[Wozich]

As you might know from last year onwards petrol powered cars sold in Europe have to be equiped with OPF - Ottopartikelfilter. An OPF is an exhaust particule filter for petrol cars, which is supposed to reduce particule emissions. OPF filters seem to be killing exhaust sound and reducing engine power. Plus the exhaust gets heavier.

The question is how much power do they reduce. Well I looked at dyno results from Akrapovič. They measured an M240i without OPF and an M140i with OPF (same engine and drivetrain).

Stock cars (blue line)
On the M240i (no OPF) it measured:
354,3HP
548,9Nm

M140i (with OPF) measured:
336,6HP
526,9Nm

Difference: -17,7HP and -22Nm

That's quite a lot.

The red line is with the Akrapovič exhaust. And even then with the OPF Akrapovič exhaust, the power is lower than with the stock exhaust without OPF.

Power is measured in kW and torque in Nm