[Shawn_speed]

I am stumped. I can't find a picture of the M54 crank case or block. If anyone has it to post , we can put this matter to rest. Here is a picture of the N52 block for reference.

Indeed the critical dimensions of N54 matches M54 but that by itself does not mean it is the same block. I don't know the M54 that well. Did it have an electric coolant pump or was it mechanically driven?

[F32Fleet]

Originally Posted by KevinC

From the new issue of Autoweek that just arrived, describing the refreshed 5-series that's about to show up as an '08 model...

...all-new inline six-cylinder engines-the turbo model fitted with the German carmaker's second-generation High Precision direct injection fuel system. The updated engines, which head into other BMW models throughout 2007, don't offer any great increase in power or torque but are more economical and emit lower levels of cardon dioxide than their predecessors.

Maybe I'm reading too much between the lines, but "2nd generation" direct injection? Does this not sound like something new already?

From what I understand, the DI used in the 335 is "2nd generation". VW/Audi used 1st generation.

[Jonn335]

i have found out that the bore spacing on the M54 is the same as the N54 at 91 mm...

[Shawn_speed]

Corrections and amplifications.

Confusion on what 2nd generation DI means.

The bible of N54 information before we had the actual car was an article released by BMW called "N54 bi turbo in debth". The article heading was misleading because it actually talked about efficient dynamics and a whole lot of other stuff beside the N54. However, in it, they seem to be referring to Voldermont "thou who shall not be named" as the culprit of 1st generation DI. They Pooh Pooh it that way and claim they sat that round out. This led to the BMW vs. them first and 2nd generation theory.

Then came four PDF gem of engine information files in our own technical forum section. These are material clearly intended for educating BMW techs.

In it, BMW clearly tells their own troops that we are going to define the 2003 7 series iteration of DI as first generation and the DI in N family of engines are going to be called 2nd generation.

Everyone here is welcome to call theirs aunt Fanny if they wish but I am going with what BMW is telling their own techs rather than the puff fourteen page we are going to save the world from breast implant pollution piece.

In either case, if you buy the marketing version and call the "other" manufacturers 1st gen and N series 2nd, what are you going to call the 2003 7 series engine's DI?

Shawn
Phoenix

[Shawn_speed]

Originally Posted by Jonn335

i have found out that the bore spacing on the M54 is the same as the N54 at 91 mm...

The bore, stroke, bore spacing AND block height are identical in M54 and N54.

All this proves is that when the whole world has abandoned in line sixes in favor of V6's (quick, name another company with a good in line 6) BMW has perfected it to the point that once you go... never mind. They found some dimensions that work and they are sticking with it, that is all.

M54 uses a traditional belt driven water pump. This requires the impeller to be inside the block and mandates totally different plumbing and water jackets in the block casting vs an external electric motor coolant system like the N generation of motors. This fact alone convinces me that the N motors are indeed a new generation of in line BMW 6 cylinder engines.

The only real way to prove or refute this fact is to procure a picture of the M54 block.

Shawn
Phoenix

[jmonier]

Originally Posted by Shawn_speed

The bore, stroke, bore spacing AND block height are identical in M54 and N54.

All this proves is that when the whole world has abandoned in line sixes in favor of V6's (quick, name another company with a good in line 6) BMW has perfected it to the point that once you go... never mind. They found some dimensions that work and they are sticking with it, that is all.

Why didn't they use those dimensions in the N52, then?

[Shawn_speed]

Originally Posted by jmonier

Why didn't they use those dimensions in the N52, then?

Bore spacing determines placement of crankshaft bearing supports in the block. If this dimension is different, the crankshafts would have totally different designs. Indeed the crankshaft design and structure of N52 and N54 are totally different. But if the blocks of N54 and N52 are identical as I claim besides the alloy, the bearing support spacing would be identical. If bearing support spacing is identical, then bore spacing would be identical. Indeed the bore spacing of both N52 and N54 are identical at 91mm.

Bore and stroke are a tooling issue; they have nothing to do with design of the block. The ratio of bore to stroke is played with during the design process to manipulate engine's power vs. torque characteristics. The larger the bore, the more low end torque, the taller the stroke, the engine revs up faster, hence development of power at the expense of lower torque.

This certainly explains the difference between the N52 Magnesium alloy block vs. the Aluminum block of N54 and its steel cylinder liners. They have totally different requirements and characteristics, hence different bore, stroke and crankshafts.

I am guessing the fact that the numbers are identical between the N54 and M54 are due to cost saving issues. They are using the same tooling for installation of the same steel cylinder liners in the two different aluminum blocks. If the steel cylinder liners and the very costly tooling and robots for its installation are the same, the bore spacing, block height and the bore dimension would have to be the same. If they have this much in common then additional costs savings can be achieved using similar designed crankshafts and connecting rods, hence the identical stroke dimensions.

The key question to ask is: why go through the trouble of changing the block design at all? The answer is the magic of electric coolant pump. Aside from all the energy efficiency and computer programing of the fluid flow vs. dependency on RPM driven flow rates advantages, removing the cumbersome mechanical water pump from front of the block frees up space for all kinds of new options. One we have already seen is the dual plumbing of intake air to the front turbo and compressed air back to the intake manifold. Both of these cross in front of the block in the N54.

Shawn
Phoenix