Anyone know a part number for an alternator pulley with a freewheel? Just about to change my alternator and a freewheel pulley would be a great addition.

PS When the gearbox changes up or down there is a great load on the alternator belt to slow or speed up the alternator. If you have a freewheel the alternator can keep spinning when the engine revs drop reducing load and increasing efficiency.

 

Did some research on this and the alternator for more modern cars have splined input shaftes which the one on the XK*8 does not . Did find one supplier with a poor photo and in Lithuania...cost more to send it back if its wrong than it costs so I think the answer is no.

 

That is a real shame because there is strong reasoning behind your freewheel idea.
Such an upgrade could reduce the overall burden on our Battery, which seem to plague our cars and is the root of many symptoms.
I, for one, would definitely upgrade if a suitable product was available.
Can you please share any shaft, Pulley dimensions/specs that you have. Thanks.

 

While the freewheel concept is applied to all modern cars and jags you have the wrong concept. When the engine is running the battery is doing nothing ,the alternator supplies all electrical loads and you are carrying a load of lead scrap.
I think the real problem is that the alternator fitted does not get the battery voltage high enough ....a dynamo would take it to 15v and an older Lucas alternator to 14.4 but the desire for no maintenance has reduced the voltage to 14v which is why we need battery maintainers to keep the car going.
I have experience with canal boats ( live on boats reliant on batteries for power) and the alternators were modified to get the batteries up to 14.7v but the owners were not bothered about topping up and did not use sealed batteries.

 

Yes, I understand.
I was referring to the Alternator function of recharging the Battery. The energy from cranking takes over 300 Amps. If we approximate that it takes 10 minutes of normal driving for the Alternator to fully recover the battery, then we can say that the Freewheeling upgrade might reduce that time period to 9 minutes (just guessing). This would improve battery health for owners that use their cars for regular short journeys such as just 5 miles to a shop and then restart to head back.

 

Sadly PK you are in old wives tail land again ..the starter draws about 120A when cranking not the 300-400 A often quoted which is the stall current. If you crank for 2 seconds thats 0.00055 hours X 120 A is 0.06 AH. Your alternator will only charge at about 15 A max ie takes 25 seconds to re charge the battery.

Them old wives were not good at maths or facts

 

Haha. I’m simply saying that there could be a measurable benefit. It’s not unreasonable to expect the free extra rotations of the Alternator to yield something.

 

25 seconds?
Batteries, and the charging of them, don't work that way.

 

Sad. JJJ .My grade I auto electrician certificate and PHD says they do along with 40 years trying to knock old wives' tails out of auto technicians.
The advantage of the freewheel is longer belt life ,slightly improved charging times and better fuel consumption ie less waste .

 

Thank you.

 

PK remember that once the alternator reaches about 4500rpm ( runs at 3x engine speed- max 15000) it produces full output so letting it continue to spin higher for a couple of seconds when you change up is a minimal charge improvement it mainly wear and mpg.
The biggest problem with our alternators is the low output voltage from the fixed regulator. Modern alternators are computer-controlled and will charge to 14.4v before dropping back to about 13.8v to save petrol.