My friend did the lower, Just came out from Alta!! Its not even on their website yet! he says the car is blazing fast.

Also sheds 20 pounds off the car. The new pulley weigh's less than a pound.
For under $200.00 sounds like a preformance bargain to me!

8Hp more!

 

that pulley it replaces doesn't even weigh 10lbs.... so how do you take 20lbs off? curious.....

 

Are you referring to the underdrive pulley? I think that is what it is called. I don't see it talked about much here though.

 

Though I heard somewhere that the underdrive pulley wasnt good for the car because it isnt balanced right?

 

he is talking about the crank pulley

 

I had not heard that, but the reason I heard from folks here was that there are potential problems with overheating or actual reduction in power. Do a search on "underdrive". Some good reads.

I think people use crank and underdrive to mean the same thing. Unless by crank you mean the pulley on the side of the supercharger. In that case crank and underdrive are two different things. Or so I understand.

 

Now I did hear about that. Because it changes the speed of the SC.

 

The other concern I've heard is about the accessories like power steering, AC... They lose power due to the smaller pulley and thus (supposedly) more power can be "diverted" to the crank.

Disclaimer: I am not a car guy. I am regurgitating what I have read, and might be making mistakes.

 

There is no Belt on the MCS for power steering. Its a electronic motor that spins the steering pump. Pulleys in MHO arent worth it. Maybe if you have something that is alittle ricey but for the mini just a upgraded SC pulley is about the only pulley you really need to change for power gains. And yeah you are right about pulleys turning the accessories at different speeds.

 

I've seen that pulley and to me it looks even less than 10 lbs. I am curious about the - 20 lb figure as well. Please enlighten us .

 

In my opinion changing the underdrive pulley on a belt driven supercharged car (roots type) will not accomplish anything because of the reasons stated above.

Ben

 

The Alta crank pulley in question here is NOT an under or over drive. The Alta crank pulley is exactly the same size as the original Mini pulley. The original Mini pulley weighs approximately 7 pounds and the Alta pulley weighs about 1 pound thus removing rotational weight.


Dave

 

No doubt my friend might have over exagerated a bit with the weight, Or its possible he shaved 20lbs "including" his new exhaust. Anyhow "My Mini" a preformance shop in Ft.Lauderdale's owner told him it is one of the fastest mini's he has ever driven. Burns rubber to third gear suposedly. I am going to drive it this week and I will let you guys know if it feels much faster than mine or not.

 

If your talking about Alta's lightweight crankshaft pulley,i installed one about a month ago and have noticed a smoother idle and quicker throttle response.

 

Why would they make an aftermarket lower pulley the same diameter as stock? Coming from the Ford Lightning world (Eaton M112) we run larger crank pullies to increase the speed of the SC just like a smaller SC pulley does. Going smaller on the upper pulley makes you belt contact patch smaller increasing the risk of slipage. Going larger on the lower pulley increases the belt contact patch for better grip. Side note on the Eaton M112 blowers many people are overdriving them by as much as 50% without any failures related to "over spinning". Also new gains coming from a little simple porting of the blower "exit".

 

First, as stated above, it is NOT an "underdrive" pulley like you see advertised for so many NA cars (NA = normally aspirated, i.e. not turbocharged, not supercharged, no forced induction -- for those of you who aren't "car guys" or "car gals"). This is simply a lightweight crankshaft pulley. Underdriving the MCS crankshaft would cause the SC pulley to spin SLOWER, thus creating LESS boost and making LESS power. The theory behind underdriving a NA motor is that the main parasitic power sinks suck less power from the crankshaft (i.e. alternator, P/S perhaps).

However, there was another thread on this site about a year ago detailing the main con of running a lightweight crank pulley on the MCS, namely the loss of the harmonic balancer. I suspect that ALTA would have known about this and probably wouldn't sell the product if there were detrimental effects...although it is certain that the 15% and 19% S/C reduction pulleys will speed up wear on the drivetrain, at least on the S/C, so who knows.

I wonder if any Cooper owners have seen underdrive pulleys yet...or if there's even a market for them.
Marty

 

.... got one on order and will give it a try. I'll post results from the butt dyno.

 

ah oh....... the INFAMOUS butt dyno

 

The problem is in the way the front of the Mini engine is constructed. There is very little space around the lower pulley.


Dave

 

I looked at this a while back, I figured a crank pulley 1/4" bigger in diameter combined with a 15% reduction SC pulley would give about the same SC speed as the 19% pulley w/better reliability. The other pulleys would spin a bit faster also but I don't think it would be much of a problem. The benefit of the overdrive CP w/lighter weight would probably be a more attractive product.

 

the stock cranker is 4" dia so doesn't 1/4" larger dia work out to about 6% speed up?

 

The number I got from another post here was 5.46" dia. yeilding 4.58%.

P.S. It was your post.

 

Now there's a great idea! My question would be which is the most efficient way of generating more s/c boost? Through a 19% pulley with its belt slip and eating belts on the track... or simply increase the crank pulley spinning the s/c all the other accessories faster with their associated parisitic drag?

hmmm... wish I had a machine shop handy, and the means to measure this.

 

Some the people tracking their 19% pulleys have taken off the AC. There is a replacement idler for it also. I bet the alternator pulley could easily be replaced with a slightly larger one.

 

I think maybe the point was missed. I do believe that ¼ inch more won’t fit.


Dave