I'm about there right now too. Trying to find out some good info as to why people are ditiching it and the potential problems. Not sure why it's so hard to design a lightweight one with a balancer/dampener

 

What do you think determines linear velocities? The diameter of the pulley and the RPM's. Linear velocity = the RPMs X the diameter X "pie". So ratios of diameters is just as valid as ratios of velocities.

It's a ribbed blt... so you won't add the full thickness of the belt since it sits down in the groves unless the pulley diameter is measured to the bottom of the grooves... just checking a stock pulley I happen to have sitting right here... The pulley is 2.59 to the top of the grooves. At best you would split the difference and use half the thickness of the belt. The ribbed side and flat side of the belt are moving at the same speed.

Since it the crank pulley is making contact with the ribbed portion of the belt, it is the ribbed side that is "travelling" at a certain linear velocity for a given crank RPM. That same linear velocity is transmitted to the SC pulley using the same ribbed side of the belt.

The bottom line is you can use ratios of pulley diameters measured to the top of the groves.

 

That's correct. The effective diameter of each pulley is the diameter of the pulley plus half the thickness of the belt. This is clearly spelled out in the Bosch Automotive Handbook and agrees with the 2.06 ratio published in the white paper on the MINI engine.

That's incorrect. Because the crank and supercharger pulleys are not identical in size, adding half the belt thickness to each one changes the ratio. Again, run the numbers both ways. If you ignore belt thickness, the ratio of crank to supercharger pulley does not add up to 2.06.

 

My feeling is there's next to nothing to be gained from replacing the balancer and until someone offers something like this: http://theoldone.com/components/fluidampr/
, there's no point in changing it.

If you think it's going to make a difference in power you are very much mistaken. Changing the ratio to the SC will make power but the weight won't and you can up the boost by other means.:smile:

 

My post was to say that if you have the diameter change percentages (and some info on the belt, to be perfectly accurate) then you don't need to use the absolute pully diameter in your calculation, as many were wondering off to do. My statement was not that this is the only way to get to the answer, but it was one of many correct ways.

All better now?

Matt

 

How do you use, only, diameter change percentages, if you want to use
belt info? I think that if you want to use belt info, you need to use pulley diameters because when the belt dimension is added, it changes the ratio between the crank pulley and the SC pulley.

 

Title says it all.

 

Glad to be correct about something. It was pretty embarrassing to start
this thread with a major error in thinking.

15 + 2 = 18.97 (% SC overdrive relative to stock , incl. belt info)

 

PILO was working on this like 6+ months ago and what ever happened to it?