New Theory

[wwest]

DISCLAIMER:

Previous post is not a simple reply – this is actually 11-th edition of “Wwest Mythology”. Previous 10 editions have been discussed and bitten to death in approximately ~1000 posts in a number of forums/sites. I have read some of those. What is the result? See here:

http://www.siennaclub.org/forum/index.php?...ic=6921&hl=

As if previous discussions do not exist, wwest posts the same stuff again and again and again…

Like a Big Propaganda Machine, wwest is in a win-win situation: if you start infinite discussions and win – it does not mater, next time he will post exactly the same stuff. If you ignore him – he will flood forums and poor readers would have to deal with it anyway.

END OF DISCLAIMER

Okay, "teacher" will take a different tact, tactic.

Do you know how many things in a car simply waste energy....???

A) Power stearing hydraulic pump when there is no "stearing" to be done. What, 98% of the time?

And yes, I do know that PS pressure helps "hold" the stearing in a "set" position, but just how much energy does that require in comparison to the HUGE losses?

The PS must have the pumping capacity/volume/displacement to help, SERIOUSLY help, turn the wheels at or near a dead stop(parallel parking...), all the while with the engine turning only at idle, of maybe slightly above.

So, 2200 RPM and driving straight down the highway at 65MPH guess how much pressurized PS fluid is simply being bypassed back into the sump.

Is it any wonder that many cars are converting to electric power stearing, even at the risk of having the solid state electronics overheat and therefore automatically going into a sub-standard power assist mode?

B] Gear-type engine lubricating pump. Again, pumping volume/capacity/displacement must accomodate full pressure and flow even with the engine at idle. So as engine RPM rises the EXTRA pumping capacity must be bypassed back into the sump.

Either BMW or MB, don't remember which, has already gone to a variable displacement engine lubricating oil pump in oder to reduce these losses and thereby reduce the engine heat load and also increase FE.

C) A/C compressor. Here again, the compressor pumping capacity must be such that it can provide FULL cooling capability at engine idle on a BRIGHT and SUNNY 100F (or above) day. In this case the A/C clutch along with a reasonably sized liquid refrigerant storage reservoir has been used for "eons" to ammiliate the effects of continuous engine loading by the A/C compressor.

So why do you suppose so many new vehicles are coming out equipped with the new variable capacity "swash plate" type A/C compressor, and the compressor clutch?

Because it is better design practice, overall, to have a continous ~2HP load on the engine rather than an intermittent load of ~7HP.

Getting the picture..?

D) And just what is the deal with the torque converter (hydraulic TURBINE pump, slush pump, etc.), just how lossy is that sucker?

The slush pump, torque converter, is really required ONLY to act as an automatic clutch. At low engine speeds, idle, the losses are so high that virtually no torque is coupled to the transaxle input shaft. NONE would be ideal, but nowadays you need a clutch pedal for that. The nice thing about the torque converter is that it also acts as a reduction gear ratio at low torque loading. But, that's where the torque converter lockup clutch comes into play. In OD it is highly desirous to have the engine operate at the lowest speed at which it can produce "just" enough torque for the current load factor...roadspeed. So at low engine RPMs the HIGH LOSS torque converter is bypassed by the lockup clutch.

E) This one is slightly off point but I bring it because if I don't someone else will.

The engine coolant water pump.

Almost all engine coolant water pumps are of the centrifical, turbine, type and thereby self limiting insofar as pumping volume is concerned. Obviously there is some "needless" loss involved here otherwise the water hoses would not "swell", balloon, as engine speed rises beyond the point wherein the thermostat will accomodate the pump volume. Other than the current crop of hybrids, all equipped, to my knowledge, with electric water pumps, other manufacturers have already converted to electric pumps, if not altogether then at least apartially so, for the cabin heater.

Get the picture..?

No...?

F) And finally....

The gear type ATF pump.

Like everything else above the most critical situation insofar as determining base pump volume occurs with the engine at idle.

Hmmmm..

Let's think this over a bit.

Just what "work" does the ATF pump have to do with the engine at idle?

Shifting from park or neutral to drive or reverse is clearly not critical insofar as pumping volume is concerned...

Upshifting once underway always involves engine RPM well above idle....

Aha, DOWNSHIFTING....

So, when does an automatic downshift with the engine at idle or nearly at idle.

Not for passing, kickdown, certainly...

But then how about just before coming to a full stop...?

Or during coastdown periods with the throttle fully closed...?

In both of these latter instances if the transaxle is to downshift lots of ATF pressure/flow will be required to ascertain the downshift clutches are quickly and firmly seated. Otherwise, with low or marginal ATF pressure these clutches would undoubtedly incur some serious level of slippage and the wear associated thereto.

So, the engineers say to each other, if we could eliminate just these two instances the ATF pump FIXED capacity could be a LOT lower and that would undoubtedly inprove FE overall while reducing the heat load and clutch wear rate.

Say, what does a stick shift driver do in these instances. Well as the cars coasts to a stop the driver would normally disenage the clutch and slip the transmission into 1st.

Well, we can't disenage the clutch....Can we...??

Sure can, simply "upshift" the transaxle a few notches, no substantial level of engine compression braking, NO transaxle clutch wear. Who cares if the upshifted clutches don't quickly fully and firmly engage...!

But what about coastdown periods at 40-30MPH with the engine at idle...?

Why not upshift then too, who's to notice?

________________________________________

The theory behind the above dissertation arose because I noticed a seeming abiguity between my earlier theory, "protect the drive train using DBW to prevent engine compression braking.'

Owners have been reporting that while in cruise control the engine/transaxle ECU will actually command a downshift to !Removed! roadspeed going down a hill.

Me..."What? Downshift a FWD or F/AWD vehicle and actually take advantage of engine compression braking?"

NOT...!

Or so I thought at first.

In cruise control the vehicle MUST be traveling ABOVE 35MPH. Engine speed is NOT at idle so the ATF pump volume is quite reasonable for supporting the downshift. Additionally with the cruise control engaged no serious level of engine compression braking will result. Once the downshift occurs the cruise control will raise the engine RPM just enough to HOLD the set speed.

So, what does all this rethinking mean..?

Not much.

Toyota, seemingly, first implemented this new upshift technique along with a significantly lower volume, HIGH EFFICIENCY, ATF pump in the 1999 RX300.

We all know by now, I hope, about the many reports of premature transaxle failures in the '99 RX300 that resulted.

Drivers still wanted quick kickdowns, downshifts, during, or worse, immediately after, those coastdown "upshifts". Or maybe even a quick "GO" downshift/kickdown if that traffic light suddenly turned green. But the new lower volume HIGH EFFICIENCY gear tyep ATF pump did not have that level of pumping capacity.

The rest, the '99 RX transaxle failures, is now history.

So by '00 the ATF pump volume was edged up a might but the upshift technique remained.

By the '01 RX model year Toyota knew they had a darn serious problem. They could not drop the upshift technique and still maintain the FE level they were touting and the EPA had published. So they raised the ATF pump volume yet again. But since the RX300 transaxle was never designed to handle the resulting level of heat load all products were shipped with the towing package, external ATF cooler included.

By the time the RX330 was brought to market the engineers had incorporated DBW "to protect the drive train". Prevent the driver, regardless of need, from being able to "command" a quick, FAST, transaxle downshift in the aforementioned circumstances.

I fully expect that very soon we will see the "final" fix for this MESS. The new Ford Edge uses a variable displacement ATF pump (To improve driver train efficiency, so says Ford). I suspect Toyota will soon follow their lead..

Ford, LEADING...??!!

[mehullica]

Wow, that's a great deal of something. All of your trans "operating" philosophy is incorrect. I don't know where you got your trans operation information from, but it's not correct. I was going to say more, but I won't.

[wwest]

Wow, that's a great deal of something. All of your trans "operating" philosophy is incorrect. I don't know where you got your trans operation information from, but it's not correct. I was going to say more, but I won't.

Good, I really do hate well-founded criticism.

[Grumpa72]

OK, those are your opinions but I am lost as to the purpose of the thread? Do I design my own car so as to be more efficient or are you just in rambling kind of mode? I see no suggestions on your part! ;)

Unfortunately, we are forced to buy what is available and not what we would want in a perfect world.

Gary

[wwest]

OK, those are your opinions but I am lost as to the purpose of the thread? Do I design my own car so as to be more efficient or are you just in rambling kind of mode? I see no suggestions on your part! ;)

Unfortunately, we are forced to buy what is available and not what we would want in a perfect world.

Gary

"..forced to buy.."

NOT..!!

But do you not gather all information available before buying...??

Knowledge, properly applied, never hurt anyone.