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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Three stage intake manifold Q with a difference - UK 2.5i to 2.5si



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      01-02-2011, 02:39 PM   #1
Fraser-Z4
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Three stage intake manifold Q with a difference - UK 2.5i to 2.5si

Hi guys,

I'm Fraser, I'm from the UK and drive an N52 (N52B25) engined 2.5i Z4. I know it's not quite the right forum but you guys seem to have the most knowledge when it comes to the N52 intake manifold.

In the UK we got the facelifted E85 Z4 (2006-2009) in 2.5i (177bhp) and 2.5si (217bhp) guise; both 2500cc N52B25, I own a 2.5i model and would like to up the power! From reading some of the 325i to 330i conversion threads on here I figured it would just be a case of installing the three stage intake manifold and mapping to gain the extra power. However when I've actually had a look at my engine I already have the DISA actuators so I'm guessing I have the three stage intake manifold as standard?

I don't know which models you guys over in the US get but the UK N52 engined 523i and 525i are the same as what I've described above; both 2500cc with the 523i having 177bhp and the 525i having 217, and both have the three stage intake manifold.

I've studied the diagrams on RealOEM for the 2.5i and the 2.5si and everything between the 2 engines appears to be identical (camshafts etc.). I've looked at the diagrams for the intake manifold and they also appear to be identical, however a couple of the part numbers are different.

RealOEM intake manifold diagram for 2.5i...
http://www.realoem.com/bmw/showparts...56&hg=11&fg=40

RealOEM intake manifold diagram for 2.5si...
http://www.realoem.com/bmw/showparts...56&hg=11&fg=40

Does anybody have any idea what could be giving the 40bhp increase for the Si? Could the three stage manifold just be deactivated as standard on the 2.5i? Or is it simply mapping? This seems unlikely as I've checked most of the well know remapping companies in the UK and they claim around a 13bhp increase on the 177bhp 2.5i (unless they aren't changing the right parameters to remove the detuning).

Thanks for the help guys
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      01-02-2011, 03:30 PM   #2
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Although the pictures are the same on RealOEM, the part numbers for the manifold are slightly different. Look at your manifold, and see if you have the adjuster box attached to it (part #2 in the picture).

If you do, you already have the 3 stage manifold. If not, you'll probably have two wires clipped in that location that don't go anywhere.

I'm stealing this pic, but look for the circled part.
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      01-02-2011, 03:41 PM   #3
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Yep that manifold is exactly the same as mine mike-y so it looks like I already have the three stage!
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      01-02-2011, 03:56 PM   #4
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So I guess the question now is where are they getting the extra power in the 2.5si?
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      01-02-2011, 04:08 PM   #5
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Exactly! You guys feel free to take a look on RealOEM as you probably know more than me but everything I've checked between the two engines appears to be identical. All I can think is that the engine is simply detuned via the map, could the DISA actuators simply be disabled?
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      01-02-2011, 04:21 PM   #6
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http://www.e90post.com/forums/showth...highlight=323i

I also posted about this too. It is all a matter of just software
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      01-03-2011, 09:36 AM   #7
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Thanks DimSum. I just find it strange that the UK tuners only seem to be able to get around a 15bhp from a remap. Would the 2.5si map need to be loaded onto the ECU? or is it more than just the engine map?
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      01-03-2011, 02:45 PM   #8
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Quote:
Originally Posted by Fraser-Z4 View Post
Thanks DimSum. I just find it strange that the UK tuners only seem to be able to get around a 15bhp from a remap. Would the 2.5si map need to be loaded onto the ECU? or is it more than just the engine map?
Could be re-map and a more free-flowing primary cat. But most likely a re-map.
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