I work on this car more than my own hygiene, hours wise at least. I have talked to a couple of people whose opinions I respect, and read several threads about mystery issues with performance that come back to a flaky CAS.
This is a post from zcar.com:
I have 3 CASâ€™s in my garage right now. The first is the original CAS that came on the motor I bought for my twin turbo conversion. I replaced it because I was forced to adjust the CAS almost completely clockwise through its range in order to achieve 15* BDC. Even then the timing mark was a little jumpy. Based on what I was able to research on the CAS, that was the issue. When I removed the CAS and rotated the assembly with my fingers it was gritty and made a failed bearing noise. No question there.
I bought the replacement (second) CAS used. Supposedly off of a low mileage JDM.. blah, blah, blah. The armature rotated as smooth as glass and would spin freely almost two revolutions when I used my fingers. I installed it and my timing adjustment was once again exactly in the middle of the CAS's adjustment range when set to 15* BDC. The timing mark was dead-on steady when I checked it. Victory! Or so I thoughtâ€¦
When boosting, the psi would build almost concurrently with the RPMâ€™s in whatever gear I was in. By the time I peaked, it was time to shift. None of that â€œpullâ€ time between peak boost and the next shift. Luminar even drove the car and agreed that something definitely wasnâ€™t right. Iâ€™ve had multiple potential culprits suggested to me through search and personal posts. Theyâ€™ve ranged from my own desensitizing to the carâ€™s power to the timing belt having slipped a tooth. One person suggested the CASâ€¦ Woody75.
At one time I even blamed my turbos and replaced them. Granted, they needed replaced regardless due to bad compressor seals and were rebuilt free under warranty (some of you probably remember the pictures) so I wasn't just diving into a $2,000+ form of troubleshooting. The turbo on the passenger side was also making a bad fluttering noise under boost and that sort of lead me to believe that it was not spinning freely and therefore affecting spool and the speed my car built boost.
Iâ€™ve been reading for months using all manner of search criteria here and at TT.net trying to find someone elseâ€™s experience that would jump out at me and say â€œThatâ€™s it!!â€. Now normally I take Woodyâ€™s information as fact, but based on everything I've read about the functionality of the CAS, mine was operating normally and so I was not ready to buy another. I had seriously considered it, but if my 2nd CAS was bad, I was not going to have faith in another used unit. At $300+ for a new OEM; I was not ready to fork over cash for something I was already convinced was not the problem.
My idle was perfect, the car did not hesitate, it didnâ€™t stumble at low RPMâ€™s or when starting from a dead stop, I wasnâ€™t having any boost drop, I wasnâ€™t having trouble getting to the low or high boost settings on my EBC (other than the slow build). I checked my wastegates to make sure that one or both of them werenâ€™t stuck partially open. I bypassed my EBC and showed the wastegates straight boost pressure in order to eliminate the EBC as a potential culprit. Iâ€™ve set, and reset, and reset the EBC again and again to make sure I wasnâ€™t loosing it there. Iâ€™ve done boost leak test after boost leak test and the system is tight. I know Iâ€™ve tested and eliminated other potential solutions that I just canâ€™t think of right now. I was starting to accept that my motor was just tiredâ€¦ But I wasnâ€™t ready to give up.
I have searched, and searched, and read, and read about slow boost issues others have had. Iâ€™ve read for hours and hours about the CAS and the failing symptoms. Nothing really related to my issue other than Woodyâ€™s posts. I was finally resigning myself to the fact that was going to have to perform a $300 diagnostic by purchasing a brand spanking new OEM CAS.
That brings us the new, new (third) replacement CAS. Beautiful, pulled right out of the Nissan part box, and removed from the sealed plastic wrapper. The first thing I did after admiring its newness was spin the armature with my fingers. Of course the bearing was silky smoothâ€¦ but surpriseâ€¦ it definitely did not spin freely! Donâ€™t get me wrong; it wasnâ€™t difficult to rotate, but if I spun it hard, it would stop moving the instant my fingers left the armature. It was considerably tighter than the second CAS that I had believed to be good. Based on the symptoms of a failing CAS that I had readâ€¦ It WAS in good condition. Wrong.
I pulled the second CAS and inserted the new one. I eyeball set it to the center of the range and went out for a drive without setting the timing with a light. I drove the car real easy until it reached normal operating temperature. There didnâ€™t seem to be any drivability difference from before when not boosting. The first time I boosted was a different story. There was a definite improvement. I boosted a few times and then went back home. When I checked the timing, it was at about 25* BDC. I set it to 15* which placed the CAS adjustment just a tad further counter-clockwise from the center of the adjustment.
I went out for another drive and now there was a serious difference. I turned down all the dials on my Profec Type-S and started setting the boost and gain. Low boost came on like crazy and I hadnâ€™t even messed with the high boost yet! Once I set the high and fine tuned the gainâ€¦ All I can say is WOW!!!
Iâ€™m only boosting 13psi on high (safe set for 370cc injectors) but dang! I get lots of â€œpullâ€ time between peak boost and the next up-shift and I swear I can feel the front suspension extending as the rear end squats even on 3rd gear pullsâ€¦ And I have KYB AGXâ€™s and the Eibach Pro Kit dialed in at 5 of 8 in the rear.
I donâ€™t think this car has ever felt like this. Not even right after the TT conversion. Itâ€™s a beast now! It runs like a raped ape! I have to admit that I am actually in shock. Happy day!