Originally Posted by DBH
This is your answer: This is your answer:
Originally Posted by AKAFP
The new S65B40 V8 engine is a high performance engine designed and built to exacting BMW Motorsport tolerances which take into account the high performance nature of this engine.
The new S65B40 V8 engine has the following characteristic sounds which dealers need to be aware of.
1.1 Knocking type sound at idle
When the engine is at normal operating temperature and depending upon the accessory loads on the engine it is possible a low frequency knocking type noise may be heard in the car. This noise is a characteristic of the engine and is not an indication that there is a defect with the engine. In the event that you receive an inquiry about this noise it is important to reassure the customer that this
noise is a characteristic of this engine. The noise in no way affects the durability of the engine and will not lead to a failure of engine components.
1.2 Resonance at 2,000 rpm under load
The M3 has a characteristic resonance which occurs in a narrow rpm and load band. The resonance is directly related to the performance characteristics of the M3 engine and in keeping with the performance nature of the vehicle.
The driving conditions under which this resonance will be heard:
• Engine speed = 2,000 rpm
• Vehicle speed = approx 70-80 km
• Gear selected = 5th gear
• Road conditions = moderate incline
The resonance band is very narrow and can easily be avoided by reducing the load on the engine or bychanging down or up a gear depending upon the driving conditions.
I think this is the only real explanation, but again it is a little vague as it leads the topic stating "at idle" but I agree this is prob right and just us M owners being crazy over every little noise.