Quote:
Originally Posted by CrzyChris5
Also just found this which answers my question better.
"The M40i’s unit was constructed with a closed-deck design, meaning that the water jacket surrounding the cylinders is sealed at the top, endowing the crankcase with an exceptionally high degree of stiffness.
BMW also gave it a new oil cooler, high pressure injectors, turbos integrated into the exhaust manifold operating at a higher boost, an optimized air intake manifold, a forged crankshaft, pistons with a modified top ring and high-performance spark plugs, and upgraded steering response."
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Not sure where you got that, but I looked into the oil cooler at least, and it's the same as the one on the X3 35i:
X4 Oil cooler:
http://www.realoem.com/bmw/enUS/show...84#17217601536
X3 Oil cooler:
http://www.realoem.com/bmw/enUS/show...84#17217601536
I don't have the time now, but I want to dig into this some more and determine the true engine differences.
Edit:
Air Intake manifold is the same.
Injectors appear to be the same, I compared the high pressure fuel system from both but I may have missed something.
Crankshaft is different and is same one used on M2.
Turbo is different, looks like the made it only for the X4 40i, but all BMWs from this era have the turbo integrated into the exhaust manifold.
Spark plugs are different brands, but I don't know if that means they are different in practice.
Pistons are different