I bought a 2006 r53 (60k miles) this fall and had a low compression issue in cylinder 4 after leaving the dealership. I took it back and they claimed to fix it. It is better but is not perfect (was140,140,140,80, now 140,140,140,130). Would you still consider it safe to do a reduced pulley on the supercharger?

 

How did you initially determine the low compression? What did they say they did to increase compression 50 lb.? Did they perform the compression test properly with a warm engine, throttle fully open, all plugs out?

 

I had a misfire in cylinder 4. I took one plug out at a time and screwed a compression tester into each cylinder. I removed the fuel pump fuse and cranked for 10-20 seconds. Did I do it incorrect. They claimed the computer told them compression was good. However the mini dealer said the computer doesn't tell you compression .they claimed it was faulty spark plugs and wires and they changed them, they did not. Im guessing they dumped some cleaner or gasket sealer.

 

Did you test the compression the same way after you got it back from the dealership? If it was down at 80psi...I'm not sure there is any "easy" fix that would boost the compression back up to 130psi. If you personally tested it, and it's up to 130psi now....I would say you are good to go, and put a pulley on it and run it. A little more boost isn't going to make or break it.

 

Ditto, if it truly is only a 10 lb variation, that is within a safe margin and pulley away.

 

+1 what BlwnAway says.

Motor On!

 

The only way "they" could've quickly increased compression was to have squirted oil down into the affected cylinder. If you did the compression test, then do it again with a warm, not hot, engine, pull all four plugs and the fuel pump fuse, accelerator to the floor, crank until needle stops rising. Be sure your compression tester has a good O-ring seal and that you make sure it's fully seated each time you test. Do the suspect cylinder first this time. Let us know what readings you get.