N52 2.5i intake manifold conversion to Si.

F

fraserbottomley

Member
Hi guys,

Been having a browse over on the e90 post forums and it appears that that the major difference between the N52 "i" and "si" engines is the intake manifold, which is single stage on the "i" and three stage on the "si". A few guys in the US have put the three stage manifolds on the "i" engines, remapped and had similar power levels to that of the "si".

This thread explains it...
http://www.e90post.com/forums/showthread.php?t=381371

It's relating to the 3.0 N52, but I'm guessing it would be the same story for the 2.5.

Has anybody on the board considered doing this? Or has done it?
 
Don't forget some of the cars in the USA are detuned to begin with compared to UK cars.

They also quote 215hp stock for 2.5 which would be the 2.5si (218hp in UK) unless I'm reading it wrong.
 
From what I gather the US 2.5 is actually a detuned 3.0, with the difference in power between the US 2.5, 2.8 and 3.0 (all actually 3.0 engines) is the map and manifold, could be wrong though? ha.
 
Yeah I think that's what it is. I'm assuming the UK N52 2.5 and 2.5Si work on the same principle though, with the manifold making up the extra power, looking on realoem.com at the 2 engines appears to support this aswell.
 
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