Today I talked with an Alpina owner about the supercharger oil leak. He told me, he has recently changed the supercharger for a new one and run only 20-30.000 km until now. I was curious what oil leak he has so I asked him to check the amount of oil in the piping. This was the result.
As you see there is some cl oil in the charge pipe and also has some oil in the suction tube. But this is a genuine almost brand new supercharger, how can this be? Is it normal?
Yes, this is normal! Don’t need to refurbish or change your supercharger, just drain the charge pipe at every oil change. So around every 10-15.000 km.
Actually (unfortunatelly) this is the normal condition of the sealing system of the supercharger. The used carbon seal is a dynamic seal, and not a 0 leak seal. These kind of seals have a given leak value by the manufacturer.
The physics behind is simple. There’s vacuum at the suction side of the supercharger because of the pre-sc throttle valve and the oil circuit is running at around 4-5 bar inside the sc. The carbon seal has a sliding surface which is sliding on an oil film and leaks some oil because of these circumstances. Than the oil hits the rotating compressor wheel and because of the centrifugal force the oil mist will leave through the charge pipe. As there’s vacuum before the sc, you’ll also find some oil there.
The leaving oil mist has a temperature around 100 Celsius and reaching towards the intercooler where it cools down and “condensates”. During the usage from time to time oil will be collected at the bottom of the intercooler because of the gravity. You just need to drain it during an oil change and you’re ok. Alpina engineers also knew this “problem” so they applied a drain plug to the bottom of the IC. So that’s the purpose of it. 😉
And what is the accepted amount of oil leak? Well some centiliters like a shot glass or a cup of a spray can. But if you experiancing like the picture on the left, start texting me immediately. 🙂
Higher amount of oil leak could kill your MAF, start running knocking, damaging and killing the complete engine! Your pistons could melt down, your rods could bend, your cylinder head can crack, etc. So don’t forget to check your IC drain plug at each oil change!
And thanks again for the pictures Dom! 🙂