Hello , I am in the process of trying to put toguether a list of things to put on my 2004 mcs. I am definitely planning on upgrading the supercharger pulley and crank pulley, but I would like to know what the difference or pros and cons are when......

Using just a 17% supercharger pulley with a stock size ati crank pulley vs a 15% supercharger with a 2% ati crank pulley.

I understand the numbers of the pulley diameters are not the same with the 2 above scenarios, what I would like to know is it best to use 1 combo over the other and for what reason.

Thanks

 

The ATI 2% also has the advantage that the aircon will run a bit better during idling, thats what I read somewhere on NAM anyway. I have the 2% ATI with a JCW pulley and will also do a pulley upgrade anytime soon. I will probably go for the 15%+2%, unless someone says to go for 17%+2%

 

I see. I guess that is a good thing when running the aircon. From what i read it seems that the oversized crank pulley will spin the alternator faster, so not sure if that would be good or bad under high rpm on the aircon ?
I wonder if by putting the oversized crank and smaller supercharger pulley will it take some stress off the supercharger ( when using the supercharger reduced pulley alone ) . I am guessing it would be better to help with preventing belts slipping off the smaller supercharger pulleys . ( 17 or 19%)

 

Here's some numbers for comparison... remember 2% at the crank plus 15% at the SC is not equal to 17%

So... at, say 7000 crankshaft RPM...

STOCK MCS: The SC pulley is 65.5mm, crank pulley is 138mm.
The JCW has an 11% pulley reduction in size...

STOCK CRANK PULLEY DIA
- 0% Charger @7000 RPM = 14,748 RPM at the SC input shaft.
- 11% Charger @7000 RPM = 16,570 RPM
- 13% Charger @7000 RPM = 16,950 RPM
- 15% Charger @7000 RPM = 17,350 RPM
- 17% Charger @7000 RPM = 17,768 RPM

2% larger Crank diameter
- 0% Charger +2% Crank = 15,043 RPM
- 11% Charger +2% Crank = 16,816 RPM
- 13% Charger +2% Crank = 17,289 RPM
- 15% Charger +2% Crank = 17,697 RPM
- 17% Charger +2% Crank = 18,124 RPM


So... From a boost perspective at any given RPM....
Order of lower boost to higher boost

1. Stock MCS
2. MCS with stock SC + 2% crank pulley (CP)
3. JCW SC with stock-CP
4. JCW SC with 2%-CP
5. 13% SC w/stock-CP
6. 13% with 2%-CP
7. 15% SC w/stock-CP
8. 15% w/2%-CP
9. 17% SC w/stock-CP
10. 17% w/2%-CP

.

 

Also... speeding up the SC will boost power... but it will also add more heat to the intake tract, and tax the bearings in the SC more.

It will be more octane sensitive at any temp as well.

At that point... when bumping up the loads... I'd make sure to service the SC ... and not just a drain.. pull it open, clean and inspect both ends IMO.

Plus.. I'd replace the water pump at the same time and flush the coolant.

BTW... most know this... but some may not... the SC must be pulled out of the car to service the SC... This will, IMO, make the pulley swaps easier !!

The big benefit for me is the improved ATI damper... and while at it... why not go to the 2%??

I'm leaning towards 13% plus 2% ATI .... New pump, SC service/gaskets/seals, tensioner, belt, idler, alternator service, timing cover seals, crank seal and anything else I see in there...



.

 

The ATI damper is highly recommend and quite easy to install as well. I documented it in my build thread > https://www.northamericanmotoring.co...ml#post4559185

 

Wow and thank you for this great breakdown. Really puts things into perspective for me

 

I totally agree with the supercharger service when doing this. That is my plan. Also am considering water pump change when doing this.

Still on fence regarding the 2% ATI as someone suggested that it is .8% bigger than stock and will actually bump the supercharger rpm higher.

Also wondering if the overspin of the 2% ATI will cause issues with my old alternator and aircon.

I guess the one good thing with going up in crank size is that u get to go down in a supercharger pulley therefore reducing risk of your belt sliping out.

Thanks again for the great info

 

Yes it looks like.its the way to go. Thanks for the build link.

As great as ATI is ,the cost seems a little steep for my budget. The prw seems more in line for what i need with a fair pricepoint . Since I won't be tracking the car I think for myself the prw would be a better buy and should be much better than the stock one I had on anyways. I know what u pay for , but from some of the reviews it seems to be quite comparable to the ati for the pricepoint.

 

A 2% ATI is 2% bigger than a stock MINI pulley. What I posted is the “stock” size ATI is supposed to be .8% larger than a stock MINI pulley so that should be factored into a pulley size decision depending on the max gas octane available in your area, or if you’re already close to pinging.

The smaller the pulley, the greater the stress and wear on the belt so I think a 15% or 17% with a 2% ATI should put less strain on a belt than a 17% or 19% alone. Others say it doesn’t really matter if you change the belt often.

I’ve read about the concerns regarding alternator and A/C speeds, but unless I’m missing something, I don’t see how the small differences in RPM’s from the chart above could really cause an issue. If you’re really concerned there are pulleys available to adjust for a larger crank pulley, at least for the alternator.

 

Thanks for the info, that is what I am trying to understand . If the 2% ATI increase takes some stress off the belt i guess its a good thing. In my area I am trying the shell v power 91 with no ethanol right now before the pulley.
We have some 93 or 94 i think but with ethanol. Would you still recommend the 93/94 with ethanol over the shell v power 91 no ethanol if I went 17 %? ( either single 17 % supercharger pulley) or a (15% supercharger with a 2% ATI crank )

 

With all my experience if you want 17% just go with a 17% on the supercharger. Trying to do a combo to make it will cost more and actually be less reliable or make less power.
So I would go with the stock ATI damper and our 17% supercharger pulley kit and be done with it. This is a known combo that works great.

Now a few reasons that haven't been considered that we feel are enough to not go with a 2% damper to try and get to 17%
1. the 2% damper and 15% supercharger pulley combo actually doesn't equal 17, it will end up being less.
2. the belt tension on the combo of 2% isn't tight enough and will actually wear out faster or even slip "stress" on the belt others mentioned is not an issue as it needs to be tight.
3. a 2% damper is heaver adding rotating weight to the crank, not ideal as we want it lighter to rev faster.
4. the 2% damper cost more than the standard size, supercharger pulley price is the same no matter if its 15, 16, or 17%.

https://www.waymotorworks.com/wmw-pulley-package.html

 

Way... Thank you for taking time to chime in here... Good points... I didn't notice that the price was different on the 2% ATI.

That being said... You sell BOTH the PRW and the ATI... What makes the ATI your go to choice compared to the PRW??



.

 

Thanks way for the info . I still have original crank pulley on mine ( 2004 111,000 km) so i was considering replacing that , new tensioner , idler and of course the supercharger pulley. Then as I dug down the rabbit hole for the mod info and I discovered that fellow members were doing 2% increases to the crank, but didn't really understand if there was many pros over cons to it or.if.it put less stress on the charger .

everyone who chimed in to this thread has made some very good points.

I did wonder if there was a different belt for the 2% crank ,17% supercharger pulley or if the same belt for just 17% supercharger pulley was being used therefore throwing things off.

Also if the ati is .8% larger than stock would u recommend sticking with the 16% pulley instead of the 17? I know the numbers may be a marginal difference between the sup pulley difference but I wonder if it will be a better combo as my charger is old.

Thanks again

 

Very informative info here, thanks all for contributing.

I will go the 17% route with this information, I'm not a red line puller, the power band I'm using is low/mid range. Also fuel quality is not an issue here in NL, RON98 (E5) is widely available + a little bit further I am also able to get RON102 (but I am too lazy to drive there).

 

I have had problems over driving the altenrator, it's hard on the regulators if you have a 7500 rpm redline and then also overdrive them with a pulley

 

Sincere questions... How many alternators did you go through? Always the regulator? How many miles on the alternators that failed?




.

 

Three so far I don't really know how many miles I only do about 5,000 a year but most of them are on the track. You absolutely cannot use a rebuilt alternator from auto parts store they can't handle an increased red line let alone increasing the main pulley it'll overdrive it and it'll Spike the voltage when it overwhelms the regulator if you search on here you'll find others that have the same problems

 

A few reasons:
1. The ATI is an inertia damper, and the PRW is a fluid damper. Years of data and arguing have shown the inertia damper will actually dampen better. So I go with what's best

2. Quality, the ATI is always perfect and lately I've seen several quality issues with the PRW and them not fitting right or even getting stuck half way on only to have a customer yell at me and blame me for their poor quality and not fitting. So I recommend the ATI and never have that issue.

3. the ATI was a bit lighter to help rev faster

 

Unfortunately, I was provided with an ATI with a small deformation, but that was fixed fast by the seller. It really is a quality bit of kit, fitting it was done within 2 hours by a DIY home mechanic (myself)

Steep price, but worth every penny!



Also weighed it, small weight difference, even though the ATI is 2% bigger.

 

Hello, I went with a 15% reduction on a R52 and with the automatic transmission, I actually felt like it hurt the performance. Anyone have information on how to replace with the original 65.5mm?

 

Any more details on what differences you're feeling in the performance and what other parts were changed when you did the pulley?

 

Nothing that in my mind would be suspect, just typical spark plugs, stock coil, stock spark plug wires. I understand that the superchargers wear over time and do not perform at optimal levels, so I'm looking to replace my supercharger with one with fewer miles. I have over 205,000 miles on my mini (2008 sidewalk SC convertible)

 

Sorry to bump an old thread, but I ended up doing strictly the 2% crank, but with titanium hardware. Exactly how much lighter is the ATI vs stock?

While I was at it I did a coolant flush, replaced crank sensor, serviced supercharger, replaced water pump and flange, replaced coolant hoses (Mishimoto), replaced thermostat, housing with the aluminum URO parts housing, replaced radiator (Mishimoto), new belt and tensioner. Expensive but I ended up getting carried away when I tore the car This is on a stock factory JCW BTW.

Personally I don’t think the extra 900 rpm vs a 17% would be that much of a difference, especially considering the trade off on reliability on these older cars.

 

I can answer that question

2.68KG for the ATI +2%



2.72KG for a stock pulley



The ATI alone makes a big difference, the power delivery becomes buttery smooth. I also went ahead with a 17% pulley (over the 11% JCW pulley), that was also a big difference.