Did You Guys See That The Rx350....

[Nebraska99]

...just won the J.D. Powers and Associates award for best mid-size SUV?

[wwest]

...just won the J.D. Powers and Associates award for best mid-size SUV?

Absent the poor FE of the RDX engine due to derating until the turbo comes on line that award would have undoubtedly gone to the RDX.

The clear majority of the time the RDX engine runs in the derated, 8:1 compression ratio, mode.

Shame.

But I wonder, like the RX350 buying public at large, if J D Powers wasn't also mislead into believing the RX350 has a center open diff'l aided by a VC.

It doesn't.

[Nebraska99]

Well thanks Negative Nelly.

[wwest]

Well thanks Negative Nelly.

If you only tell them what they've done right.....

[rx350guy]

...just won the J.D. Powers and Associates award for best mid-size SUV?

Absent the poor FE of the RDX engine due to derating until the turbo comes on line that award would have undoubtedly gone to the RDX.

The clear majority of the time the RDX engine runs in the derated, 8:1 compression ratio, mode.

Shame.

But I wonder, like the RX350 buying public at large, if J D Powers wasn't also mislead into believing the RX350 has a center open diff'l aided by a VC.

It doesn't.

Would you mind translating this into plain english for the rest of us? :(

[wwest]

...just won the J.D. Powers and Associates award for best mid-size SUV?

Absent the poor FE of the RDX engine due to derating until the turbo comes on line that award would have undoubtedly gone to the RDX.

The clear majority of the time the RDX engine runs in the derated, 8:1 compression ratio, mode.

Shame.

But I wonder, like the RX350 buying public at large, if J D Powers wasn't also mislead into believing the RX350 has a center open diff'l aided by a VC.

It doesn't.

Would you mind translating this into plain english for the rest of us? :(

When the RX330 was first introduced the marketing material touted the fact that like the RX300 the center open diff'l F/R torque distribution was modifed with wheelspin/slip via the use of a VC, Viscous Coupling/clutch mounted across the F/R outputs of that diff'l. The shop/repair manual indicates that the RX330 did not include this feature and when I pointed this out to Lexus via customer_satisfaction_inquires@Lexus.com the RX330 marketing material was corrected.

This marketing mistake seems to have now been repeated for the RX350. All of the marketing material for the RX350, even to this date, printed and online, indicates that the RX350 has again adopted the VC. The NCF, New Car Features, section of the online (techinfo.toyota.com) documentation for the first production year of the RX350 states that the RX350 uses the MF2AV center diff'l vs the MF2A used in the RX330. The included pictorial shows the MF2AV as including the VC. On the other hand NONE of the online shop/repair manuals, or any subsequent manual/year or for all/any year of the RX350 indicates the MF2A remains in use, not the MF2AV.

Only the NCR for the initial production year of the RX350 makes any mention of the VC or the MF2AV diff'l.

Also.

On three separate occassions I have attempted to question, bring Lexus attention to, this via emails to customer satisfaction. The dessertion resulting from thse emails always results in conversion to phone conversations at Lexus request and in each case has resulted in a promise to get back to me with an answer within 48 hours. The return call has yet to happen. Three separate tries....

In addition I have tried to order, obtain a price quote, for a MF2AV center diff'l for a 2008 RX350 (VIN# supplied) from at least two online suppliers. One of which, Carson Toyota, I have done a fair amount pf past business, parts purchasing. I never get any response.

In addition to all that if one reads the detailed theory of operation for the TC, Traction Control, system for the RX350 it seems improbable that even were the VC in place it could ever come into use. And that TC operational theory also reads exactly the same as the RX330, which Lexus has admitted, after the fact, that does NOT include the VC.

So, IMMHO, if you have purchased an AWD RX350 you might have a good legal claim for some level of compensation against Lexus.

Oh, one more point.

I understand that as of the '08 MY the TC function can be disabled, turned off, by the driver. If that is done and if the RX350 actually does have a VC in that case it may actually be useful provided the VC fluid's formulation, activation "time constant" is conducive to same.

[SmilingBoognish]

Would you mind translating this into plain english for the rest of us? :(

I think he's trying to say that the RDX has a more robust all wheel drive system and the engine exhibits turbo lag, but that's just a guess based on what he's written. :P

[SW03ES]

I stopped trying to read them years ago.

[smooth1]

traction control can tell the ECU to lock the drive train temporarily together a differential's output shafts, which makes all the wheels turn together at the same speed, providing torque in case of slippage. It's contolled by and used for the center differential, which is what distributes power between the front and the rear axles.

The two most common locking differentials use either a computer-controlled multi-plate clutch or viscous coupling unit to join the shafts. In the multi-plate clutch the car senses tire spin and locks the shafts, you can feel that in the ride when it activates, which most people complain about. And it can cause the tires to spin suddenly when they do lock. In the viscous coupling differentials the shear stress of high shaft speed differences causes a dilitant fluid, ( a fluid that increases in viscosity with shearing force) in the differential to become solid, connecting the two shafts. Some use a gearing to reduce the rotational difference.

The third is the Torsen differential, which just allows the output shafts to receive different amounts of torque, but doesn't do much for real usable traction. And of course there is the locking differentials used for off roading, but I don't think we need to cover those.

So, the RX uses the multi-plate clutch?Actually, if it does, it is a better system. The VC system has fluid wear issues and leaks are common.

[Nebraska99]

traction control can tell the ECU to lock the drive train temporarily together a differential's output shafts, which makes all the wheels turn together at the same speed, providing torque in case of slippage. It's contolled by and used for the center differential, which is what distributes power between the front and the rear axles.

The two most common locking differentials use either a computer-controlled multi-plate clutch or viscous coupling unit to join the shafts. In the multi-plate clutch the car senses tire spin and locks the shafts, you can feel that in the ride when it activates, which most people complain about. And it can cause the tires to spin suddenly when they do lock. In the viscous coupling differentials the shear stress of high shaft speed differences causes a dilitant fluid, ( a fluid that increases in viscosity with shearing force) in the differential to become solid, connecting the two shafts. Some use a gearing to reduce the rotational difference.

The third is the Torsen differential, which just allows the output shafts to receive different amounts of torque, but doesn't do much for real usable traction. And of course there is the locking differentials used for off roading, but I don't think we need to cover those.

So, the RX uses the multi-plate clutch?Actually, if it does, it is a better system. The VC system has fluid wear issues and leaks are common.

I dont know about all that engineering stuff. All I know is that my 2008 went through a lot of midwestern snow in a bad winter and I had no issues getting anywhere at all. It was pretty darned amazing. That's about as technical as I get. lol

[SmilingBoognish]

Umm, a Torsen set-up very effective. Most, but not all, Audi's badged "Quattro" have this set up.

Also, the VC in my Subaru worked flawlessly this winter in a blizzard with 110K miles on it, with no leaks whatsoever. The trick is to keep the tires rotated if you want a VC to last.

[wwest]

traction control can tell the ECU to lock the drive train temporarily together a differential's output shafts, which makes all the wheels turn together at the same speed, providing torque in case of slippage. It's contolled by and used for the center differential, which is what distributes power between the front and the rear axles.

The two most common locking differentials use either a computer-controlled multi-plate clutch or viscous coupling unit to join the shafts. In the multi-plate clutch the car senses tire spin and locks the shafts, you can feel that in the ride when it activates, which most people complain about. And it can cause the tires to spin suddenly when they do lock. In the viscous coupling differentials the shear stress of high shaft speed differences causes a dilitant fluid, ( a fluid that increases in viscosity with shearing force) in the differential to become solid, connecting the two shafts. Some use a gearing to reduce the rotational difference.

The third is the Torsen differential, which just allows the output shafts to receive different amounts of torque, but doesn't do much for real usable traction. And of course there is the locking differentials used for off roading, but I don't think we need to cover those.

So, the RX uses the multi-plate clutch?Actually, if it does, it is a better system. The VC system has fluid wear issues and leaks are common.

The RX300 used, uses, a VC mounted, connected, across the two output shafts of the otherwise fully "open" center diff'l. There is a delay time involved, always, in a VC "stiffening" upon differential F/R wheelspin rates, otherwise the VC would cause driveline "windup" during a turn, especially a tight turn. The onset of VC coupling, enough for changing the F/R torque biasing form 95/5 to about 75/25 is about 10-15 seconds measured on a 4 wheel dyno. 75/25 seemed to be about the maximum level we could get without beginning to worry about compromising the VC's operational life.

Lexus admits, willingly, that although the early advertising indicated the RX330 series also had a VC, it does not.

They are yet to make the same admission for the RX350 but then I'm still working on that.

The VC in my '01 AWD RX300, in reality, has little real practicality. TC, even in my '01, quickly applies the front brakes and dethrottles the engine (EFI fuel starvation for the RX300, no DBW) the very instant wheelspin/slip, FRONT wheelspin/slip, is detected. That's likely why the VC has now been dropped altogether across the entire Toyota/Lexus F/AWD product line. Absent owner knowledge, being somehow aware of how to disable TC, and thereby allow enough of a duration of wheelspin/slip to occur the VC would/will never become functional anyway.