Hi could anyone give me some advice please i am from the united kingdom so will probably be some time after that i can reply to you due to the time difference, i have recently purchased a 2003 mini cooper s John cooper works, on acceleration i noticed it hesitated slightly before taking off i checked the plugs and found that cylinder 3 was very sooty i have done a compression test and found all four cylinders where reading 8 bar i also noticed that my oil consumption had dropped and found that on start up i was getting light blue smoke, which indicates valve seals it clears once the engine has warmed up,my question is please does any one know what the compression should be on a cooper works engine as people are saying that it is lower than the cooper s but no one seems to know what the actual figure is , the mileage is 87000 miles i would be very grateful of any advice you could give me please thank you kindly Darrell.

 

I don't believe the static compression on a JCW differs from a standard S. My reason for believing this is because JCW heads are sometimes used on naturally aspirated R50 motors, and the static compression difference between the R50 and R53 is in the pistons. At least until the 2005 or 2006 switch from dealer installed kits to factory built JCW's, the pistons are not changed. Your 2003 is a dealer installed kit.

According to the Bentley manual, the compression range for an R53 is 9 - 13.5 bar with a maximum deviation of .5 bar between cylinders. My Bentley book covers the JCW models, and does not list a separate specification for them.

 

Thank-you blackbomber i appreciate your info do you think that the valve stem seals are causing a sooty plug on cylinder 3 or is this due to compression ie piston rings worn thank you for your reply darrell