Why is BMW going backwards when it comes to choosing M3 engine materials?
As many of you know, Automobile magazine's August 2001 issue is on newstands now. The front cover and cover story is devoted to "///M Power! Exclusive Test of All Five 155-mph BMW M Cars"
This is what they say about the M3's engine:
"It should be noted that the standard BMW six-cylinder engines have aluminum cylinder blocks and heads, but the block of the M-spec six is cast iron. The use of iron was dictated first by the desire for compact dimensions--the liners in an aluminum block take up space, necessitating a longer engine. The second reason was the sheer strength of iron: This engine produces a lot of power for its displacement, and cast iron does a superior job of sustaining the extraordinarily high cylinder pressures and rpm."
If iron is superior in strength and durability, why didn't they use an iron cylinder block for the M5 instead of aluminum?
I think that both the iron and aluminum blocks are cast. Casting is several times more expensive for aluminum than iron. After the cast blocks are made, some amount of machininig is required to clean them up, etc.
Casting is inferior to machining from a solid billet, but amazingly cheaper.
My dream engine block would a billet of titanium that is CNC machined, I suppose.... I wonder what they use in F1?
The choice of material for the engine block can be dictated by a number of parameters - weight distribution, production cost etc. In the case of the M5, the car is front heavy so aluminum makes more sense. The M3 motor probably (I don't know this for sure) shares a common block w/ more run o the mill 3ers. Economies of scale.
BTW, I read somewhere (Racecar Engineering perhaps) that the engines used in F1 literally start to disintegrate on a molecular basis after about 1000 km, such are the stresses. Wow.
I have another theory as to why they are using cast iron instead of aluminum. I buy the reasons of cost and space, but not strength. Rather, I believe that BMW is just feeding a line of BS to the press.
I think the real reason why they are still using cast iron is because the engine in the "new" M3, M Roadster, and M Coupe, is the same engine as the one that those lucky *** Europeans have had for years in the E36 body. Remember guys, the new M3 engine is not new at all, it's just that BMW "magically" got emissions approval and decided to finally import the M3 Evo 3.2 motor. That motor put out 320hp!!! I don't know about you guys, but I am sure glad that the US M5's have the identical engine to the Euro counterpart, and didn't get SHORTED 80 HP, like the E36 M3 guys did. I can live with 6 less hp, cause you can fix that with an exhaust and CAI, but 80???
BMW NA said that they didn't use the Euro engine at the time due to emissions but also cost, as the car would then be priced at over $50K. Well SURPRISE! The new M3 sticker is now over $50K! And by tweaking some stuff with the intake and exhaust, they were able to bump the power a bit to 333 hp.
Anyways, the point I am trying to make is that the lazy asses at BMW are recycling an engine that they have had for years, so why should they change something that ain't broke? It was cast iron back then, as it is now! I think BMW is laughing all the way to the bank on the E46 M3, because they could get away with putting out a "new" M3 with the same old engine! They, like Microsoft, are a great MARKETING company!
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The reason the M3 engine block is cast iron is that it is based on the M50 engine family. The European S52B30 and S52B32 engines for the E36 ///M3's have a cast iron engine block because of this. And for the same reason the S54B32 engine block is also cast iron.
The engine for the E46 ///M3 is the S54B32, but this engine is quitte different than the previous S52B32 engine.
First of all, The S54 has a completely modified valve train to reduce friction losses and to improve immesions. Also the intake system is completely modified and shaped differently. The bore and stroke is also different compared to the older S52B32. As a result, the S54B32 is allowed to rev up to 7900RPM which is quiite a bit more than what the S52 could (7400RPM).
Cast iron is still superior compared to aluminum, but a cast iron block for a V8 would add to much weight to the front axle. The 4.0 liter biturbo diesel is made from cast iron because cast iron, but you only see this engine in the E38 7 series.
Why is BMW going backwards when it comes to choosing M3 engine materials?
I wonder what they use in F1?
Haha, someone should tell Porsche
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