Hi. I've got a 2002 facelift and when the engines warm the whole car vibrates on idle you can see the steering wheel vibrating. It idles at 640 rpm according to torque on my phone. Any ideas why??
Car air filters are generally around an F7 or higher efficiency which should remove most particulate down to 1- 3 micron particle size.
Running without an air filter is much like sand blasting the internals of the engine / pistons / valves .......... and it likely wont last long....... although i expect the piston crowns are well de-coked.
Without an air filter your looking at 30% of contaminents running out of the exhaust, 50% goes into the oil to party elsewhere and 20% is unnacounted for .... ie inbeds itself into the engine surfaces.
ive run this engine for 35,000 miles and put it through 2 MOTs like that, and my previous one was the same, which ran 50,000 miles and also went through 2 MOTs, without any emissions failures. Sadly my pistons are still fairly coked up, on the last check approx. 1000 miles ago. i have a good supply of good oil which i change every 5000 miles, as well as a flush and a new filter afterwards.
i do look after my baby! i know its probably not the best solution for an inlet system, but you can't deny its simplicity and i love the noise!