Single Pulley?

[65 mat]

My friend's RS is fitted with a single pulley ( fan pulley ) as opposed to the usual triple one ( fan/ air con/ power steering). He swears that it allows the engine to rev more freely and that it releases extra BHP at the top end of the rev range. He has no dyno evidence to prove this however so I'll just have to take his word for it ([:-]).
Is there any truth in what he is saying? By the way, you cannot buy the single pulley, he had it made especially.

 

[PhilRS]

Does he have an RS or a CUP engine in his 964 RS? Check numbers...

CUP engines, I believe, had a single pulley.

ORIGINAL: 65 mat

My friend's RS is fitted with a single pulley ( fan pulley ) as opposed to the usual triple one ( fan/ air con/ power steering). He swears that it allows the engine to rev more freely and that it releases extra BHP at the top end of the rev range. He has no dyno evidence to prove this however so I'll just have to take his word for it ([:-]).
Is there any truth in what he is saying? By the way, you cannot buy the single pulley, he had it made especially.

 

[Tony]

Matt,
I think all the RS's have a single pulley, certainly the LHD ones do - it's a function of the smaller altenator and combined fan/altenator drive. The pulley is made up of several parts and these vary by engine type but m64/03 (RS) are available.

Tony

 

[Tony]

If it is the crank pulley, these are normally fitted with a crankshaft damper so it is a bit of a lump, however I believe a pulley is available for another model (993RS ?) without the damper.

Tony

 

[964RS]

This photo is the crank pulley arrangement on my 964RS Lightweight.

The additional pulley wheels would be for the non-existent air-con/power steering/anti-smog device. This pulley wheel is on the end of the crankshaft - lightening the pulley will not add any more horsepower but does leave more of the horses available to accelerate the car because less are wasted accelerating the crankshaft. This is surely a neglible effect as the pulley only weighs 1.162kg so estimating, optimistically, if we lose 2/3 then we are saving - 0.75kg? There will be less inertia in the powertrain yes and a negligible effect on idling.

Although there should be no rotational effect I'd consider that as the engine was conceived with the large pulley - that's how the crankshaft should be dynamically/harmonically balanced.

 

[65 mat]

Excellent summary Paul!...and that concludes todays lesson pupils.

 

[ChrisW]

Paul, how on earth did you discover the weight ? Or should I say, mass ?

Both mine are triple pulley -- RS and RS C/S.

 

[964RS]

I managed to snaffle a comprehensive list of weights for loads of components off the Rennlist forum. 'Tis great reference. [8|]

 

[Tony]

Just for completeness this is what one looks like without the crankshaft damper.

 

[65 mat]

So is that a double pulley looking at the picture Tony?

 

[Tony]

Technically I suppose it is - al I know is it's the std one without the damper.

Tony