Difference between the 2.5 litre Z4 engines

[Matthew.]

Hi,

After some head scratching today whilst car searching; I came across something I couldn't get my head around.

Why did BMW have a 2.5 engine with 189hp between 2003 and 2005, then a 2.5 with only 175hp between 2006 and 2008, but introduce the new 2.5si in 2006 with 215hp?

Why introduce two new 2.5's in 2006 and lower the output of one to 175hp?

Can anyone enlighten me?

 

[Leesfarm07]

So what did they do to increase the horsepower from 189 to 215 then?

 

[Matthew.]

From what I have gathered, the 2006 2.5's are new engines compared to the 2003-2005 2.5. Just with two new out puts...

From Parkers: In early 2006 the Z4 was facelifted and the engine line-up overhauled. A new 3.0-litre was launched (badged 3.0si) which boasts 265bhp and a 0-62mph time of 5.7 seconds while a fresh 2.5-litre was also introduced and comes in two outputs. The higher-powered 2.5si has 218bhp and records a zero to 62mph time of 6.5 seconds before going on to a top speed of 149mph. The Z4 2.5i with its 177hp engine offers drivers the smoothness of a six-cylinder powerplant but with a slight reduction in top end performance.

I appear to have answered my own question

 

[MrPT]

I've never been sure about this, but if it's the same as the 3 litre N52, the difference in the "si" version of the 2.5 will be 3 stage induction vs single intake manifold for the non-si, plus an ECU detune. The 2.5 and 3.0 N52 have a different bore/stroke, unlike some other engines for the "25" and "30" designated models in the BMW range which are actually the same capacity - a bit confusing sometimes!

I can't imagine the 2.5si and 3.0si being much different to drive, but the 3.0si is much rarer and tends to be better equipped. Price-wise there isn't really much in it (which I guess makes the 3.0si a better deal if you can find a good one).

Really nice GTI, by the way.

 

[Matthew.]

I've never been sure about this, but if it's the same as the 3 litre N52, the difference in the "si" version of the 2.5 will be 3 stage induction vs single intake manifold for the non-si, plus an ECU detune. The 2.5 and 3.0 N52 have a different bore/stroke, unlike some other engines for the "25" and "30" designated models in the BMW range which are actually the same capacity - a bit confusing sometimes!

I can't imagine the 2.5si and 3.0si being much different to drive, but the 3.0si is much rarer and tends to be better equipped. Price-wise there isn't really much in it (which I guess makes the 3.0si a better deal if you can find a good one).

Really nice GTI, by the way.

Thanks

 

[srhutch]

I wouldn't say the 3.0si is rarer than the 2.5si. As with all BMW's is just them giving you a choice of engine size/output.

Pre facelift the 6cyl were 2.2, 2.5, 3.0 M54 and post 2.5, 2.5si, 3.0si N52 engines.

 

[MrPT]

Sorry, I should have said that I meant rarer on the second hand market. I found a lot more 2.5si's than 3.0si's available when I was looking and others seem to have had a similar experience.

May well have changed in the past year though - I tend to not look on autotrader etc. these days because I always end up wanting a z4mc! :roll: