It just didn't have the impact on me as i would've imagined..

boost is there... by my readings at about 5-6k rpm i get about 1.2-1.3 bar, before my peak was a bit below 1.1 with the 15%

throttle response has improved.... not much but at least noticeable

but overall i dont feel the AMAZING increase alot of you raved about, i guess i got so used to the 15% by now the slight increase isn't that noticeable

bottom line is that... for me who's gotten so used to the 15% by now it is merely a driveability upgrade... nothing more...

3 out of 5

if you ask me, stick with a 17% if you want the 17%'s power without the 'possible catastrophic failure' that alot of people here have claimed with this mod

my old pulley is sitting on my shelf.. the moment any rough shakes i get at idle im throwing the stocker back on, even randy re-assured me that nothing's gonna happen i aint taking any chances

 

Did you get the stock sized pulley or the +2% pulley? What brand?

I would agree that the extra power isn't as dramatic as when I first added the -15% pulley on the SC... but it is indeed there. I notice more mid-range punch and I can definitely tell there is less drag on the engine.

Considering the low cost of the crank pulley, do you not feel that this was worth it? (Presuming that you never have any negative issues with it.)

 

oops.... i neglected to mention i got a 2%... just i guess when you read so many rave reviews on the pulley it seems natural to build up your hype...

for 150 bucks... it is worth it... but in the same time, even the so called 'catastrophic failures' the few claim will happen or might happen has me a bit worried and slightly defensive about this product

 

what brand is ur crank and 15% pulley?

 

I have a 15% and a 0%crank and the difference is dramatic. Maybe with a 17% the boost is so great that the lightened crank doesn't make that much of a difference? But then again most of our writings here can be our own opinion based on our car and our driving style eh? My car is a MCSa and the lightweight crank made a difference I noticed faster then when I put on the 15% supercharger pulley.

 

Sorry, but I completely disagree on your assessment of the pulley! I got mine done last Friday, and it's SWEET! I got the M7 2%. It fit well, and losing that weight was instantly noticeable. The car is more manageable and smooth at lower rpms! Gear engagement and rolling from a stop and up hills is really a good bit easier. My gas mileage even went up 2-3 mpg, at least. And, I've got a good amount more power!

The only thing I can think of is maybe you need injectors? I don't know if you have them or not, but running 17% you could prolly use some more fuel up high. I run 400 cc injectors in a full Cosworth/M7 S. Adding the pulley [now effectively 18.x% pulley on the SC] made a really sweet difference in the character of the car. More power all the way up my powerband!

 

guys which would be the better option??
15% + 2% OR

17% and 0% ??

 

Many threads have said running a 15+2 combo is better. I do not recall why but if I was to dig up an old thread it would make sense. In all actuality it's more like 16.3% reduction if I read right.

 

15+2 if you can stomach the little uncertainty regarding lifespan. I consider myself to be a fairly conservative guy [wouldn't put a twincharge on my car unless I knew multiple people for whom it was safe], and I ultimately chose to get one. I love mine now !

 

More like 17.3, I believe.

 

thanks ingsoc! coz i was sorta leaning towards 17% for some reason.

 

ok let's clear this up.. seems a few people are a bit confused!

i got a 15% alta pulley about a year and a half ago.. i regularly track the car, autox the car.. etc... u name it ive probably done it... and now i got a 2% alta crank pulley

im not slamming the 2%... there is a noticeable throttle response improvement, as well as spool up, the boost reading confirms im getting effectively a 17% boost level of 1.2-1.3 bar (about 18 psi)

yet in the same time, i do not feel that it is another 'ultimate' mod that everyone proclaims it to be... it is a worthy addition, i guess being a bit defensive about it also dont help it any

 

thanks for clearing that up.


tho im still stuck in deciding either the 17+0 or the 15+2 combo. :impatient

 

The 17.3 was my error.
It is 16.67 if you do not consider the effect of belt thickness.
If you do not consider the effect of belt thickness, a 17% pulley
overdrives the SC by 20.48%. 15 + 2 overdrives the SC by 20.00%.

If you DO consider the effect of belt thickness, a 17% pulley
overdrives the SC by 19.34%. 15 + 2 overdrives the SC by 18.97%.

https://www.northamericanmotoring.co...5&postcount=17

 

I have a 15% Alta that should be in this week, and I am fighting with the dealer to replace what seems to be a failing harmonic balancer. I am very close to just getting the Alta 2% crank pulley and calling it a <fun> day! I have not heard of any negative impacts from the crank pulley, and have seen several sources quote that BMW attests the car didn't need a harmonic balancer, it there to make the engine idle smoother. Sooo, the dealer response today will determine my next steps...

 

So your existing Crank Pulley is having issues? What seems to be the problem?

 

What are your before and after MPG numbers? Tough to believe a few pounds off the crank (AND extra boost) would increase your MPG by over 10%! Was your first tank after the crank all downhill?

 

It's the rattle on hard acceleration (between 3k and 4.5k RPM) that emanates from the front right side of the car. There are several threads here (this being a couple of them)

https://www.northamericanmotoring.co...ad.php?t=18230

https://www.northamericanmotoring.co...ad.php?t=50647
At any rate, mine fits the description to the T, and my conversation this morning is also on the money (we can't hear anything, there's nothing wrong, etc.). So, I'll deal with it myself and assuming the problem goes away, make sure the GM of the dealership knows I had to cure it myself.

 

Lol. No, my tank was consumed on my usual 5 hour commute north to school. I drive the same road, it always takes around the same time, etc. This time, fresh off of my new part , I even had some extra fun with both a Porsche 911 and an Infiniti G35 [Infiniti had no chance, the 911 pulled half a length down low, but couldn't gain anymore to the posted speed limit [60]].

Anyways, I made it about 30 miles further [even after having a little fun!] on my tank before running close enough to empty. That's about 2.5 mpg more. Since making that trip, these past few days, I've noticed that mileage is still up. I guess it's just because of the lowered rotating mass. The car sure revs easier. Proof positive, here's a video:

www.teammightyminiz.com/~ingsoc/DSCN0233.avi

edit: The video should show an approximation of how smooth my low-rpm power curve is. Notice, there's hardly any lag down low. It was not that way before the new crank pulley. I feel bad cause I didn't think to do a 'before' video. grr.

 

Hello everyone!!
I have an Alta 15% pulley and my next mod will be to add an Alta 2% Crank Pulley. My question is: install the 2% Crank or replace my Alta 15% pulley for an Alta 17% pulley and forget it about the crank pulley and stay stock on the Crank? Henry

 

The reason we came out with a 2% pulley is that when coupled with our 16 % or anyone elses 15% you are improving the life and performace of the belt verses one smaller pulley. You have a bigger turn for the belt to make which will help to keep the slipage/ temps down . Additionally it makes for a better fit with a stock sized belt as it takes up some of the slack when going to the smaller SC pulley.

Randy
m7 Tuning

 

I put the Alta 15% and the Alta 2% crank (to cure the "playing card in the bicycle spokes" issue, which it did) on the car at the same time. I am happy with the mods.

 

I have a 19% + 0% and I could tell the difference right away.... It is not the "super mod"..... but for the cost i think well worth doing..... throttle response improved.....the engine idles and runs smooth...... I like it

 

Has anyone tried the a 17% and 2% combination? What belt would you use? Thanks.

 

I have an Alta 0% available for purchase if anybody has interest. has about 150 miles on it. Send me a PM. Thanks Andy