[FSU_Logan]

All I hope for is the AA midpipe and an axleback that will have a deeper tone.

[doughboy]

Originally Posted by phil_m2

Since the engine injects fuel while you are not on the gas to burn everything in the OPF... It will crackle like shht if the OPF is missing.

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....

[phil_m2]

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!

[doughboy]

Originally Posted by phil_m2

Thank you!

Just remove the OPF and find out!

I don't doubt your judgement that it sounds awful! I'm thinking of tuning benefits of removing secondary cats (US) / OPF (EU) for better gas flow.

Maybe a full downpipe back system would need more silencing in the back silencer to tone things down a bit?

Be interesting to see what a variety of exhaust manufacturers come up with over the next few months...

[Robin_NL]

This is Romo M2 2016. And my M2C. Both still stock.

FWIW...

Cheers
Robin

[untzklee]

damn... that sounds like a fart can very disappointed.