Whenever someone asks if it's worth swapping in the XFi 1-ring (compression ring) pistons in place of the garden variety 2-ring style, the opinion seems to be: probably not worth (it in terms of fuel economy gains), unless you're taking the motor apart anyway to do something else.
The implication is that the gains are probably pretty insignificant.
Then Peter7307 posted some interesting figures about the relative amount of friction from bearings, pistons & valvetrain for a Mercedes 2.0L gas engine operating at 2500 RPM and medium load (in the
thread about valve spring strength as a possible efficiency mod).
Total engine friction losses were estimated at 1.5 kW:
- 42% - piston assembly contributing
- 39% - bearings
- 19% - valve train
(Source:
Engine friction lubricant sensitivities: A comparison of modern diesel and gasoline engines)
(Anybody know approx how much power a 2.0L gas engine would be making in those conditions?)
Anyway, the relative amount of piston drag got me thinking about the XFi pistons again, and thus the
Dumb Idea of the Day(?) TM:
Would removing the bottom compression ring be feasible for non-XFi owners?
Here's the XFi piston. Anyone got a pic of a regular piston to compare to it?
