Quote:
Originally Posted by EEBreh
Are you afraid of eventually passing the limit of the pistons and rods? The N55 engines don't have forged components like the N54 except for the crank.
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For what its worth, the only forged component of the N54 BMW listed in the technical manual was the crank. Pistons and rods were never mentioned bar to say they had been modified to withstand higher torque. People can take from it what they will.
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Pistons and rods
As with the cylinder head, the piston designs differ between engines. The N54 uses a special piston for compatibility with the direct injection system. The piston crown is modified to meet the mixture formation requirements.
The N51 engine uses a lower compression ratio and accordingly uses a different piston design. The N52KP uses the same design as the N52 engine.
The connecting rods on all of the NextGen6 engines have been stiffened with a thicker beam on the rod. This design has also been in production on the N52 since 6/06.
Crankshaft
The cast iron crankshaft is retained for the N52KP and N51. To accommodate the increased power output of the N54, the crankshaft is forged steel."
I know its been beaten to death, but I'm sure they'd have jumped on marketing the pistons and rods if they had been forged like they did with the crank.
But yeah, a forged piston and rod set would be a wise investment on an N55 running high boost.