Engine friction torque and power loss quantified

[RobertSmalls]

Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI

Here's an SAE technical paper that reads a bit like a Honda press release, but it's full of good technical information about the Insight.

Page 8 has a plot that gives engine friction torque at 1500RPM for a number of different engines. The Insight's appears to be about 10Nm at 1500RPM, i.e. 2.1HP. That's about half the value for their baseline 1.8L engine.

It means that engine friction is about half as large as road load at 45mph, which explains why the Insight's EV mode is so disappointing. It's also a reminder of how important it is to shut down your engine when it's not in use.

[Frank Lee]

Pretty much everything has gone to rollers in the valvetrain now.

The piston dimpling is a new one for me... but I confess, I don't get the reasoning as cylinder cross-hatching has been used forever for the same function (as I understand it or misunderstand it).

[roflwaffle]

I think the point of either is that there is more lube per unit surface area to avoid dry spots, up to some point where the surfaces become too rough and the lubricated friction starts to increase.

[Christ]

Re: cross hatching- on old splash lubed briggs engines, one of the tricks we used to use to keep higher hp engines running longer was lightly scoring the outside of the piston below the ring lands, so that oil mist in the crankcase would more really sick to the rough surface.

Likewise, a mild polish to the exposed areas of the crank and rod would help keep oil off them, reducing rotating/reciprocating mass.

[Old Tele man]

...analogy: piston "...cross-hatching..." is to oiling as "lightly sanding" is to good paint surface preparation...they both provide "holding" power (surface area) for the applied liquids, oil and wet paint.

[Christ]

Radially grooving the skirts (around the circumference of the piston, just below the ring groove, supposedly makes the oil sweep more effective, by giving the oil an area in which to be displaced from the cylinder wall.