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07-23-2001, 12:29 PM
Little sibling 330 has an aluminum engine while the m3 uses iron like the old m3 even though 90% of the parts are new or modified, WHY??? Thanks for any insight...

07-23-2001, 12:31 PM
probably because the extreme heat that M engine gives off.Steel is probably more durable.

07-23-2001, 12:34 PM

07-23-2001, 12:37 PM
ooops i meant iron,

07-23-2001, 12:38 PM
I recall reading some interesting metalurgy about the "iron" in the S54 block. Yes, it's heavier than aluminum, but it seems quite clear that the iron was used in the interest of strength, the better to hold together under 8000 rpm loads.

Will Gilbert
07-23-2001, 12:40 PM
It would take so much more aluminum to get the same strength as an iron block it is just not worth it. Using aluminum would make the cylinder spacing be greater which in turn would create a longer engine which would mean more cylinders over the front axel which which create increase rotational inertia and the polar moment which would mean crappier handeling. Any questions?

07-23-2001, 01:15 PM
BMW choose “iron” because of the high pressures and vibrations in an 8000 rpm I6 engine. This could not be done (within design specs) with AL. However, this not your typical “iron”. It is GGV cast iron.

Cast-iron with vermicular graphite (GGV) is a cast-iron specialty is a transition metal between grey cast-iron (lamellar graphite) and spherical graphite cast-iron. It is formulated to provide the best combination of tensile strength, flexibility, heat conductivity, and resistance to scaling for workpieces subject to high thermal and loads.

Note that this GGV iron is about 20% lighter than gray cast iron used in American car engines.

BMW is the first auto manufacturer to use GGV iron. I believe they introduced it in the 740d in Europe.

They know what they are doing!


07-23-2001, 02:37 PM
I read in Roundel last month or the month before that BMW is experimenting with magnesium blocks. Any other word on these if they will end up in our beloved "M"

Thanks guys for your responses. The breakdown of the use of iron was exactly what I was looking for.

07-23-2001, 02:39 PM
precise with all the facts. Gotta love this board!!!

of magnesium 3.6L I6 for possible BMW supercar
07-23-2001, 03:01 PM

07-23-2001, 03:08 PM
Now wouldn't that be a fun setup. A small displacement F1 style V10, carved from solid magnesium giving you an M5 4 door sedan that weighs maybe 3000 pounds and has 500 or so horsepower... drool... Talk about the ultimate sleeper.

07-23-2001, 03:09 PM

07-23-2001, 03:19 PM

07-23-2001, 03:28 PM

Mr. Grinch
07-23-2001, 04:27 PM
to create the structures in this kind of iron? I forget most of my old materials science... what is the structure of the metal when you add this kind of graphite? Any links where I might find more info on it?

07-23-2001, 05:46 PM
Bimmer mag had some info about the use of GGV iron in BMW engines about a year ago. I am working off of my memory. The article stated the use of this type of iron was a first in auto applications and that it is about 20% lighter than the grey cast that is normally used (e.g. American engines.)

As far as the cooling process, I believe (again, working from memory) that the iron is still in alpha phase (near the alpha + gamma transition), and then rapidly cooled leaving a FCC structure (from a BCC structure.) The iron has a high carbon (graphite) content and can be alloyed with Si and Mo. I don’t have a book or web reference, but check out the Iron-Carbon diagram:

The GGV is (a.k.a. pearlite) in the cast iron region (the lower right region of the diagram ~1333 deg. F).

Hope this helps! I’m just a simple patent attorney.


Mr. Grinch
07-23-2001, 06:10 PM

07-23-2001, 06:22 PM
If you run an Al block you need steel sleeves for the cylinders. Iron blocks don't need the sleeves. Therefore- an iron block can be physically smaller for the same engine displacement. I read somewhere that was BMW's main reason- the Al block would have been too large for the engine bay.

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