PPower

Since the 05-08 RL are 70/30 F/R distribution, I remember seeing that it was changed for 2009 to be more rear bias. I tried searching to find what that is but must not have searched the right words. So 1) what is the F/R bias for 09/10, and 2) is there any way to adjust this to something like 40/60?

FarginRL

How do you make that adjustment on and 05 RL

PPower

That's what I'm asking. IIRC, the max it could go to is 50/50, but I don't know what distribution the new ones have or if it can be changed.

OLD_HATCH

Is the bias computer or mechanically controlled?

I figure computer controlled would be the easiest to change if someone knew what they were doing.

or maybe it be as simple as swapping a diff from a newer RL???

PPower

Seems like maybe I'm wrong about the new ones being more rear biased from this thread. It says that there would be no change in the 70/30 standard to 30/70. Max power to the rear is 40% under acceleration. My understanding is that this is all electronically controlled, so I thought that maybe there was something to "chip" the drivetrain's computer.

I just think that Acura really missed the boat with the AWD and not giving it at least 50/50 if not rear biased. The NSX "replacement" was going to be a complete opposite 30/70.

BigKat103

Found this on Wikipedia, if you scroll down a bit it talks about the changes from '05-'08 to '09+.

http://en.wikipedia.org/wiki/SH-AWD

Outside of that I have absolutely nothing to add to this conversation.

robarsan

SUPER HANDLING ALL-WHEEL DRIVE™ SYSTEM

The previous RL's SH-AWD™ system didn't initiate rear side-to-side torque distribution until Second gear. However, on the 2009 RL new control parameters allow rearward torque delivery in First gear. Plus, front-to-rear and side-to-side power transfer happens much quicker with improved precision. The benefit of the revised SH-AWD™ system is improved accuracy, quicker response, and more power able to be applied to a specific rear wheel.
Torque splits are as follows:
During straight-line cruising and moderate cornering below half throttle, up to 70-percent of engine torque is delivered to the front wheels.
In full-throttle straight line acceleration, up to 40-percent of the power is sent to the rear axle.
In hard cornering, up to 70-percent of available torque goes to the rear wheels for enhanced chassis balance. Up to 100-percent of this torque can be applied to the outside rear wheel that can also be overdriven up to 5.7-percent by a built-in acceleration device.
SH-AWD™ incorporates a unique rear differential that continually varies the amount of torque delivered to the left and right rear wheels. SH-AWD™ generates a yaw moment during cornering by specifically routing torque from the engine. When cornering, a planetary gearset overdrives (or accelerates) the rear wheels while individual right and left clutch packs selectively direct torque to either or both rear wheel(s), driving them faster than the average of the front wheels to dramatically enhance the cornering, steering feel, overall handling and stability of the RL. The result is class leading cornering precision as well as enhanced traction in inclement weather.
Direct Yaw Control System Theory
SH-AWD™ counters understeer with a unique Direct Yaw Control system. Rotating an outside rear wheel faster than the average speed of the two front wheels allows the system to generate vehicle "yaw" while turning. By relieving the front tires of some of the work of turning the car, the system reduces understeer and the vehicle stays more balanced and controllable. In addition, with the cornering load more evenly distributed between the front and rear tires, the total cornering grip is increased. In conventional vehicles, cornering is created almost entirely by the steering angle of the front tires. With the RL, cornering is created by steering angle of front tires combined with the extra drive torque supplied by an outside rear tire.
Direct Yaw Control is a significant advance over conventional drive systems. To deal with high power output, front- or rear-drive systems generally use some type of limited-slip differential to maintain traction while under power. However, a linking effect of the inside and outside drive wheels in these systems resists turning. This linking effect is a factor that works against the front tires as they attempt to turn the vehicle. Conventional AWD systems have a similar linking effect between the inboard and outboard tires as well as between the front and rear axles, thus causing a similar resistance to turning. This is part of the reason why traditional AWD systems typically lack the more nimble feel of the best two-wheel drive systems. By using drive torque to help rotate the car, the RL is more responsive, neutral and predictable, while simultaneously offering all of the usual foul-weather benefits of all-wheel drive

rtr

you want 70/30 for awd

PPower

Do explain why. I would really prefer 40/60. Subaru automatics and Audi Quattro are native at 45/55 and distribute electronically from there. I guess it's not that big of a deal. In the constant argument about Acura needing RWD, I think they are much more likely to transition to SH-AWD w/ rear bias.

So far from searching, it looks like there is nothing available yet so this is all really a moot point. It really seems odd to me that this hasn't been addressed, but maybe I guess it is too new for the TL community that would be more inclined to tune. I wonder if there is something from the Japanese Legend forums.

psheu

it's all computer controlled..... the rear differentials are identical throughout the 2nd gen RL.... I happened to come across a new '09 rear differential (thought it'll be different from mine, appearently not, now it's a very heavy good looking paper weight in my garage).... the difference is the SHAWD computer, i guess if you swap that unit, your RL will drive like the '09+ RL