I think the compression ratio of the supercharged M111 is slightly lower IIRC, maybe like 8.5 to 1?

The other thing to keep in mind is that for most of its life the supercharger is just basically rotating without putting out boost. Mercedes uses a bypass switchover valve which short-circuits the input/output lines on the blower. It basically allows the blower to free-wheel when boost is not needed.

Here's a quote from a Ford web-site that describes the function better than I can......

"The bypass is especially important. We tend to forget that in normal driving the engine is very
seldom in full-power, wide-open throttle (WOT). In a supercharged engine, this is the only time the
blower is actually being used. The rest of the time, at part-throttle cruise, idle, or deceleration, even
a supercharged engine has vacuum in the intake manifold. This vacuum is used to open the
bypass valve to open a passage between the throttle and the manifold (bypassing the
supercharger). This equalizes vacuum in the entire system so that pumping losses in the blower are
minimized. Factory tests have shown that an Eaton M90, with this valve, produces only a 1/3-hp
parasitic loss while cruising at 60 mph. As a result, the V-6 factory applications with this blower
average about 30 miles per gallon"

Even at "full-boost" on an M111 I don't think the blower would use anywhere near 20-30 HP. Compressing 6-7 psi into a 2.3 liter engine just isn't all that much work IMHO.

I'm be watching your thread to see if anybody else has tried to delete the supercharger but I think I'm going to fix mine when it finally dies.

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