I'm installing a 17% alta pulley this Saturday and I was thinking of putting a lighter crank pulley. Is this a good idea. Does the MCS need a heavier crank pulley for balance? Would I be opening a can of worms? If it does work, then how well. Does anyone have any good hp numbers or butt dyno's?
Mario

 

Yes! People go from "you don't need a balancer" to "your car isn't going to last very long" approach. I have one and it did way more than I expected. In all honesty I didn't think it was going to do anything at all (I have a 0%) It most definatly runs through the RPM range a lot quicker. I have a dyno graph HERE. I did it right after the crank pulley install. I didn't do a before run because the dyno's not cheap. Good Luck -- Johan

 

If your worried about it...go with a 0%. It's like 6 lbs lighter and won't underdrive the crank.

 

So the 0% helps quite a bit? I had the 2% on my last MCS but my current MCS I'm trying to keep it in STX class in autocross and it doesn't allow larger than stock pulleys. So I've thought about the 0% but was unsure if it would actually help since no boost was added. Just weight reduction......which is good for the benefit of revving up quicker.

 

Overdrive the crank. +1-4%

 

Yea like I said I was really impressed. I did get more boost too, I have no clue why Also boost comes up quicker with it revving quicker. If you could run a 0% and get away with it, I would in a heartbeat! That's just me. -- Johan

 

There are limits to every mechanical device.
there are so many threads that already exist that discuss the benefits and the great woes of overdriving the supercharger to 19% and beyond. RPM realms and driving styles are often the watershed issue with overdriving pulleys.
I would be very careful and get to reading the threads that have alread discussed this at great length.

Paul

 

why? what benefit does this have

 

Larger crank pulley and a smaller supercharger pulley result in spinning the supercharger faster...

 

We did quite a bit of research then testing on the crank pulley. I am willing to warranty it with the WMS warranty.

Just to clear a few things up - the crank is what is being powered by the power stroke of the engine. The piston moving down the cylinder turns the crank, so it is the crank that turns everything else. You can't over or underdrive the crankshaft. By putting on a larger pulley you are overdriving (spinning faster) all of the other components - A/C, alternator, and supercharger. Obviously, the last one is why we oversize the crank pulley. I do a 2% oversize as the limit, but there are other more aggressive tuners out there that take it all the way to 4%.

We have done extensive track time and street time with both the 0% and 2%, and we have yet to see a failure on an engine from it. That backs up what our research found. I have since installed over 150 crank pulleys.

Why do a 0% and why does it work? You are removing parasite drag that the motor has to turn in the form of weight. It isn't that you are really making more power, but more that you are releasing power that was being used to turn the crank pulley instead of the wheels. With reduced mass, you also have faster acceleration - rate of change of velocity. So you can go from a steady RPM to another steady RPM in less time.

Here's a link to our pulley.



Hope that helps!
Randy

 

That's why you make the big bucks Glad to see you posting again Randy -- Johan

 

I only make the big bucks if you guys buy stuff from me because of my freely given knowledge .

Randy

WMS Store

 

Well I guess i will order it today. What do you think if I go 2% to my 17% Pulley? Does this spin the supercharger slower than just going with a 19% pulley?
Mario

 

Yes, it does spin the supercharger slower than a 19% due to the ratio. I would do the 0%, or a 15% sc pulley and 2%, but I am conservative. I do have several customers with the set up you are looking at.

Hope that helps!
Randy

 

The percent of sc overdrive with a stock crank pulley and a 19% sc pulley is 22.12 and the percent of overdrive with a 2% crank pulley and 17% sc pulley is 21.68. They are very close.

 

So with a stock crank pulley and a 19% supercharger pulley, the supercharger is actually overdriven 22.12%?? Where does that come from? I thought the "19%" in the pulley description was a measure of how much the supercharger would be overdriven with that pulley installed.

Scott

 

It sounds like a good mod for MC owners... lighter weight to cause the engine to spool up faster.

Should also be obvious to the MCS Croud as well

 

From what I've read in these threads, I believe that the 19% reduction is in s/c pulley size and the 22.12% is the increase in supercharger spin rate. BUT, I am not close to being that knowledgeable on the topic, so someone else should definetely chime in on that one...

 

It is my understanding that the effect on the MC is a lot less since you are only loosing a pound, or two. (The MC pulley is lighter than the MCS one).

 

I was thinking that, too, but if 19% is the actual reduction in size, then the pulley would be spinning 23.46% faster, not 22.12%.

Oh well, like you said, maybe someone else will chime in.

Scott

 

i'm of the old school of thought. the harmonic's there for a reason vibration over a period of time can't be good at the rpms we run these cars at. if you've got a pre= 05 then look into the new balancer.it's the best compromise ;it's lighter and still sucks up the vibes(better than earlier one).

 

I just bought an Alta 0% crank pulley and now some people have me scared about warranty issues or possible problems in the long term of use. I havent put on yet cause i have doubts, i would like to clear up any doubts i have and know if its going to cause any problems.

 

No worries! Just read Randys post again and you'll be fine! -- Johan

 

Can you expound on the warranty.

 

Here are the links to the warranty and installers.