Would somebody please measure the pitch diameter (see D below) for a V6 or V6S supercharger pulley? I would greatly appreciate it.

 

Since you don't have an F-Type yet, you may or may not know that there's a larger than average plastic cover hiding just about everything under the hood. I'm sure it's probably easy to remove and re-install once you figure out how it comes off and reattaches, but most (me included) probably aren't willing to go to the trouble of removing it and figuring out how to get it back on securely without breaking a clip or something. Moreover, once it's off, and not having seen how it's laid out underneath, I'm not sure if it's easy to get an accurate measurement of the pulley.

What's the urgency? You've got 6-8 months to figure it all out.

 

I suspected all that, but still hoping there are some gear heads out their who are tearing into the drive train. (I never leave things well enough alone).
No rush other than to begin analyzing the pressure curves of the SC to identify the ideal pulley diameter (and nothing else to occupy my spare time for the next 6-8 months). My goal is to increase the torque by about 40 lb-ft. I am not satisfied with the low end torque.
The S mapping is probably as far as you can take the V6 engine without additional boost. The tuners' claims always refer to the improvements they can produce on the base model, never on the V6S.
Note: If the R were putting out as much power on a displacement basis, it would be producing 633 hp. That also begs the question whether the V6S engine is already stressed to the limits, which was already brought up in another thread.

 

That the torque curve is so flat (and the peak values so similar) on both cars does suggest a degree of caution is being exercised.

Or that the Marketing Department is getting out of hand...

 

I think you're right on the former. I suspect that any marketing department would beg for more on a car like this.

 

Question: is the diameter of the pulley useful at all without the diameter of the blower shaft?

Is what you're really after the supercharger drive ratio?

 

Already know the shaft size. Trying to determine what the stock pulley size is so that I can calculate the necessary reduction for the additional 1-1.5 psi boost I'm looking for. Still not certain I'm going to do this before I've gotten some feed back from others who have done it.

 

Got it, thanks. That makes sense.
FWIW my understanding of the Eaton supercharger is that the pressure is not a direct linear relation to the drive speed, ie increasing blower rpm by 20% will increase pressure but not by 20%.

 

That is correct. Eaton publishes performance curves for its compressors that I can use for this exercise.

 

Having come from Fords that use eaton superchargers. It's more effective to increase the diameter of the crank driven pulley. This give you more contact instead of decreasing contact by using a smaller supercharger pulley. I know this increases the difficulty of installation but on my Lightning truck it was performed easily from below. Something to think about....

 

Understood. On the MINI the mild boosts are accomplished with a smaller pulley on the SC. Radical boosts are additionally done with an oversize pulley on the crank. The advantage of doing the SC pulley on the Jag is not only the relative ease of installation, but also the ability to use the same size belt since the idler can take up the difference. Due to crank pulley being larger than the SC pulley, a greater change in belt length for the same ratio change is required and no longer within the idler adjusting range. Of course, different size belts are easy to come by.
Another factor to is that no one is offering over-sized pulleys for the F-Type yet. Lot's of pulley sizes for the Eaton shaft. However, since the engine is a Ford design, it is possible that the crank pulleys built for the Ford might fit. I will look into this. Thanks!

 

These guys have extensive knowledge of ford engines. I know Jim D'Amore had the inspiration that convinced ford to build the Lightning truck. They're located in New Jersey. Maybe you can convince them to take interest in Jaguar tuning also. Good Luck

Contacting JDM Engineering

 

I like the picture...

 

Great thanks!!

 

Increasing the size of the crank pulley will indeed produce more overdrive for the blower, however, it also increases the speed of all of the accessories. Typically, this consumes more power as well as puts more stress on the accessories.

 

Partially true. Certainly to the extent that your engine is above 6200 rpm, the accessories will be seeing higher rotating speeds than they otherwise would, but I suspect they would still be well within their operating limits. The power drain from the alternator and oil pump are regulated with the voltage regulator and bypass valve respectively, so additional power drain will be minimal. The water pump however, might indeed draw another 10% parasitic loss. All together I suspect the incremental parasitic losses are minor compared to the gains offered by the pulley.

 

Isn't the lower pulley dedicated so it won't increase other items speed because they are still on stock crank pulley.

 

Yes it is. If you change out the supercharger crank pulley exclusively, you will only affect the idler pulley and the supercharger itself. In theory the pulley shouldn't be too expensive if you can source the right length belt, as you don't need to incorporate a dampener as that's left on the vehicle.