Does anyone have any experience with underdrive pulleys on a MC?

 

I also would be interested in this.

 

I don't have the pulley on my vehicle at this time. I'm actually utilizing it as a paper weight. I bought a pulley from Alta and tried to put it on with negative results. I had difficulties fitting the pulley flush to it's mark. I had the MINI towed to a local MINI Shop (The Custom MINI Shop in Fresno, CA) to see if they could help. Steve Tech also had some difficulties and called Alta himself. They informed him the crank shaft on the S is a bit smaller than the Non-S. In order to fit the pulley onto the Non-S, you have to heat the pulley prior to applying it to the crank shaft. They did't have an oven handy at the time, so the stock one went on. Steve showed me the difference between the two stock pulleys (S/Non-S) and theres a huge difference. The S pulley is three times as heavy as the Non-S. So, I chose not mess with the hassle of applying the lightened pulley when there wasn't really a significent difference with the lightened one. Don't get me wrong! The lightened pulley is lighter than the stock one, but not much.
Just my two cents....good luck!

 

^Yeah, the weight thing is one thing but he was more interested in the under drive pulley. I believe Alta makes R50 specific underdrive pulleys, don't they?

 

I have read that the idea behind an underdrive pulley is to gain HP by reducing the parasitic torque of the alternator, water pump and any other accessory run by the belt. I am just wondering if there is any real gain with it?

 

I'm a bit confused when you guys say "underdrive pulley." Besides the crank shaft pulley, is the Alternator pulley, the coolant pulley, the air conditioning compressor pulley, and the tensioner. Alta does sell a stock sized crank shaft pulley, and that was the one I was talking about. Alta also sells an Alta-Nator reduced pulley, but it's only to be used with oversized pulleys. I called Alta and asked if an Alta-Nator could be used on a non-S. They said yes, but the alternator would not charge the battery and problems would start from there.

 

I have been reading that the theory behind the underdrive pulley is to slow down the alternator, water pump, and any other components driven by the belt. The theory is that this reduces the parasitic torque of those components, and increases the torque available to the wheels. My concern is that by slowing down these components is what happens to the cooling, and charging capacity of the car driven under normal circumstances.

 

alta does make a stock size crank pully. And a 5% undersize alternator pully. The ac compressor is clutched, so unless its on, not a huge point in doing anything with it. A water pump pully might work good, but might also cause overheater in traffic, and long idle periods. However, most waterpumps spin way to fast at high rpms, which would help top end power with an underdrive pully, but dont know if it would be worth it, depending on your cars useage. Personaly, i dont give a hoot about driveability, i think we are all pampered with ecu controlled vehicles, and have not problems with driving a beast. So mods like that would be up to your personal taste, but you will probably be on your own as far as making them, as i dont see anyone making them in the future. Namely because the waterpump on the s is integral with the SC. They would be a great seller if the waterpump was not on the sc, due to the oversizing the crank pully.

Just my 2 cents

Beecher