Hello all. I'm new in the forum and new mini cooper s r53 manual gear box owner ,and already have some questions.
So when i get the car i make complete service. Filters belts pulleys oil spark plugs etc. The car runs fine no check engine light and no other problems.
The biggest problem i have is that the car is missing power after 4000 4500 rpm. Before 4000 4500 rpm it pulls really nice ,but after that is really bad.
Already checked the bypass valve it seems fine me, also make a good look on the vacuum lines they also seem fine.
I don't have a boost gauge so i don't know how much boost is the car making.
So i really need your help how to diagnose what is making the car to lose power after 4000/4500 rpm. Lets hope its not the supercharger.

 

Had a similar problem after doing a bunch of upgrades (cam, header, tune etc.). I have not gone back on the dyno to confirm, but power is better and fuel mileage up noticeably on cruise. Turns out the vacuum line that runs behind/below the intercooler was not seated at the left front of the motor.

To access the line, the IC has to come off (not a big deal, I think #30 torx). Also helps to have a little pick tool to help the rubber bellows get seated on the ends.

Regards,
Jerry

 

How old are the plugs, wires and coil?

 

I suggest checking the following that can cause you to loss boost:

• the rubber coupling boots for the intercooler
• ancillary drive belt to make sure it is not slipping at the SC pulley
• drive belt tensioner if bouncing up and down the belt can slip just when it needs to drive the SC the hardest - think a few 10s of HP
• the crank pulley/damper - if the rubber has delaminated it can cause the drive belt to slip at the SC pulley as it has a tiny diameter

Most on this list will take some careful observation and thinking to isolate down which it is. A boost gauge will take out a lot of guess work and this list may not apply at all. A defective bypass valve can also be the cause but I list it as less likely given your symptom.