Alpina B3 crankshaft

[pizdel]

Hello,
Does anyone know the weight of the Alpina B3 2.7 crankshaft?
How about the counterweight radius?
As I understand it Alpina used a lightened M21 crankshaft. This does make sense since the diesel pistons are about 200g heavier each, however I'm curious how Alpina solved this. Did they skim material off the counterweight top or did they drill holes until the assembly was balanced?

[digger]

its the same crank AFAIK, ive not heard they lightened them.

being an inline 6 you can machine the C/W without too much fear

[pizdel]

I read about it in Everett's bookunder C2 2.7
I'm thinking Alpina would have made them as light as possible, still they would be balanced for the special Mahle pistons, but it would be a good ballpark figure.

[digger]

Use an eta crank if you can. All the work done already

[pizdel]

OK, so after a bit of research I think I know what Alpina did.
I have acquired a forged steel 81mm crankshaft with cast number 1275884 with a weight of exactly 23kg. It was weight bare, the only component still attached being the small pilot bearing. I believe Alpina used these lightweight M21 cast numbers. I saw an old auction on Yahoo Japan and up for sale was an Alpina crank with the above cast number.
However, there's also cast number 2488224 which is also from the M21D24. These look to have less machine work on the counterweights and is possibly the 24.5kg version that Metric Mechanic mentions in their article.
It could also be that different regions got different versions or that the 24.5kg is an early design. According to the ETK the US only got the diesels on the E28 and only until 1985, while in Europe the E30 diesel was still made in 1993. All US and EUR versions are listed with the same part #.