Starters

[snaponbob]

Anyone using an M54 starter in an S54? I have a couple good M54 starters, and my S54 starter is acting up.

[powershiftgear]

checking RealOEM part number 12417835735

it seems they aren't interchangeable. S54 requires 1.3kW starter.

[snaponbob]

checking RealOEM part number 12417835735


it seems they aren't interchangeable. S54 requires 1.3kW starter.

I appreciate your research. But, did that as well. Physically, all the 50/52/and 54 starters are physically the same where they mount and engage the ring gear. There are active part numbers for E36s (all gas) and E46s (all gas, exc M3) and a part number for the S54 only. Here is where it gets confusing ---- The S54 starter is 1.3kw, and all of the others are 1.4kw. M50/52 have a c.r. of 9.5:1, the S50/52 is 10.5:1, and the S54 is 11.5:1.

So, why would the highest comp have a lower power starter? BTW, I called Bosch USA -- NO help. Is this just another example of BMW "overthink"?

I have two fresh non-S54 starters on a shelf. I am trying to avoid spending $200-250 if I can.

[snaponbob]

I think I have my answer ... different gear reduction ratios.

Given the occasional "click" and no start, I am suspecting the starter solenoid. Regardless of starter, or just the solenoid, the starter has to be removed. WHAT FUN !!!!!!!!

[aeronaut]

I'm interested also, I have a fairly new S52 starter, and an S54 build on the way.
We know an S54 starter will work with an S52 flywheel.
So the pinion gear on the starters have a different number of teeth?

[snaponbob]

I'm interested also, I have a fairly new S52 starter, and an S54 build on the way.
We know an S54 starter will work with an S52 flywheel.
So the pinion gear on the starters have a different number of teeth?

Not sure what the difference, but is not the 9 tooth gear that turns the flywheel. Since the M52 starter is rated at 1.4kw and the S54 starter is rated at a lower 1.3kw, it stands to reason the the planetary reduction gears are different. There is only a 1 point compression ratio difference, I do wonder if this is just the result of typical micro engineering. The starter WILL bolt up properly, but I wonder about longevity.

[aeronaut]

Yea, folks build S52's to higher compression, and no one screams about starter failure.

Mine is for a track car, so many less start cycles/engine life, so I'll likely try my S52 starter on the S54.

[snaponbob]

I finally found the differences of the E46 M3 starter and the others (M54 and M/S 50/52)

The M50/52 shows different P/Ns (even though they ARE interchangeable) and the M54 starter P/N covers 50, 52, and 54. All are 1.4kw. The S54 starter is a 1.3kw, which confused me. Turns out the planetary gear reduction ratios are different. So, the S54 starter is "weaker" but the torque is multiplied further in the gear reduction gear set.

[aeronaut]

Good info, and interesting. So the S54 has a weaker starter, and geared to turn the engine slower.

Mine's going into a S54 swap, with an S52 clutch and flywheel, so I'm def using my almost new S52 starter.

[snaponbob]

Good info, and interesting. So the S54 has a weaker starter, and geared to turn the engine slower.

Mine's going into a S54 swap, with an S52 clutch and flywheel, so I'm def using my almost new S52 starter.

Not really. The electric motor produces .1kw less power, but the planetary gear set multiplies it more. Think of it this way --- less IN ... more OUT. Planetary gear sets can reduce or increase the output of a motor/engine, depending on the need is designed for.

[MauiM3Mania]

Good info here!