and ignition modules are a phenomenal price. A possible alternative to the Jolley unit is advertised on ebay for Lucas distributors which retain the speed limiter of the original B series engine as does the Jolley Unit. The Jolley ignition module is easy to fit albeit priced well beyond what it should be.

 

There seems to be no purpose to reinventing the wheel by attempting to modify a J60 Lumenition module.

 

Diana

 

Old squaddie trick to make your CVRT go faster-speed limiter grounds through a fuse mounted on the thermostat housing-take out fuse=go faster! sshhh.......

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Hi David,

The CVR(T) and Fox were both introduced with conventional points set up, but due to the distributor rotating opposite to the B Range engines, there was a problem with wear of points cam heel, and the regular resetting of points, which entails a lot of work on both vehicles. A modification was introduced to convert the distributors to the new Lumenition system. The Fox had no speed limiter in the circuit, only CVR(T) had it. To be honest if driven with respect, a limiter is not necessary. I understand the speed limiter rotor arm was not satisfactory on the J60 and thus not used. I was told why many years ago, and think it could have been something to do with causing engine damage.

This may be a stupid question, but how would I tell if my Fox J60 has Lumenition system? Is this system the same functionality as electronic ignition?

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TerryB,

Thanks for that, I was pretty certain that would work but it's good to know for sure. As I understand it from Richard Farrant's post Foxes didn't have a speed limiter but I suspect that the module (or more precisely the Luminition base plate rather than the optical module) was identical and the black wire and the fuse were simply omitted.

 

Datadawg,

Take the distributor cap off and look inside the distributor. It will either have contact breakers and a capacitor or the Luminition optical electronic unit. See Clive's (fv1609) article 'Ignition Matters' in 'Clive's Corner' section of this forum for nice photos and info. The Luminition unit is relatively unusual for an electronic unit in that it directly mimics the contact breaker system in that it is realy just a switch that doesn't need a capacitor to stop the points burning. You could even adjust the dwell angle by modifying the shutter disk (smaller gaps = more dwell). It seems that the vast majority of CVRT / Fox J60s got the electronic ign conversion fitted well before disposal.

 

Most electronic ignition modules charge a capacitor and release a pulse to the coil when a hall effect sensor is triggered by a rotating magnet that replaces the cam - or nowadays by the engine management computor. The Jolley engineering unit seems to be more like the Luminition one but driven by a hall effect sensor. I could be wrong but I believe it does not create its own pulses but switches the coil as a contact breaker would.

 

David

Edited by David Herbert
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Usually the J60s with electronic ignition have a warning sticker on the distributor. If the engine has been painted since it left service it might be missing.

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