So I recently had the VAP tune and crank pulley installed on my V8R. On the dyno pull, the car had a weird power curve where it just suddenly lost power after 5800 rpm.
At the time I had a catless downpipe installed so we couldn't hear anything strange and the theory was that it was perhaps a little heatsoaked or octane may have been an issue.

With the catless downpipe off the car now, I took it on a run this weekend when I heard it. The belt is slipping on full throttle application around 5800 rpm.

It's going back to the installer this week but I just want to see if anyone else has experienced this issue before? I assume it would be a tensioner issue but I'm simply speculating...

 

 

No clue on the belt number. It's the standard issue double sided belt included with the VAP kit.

 

I understand that with the VAP double sided belt you don't need a new tensioner and you stick with the OEM tensioner, in which case your belt tensioner may be nearly worn out and/or right at the end of it's allowed movement. Your installer should be able to check this fairly easily.

 

Drop us an email please with name & order number. We had a few belts that came in out of spec. We can send you a replacement if it is slipping.

 

Sent you a mail, thanks Stuart!

 

 

Shouldn't the tensioner be able to handle a 2cm change in belt size?

 

It will not. The double sided belt need is a DK080568. The single sided is a K080575.

 

The Gates K080575HD belt is 57.5". There are 25.4mm per inch, so the correct length is 1460.5mm. We specced the belts at 1460mm. The measurement method is the center of the belt, with the double sided grooves it won't lay flat in the same way the single does, so if you lay them back to back the double sided will appear to be longer.

Our first run of 66 belts came in QC at an average length of 1468mm. That's an average. The longer of these have seen a couple slip over 5800RPM.

Our second run of 134 belts came in at an average length of 1464.5mm. So far there doesn't appear to be slippage from this run. I've checked several belts, even from the first production run and none of them were 2cm longer than the Gates belt.

 

Seems like I got one of the longer belts. Stuart is sending me a new belt so let's see it that fixes it

 

Kudo's to Stuart for sending me a new belt! I'll be properly testing it this weekend and then report back

 

 

I did, and the high RPM belt slip seems to be gone.

I now have an idler pulley squeak when cold starting the car... It goes away as soon as the car is up to temp, but it's obviously an early warning that the idler is on the way.

 

Nothing wrong with the idler pulley. Mine's been doing that for 2.5 years (since installation). Only occurs when it's less than 65 degF outside, and only until the belt warms up.

 

Nothing wrong with the idler pulley. Mine's been doing that for the 2.5 years since installation (new idler). Only occurs when it's less than 65 degF outside, and only until the belt warms up. But this is with a one sided pulley and smooth idler. I thought reverting back to a 2 sided belt would resolve this matter. Maybe not.

 

 

The new version replacement QA'd double sided one.

 

 

Not sure if this in the same region of belt slip but my crank pulley belt is shredded (currently waiting for flatbed). I got the The crank pulley upgrade on my v6 and I wanna believe it was the right belt from vap per vin provided but any thoughts on where to go from here, is this belt something I can buy local or is it a custom belt?