Originally Posted by
grip grip
I had an early used Karmen pulley for a couple weeks. I noticed when I would start the car up it would make noise for a few minutes and then quiet down. When datalogging I noticed it would stop making boost at a point on the graph and fall off. After a lot of head scratching I determined it was pulley slip causing the noise and boost issues. In my case, there wasn't enough friction between the pulley plate and clutch.
The heat buildup on the plate makes sense based on the clutch-to-plate slip I observed.
I have the same problem with what feels like hitting the wall. I see the same data in my logs. Because I'm stacked, I attributed this to fuel starvation. But then added injector Duty Cycle to my logs and saw that this issue could happen at any time and never above 75% IDC. As if once it is engaged at higher RPM, it would stay engaged. And it would slip when I was not even pushing the car hard. Well... during my testing is when the pulley broke and I've been running my larger crank pulley with a EC 65mm pulley for the last 6 months. No problems.
A week ago installed the Karmen pulley again and this problem reappeared. Not as often since I removed one of the spacers and gapped it to 0.3mm. But this cutout of power still happens on occasion. Fuel should not be effected that much after switching from 65mm to 62mm, especially when just cruising at 70mph. All this leads me to agree with Anthony now. The pulley is coming off. I may even try the EC 61mm and see what that does.