alternator / dynalite conversion

[3759allen]

hi all. as explained on a previous post i've started working on a friends +2 but need to address several issues so listing different posts for each issue.

i'm looking at converting the dynamo to either a dynalite or alternator. whats peoples opinions on either of them and how much wiring is involved with each option?

i've replaced the regulator already but still hasn't fixed the over charging issue, i've heard most people say these are notoriously unreliable even when new so ideally looking to not use it anymore.

thanks for any help.

[mark030358]

I used a dynolite, modified the “box’ and looks 100% original with more reliability.

Cheers

[TBG]

Go for a modern light weight alternator. Who cares what it looks like and save a lot of money........D

[2cams70]

i've heard most people say these are notoriously unreliable even when new so ideally looking to not use it anymore.

Not true - properly set up the electro-mechanical regulators are quite reliable. Problem is few people know how to set them up. Alternators are much better than generators insofar as being able to supply a reasonable charge current at low engine RPM. If you don't get stuck in traffic much and you are not not running a lot of extra high current draw add-on accessories then there's nothing really wrong with the original generator.

[Andy8421]

It all depends on how much you care about originality.

The dynalite is an alternator in drag, and is clearly not original, but if under bonnet cosmetics matter, than that is a way to go. My own view is put an alternator on and tuck the dynamo away should a later purchaser want 100% originality. Its a bit like the 'heritage' Jenvey throttle bodies that look like Weber carbs. While they are very impressive - what's the point?

As for functionality, there isn't much competition, an alternator has higher output, lighter weight, better voltage stability and lower cut-in revs.

There are two alternator routes to go, an in period Lucas 17ACR (which was fitted to later Elans, so arguably is correct) or a modern alternator which is tiny, weighs a fraction of the Lucas unit and has higher output. Your choice.

In answer to 2cams70 point, dynamo / control box combinations did work surprisingly well in period for a mechanical system, but apart from the low output at low revs problem, voltage stability was all over the map. Lead acid batteries are picky when it comes to charging, and really need to be floated at 13.6V. In period, 'boiling the battery' or undercharging the battery was not an uncommon problem. This is particularly the case with our cars that don't get used that often. Unless you use a float charger when the car isn't being used, the battery really needs all the help it can get.

The lack of use also impacts reliability. In the days before electronic ignition, none of my garden equipment would start after the winter - the points had corroded and needed cleaning. The innards of a control box are similar in that they have a number of 'points' that open and close (fairly rapidly in some cases) which can corrode. Use the car every day, and it didn't matter as the arcing at the points cleaned the contacts. Put it away for the winter, and like my mower, you might find you don't get a charge first outing in the spring.

[2cams70]

Lead acid batteries are picky when it comes to charging, and really need to be floated at 13.6V. In period, 'boiling the battery' or undercharging the battery was not an uncommon problem. This is particularly the case with our cars that don't get used that often. Unless you use a float charger when the car isn't being used, the battery really needs all the help it can get.

Not true. The voltage stability is fine when the regulator is set correctly. You really need to disconnect the battery to avoid parasitic losses if a car stands for any length of time. It should be given a charge every month and a half or so or put on a float charger. That should happen regardless of whether you have a 20 amp generator or 100 amp alternator.

One of the problems with the twin cam insofar as low RPM output is concerned from either a generator or to a lesser extent from an alternator is that small 4" crankshaft pulley. Regular crossflows had a 4.5" pulley. If you run your Twin Cam at sane RPM's you can move up to a 4.5" pulley. My later Escort Twin cam has a 4.5" pulley - it may have been an original field service fix to appease complaining customers! May help with low RPM engine cooling too but that problem is largely people just getting panicky over nothing.

But who on earth these days drives a toy car with a LTC engine regularly in congested traffic!!

At the end of the day you really need to do a few sums and work out what your current draw versus your current supply is and estimate the proportion of time you vehicle operates at low RPM. From that information you can work out whether you need to upgrade or not. Unfortunately it is very difficult to extract from the aftermarket an exact plot of alternator output versus RPM. OEM's with access to the design drawings can get it easily!
An alternator may have a maximum 100 amp output but it may only put out the same as a 40 amp alternator at low RPM - particularly if the gearing is not right.

[2cams70]

Lead acid batteries are picky when it comes to charging, and really need to be floated at 13.6V. In period, 'boiling the battery' or undercharging the battery was not an uncommon problem. This is particularly the case with our cars that don't get used that often. Unless you use a float charger when the car isn't being used, the battery really needs all the help it can get.

Not true. The voltage stability is fine when the regulator is set correctly. You really need to disconnect the battery to avoid parasitic losses if a car stands for any length of time. It should be given a charge every month and a half or so or put on a float charger. That should happen regardless of whether you have a 20 amp generator or 100 amp alternator.

One of the problems with the twin cam insofar as low RPM output is concerned from either a generator or to a lesser extent from an alternator is that small 4" crankshaft pulley. Regular crossflows had a 4.5" pulley. If you run your Twin Cam at sane RPM's you can move up to a 4.5" pulley. My later Escort Twin cam has a 4.5" pulley - it may have been an original field service fix to appease complaining customers! May help with low RPM engine cooling too but that problem is largely people just getting panicky over nothing.

But who on earth these days drives a toy car with a LTC engine regularly in congested traffic with headlamps on, etc.!!

At the end of the day you really need to do a few sums and work out what your current draw versus your current supply is and estimate the proportion of time you vehicle operates at low RPM. From that information you can work out whether you need to upgrade or not. Unfortunately it is very difficult to extract from the aftermarket an exact plot of alternator output versus RPM. OEM's with access to the design drawings can get it easily!
An alternator may have a maximum 100 amp output but it may only put out the same as a 40 amp alternator at low RPM - particularly if the gearing is not right.

[Andy8421]

Not true. The voltage stability is fine when the regulator is set correctly.

I think we may have to agree to disagree on this point. The following link is to one of the excellent Lucas technical correspondence courses. The top of page 22 gives an idea of what to expect. To be fair, the overall system relied on the battery itself being part of the voltage stabilisation system - which was rather my point.

https://www.mg-cars.org.uk/imgytr/pdf/lucascourse5.pdf

Unfortunately it is very difficult to extract from the aftermarket an exact plot of alternator output versus RPM.

Here you go:

[2cams70]

I do of course agree with you that an alternator is better than a generator when it comes to current output. Both my cars came with alternators and I wouldn't consider reverting back to a generator!

What I am saying however is that I have had daily driver cars with generators in the past (not LTC with that small diameter pulley!) with completely standard electrical systems (i.e no high drain driving lamps or high drain ignition systems, etc.) and never have had a problem with over or under charging. The generator has been completely reliable. Brush failure due to wear yes but only after a considerable mileage. In one of them the battery lasted 8 years before requiring replacement.

[alan.barker]

Still running Generator on my Sprint 23 years no problem.
Alan

[alan.barker]

Still running Generator on my Sprint 23 years no problem.
Alan