Why does the G40 have a 65amp rated alternator?

Old Mk2 have only 45amp rated.

From Mk2 to Mk3 the big new electric consumer is the fuel injection pump.

The Mk3 GT and G40 fuel pump requires 6.7 amps.

There is also a transistorised ignition amplifier which needs a fraction more than points I think.

Mk3 have 55amp rated alternators.

Heated rear screen? No, no change there.

They had manual window winders and manual sunroofs, no heated car seats.

The electric fan was two-speed, but didn't consume more current on fast speed, just less on slow speed.

It wasn't the car hifi. Sure Mk2 had 6Watt mono radio with single front dash speaker, or later stereo cassette player maybe 2x10watts

but not 2x100watt amp.

Halogen headlamps, foglamps. Silly dim-dip resistor. Slighlty more than old incandescent bulbs, and some Bosch headlamps can take either shape bulb 920? or H4.

Same 063 capacity battery.

The alternator shape is presumably Mk2-like cause the development project produced 500 Mk2 G40.

Polo engine development was called appraently Projekt Prometheus in Wolfsburg.

None of it enough to demand an extra 13.3amps.

Anyone think of anything else?

Theories

• Could it be that the G-lader is also tapping power from the aux-belt(s), so the alternator needs to produce more current per rotation?
• Or, due to the charger it will spin up faster and VW did not want the windings to fuse or the regulator to melt, so went for the next bigger Bosch model?

humm anyone no of a higher amp alternator upgrade for polo gt g40 ?

other than just fitting a smaller pully to it so it so it has more rpm then have problems finding shorter belts g40 humm

One thing I read somewhere, possibly in the brochures was that when you specified foglamps for a Mark3, they uprated the alternator to 65amps.

It was a similar story with the Mark2, as my Coupe S has a 65amp alternator, and was fitted with grille mounted foglamps.

other than just fitting a smaller pully to it so it so it has more rpm

That's the whole advantage of an alternator over a dynamo it will give it's output at any rpm (within reason) so spinning it faster will not make it give more output

Not sure if you're only talking about mk2 GT's/g40's or 2f ones too but i happened to find my manual yesterday for the 2f wich is only an spi 1.3 and it does point out a switch for heated seats if the person had then installed. Not that long ago i saw a thread on here where the optional extras list was posted and that claimed electric windows were an extra too, don't know much about electrics but i would of thought they use a reasonable amount of power maybe? But as i said that's a manual for a 2f so i don't know if those extras were put on pre 90's cars.

Because racecar.

G40 alternator is g40 specific so I guess they just made one to cover all possibilities, you could spec them right up in some markets, electric sunroof and the like.

If they are used for optional extra's, surely some non g40s would've come with more optional extra's..

You can get 65amp non g40 alternators too. I've got a couple.

Ah right, how is the g40 specific alternator specific to a G then?

Other than the twin V belt pulley?

Dunno

3 part no's on vagcat for 65a alternators no mention of them being tied to an engine code

036903017HX

alternator

55A

(1) 031903017CX

alternator

55A

(1) 036903017KX

alternator

65A

(1) 068903017TX

alternator

65A

(1) 068903017MX

alternator

65A

Also lists 65a altys for a 1980 polo

036903017AX

alternator

45A BOSCH /

(1) 036903023NX

alternator

45A MOTOROLA /

(1) 052903017AX

alternator

55A BOSCH /

(1) 036903023PX

alternator

65A MOTOROLA /

(1) 068903017MX

alternator / also use:

65A 068 998 329

cant make alot of difference as people use a GT alternator on a G40 when going down the turbo route....except me

The early alternators have a plug while the later ones have a bolt for the output. I have one of each in 65A. Makes swapping them a bit awkward as I have to change the loom as well.

Wild speculation:

The G40 alternator has no need for the tensioning system as the charger does the tensioning, so something missing from it perhaps in that department?

Also could be that the shaft length is different to accommodate for the wider pulley, although I'd've thought a high offset centre on the pulley would get around this.

there is another page on vagcat listing the alternator securing parts, quite a few are g40 specific. i should have posted the link but its easy enough to find

2 030199181E engine carrier/ G40

(4) 030145933A v-belt 8X1015MM / G40

5 030903147 bush/ G40

7 068903147E bush/ G40

(10) 030903253B support/ G40

11 030903275 spacer bush/ G40

12 052903285 flat round head bolt M 8X27 / G40

15 N 0103933 hexagonal head bolt M8X120 / G40

19 N 90908301 shouldered hex. nut, self-locking M8 / G40

Edited 26 January, 201313 yr by grungeisdead

i may be wrong - but it was my understanding that when an alternator is turning whilst charging it creates a parasitic drag which gets worse with 2 things :- load and speed.

A larger alternator for no real reason is a bad thing as there is more rotational mass from the coil windings so you create unecessary drag.

BUT! going back to load and speed- a larger gear on a larger alternator will create the same/higher power output for less rotations. Bare with me on this.....if you had a 45amp alternator and used 30a then you would be utilising the alternator 66% and it would create a good bit of drag but not much, but if tou had lights stereo and loads of accessories on then just suppose you are up to 40a - now the alternator would be getting bloody hot- working really hard and creating a lot more drag - also will eventually die quicker.

if you had a 65a alternator you could run at the higher amp draw without creating a high drag/load on the charging system.

The G40 has the supercharger creating a large drag already- so the ability to have a larger alternator (stolen from the scirocco 1.6GLX) means it could be geared to spin less and create the same output for less load and drag.

I'm sure theres something else I've missed but its early and i apoligise.

So, I guess these would just bolt straight on any coupes.

no- the G40 used the charger to tension the belt, and as such the normal adjuster wont fit a G40 alternator- you will need to make up a bracket.

i made a simple bracket on my G40 turbo to use a 90a golf alternator:-)

i may be wrong - but it was my understanding that when an alternator is turning whilst charging it creates a parasitic drag which gets worse with 2 things :- load and speed.

A larger alternator for no real reason is a bad thing as there is more rotational mass from the coil windings so you create unecessary drag.

BUT! going back to load and speed- a larger gear on a larger alternator will create the same/higher power output for less rotations. Bare with me on this.....if you had a 45amp alternator and used 30a then you would be utilising the alternator 66% and it would create a good bit of drag but not much, but if tou had lights stereo and loads of accessories on then just suppose you are up to 40a - now the alternator would be getting bloody hot- working really hard and creating a lot more drag - also will eventually die quicker.

if you had a 65a alternator you could run at the higher amp draw without creating a high drag/load on the charging system.

The G40 has the supercharger creating a large drag already- so the ability to have a larger alternator (stolen from the scirocco 1.6GLX) means it could be geared to spin less and create the same output for less load and drag.

I'm sure theres something else I've missed but its early and i apoligise.

i have my polo gt 3f alternator infront of me and it says 65A on the bosh sticker

what amp are the scirocco 1.6GLX do they fit straight on ?

the scirocco GLX was 65a and comes in 2 forms - round eyelet and spade connection plug - thats it! its identical to the G40 alternator and i bought one for my G40 and I've still got it brand new in its box.

you may find that most VWs share there alternator from another car in the range/past range but with a different part number revision.

what are you trying to do? fit a bigger alternator to a GT? - its in the FAQ if you are

mine tensions just fine without the charger to tension it but there is some 'modifications' done to it.

my 83 bready had a 65a alternator on it maybe it was upgraded at some point :/

the front plates are different on the G40 one to the rest of the range in terms of lower fitting and bolt location. so like Kiz says you need to make a small metal bracket. There was a template on here a while back and a fitting guide.