jangy

I thought I would start a new thread since we have a number of relevent discussions going on. A few things I'd like help getting my head around are the "best" size and weight for our SC crank pulleys.

As for size, when is bigger not better? I've noticed a slight lag in the shift from my OEM pulley to my VRP one. I assume it is because of the size of the pulley. I figured the extra mass along with the added boost needed more umph to get going. So, again, i wonder if there is an ideal size or if we just want to go bigger until we simply can't fit a pulley on there?


Now, weight. Why does the pulley need to have a minimal weight? I can understand it needing structural rigidity and that comes with mass, but why does the mass need to be there? I would think having a lighter pulley would make it less suseptible to the drag concerns I hit on before. Is the pulley weight somehow counterbalancing or adding momentum?


School me, fools!!!

bobgodd

I cannot school you as this is my first F/I motor, but I plan on taking my stock S/C pulley to a machine shop to get a smaller one fashioned. It just seems so much more efficient that way, rather than changing the crank pulley and affecting all other accessories....

jangy

I'm not going to stop you, but it has been tried before. I haven't done it or know what the wall is, so I won't say it ain't gonna happen. if I remember it all had to do with the electromagnetic clutch being an issue. If it is something that you can get to work, we are looking at a new part for these cars.

TopGun32

the S/C pulley is limited by the OEM bearing size..

while there are some gains for the E55 SC clutch pulley.. not as much as the C32..

Code3 already has a prototype and still testing..

I rather have a mild crank pulley and slightly smaller S/C pulley..

believe it or not.. the S/C pulley shifts the power band sooner.. about 300-400 rpms sooner on the torque. Atlest in the C32 I have been running for about 4 months. No torn belts and no excess wear.

Once the S/C pulley is available for the E55.. I will try both on my car.. but need to have the tune first to close that bypass valve.. and manage the torque

jangy

I like the idea of a minor change to each vs a drastic one to either. it remind me of gearing on a bike and I felt like we were pushing the crank one so far.

bobgodd

I know most members here say it cannot be done but damned if I won't try anyway! lol.

I think I remember seeing an exploded diagram of the clutch assy somewhere and the pulley and clutch were indeed two pieces. If they are two seperatly machined pieces I don't see how a new pullay cannot be machined, but I am working off of limited knowledge at the present time.

dyno

true !!
I also noticed it, even with my small 161 mmID modded pulley ... I can figure how much lag you feel

infact I have another bigger outer rim 168mm ready to swap on my pulley, but decided that it's bette rto wait after bigger TB and Exhaust will be installed.
I will try but I'm quite sure that lag will be too much for myy tastes.

- OEM pulley is 151mm ID and weighs 4.74kgs

- modded pulley like Evo are 3.08kgs only. don't know how much is VRP's

I chose the way to mod the stock pulley because I'wouldn't like to worry about dampening and balancing issues .. even if it makes sense that a lighter pulley should cause less lag.

I think that trying to machine down a bit our SC pulley is a must do considering that Code3 made C32's 0.5" smaller .. maybe me can simply machine our 0.25"smaller.

a few data:
- our Stock SC pulley is 91mm
- our stock Crank is 151mm ID
= 1.659 ratio.
-if crank is 161ID, ratio = 1.769;
-if 175ID, ratio = 1.923

if we can have our 91mm machined down to 85mm

- 151(stock)/85 = 1.776 .. that is quite close to my current combo

... do you remeber MKB ? ...

or play further:
- 161/85 combo = 1.89 ratio
- 168/85 combo = 1.976 ratio, .. i.e. bigger than a 175 crank only.


if you BOBGODD can find out how much it's possible to machine down, it will be great

supre55

MKB uses a smaller s/c pulley and they claim to have gone 201mph and 0-124 (0-200kmph) in 12.1 at Nardo with a 55 wagon... can't be that bad of an idea.

Yacht Master

Bobgodd,

If you do turn down the SC pulley, I would suggest you consider the VRP extreme belt wrap kit, the smaller pulley will greatly increase load on belt and decrease the contact patch of the belt.

rflow306

That's why I think the best scenario is to change the drive gear of the blower like the slr blower. That would give us 17-18lbs with an asp size crank pulley.

dyno

if the belt is the correct lenght, so as to keep the tensioner correctly positioned close to the SC pulley, I think no kit is required
... or, if you like, you could replace with a slightly bigger tensioner pulley. IMHO.


ps: I had a quick look at the SC pulley but I'm afraid it will be difficult to file 2-3mm down all around it for getting 85mm diameter

dyno

time ago I asked for that part .. don't remember exactly but seems to me it's not for sale.

stevebez

MKB change the S/C gearing. The do this because they dont want to mess with the damper. Main reason they went to all this extra effort to regear the S/C. The damper is important - very important.

Think of it as a seperate part of your car and seperate even from the S/C ring and access. drive ring. Thats what the rubber does. Seperates the damper from the belt drive rings.

Dont mess with the damper guys its tuned for your crank and internals.

bobgodd

Anybody know how to get this thing off?? lol

Dogshine

Jangy - heres another thing to think about. You went from a stock pully to a vrp one, which will increase your boost. You think it reacts slower, but it may be reacting the same as always but you couldn't notice it before.

When I was speaking to Serge, he was showing me all of the things he can do to the 55 motors and one of which is the 08sl55 s/c clutch pack which makes the s/c clutch engage much sooner for higher horsepower cars. We drove the sl55 that he completely modded and it is a beast. Serge seems to have all of this stuff dialed in.

Exotic-metal55

I would like to see a 182 mm pulley, that has the same rotational mass as stock.. I would like it to be of high quality cast and machined to spec. Of course it has to have the best vibration damping qualities too. Must be equal to or surpass stock spec.. Plain black color will be fine! The kit should include lighter accesory pulley`s too.

Murtaza

Well it costs energy or HP to rotate the SC rotors, bigger pulley means your spending more energy out of the crank to spin the rotors at a faster rate.

bobgodd

Success... Well partially.


Pulley is off and in good shape, but machine shop won't be open again until Wednesday lol.

Hammer Down

VRUS, what are your thoughts on this?

Yacht Master

I concur, 100% changing the gear ratio is the most correct, I would bet somebody that has had their blower blueprinted also is fooling around with these gears

Photos by Finny

ChicagoX

The accessories are driven off of a 6-rib ring behind the Kompressor's 8-rib drive ring and are unaffected....except on the setups where the size of the pulley forces a change to a smaller waterpump pulley.

bobgodd

OK so I won't be able to make any progress until after the holiday weekend but I've been pondering the pulley situation in the meantime and I do see some problems. As I had originally hoped; if the pulley was a completely separate piece from the clutch it shouldn't be too hard to either have a new pulley machined, or to have this one cut smaller... It is not however, a fully separate piece.



I can see the major problem being that the machine shop won't really have a way to secure the pulley in order to turn it properly. If the "clutch plate" part of it were easily separated then it could be done rather easily I suspect. The bearing inside the pulley is free moving so that is not an option for holding the pulley still. If it were possible to drill out the rivets that hold the straps that bond the pulley and the "clutch plate" together, those holes could be used to secure the pulley, then after the pulley is cut down, install new rivets or an equivalent fastener... But I don't know how feasible that would be honestly.

Hopefully the machine shop guru will have more insight and will be able to work his magic on my pulley!!

splinter

C32 pulley:


hardware courtesy boohooramblers

Your M113K’s is similar.

bobgodd

That picture does look promising but I am afraid that if I have the machine shop cut the pulley away from the part of the clutch, and remove the bearing inside, that it will be impossible to get the pulley securely fastened to the clutch plate again, and also to get a new bearing pressed in (is the bearing even offered as a separate part??). Those are my major concerns at this point. Where there is a will there is always a way, I hope I am not limited by the machinists willingness to pursue a completely one-off part, or do completely custom work... Unfortunately, not all guys out there want to get involved with something like this. Lucky for me, I can just keep looking around 'til I find the perfect shop!

bobgodd

OK so I was able to take the pulley to a machine shop here in San Diego and they are going to make it happen!! I had taken it to two places prior to this one with no luck. San Diego Precision Machining is the place.

Based on the picture in the post above, I wasn't sure how much to ask them to take it down, so I just told him 3mm. Now I'm not so sure if that will even make a difference worth all the effort.

What would be a reasonable ammount to have taken off of the pulley?? I'd like to go big on this project so I don't have to do it twice, so I'd like as much taken off (safely of course) as possible in one shot!!

TIA!