[roland2003]

Hi Guys, an interesting one this,we have a jcw car for some work, the SC pulley appeared bigger than normal so we decided to measure it up accuratly. Measured at the top of the V groove form, stock pulleys measure 65.4mm diameter, this JCW one measures 58.1mm diameter. Thats a decrease in diameter over stock of just over -11%. No wonder the car is so slow . They are normally typically -14.5%
Regards Roland . GT Tuning

[C11 XFF]

Interesting, what year is the car ?

[TallAndy]

That is interesting. I have a Works 210 (05 coopers) I've raced *ahem* a little with Mr Colink with his GTT 220 and theres hardly anything init very closely matched.

If you use a 15% reduction pully and the JCW is only 11% how do JCW claim 210 surely air filter / spark plugs and that new cylinder head dont do that much, the exhuast is only cat back so i wont do that much?

[roland2003]

Normally jcw is -15% and quoted at 210bhp. This one has -11% pulley and feels alot less than 210bhp. Not for long though JCW210 conversions (-15% pulley ) on the rollers on the same day as a GTT210 produce almost identical power.
Regards Roland Gt Tuning

[TallAndy]

Ok so JCW pullys are normally 15% that would make sense.

Is that one your working on the old JCW 197 BHP?

[roland2003]

No its a March '05 car with JCW210 .

[TallAndy]

I seem to remember a thread somewhere that found that all JCW pullys where about a 12% reduction.

[St00ge]

i've heard almost consistently that the JCW has a 14.3% reduction pulley

[TallAndy]

So an 05 JCW has 11% smaller pully, maybe thats a mistake but I cant see how they could get the pully wrong standard part etc. SO surely that must mean that all Works cars have an 11% smaller pully.

This brings me back to my previous point, how can my car easily keep up with a 220BHP one with a 15% smaller pully

[St00ge]

Quote: Originally Posted by andeh

So an 05 JCW has 11% smaller pully, maybe thats a mistake but I cant see how they could get the pully wrong standard part etc. SO surely that must mean that all Works cars have an 11% smaller pully.

This brings me back to my previous point, how can my car easily keep up with a 220BHP one with a 15% smaller pully

you have a car that has more mods than a GTT220. You have a better head, exhaust, injectors, induction kit

[Andy@Ross-Tech.com]

That's pretty odd. Every JCW pulley I've seen has been 56.1 mm. Maybe Eaton slapped the wrong one on there.

BTW, here's an interesting little snippet from the Bosch Automotive Handbook about pulleys. For a standard 6-rib DIN 7687, the effective diameter is the diameter of the pulley peaks plus 3.2 mm (0.126" for you sliderule types ). This of course applies to both the drive and the driven pulleys.

So, stock:

(5.460+0.126)/(2.58+0.126)=
5.586/2.706 = 2.06

This matches up nicely with the MINI tech documents.

Using my calculations, the percentage increase in blower speed for each pulley over stock is:

stock: 0% (duh!)
jcw: 15.8%
p&d "15%": 16.8%
p&d "17%": 19.4%
p&d "19%": 23.2%

Quote: Originally Posted by roland2003

Hi Guys, an interesting one this,we have a jcw car for some work, the SC pulley appeared bigger than normal so we decided to measure it up accuratly. Measured at the top of the V groove form, stock pulleys measure 65.4mm diameter, this JCW one measures 58.1mm diameter. Thats a decrease in diameter over stock of just over -11%. No wonder the car is so slow . They are normally typically -14.5%
Regards Roland . GT Tuning

[twouptons]

Quote: Originally Posted by Andy@Ross-Tech.com

Using my calculations, the percentage increase in blower speed for each pulley over stock is:

stock: 0% (duh!)
jcw: 15.8%
p&d "15%": 16.8%
p&d "17%": 19.4%
p&d "19%": 23.2%

So I wonder when the efficiency of the blower starts to drop because of excessive speed...
At some point, the blower will blow less with an increase in speed, which would lead to a drop in top-end power.
Has anyone done a set of flow rate measurements to correspond with the different pulley sizes?

-Eric

[Andy@Ross-Tech.com]

Running the supercharger faster than stock has two undesireable side effects. First, the air is heated to a greater degree so the engine is more prone to detonation. Second, drive power of the supercharger goes up so less horsepower makes it from the crankshaft to the wheels. Here are some graphs of a stock Eaton MP45 blower (not exactly the same as ours but similar):

Quote: Originally Posted by twouptons

So I wonder when the efficiency of the blower starts to drop because of excessive speed...
At some point, the blower will blow less with an increase in speed, which would lead to a drop in top-end power.
Has anyone done a set of flow rate measurements to correspond with the different pulley sizes?

-Eric

[roland2003]

The pulley (now removed ), has the ID 315 0 58 XL stamped on it. Could be the last 2 digits refer to the diameter ie 58mm? The XL for extra large (ha ha) ?

[TallAndy]

LOL

What size is the stock pully (diameter is mm?)

[MINIAC]

Quote: Originally Posted by andeh

What size is the stock pully (diameter is mm?)

2.58in = 65.5mm

[TallAndy]

Quote: Originally Posted by roland2003

The pulley (now removed ), has the ID 315 0 58 XL stamped on it. Could be the last 2 digits refer to the diameter ie 58mm? The XL for extra large (ha ha) ?

Interesting do we know what the ID is of a stock pully? Maybe its

ID 315 0 65 XL?

[Tonyt3]

Thing is Roland, if the guy with the JCW 210 is getting his car re-tuned with you to a decent level, really speaking, you should first send the guy back to JCW so that the error can be seen, and that he can either get his money back or get it fixed proper.

I'd be fecking insenced if this occured with mine. Think I'll just go measure my pulley just in case.....

Can you measure it whilst still attached to the car... suppose not...

[MINI-Morgan]

Very interesting thread. Dont suppose JCW has reduced the crank size instead a bit??


Right answers please to this one, i've always wanted to know whats best and causes most usable HP. Either 19% reduction pulley or 17% pulley with 2% crank pulley??

Now theory has it that a bigger pulley means less force to turn the SC so getting 19% smaller will make the SC much harder to turn and put alot more load on the belt. But changing the size of the crank pulley will cause more work to drive everything else aswell as the SC. And personal experience anyone can add to work out what is the best way to do it??

[roland2003]

Tony Not only the pulley size error but 2 days at dealer with small running fault only to be told 'upstream sensor faulty ,we havnt got one, so weve just cleared the code' .Fault still there, we get the car in and find its not the sensor (which is correctly telling the ecu 'low input from upstream map sensor') it turns out its the small pipe that operates the JCW airbox flap is not connected so flap not working and its drawing in unfiltered air from the wrong side of the throttle body! Time taken to diagnose & fix at GTT; 30 minutes- no parts needed. On top of that one of the bolts that holds the rocker shaft had its hexagon head almost completly rounded off from when the JCW head was fitted. Thats 3 faults from one JCW conversion.
Would you want it to go back again? Maybe yes maybe no.
ps To all you JCW fans , please dont grill me , Im merely pointing out what we have found on one car. You can make your own minds up if at £3500 its ok.
No ones perfect even we make mistakes, but hopefully less of them !


Regards Roland GTT