Power pulley / underdrive pulley kit
- Thread starter Frentz
- Start date
If it what I thing it is looking at the pictures etc.
It is an undersized pulley, for a pump, to understand these you first need an understanding of how the pumps work on your car they need to do a couple of things move enough volume and at the required pressure, the pump will have a ‘pump curve’ this is where it works best
Too slow and it under performs too fast and you need to bypass/bleed off the excess
So the BMW engineers calculated it for normal driving conditions and the very top and bottom of the range is likely to be a small compromise
So in motorsport when the engine is at 6500rpm or above for most of its use in anger the wasted or the bit that is bleed off can now be recalculated so a smaller pulley is used and at 7000rpm the pump is at the most efficient, but at lower rpm it is under preforming
So unless it is a race engine best to leave it as the cleaver engineers at BMW designed it (yes I know a 4yr old did the roof motor location)
It is an undersized pulley, for a pump, to understand these you first need an understanding of how the pumps work on your car they need to do a couple of things move enough volume and at the required pressure, the pump will have a ‘pump curve’ this is where it works best
Too slow and it under performs too fast and you need to bypass/bleed off the excess
So the BMW engineers calculated it for normal driving conditions and the very top and bottom of the range is likely to be a small compromise
So in motorsport when the engine is at 6500rpm or above for most of its use in anger the wasted or the bit that is bleed off can now be recalculated so a smaller pulley is used and at 7000rpm the pump is at the most efficient, but at lower rpm it is under preforming
So unless it is a race engine best to leave it as the cleaver engineers at BMW designed it (yes I know a 4yr old did the roof motor location)
this kind of spare parts is really common in V8 tuning in USA.
it seems strange to me that they are so common if they can cause problems.
the first advantage is that the pulleys are lighter: no doubt about this improvement.
the other advantage is the different ratio, but usually 10%. it should be very little...
an acquaintance only changed the primary pulley on the 3.0si, and clearly had no problems.
Edd China also changed the pulleys on an '88 mustang, the idea comes from here.
then I found that these kits also exist for the S54.
they declare that there are no problems, and as far as I can know I do not find it hard to believe.
I was just looking for some feedback, I'm going to look for it on M3 owners in the USA
Edit: from M3 forum
"Turner offer 2 differents sets of power puller: the street version and race version."
it seems strange to me that they are so common if they can cause problems.
the first advantage is that the pulleys are lighter: no doubt about this improvement.
the other advantage is the different ratio, but usually 10%. it should be very little...
an acquaintance only changed the primary pulley on the 3.0si, and clearly had no problems.
Edd China also changed the pulleys on an '88 mustang, the idea comes from here.
then I found that these kits also exist for the S54.
they declare that there are no problems, and as far as I can know I do not find it hard to believe.
I was just looking for some feedback, I'm going to look for it on M3 owners in the USA
Edit: from M3 forum
"Turner offer 2 differents sets of power puller: the street version and race version."
I have the VAC MotorSport pulleys installed for over a year now with no issues. Underdriving the PS pump makes the steering a bit heavier, which is what I prefer. The pulleys themselves are hardly any lighter than OEM as they are bigger to under drive the ancillaries and therefore reduce power losses. As said above, don't be deceived by the claimed HP gain but they should provide a few extra HP to the wheels.
