After lurking for a few years I decided to join the crew.

I searched and read every thread on these and other forums on tunes and pulleys. I decided on RC the preserve whats left of my warranty.
Reading post on the install had me a little worried but the show must go on, so I ordered a RC RS.
Install for me was about 30 mins. Beginners luck? The key to a quick install is enough padding on your fender and under the hood to really get in "There". A long hook and screw driver is really helpful for releasing the lock tab on the plug. The most challenging part is plugging
the plug back in because its all by feel.

Does it make more power? Heck yes it does.
Does it drive a smooth as a ECU tuned vehicle? Nope....Map 6 which I love for its partial throttle and low RPM load request cause wheel hop ( which you dont want unless you like to replace axles) when using the paddles and aggressive throttle in first gear and second to third. So I went down to map 5. Map 5 matches 6 in the upper RPM range but lacks the torque in lower RPM and partial throttle of map 6.
How much power do you think it added? My uncalibrated butt dyno thinks may 25 to 30 HP/TQ to the wheels. Probably closer to 25.
Is it worth the money? I feel thats it $450 well spent.
I can provide an apples to oranges comparison between the RS and VAP tune only.

I owned a 2015 XF with AWD and VAP none pulley tune.
My current car is a 2017 XF-S rear wheel drive with RC,

My 2017 with RC feels a lot more powerful than the 2015 with VAP. I believe the load request on the RC is more than what the VAP tune request. The feeling of the 2017 being faster than the 2015 with VAP maybe the lack of AWD robbing power to the ground and the dropping of over 300 pounds of vehicle weight.



Next up, 58mm upper pulley. I know... I know its a waste of time. Im going use a pulley puller that will preserve the stock pulley if I need to swap back to stock. Im looking to move a little more torque down in the RPM range.

Sorry for the long post.

 

They say the lower crank pulley is better ,it wont slip

 

If the pulley is machined correctly then it shouldnt slip. My concern is the pulley fitting on the supercharger snout without grinding needed. The manufacture assured me no grinding is needed.

 

It's not the machining that's the problem.

As you reduce the diameter of the upper pulley to increase boost you have reduced the belt wrap. No amount of machining can correct for this. You must increase belt tension if slippage occurs. Which we can't do because the car uses a spring loaded tensioner. But they don't seem to slip because we only have one or two vendors supplying pulleys. Cars with a lot of following like a Vette or a Mustang there is an entire range of upper pulleys and as they get smaller and smaller they do start to slip.

The lower pulley increases in diameter to increase boost. This increases belt wrap and reduces the possibility of slippage.
Plus it's a BUNCH easier to install the lower pulley. On these 5.0L SC engines it's only about 30 minutes or less. Just too easy compared to the upper pulley and all it's related problems.
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My bad, I was thinking you were referring to slip on the supercharger shaft. I get what you're saying about belt wrap and slippage. When I was emailing the manufacture they told me the stock belt can be used. I have a 3.0 V6. I read through install instructions a few times and
it seems like a lot longer than 30 mins. Ease of install isnt my concern. Its the 2k investment to run a lower pulley which would be cool if I ever kept a car longer than a year and a half.

 

I was thinking he was referring to slippage on the supercharger shaft. When emailing the manufacture they assured me that the pulley would fit with no grinding and the stock belt could still be used. I understand about belt wrap and slippage. Its a 4mm drop in size so I
assumed I wouldnt get slippage.

You mentioned 5.0 but I have a 3.0 and I read the install on the lower pulley and it seems like it takes longer than 30 mins. I may go the lower route but I havent kept a car longer than a year and a half so I didnt want to make the 2k investment for a short period of time.

 

can you put the lower crank on without a tune

 

It will throw an over boost error or something like that.

 

This has been answered a few times before and the short answer is NO.
The long answer is yes you can but if you do the car will throw a hissy fit if you push it over 4,500 rpm and go into limp mode AKA "restricted performance".
To prevent this you need to apply a suitable tune.