Quote:
Originally Posted by funola
So you're saying the starter has to overcome only compression, and the mass and drag of an additional cylinder has no effect on starter design?
I am sure the MB engineers did their home work. Maybe the very first 240's used a lower powered starter. When an additional cylinder was added, MB decided to upgrade the 240D starter to a 300D starter for commonality and reduced cost?
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Quote:
Originally Posted by t walgamuth
If you can offer some proof that the mass is a significant part of the sizing of the motor as compared to the compression, I will be happy to step back and call you teacher.
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I did not say mass is a significant part of sizing a starter motor. I said mass should be accounted for. When you build a car that weighs 9000 lbs vs one that weighs 3000 lbs, do you put in a bigger HP motor in the heavier car? When the engine is at rest, before there is any compression in the cylinders, does it take more HP to get the motor turning in an engine with more cylinders and more rotating mass?
Quote:
Originally Posted by t walgamuth
I also have thought of a good reason they may have upgraded when they went to turbocharging the motors. The starter lives right under the turbo so there should be considerably more heat generated from the turbo. More heat = more resistance for the electricity flowing through the starter so it would follow that they would make the wires, brushes and all electrical devices a bit larger to insure reliable operation with the extra heat.
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More heat does not = more resistance for electricity. Heat may affect magnet wire insulation breakdown and expansion tolerances of parts inside the starter. That's why there's a heat shield for the starter in the turbo motors.