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Originally Posted by metromizer
therefore, less pump pressure equal better FE?  LOL I'm just having some fun at my own expense.  |
Yes, a lower pump load would cause less engine load. You really only want JUST enough pump output to keep the clutches from slipping. Many modern trans controllers work by inferred engine torque -- they back off at low pedal inputs, or if the ECU commands less torque, to save gas. Also, overpumping when not needed is, itself, another heat maker.
Quote:
Originally Posted by metromizer
But seriously, I love the modification, I'm just trying to figure out how to fix a secondary problem (that probably doesn't even exist, but someone above mentioned it).
I am sure there is a happy medium between higher parasitic loses from the front pump and better efficiency through more crisp shifts and less slip. Too harsh a shift and the transmission would undoubtably eat itself up in commute traffic, not to mention spill your coffee. A smooth shifting transmission or a real tall geared one has a lot of slip and therefore must generate heat. Heat is a result of friction, so the coolest running transmission will likely be the most efficient one. A gage might tell the tail, unless the trans cooler is already an over-acheiver. One thing is for certain, the guys who sell new cars want the buyer to experience a good 'feeling' transmission, and low warrenty repairs numbers.
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Trans. efficiency goes UP with temperature -- to a point. The oil viscosity reduction is good for FE, the metal clearances open up and both fluid flow losses and bearing friction drops with higher temperature, UNTIL the oil is so thin that it looses film strength. Once that happens you get MORE friction and wear takes off.
Quote:
Originally Posted by metromizer
I'm not saying slippage is a problem, but if it were...
On that same note, my '95 Toyota Celica's slushbox was leaking and slipping a little, so I bought this stuff that claims to remedy those ills. I put some between my fingers before feeding it to my Celica, and it was kind of sticky, like oily honey. The claim was "reduces leaks, reduces clutch plate slipage while retaining lubrication and cooling properties of your trans fluid" I don't belive in miracle additives, but it was already leaking and slipping, nothing to loose so I dumped the stuff in. Shifts definately became stiffer (but not harsh), and I noticed FE got a little better, maybe 2mpg. it slowed the leak down. 30k miles later the leak is bigger than ever...
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The big question is what it was like at operating temperature. If it increased the lubricity it might have helped. Worn components may benefit from higher viscosity if it helps prevent metal to metal contact (worn parts often have rough spots, at least on a microscopic scale).
ETA: You mentioned shift quality. Yes, it is a HUGE buy/no-buy issue for buyers. Even Consumer Reports will call out a car with "harsh" or "slow, ill defined" shifting. Knowing what makes a shift feel good, through both the torque and inertia phases, is a refined art. Calibrating all those clutches to get it right can take weeks.