no alternator

[tylernt]

the alternator is a rotating mass though... surely you could gain more revvability

Oh I agree the removing the alternator entirely will gain some HP -- not only the rotating mass, but also the extra friction on the V-belt. But a cutout swich will not do anything about those. You'd have to get a smaller V-belt to go around just the crank and WP and use shims to tension it, which is a pain and wears out the belt faster.

[Vincent Waldon]

Once the alternator "self-excites" it's pretty much off to the races, although in the old days of bulbs (before the red LED) a burnt out bulb was often the cause of the battery going flat ie no output from the alt... maybe it would still work.

I'm sticking to the my story... yes the altenator does produce all current when the car is running (that's why your volt meter jumps from 12V (battery voltage) to 14V (alternator) when you start the car) but a diesel during the daylight has very little demand for current.... the gains by turning off the alternator are likely to be slight (unless the headlights are on, the blower is running, or the rad fan is on).  My guess is that a large part of the omph you see running without an alternator is not having to spin another shaft with a fan on it.

[burn_your_money]

Once the alternator "self-excites" it's pretty much off to the races, although in the old days of bulbs (before the red LED) a burnt out bulb was often the cause of the battery going flat ie no output from the alt... maybe it would still work.

I don't think that will work. The LED is tied to the exciter wire. I'm actually driving my car without the exciter wire even hooked up and it's charging fine

[Vincent Waldon]

yup that would have been my guess... generators were much more sensitive to that than alternators.

[Black Smokin' Diesel]

My guess is that a large part of the omph you see running without an alternator is not having to spin another shaft with a fan on it.

Never thought about the fan. An old alternator with worn bearings will also produce drag. Most MK2s and later vws' have DRL. Albeit working at only 90% or their capacity, it still needs a bit of current.

So killing the alt by interrupting power going to the battery will cause premature death and interrupting the exciter wire won't work.

I was looking at an AC compressor with a magnetic clutch pulley. It's a rather simple design. One two prong electrical connector and the clutch system. Main problem with this is the size of the compressor pulley. Mated to the alt, it would rev a lot less.

[tylernt]

How about using the smallest alt possible (55A as I recall) and grinding down the fan blades a bit? Switching to a serpentine belt should reduce belt friction a lot too. V-belts are very draggy.

[Black Smokin' Diesel]

How about using the smallest alt possible (55A as I recall) and grinding down the fan blades a bit? Switching to a serpentine belt should reduce belt friction a lot too. V-belts are very draggy.

I think you'd see better performance with simply going with the serp belt setup. It can't be that hard to switch to a serpentine setup without using a MK3 alt. Simply swap the pulleys for the crank, waterpump and alt. If you got AC and PS, I think you're screwed (but if you're looking for less drag, you probably dumped them anyway ).

[Zulfiqar]

well - according to the workings of the regulator and some silly experience, the bosch alternators give no load once the battery voltage climbs up to 14.1

Over here we call them bosch ones easy going alternators, when charging they will load up the engine and when purpose fulfilled they will freewheel, unlike the jap hitachi and denso ones which constantly have a brake applied on the engine - and also tend to overcharge the battery if you only use your car in daytime

[Black Smokin' Diesel]

well - according to the workings of the regulator and some silly experience, the bosch alternators give no load once the battery voltage climbs up to 14.1

Over here we call them bosch ones easy going alternators, when charging they will load up the engine and when purpose fulfilled they will freewheel, unlike the jap hitachi and denso ones which constantly have a brake applied on the engine - and also tend to overcharge the battery if you only use your car in daytime

Overcharging the battery? wow that's no good :?

[Zulfiqar]

^^

isnt it, it tends to boil the battery and reduce its service life.