So I Rev my Mini Cooper r56 in neutral and it won't go past 4K rpms? Please help :)

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It should Rev until 8k rpms and does when driving just not still, help please :)

Engine cold maybe it’ll prevent revving too high so the engine wont be ruined?

Maybe it’s a system preventing the engine from overheating. The radiator needs air to cool down the water but if you are still it can’t do it so it prevents a situation it can’t handle. This is my opinion. My suggestion is to go to a shop and check the car’s computer but don’t be worried

Maybe some kind of protection?

When stationary alot of cars will limit the revs

Like with the corvette when youre not moving its limited too 3500 rpm’s

Some weird launch control mechanism?

Thats normal, a lot of cars do that. In a VW i think turning off the traction control also turned the revlimiter off so you could try that maybe.