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Old 10-09-2012, 10:23 AM
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Originally Posted by fmugur View Post
Is the 4.8 running cooler than 4.4? I was under the impression they would both run at around 108C. It looks like TB runs much lower than us.
Probably does run cooler. The ME 7.2 used on the 4.4 in our cars was amost a left-over "operating system" if you will by the time it was used in the 2000 X5 4.4i. It does not have the sophistication of, say, the then current Japanese systems employed. For example, my Toyota V8 from that era maintains active control of the engine operation from idle to WOT, whereas your X5 goes into open-loop at the drop of a hat (which is not a bad thing if you like to tinker with parameters and sensors, BTW)

Anyway, the high operating temperature on our 4.4i engines is a band-aid to help the car deal with increasing emissions requirements, and maybe a token throw at a little bit of economy. The previous iterations of this same engine ran 30 degrees cooler. The 4.8 is the same basic architecture, but uses the ME 9.2 engine management system. While I have a great deal of familiarity with the ME 7.2, I have not delved into the 9.2. However, it is likely that engine management system has evolved sufficiently that BMW can run a more optimum 195 or so coolant (& cylinder wall temp), and still maintain emissions compliance.
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