i just got a 98 323is, it has an m52b25, the difference between the two
the m50b25 has more hp than the m52b25, 189 vs 168, the m50b25 has different compression than the m52b25, 10.0:1 vs 10.5:1, the bore and stroke are the same, the torque is the same, the displacement is the same 2.5l, 2494 cc, anything else you want to know, oh and also the m52b25 is obd11, and the m50b25 is obd1, there is also an m52b28 that has 190 hp, that is what was used in the 328's, ok now is there anything else you want to know, lol
The M52B28 is probably the one in question, and it is indeed a 2.8L engine. The M50 is undoubtedly the 2.5L used in the 92-95 e36 cars equiped with a 6 cylinder powerplant. While you only gain a couple of hp with the M52, there is a massive difference in torque available througout the powerband (thanks to VANOS).
There is no doubt that the M52 is vastly superior (0-60, feeling of power, acceleration at almost any speed, etc.), and certainly worth the money. The M50 is however equipped with the OBDI engine management system, which means there is much more available in the aftermarket world. Of course you could always do what I have, and that is an M52 engine mated to an OBDI induction system.
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