Well, I don't know if the cam was the culprit haha. I've been having low rail pressure for a while now. Car is running great but still throws codes.
Heres a quick writeup on the cam lobe (which otherwise looked normal on initial inspection)
A little background... I had been getting some cam follower codes for a while... intermittent, and usually would only throw if I went over ~4000 RPM at more than half throttle. I did some logging, and I found that I couldn't really get over 95bar on the HPFP. I got a complete APR HPFP approximately 2 years ago, and have rebuilt the motor after a connecting rod failure. As much money as I spent on the rebuild, you'd think that I would have just thrown a $200 cam in there.. but.. it looked perfectly fine to me. I could see some visual wear, but nothing I could catch my finger on and it didn't appear to be significantly worn to my eye. Well -- I was wrong. I wasn't looking at the problem the right way.
I finally got a new intake cam and set to changing it this weekend. The following are some photos showing how I finally determined the old cam was worn.
First, the overall appearance of the HPFP lobe:
Next... this is what the new cam's HPFP lobe looks like:
And finally what the old cam's HPFP lobe looks like:
In the photos I've marked the contours of the perpendicular faces of the HPFP lobe in red... on the old cam you can see there is a slight deviation showing that it doesn't follow the original contour that was machined for it. I might have considered this okay if I did not have a new one for comparison (not knowing whether there was an eccentric lobe profile).
So... lesson learned... unless you look really really closely and determine that the machined faces are indeed still preserved (there is a 45* chamfer between the two faces that will constrict near the lobe apex that you can closely inspect as well). But, if in doubt, just rip it out. They're so damn cheap... all it takes is time to replace.
Hope someone finds this useful. :beer:
