617 starter in a 616 - PeachParts Mercedes-Benz Forum

t walgamuth · #1 01-09-2013, 03:12 PM

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?

No I did not say that. I said the effect is small compared to the compression. And I said you can turn a motor with your hands if the compresson is eleminated.

funola · #2 01-09-2013, 03:15 PM

Quote:

Originally Posted by t walgamuth

No I did not say that. I said the effect is small compared to the compression. And I said you can turn a motor with your hands if the compresson is eleminated.

Try turning it at 160 rpm by hand. Ultimately both compression forces and the extra mass has to be accounted for in designing a starter motor.

t walgamuth · #3 01-09-2013, 07:15 PM

Quote:

Originally Posted by funola

Try turning it at 160 rpm by hand. Ultimately both compression forces and the extra mass has to be accounted for in designing a starter motor.

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.

Just for kicks I looked at the part numbers for all diesels offered starting with the 220 in 1968 to the 300 turbo offered in 1985. All call for the same starter.

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.

barry12345 · #4 01-09-2013, 08:01 PM

I am not sure why a civil discussion on starters has degenerated this far. . Many minor internal changes inside this series of starters may have been modified to improve costs or performance over their span of run.

Larger earlier starters may just have been much more rugged at one time acounting for the larger case size on the earlier four cylinder I90 starters for example. Or they were six volt units perhaps is another good possibility.

I think starters where never in house manufactured by mercedes. I often wonder why mercedes engineers did not have a decompression arrangement to get the speed of engine rotation a lot higher before trying to start the engines. even if only on a few cylinders. It was pretty obvious their design of engine was not too responsive to starting in colder conditions. Maybe the presence of glow plugs eliminated this as a possibility. Even the option of drilling and tapping the intake manifold for really hot input air to start on from a couple of more glow plugs was never utilized. It may still be a worthwhile modification for some of our older engines.

Mercedes to me had from time to time had some great engineers in their organization. Whatever happend over time to make them less common must have been obvious to their organization.

Some of their research and development seems to still be good. Their execution to production levels may be somehow flawed though. Their attempts to modify problems in production runs seems not that common anymore either. They used to address common problems from the field a lot faster at one time. Running changes in current production where common in the day.

t walgamuth · #5 01-09-2013, 10:05 PM

Quote:

Originally Posted by barry12345

I am not sure why a civil discussion on starters has degenerated this far. . Many minor internal changes inside this series of starters may have been modified to improve costs or performance over their span of run.

Larger earlier starters may just have been much more rugged at one time acounting for the larger case size on the earlier four cylinder I90 starters for example. Or they were six volt units perhaps is another good possibility.

I think starters where never in house manufactured by mercedes. I often wonder why mercedes engineers did not have a decompression arrangement to get the speed of engine rotation a lot higher before trying to start the engines. even if only on a few cylinders. It was pretty obvious their design of engine was not too responsive to starting in colder conditions. Maybe the presence of glow plugs eliminated this as a possibility. Even the option of drilling and tapping the intake manifold for really hot input air to start on from a couple of more glow plugs was never utilized. It may still be a worthwhile modification for some of our older engines.

Mercedes to me had from time to time had some great engineers in their organization. Whatever happend over time to make them less common must have been obvious to their organization.

Some of their research and development seems to still be good. Their execution to production levels may be somehow flawed though. Their attempts to modify problems in production runs seems not that common anymore either. They used to address common problems from the field a lot faster at one time. Running changes in current production where common in the day.

the starters I reference in my old fintails were both for gas engines....not that it should really matter much.

funola · #6 01-10-2013, 11:47 AM

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?

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.

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.

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.

funola · #7 01-10-2013, 12:00 PM

FYI, a "physically bigger" starter motor does not always translate to a "stronger" starter. Bosch rate their starters in Killowatt. You have to look up the starter by p/n and its KW rating in order to compare.

t walgamuth · #8 01-10-2013, 01:49 PM

Well, it sounds like we agree.