
Shared N20 2.0 engine components between an F30 320i and F30 328i:
- Cylinder head - PN 11127624778
- Connecting rods - PN 11247624616
- Crankshaft - PN 11212212762
- Intake manifold - PN 11617588126
- Air box - PN 13717597589
- Air filter - PN 13718507320
- Intercooler - PN 17517618809
- Radiator - PN 17117600520
- Throttle body - PN 13547588625
- HPFP - PN 13517584461
- MAF - PN 13627602038
- MEVD 17.2.9 DME/ECU - PN 12148604210
- Exhaust manifold/turbo - PN 11657642469
Does the pistons not being shared mean the 320i pistons are weaker? Who knows at this point. They have the exact same compression ratio but different part numbers. Interesting that BMW would go to the trouble of changing the pistons but nothing else. Does the N20 320i have a tuning disadvantage to the N20 328i? Not at this stage, check out these dynocharts.
Here is the 320i N20 stock, yes, weaker than the 328i as it should be as the 320i N20 is rated at 180 horsepower and 200 pound-feet of torque versus 240 horsepower and 255 pound-feet of torque for the 328i N20:

It gives up in the ~40-50 whp range versus a stock 328i N20. All through software. Look at the 320i with an increase of 3 psi of boost:

Just like that approaching the 328i level with some more boost. Now let's look at an additional 4 psi and the Stage II 5 psi map:


And now all of them in one graph:

That is just about another 80 wheel horsepower with just some minor tuning. The F30 328i is not the best tuning value in the BMW lineup, the F30 320i is. Keep in mind pushing the N20 motor beyond Stage II is currently not recommended as there may be a head cracking issue past 331 pound-feet of torque.
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