218hp n52b25?

[Bonnygator]

Hi all,

Just a quick question. I can't help but notice that BMW also sold a version of the N52B25 that made 218HP (e.g. on the E85 2.5si) instead of the 204HP that mine has (sDrive23i). Does anyone know the difference between these two engines?

My guess is it's some sort of ECU tune difference, as I can't really find any meaningful differences on realoem so it's basically the same engine. But if it is simply a tune, then I'd imagine both the 2.5si and the sDrive23i could be cranked up to the same HP level. Screening some tuning websites shows that the 2.5si gets up to 235HP and the sDrive23i to about 220HP, which doesn't really make sense if it's the exact same engine.

Thanks! (not sure this was the place to post this)

[MTC]

From my understanding, the power differences is mainly due to the intake of the E89 23i being inferior to the E85 25si, with 25si being the one with full VANOS/3 stage intake equipped DISA Actuator which the 23i lacks. You could find more about this on N52B25 E90 323i and 325i.

[Bonnygator]

Thank you for the reply! That was my first thought as well, but I can't really find a clear cut answer as to whether or not the sDrive23i does or does not have the 3 stage manifold.

Looking at the realoem parts list for the intake system for both the 23i and the 2.5si, I don't really see a difference.
23i:
https://www.realoem.com/bmw/enUS/sho...diagId=11_3756

2.5si:
https://www.realoem.com/bmw/enUS/sho...diagId=11_3756

To me, that implies the 23i already has the upgraded intake. I also imagine this mod would be more common if it were indeed a possible upgrade, since it seems one of the best increases in power you can get from the N52.
If anyone has an idea where these additional 15-ish hp come from, I'd be glad to hear it

[tintoverano]

it is software, bmw restricted the z4s

it seems though, that roughly 16hbp is the most, what tuners can get out of the engine still