VelocityAP Stage 3 Belt Slip
 

I have read of a few instances of belt slip with pulley upgrades on this forum. I have a 2016 F-Type R with both the crank and supercharger pulleys from Velocity AP. I have been working through belt slip issues above 5K rpm, and part of that process has been checking on all of the pulleys contacting the supercharger belt. I noticed that the tensioner pulley on the car is smooth, while the belt is obviously ribbed. My previously supercharged non-Jaguar vehicles all had ribbed pulleys contacting ribbed belts and smooth pulleys only contacting the smooth side of the belts. Does anyone know if the smooth tensioner pulley is designed that way, or is that a possible point of concern?
On a related note the support from Stuart and Chris at VelocityAP has been second to none. They have been super responsive in helping me narrow down the issue and are sending me a new belt to try.
Thanks

All of my pulleys are ribbed, including the tensioner pulleys.

DC

https://cimg6.ibsrv.net/gimg/www.jag...26ae1a57e7.jpg

Thanks for the info. I ordered new tensioners from my local Jaguar dealership and the design and pulley sizes are different. Mine say they are Ford Motor Co. parts, and the new ones say Jaguar/Land Rover. Makes me think there was a redesign of the serpentine between the 2016 & 2017 models. Are you using the long belt from VAP?

Interesting. I have the stage 3 tune and 2 pulley setup as well. I noticed that the belt does slip under load, but have not yet reached out to Chris and Stewart. I'll do that. Thank you!

I am using the VAP belt with no issues. I have Stage II tune, as I did not/do not feel the hassle of installing (and potentially having the slipping you have) was/is worth the very marginal improvement. The OEM SC pulleys are already very small and the reduction is minor on the upgrade.

Good luck with your issue.

DC

I think your thinking of the v6, which is only 2-3% difference in size.
Where as the v8 upgraded pulley is a lot smaller, cant thing what the % is but my car made 78hp more with just map and upper pulley.

Most of that comes from the tune. When I went stage 2 to stage 3 I gained roughly 25 hp. I was trying to shift the torque curve back because I like to short shift the twisty bits. It did make a noticeable difference in the 3-5k range.

Yep...As mentioned...Most is from the tune. The V6 is even less as you said, but to me was just not worth the marginal increase for the hassle. Others may feel it is worth the bump...I do not. If I run out of other stuff to do, perhaps I will add it one day for fun...Maybe if/when I need to do the SC snout and coupler?

Per VAP, it adds about 1.5 lbs boost.

DC

You are a wise man. The upper pulley install was a bear. Wouldn't attempt it without removing the snout.

very simple the smaller pulley will always slip

Now you tell me! Sadly, I didn't figure this out on my own, nor watch this video beforehand. I will say, however, that I did have the smaller pulley on before the crank pulley and there was no slip. (stock belt)

Because it wasnt being over driven by 20%

Yes it makes perfect sense now. I'm sure this won't be the last thing I learn this way. :o

Mine doesn’t. If the OP has a smooth tensioner pulley, it is not OEM and was installed to accommodate a 1 sided belt when the right sized 2sided belts were unavailable for the lower pulley upgrade. The right belt sizes are now available so the ribbed tensioner pulley can now be reinstalled.

Hehehe..you said "ribbed".

you think its not slipping but it does

Wouldn’t that wear out the belt after 35k hard driven miles?
We may be talking apples and oranges. There’s not much difference between a 62mm OEM pulley on the V6 and the 60.5mm aftermarket pulley. (OEM pulley on the V8 is 66mm).

I discovered that early model F-Types actually came with the smooth tensioner pulley from the factory. Somewhere close to the time of manufacture of my R the design was updated, and those changes included a ribbed pulley to prevent the belt from contacting the tensioner arm.
The good news is that I swapped to a Gates HD belt and it eliminated almost all of the slip, so belt length was the culprit. I might even go half an inch smaller on the belt as the only slip I can see in the new data logs is above 6500rpm.

Would you mind sharing the part number of the Gates belt you are using?

When I had slip I went to this belt:

Gates DK080568. This is a double sided belt.

I think its close to the shorter one VAP sells.