Alternator swap (45A Marelli to 65A Bosch)

[droptop]

Following yesterday's successful exhaust repair, I went about fitting the 65A Bosch alternator today.
the main concern I had was that while the Marelli unit is secured with a 12mm bolt at the bottom brackets, the Bosch utilises an 8mm bolt.
After removing the Marelli, I noticed that there was a 19mm hex head at the oil filter end of the lower bracket which forms part of the filter unit housing.
I was pleasantly surprised when it turned out to be a removable guide bush and then it was off to my HiFi donor to rob the one which had a 50A Bosch unit mounted on it.
A couple of differences I've discovered in the process are that the Bosch has a slimmer body which allows it a wider arc of adjustment thereby making it easier to fit the belt and since it's mounted on rubber bushes rather than the steel ones on the Marelli, it requires an earth strap to the block.
This led me to add an additional earth directly back to the battery figuring it mightn't be necessary but it certainly wouldn't hurt.
The other slight change is I now need a shorter belt as the pulley I fitted is less than 2/3 the diameter of the OE item.
I did this as the charging light was slow to extinguish at idle and this was a simple solution, although fitting what I consider to be a better alternator may cure this anyway.
One question regarding retrofitting alternators-
Has anyone used a Japanese alternator on a Beta?
Jap units typically produce 14.4 volts compared with Marelli's 12.5-13.0v and Bosch's steady 13.2v and  would represent a major improvement in the overall running of the car, possibly even increasing ignition spark strength.
If you've found a suitable Jap unit, I'd be interested in hearing the which and how of the conversion.

Next trick will be the electronic ignition conversion from the HiFi which I'm really anxious to complete and try prior to a 400 mile road trip in a little over two weeks.

[peteracs]

Hi

I guess I am a little concerned about the reduction of the alternator pulley diameter. My main concern would be extra wear on the bearings due to excessive revs. Was this pulley the standard on this alternator or one you happened to have and fitted it?

I would be tempted to try it with the standard pulley and see what happens.

Also a note of caution on the voltage, I would guess the system is designed to charge the battery with the nominal 13v and the other items on the system also spec'd for this. Increasing the voltage could lead to premature failure on parts due to the unexpected higher voltage, specifically the elect ing notion unit which is a very early unit and hence will most likely be much more fragile than later units.

Sorry, just my 2 penny worth.

Peter

[droptop]

I can understand your caution regarding excessive voltage to the ignition system if I were to fit a 14.4v unit and as a result of your comment, I would need to fit a voltage regulator in circuit but the Bosch alternator is standard in the series 2 f/l cars which are the first to have electronic ignition and the smaller diameter pulley I've fitted is standard on a lot of VW models which are equipped with a similar alternator.
The upside of the higher voltage item is that current would be somewhat reduced so less stress on the sometimes under spec. cabling.
The RPM of the alternator will be approximately twice that of the crank so occasional bursts ok 12000 RPM will be experienced but on normal distance driving, it will be running 6-7000 and the FAG bearings I've fitted are capable of sustained running at very high speeds.
On the positive side, (no pun intended), I have spare everything available if my experiments go horribly wrong!

[Thotos]

Jap units typically produce 14.4 volts compared with Marelli's 12.5-13.0v and Bosch's steady 13.2v

  All car altrenators should give about 14.2 to 14.4 volts. If you have anything less that 13.8V or more than 15V then you have a fault.

Not all Bosch units have the 8mm bolt. The reduction in bolt size is something introduced to all alternators on later models. Your Bosch unit must be intended for a later model car.

[rossocorsa]

Jap units typically produce 14.4 volts compared with Marelli's 12.5-13.0v and Bosch's steady 13.2v

  All car altrenators should give about 14.2 to 14.4 volts. If you have anything less that 13.8V or more than 15V then you have a fault.

Not all Bosch units have the 8mm bolt. The reduction in bolt size is something introduced to all alternators on later models. Your Bosch unit must be intended for a later model car.

yes that's what I thought! voltage drops are the main issues on a beta to bad connections/earths

[droptop]

Jap units typically produce 14.4 volts compared with Marelli's 12.5-13.0v and Bosch's steady 13.2v

  All car altrenators should give about 14.2 to 14.4 volts. If you have anything less that 13.8V or more than 15V then you have a fault.

Not all Bosch units have the 8mm bolt. The reduction in bolt size is something introduced to all alternators on later models. Your Bosch unit must be intended for a later model car.

yes that's what I thought! voltage drops are the main issues on a beta to bad connections/earths

The output voltage of both my Marelli and Bosch wawere measured on a dedicated test bench while loaded at 25 amps and in my experience (10 years in autoelectrics  in the 80's to 90's), Marelli units such as the one fitted to my Lancia and other Fiat group products of a similar age were normally only capable of putting out little above battery voltage.
The Bosch units provided higher output, but never matched that of Japanese units.
Regarding voltage drop, the charging voltage on my car, when I checked it, was measured at the battery terminals and all assocaited charging circuitry was replaced and upgraded to a minimum of 10 sq. mm cable by me when I recomissioned the car five years ago.
As for the age of the 8mm bolt, they were fitted on both my facelift (1979) Betas which leads me to beleive this was period-correct.

[peteracs]

The upside of the higher voltage item is that current would be somewhat reduced so less stress on the sometimes under spec. cabling.

Hi

Sorry to ask, but I do not understand how this can be?

The higher the voltage for any given resistance the higher the current hence more stress? Or have I misunderstood what you mean?

Peter

[rossocorsa]

Peter I think you are correct for a given resistance more current will flow if voltage is increased V=IR or I=V/R if I recall correctly(?)