Quote:
Originally Posted by doughboy
With all respect, I'm not sure it works that way, there is no way unburnt fuel could get through the hot turbines and then hot primary cats to reach the OPF way back under the car.
I've been reading up on the technology and GPF's (English name for OPF  ) (both upfront-with-CAT "VW style", or separate-under-car "BMW style") have only passive regeneration. They use oxygen present only under overrun conditions to ignite soot in the GPF and burn it off naturally under normal conditions with normal exhaust gas between 400-700degC. In cold / constant speed situations the DME will retard ignition to heat the exhaust gas flow and run it lean to allow oxygen to increase in the exhaust gas and start regen that way.
No fuel is passed to the GPF as far I can see, so it should not cause any "popping" - but this maybe due to other reasons like a different DME map for OPF cars?
As EU & US cars have the same rear silencer, only the US secondary CATs or EU OPFs can make the difference sound wise. Be interesting to hear US cars with secondary CAT delete to compare...
Anyway, nice exhaust phil_m2, it sounds / looks great  looking forward to price and availability.... |
Thank you!
Just remove the OPF and find out!