Bosch Alternator- change to a smaller pulley?

[pmb0186]

also embarrassingly I’m an electronically engineering and chased electrical fault on my 66 and didn’t notice the missing ground lead going from the engine to chassis

[AussiePhil]

Hey Pete,
Thanks for the reply.
I know what you mean about the battery in the boot but I have no alternative as the engine bay is crammed packed.
A job planned soon is to run the battery cable through the firewall to the starter motor and then onto the alternator, but it would need to be well protected from heat from the headers. This should easily shorten four foot of battery cable.
It’s only raised it’s ugly head when I’ve fitted these Flex-a-lite thermos, they are rated up to 29A combined.
Today I checked the supply cable to the Davies Craig controller and cables to the thermos.
They were big enough to support the 6A thermo fans, way out for these bigger fans.
I purchased larger cables today and will start fitting them tonight.

I googled this today.

Q, Why is my electric motor pulling high amps?

A, This can be caused by a low supply voltage, resulting in the motor drawing in more current in an attempt to maintain its torque.

I’ll complete this job and if the problem persists I’ll test as per your recommendation.

Hey Pete, I’m located in Bathurst.

Cheers Phil.

[FickleLife]

Hi AussiePhil, sorry it took me a while to reply - I haven’t checked this thread in a while!

So it’s still not 100% solved but I've taken some steps

I’ve bought and installed an aeroflow 140 amp alternator. I’ve been chatting to their tech support and they have been great. They provided me with this which is very helpful. https://i.imgur.com/d1YlyI9.png and here’s the manual for the alt https://aeroflowperformance.com/pub/media/Instructions_PDF/AF4273-1140.pdf

The manual states to calculate pulley on the inside diameter (where the belt sits) not the outside diameter. I’ve spoken to aeroflow tech support and they insist on the 44mm number (as stated in the manual) for the calculation. The alternator came with a 68mm OD, 44mm ID pulley (and the manual is wrong stating an 81mm OD- they are fixing it). Pair that with my March underdrive crank pulley at 140mm OD and I’m calling it 117mm ID, I have a 2.65 ratio.

I am guessing I am idling at 600rpm (I like it low ish) but I am not sure so I have a nice moon eyes tacho that I’m going to install. At 600, the alt would be spinning at 1590rpm which is too low at idle. My target is 2000rpm to give me 60a to be safe with the elec fan running at idle, but 1800 for 42a might be enough.

That powermaster pulley you mention Phil is interesting. Is it this one  https://www.ebay.com.au/itm/255692844342?mkcid=16&mkevt=1&mkrid=705-154756-20017-0&ssspo=V0KU3YCwQTa&sssrc=2349624&ssuid=v5w5lP4lS-O&var=&widget_ver=artemis&media=COPY ?

At 54 OD and my crank pulley at 140 OD I’d be on 2.59 but it would have to be better than that as the aeroflow is a 68mm OD. Aeroflow insisting to calculate on the 44mm number is making it hard for an apples to apples comparison so I’ll prob get that power master pulley and install it as it’s quite a bit smaller

so:
1) next step is to put in phat pos and neg ground cable (existing cable looks small ish)  to the alternator.
2) hook up tacho to calculate my true alt rpms
3) power master alt pulley
4) if all that doesn’t work, get a larger crank pulley

The crank pulley is interesting. I have a 4 bolt and I can’t seem to find anything aftermarket (billet alu) that is larger than 5.75 inch/146mm in a 3 groove (I’ll be putting on aircon at some point). Had a look at March and cfv and no 6inch plus sizes. 5.75 might do the job, just won’t know until I get the tachometer set up.

[AussiePhil]

Hey Ficklelife,
Funny you raised this post, I fitted Flex-a-lite dual thermo shroud fan setup and draws a heap of amps over my previous ones.
I’ve machined my alternator serpentine pulley down to 48mm OD to get the engine / alternator ratio back near to standard but my 95 Amp alternator can’t handle two fans and headlights on.
I’m looking for a 140A alternator myself.
My alternator is attached to my supercharger brackets so I have no idea what the alternator came off.
I need to buy something like you’ve bought but I need preferably locking tab 120 degrees to the left of the pivot.
I’m going to have to take it of and see if the auto electricians can identify what car it’s off.
I know it’s a Jaylec 65-0007 and is advertised to fit a Falcon EB EL etc. but eBay don’t have 140A for these cars.
Jaylec won’t get back to me, I’ve left message off there web site and phone call, I’ll get my husband to reply?
Think I may machine a bit more off the pulley and see!

[AussiePhil]

Hey All,
After spending two weeks thinking I had an alternator problem, machining down the alternator pulley to get back to the original Engine/Alternator ratio, and machining a new idler pulley to suit and redoing some electricals, But in the long run all for the better. One good thing I also machined a smaller power steering pump pulley, it was a bit lazy down low.
It turns out with an EFI engine with a bad Idle Air Control Valve shows the same symptoms as an overdrawn alternator shutting down the engine.
Took the idle air control motor out and one side of the tapered Bakelite plunger was bruised.
Machined to bruise out refitted to the car and guess what?
It was the idle air control motor all the time! I had no idea the Idle Air Control was so critical in an EFI engine idle function, not sure how a carburettor engine handles change in load.
The engine did take a bit to get going but I suppose the IAC had to reset itself, two fans started with no effect to the idle, waited 10 seconds and turned the lights on with no effect to the idle.
I will buy a new good quality IAC soon. I won’t skimp on this one! The more expensive ones have steel or brass plungers.
I’ve got a charity do on Sunday so just in time.
I can not believe the work I’ve done thinking it was the alternator, and to top it of was the timing of fitting the fans, and you cant believe the symptoms are exactly the same at idle! Except IAC causes hard to start!
I 100% thought it was the alternator!
Cheers Phil.

[FickleLife]

Glad you’ve diagnosed your problem finally! (And very glad for your help with my problem while you went down that alternator rabbit hole :)

To give an update, I installed the tacho. I’m idling at a nice lazy 500rpm when warm haha so that needs to go up. I’ve ordered the 54mm alt pulley and that should give me 2.6 ratio over the current 2.05 (need to calc at OD for apples to apples comparison). So idle at 700 and we should be at 1820 alt rpm getting 42a according to the aeroflow alt manual which should be enough for the elec fan but if not I’ll just keep adjusting the idle up for now until the voltage is acceptable when the fan kicks on.

I also found https://store.alternatorparts.com/pulleys-and-clutch-pulleys.aspx in the US which basically has every alternator pulley you’d ever need, no doubt at a spicy shipping rate.

[FickleLife]

Prob no need for the new pulley. At 600 rpm I’m at 14v. Nice!

[AussiePhil]

Hey Ficklelife and Peter,
My idle still not 100% right, I think the alternator is on the edge with no reverse.
I’m running the car with only one thermo fan that keeps the temperature at somewhere near 180 degrees, + or - depending on traffic or travelling.
The flex-a-lite fans have a bit of a spike on start up, I don’t think that’s good for the ECU.
I’ve ordered a PowerMaster 200A Street alternator from Summit.
It should be here next Wednesday.
Cheers Phil.

[pmb0186]

That what I would do

[AussiePhil]

Hey Peter,
I’m also going to fit a Flex A Lite 107012 PWM Variable Speed Controller.

Cheers Phil.

[AussiePhil]

Hey Peter,
PowerMaster alternator turned up today.
Absolutely brilliant service from Summit USA.
Ordered on the 9th and delivered on the 19th.
Fitted like a glove, instructions were brilliant, had to fit a supplied resistor to the 12v ignition wire.
Need to adjust belt tension next and give it a go.
Not sure if I’ll go ahead with the flex-a-lite Variable speed controller, it doesn’t have a temperature display like the Davies Craig controller and it turns both fans on together, and is a bit hit and miss control adjustment, were Davies Craig Controller has a digital set and 10s delay between fans coming on. But it does vary fan speeds compared to water temperature.
Cheers Phil.

[pmb0186]

Simple advice for all, above 12.6v battery charging and under 12.6v battery discharging.