Quote:
Originally Posted by tiltmode43
That's interesting to hear from Dinan. Can't guarantee it's correct but this is what I picked up back in 2012 when the F30 was newer and it seemed there weren't many N26 on the block.
N20 is the ULEV (Ultra Low Emissions Vehicle) motor while the N26 is the SULEV (Super Ultra Low Emissions Vehicle) motor. This equates to the N26 having additional emissions equipment:
-V-band downpipe-to-catback exhaust flange (N20 is slip on)
-Electronic waste gate (N20 is pneumatic)
-Larger cats (detailed by Dinan)
-Crank case oil vent recirculation (I believe that's what it is at least - N26 has a tube from valve cover leading back to the intake post-MAF while the N20 does not)
I'm guessing their tune difference is due to the differing wastegate types (electronic Vs pneumatic). I know when Burger Tuning was initially releasing their F30 tunes the Stage 2 tune produced slightly less horsepower on the N26 than the N20 due to lack of ability to control the wastegate effectively. I'd imagine stock, they should dyno the same given OE boost levels (10% HP difference between N20 and N26 at peak RPM is a pretty substantial difference).
What baffles me is why BMW produces both N20 and N26 in states with high emissions standards. It was my impression the N26 would be in the tighter emission states (CA, NY, and a few others) while the N20 would be the standard version yet here in CA I see tons of N20 in addition to some N26.
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Thanks, yes, further research reveals that it's all about emissions. People are also saying there is less turbo lag on the N26. I have also heard that all 6MTs are N20s; I am a bit skeptical about that. I cannot imagine any new 228is in CA with anything but the N26.
While I am a little disappointed that I have a slightly down-rated engine (although, as you say, 10% HP at 5500 is not incidental), there may be maintenance advantages for an engine with metal parts in place of rubber hoses. Either way, catalytic converters can be a gigantic, hideously expensive PITA and the fact that the M26's is robbing the engine of more power than the N20's bugs me a bit.
FWIW, my BMW performance tech, who has done a lot of Dinan Stage 1 installations on the N26 (because they are all California cars) says it's an exceptionally effective tune and that it makes a really significant performance difference even if there is slightly diminished output numbers compared to the N20.