> ....1. Let us assume that the engineers want at least 50psi oil pressure > at cruising > speed, and that takes about 1/2 gpm. Let us also assume that a mechanical > drive > oil pump puts out 1.5gpm at that engine speed, and the pressure relief > valve is > set for 90psi. So the mechanical pump has to pump 1.5gpm at 90psi, while > the > electric one pumps .5gpm at 50psi. There's room for a large percentage > savings > in pump power... > > Let us just throw all that out for this engine. All of it.
I recently read a too-short article (don't recall where for the moment) superficially explaining how these electric oil pumps operate in this application. After considerable testing and development, it has been discovered that the oil pressure and flow requirements for these engines (and others, presumably) varies considerably during various operational phases. So, you don't need 50psi all the time except when the engine is really working and most of the time it's less, sometimes a lot less, just maintaining the oil cushion in the bearings. Depending, I suppose on engine temp, manifold pressure, throttle position etc. all sending signals to the ECU which then varies the oil pressure by some quick change method. This was found to save power which eventually translates into economy. Since this is a dry-sump engine, the separate larger scavenge pumps operate at higher speeds because they pump mostly foam back into the tank. > 2. A mechanical drive water pump has to pump enough water to cool under > maximum > cooling needs at all times, the thermostat controls how much actually goes > through the engine. With our electric PWM drive water pump, we get rid of > the > thermostat and pump just enough water to cool the engine. I bet the > savings are > over 90% in the winter, and substantial in the summer except when you're > climbing a hill with the A/C on or towing a heavy load... > The thermostats are now electronically variable (my C300 is this way) and the electric water pumps (back to the Porsche) move just enough water to maintain temps, working with the variable speed electric cooling fans. My C300 has one big variable speed electric fan behind the radiator and nothing else. No aux fans any more. The C-300's swash plate AC compressor (still belt driven but no clutch) pumps enough R-134 to cool the cabin and no more. This is all progress and seems to be reliable. RLE > > _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
