Originally, I was thinking of using a 17% SC Pulley and a 2% Crank Pulley in Morgan.

However, after reading many of the threads, it doesn't seem like any significant benefit can be attributed to the lightened characteristic of the flywheel. I'm only concerned with the lightened aspect since it seems to be the only real benefit. If I wanted to get the effect of a 19% SC pulley, why wouldn't I just buy the 19% SC pulley and save myself $150? Obviously, this is different for people that already have a SC pulley, but want more boost.

I guess what I'm really asking is why I would want a 17/2 combo instead of only a 19% SC pulley and save myself the $150 and installation hassle.

 

The small size of the 19% pulley can lead to belt slip (loss of boost) and in high rpm use (track) can lead to belt failure. The 17/2 combo gives improved contact to the belt, and helps reduce the amount of slip.

Your thought process makes a lot of sense, just thought I'd give you the flavor of the reasoning for the 17/2 combo.

 

Strictly speaking, there is a performance benefit to getting the crank pulley, since it's lighter and you therefore lose less energy to it.

Practically speaking, you also get the benefit of less low-rpm hesitance. My car got smoother and easier from the roll.

But, although I have experienced absolutely NO ill effects, there are unanswered questions for some about the reliability. It's like the SC pulleys a couple of years ago- people are nervous.

I have an M7 16% SC and 2% crank, so you know. And, I love them!

 

Thanks for the quick replies.

I'm aware that a 19% pulley will cause more belt wear and possible belt failure and I think I can accept that. I'm not yet sure, but it seems like a lot of 19% pulley people love their pulleys, despite the belt wear and belt failures.

Regarding the belt contact/belt slip, isn't it remedied by a 19% belt?

I'm only an economics major, so I don't understand much about physics and the loss of energy. It makes perfect sense, but what does it really mean practically?

Is the line of thought?
Lighter Crank Pulley => Lose Less Energy => Less low-rpm resistance

If this is true, doesn't getting a more reduced SC pulley (e.g. - 17% to 19%) also reduce low-rpm resistance. I'm sorry if I'm convoluting the whole idea of a pulley. I only have what I've read to base my observations. From what I've read pulleys basically produce more boost across the rev range, producing more power across all rpms including low-rpms. If that's the case, couldn't the decrease in low-rpm resistance due to the effect of a more reduced pulley?


It would be nice to see a person with a 0% crank pulley respond since they can isolate only the lightened aspect of the crank pulley. Any takers?


Quick Question: One of the benefits of the lightened flywheel is that the decrease in mass decreases rotational weight amounting to ~100 pounds, I think according to the ALTA website. Does this mean my car is actually 100 pounds lighter? As I said, I'm not very good in phyics and never really understood the idea of rotational weight removal being so much more effective than removal of static? weight . I just took it for granted.


Sorry for the long post, I hope somebody takes the time to read it.

 

The stock crank pulley weighs in at a hefty 7 or 8 lbs. The lightened crank pulleys from Alta weigh a scant 0.9 lb. This means that when you drop the hammer, your engine will be able to accelerate quicker, because it has to rotate slightly less mass than before. As we all know, weight is horsepower's arch nemesis.

Some argue that it doesn't give you an actual measurable horsepower gain with a lightened crank pulley; you'll just notice that it will accelerate a tiny bit more vigorously, especially if you floor it abruptly. Basically, the engine will be able to start accelerating quicker—a quicker response to your foot's input...

Think of it like this: compare the effort it takes to spin that big wheel on the Price Is Right, versus a bicycle wheel. Which one takes less effort? Why, the lighter bicycle wheel, of course...


You've also mentioned a lightened flywheel. I'm not sure if you're confusing the two of these parts, but they're totally different parts...

I cannot comment on the effects of a lightened flywheel, but I would do a search for just that: "lightened flywheel". This thread might also help enlighten you on that subject: https://www.northamericanmotoring.co...tened+flywheel

 

Sorry, I didn't mean flywheel, I meant lightened crank pulley.

I understand what you're trying to say, but it still doesn't seem to matter that much.

I mean why spend money for two pulleys, when you can have the effect with the one SC pulley.

As of now people have only answered the additional benefit of a crank pulley compared to that of their previous setup (e.g. - 15% ==> effective 17% via 15/2 combo) and what I'm asking is what are the differences between a 19% pulley and a 17/2 combo (e.g. - 19% vs. effective 19% via 17/2 combo).

Why would I want a 17/2 combo instead of only a 19% SC pulley and save myself the $150 and installation hassle? Maybe I'm just being nitpicky, but I mean it's still $150 and time spent asking on a forum is cheaper than that.

Thanks.

 

Not really - the smaller pulley diameter means there is less surface contact for the belt, even if it is 'rightsized'. Thus the move to 17/2 to gain extra surface area for the belt/pulley interface. Again, I think your thoughts make perfect sense, I'm just giving you the answers to some of the questions.

 

I've run both the 0% and 3% Alta pulleys. I could notably feel the quicker throttle response from the 0% and also a bit of a boost from the 3%.

 

It would be follow that a move from 0% to 3% would have more boost.

But the real question is could you feel the difference when you went from the stock crank pulley to the 0% ALTA pulley.

 

I run a 15% supercharger pulley and a 0% crank and the difference after the crank is amazing. The engine revs up much faster. So changing lanes and accelerating occurs much faster

 

Thank you all for the help, I guess that answers it since a 0% crank pulley isolates the effect of the lightening of the flywheel as opposed to a >0% crank pulley which would increase boost.

Okay, so here's the next question 19/0 or 17/2? Any difference other than overdriving some of the car's components?

 

...ummmm, I think I covered that in my answer, but maybe was not clear. Throttle response was notably better with the 0% ... over the stock pulley.

 

Yes, as was stated here already, the smaller SC pulley is hard on belts. By using a 3% crank and 16% SC you are getting roughly 19% reduction. Using a 0% crank and a 19% SC is much harder on the belt.

 

Thanks