Quote:
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Originally Posted by Chiketkd
UberRoo,
What you're saying makes good sense in theory, but is hard to prove in reality.
I've posted my results using the SSM when in the awd diagnostic mode. The excerpt I posted at the start of this thread from the Road & Track Guide about the multi-plate transfer clutch seemed to reiterate these findings.
If you or Harv can think of an elegant way to show the torque split is closer to 90/10 than 60/40 in normal driving (with no braking, acceleration or steering inputs affecting transfer) then by all means prove these results wrong. 
-Chike |
You're definitely very right about one thing: It's very hard to prove. The best way to attempt to prove my theory is to hook up a pressure gauge to the transfer clutch pressure lines. I'm quite confident that if you compared the pressure readings to the duty cycle indicated on the select monitor, the readings would not closely relate. The pressure applied to the transfer clutch is a
very good indicator of the amount of torque available to the rear wheels. (It is
not however, a good indicator of the
percent of torque applied to the rear wheels. This depends on the amount of traction available to the front wheels, the amount of slippage, and the amount of engine power supplied.)
Measuring the torque applied to the wheels requires some pretty fancy engineering. I don't think any of us are going to be proving anything any time soon. I'm pretty sure even Subaru doesn't know. They theorized, no doubt, but I'm sure trial and error was the method used to get it right. I do know for a fact that valves do not behave in a linear fashion. Even needle valves and other, more exotic, specially designed valves only behave in a linear fashion at specific available rates of flow and pressure with specific viscosity fluids. Fluid systems just aren't that well-behaved. Much like 1/4, 1/2, and 3/4 throttle doesn't make you go 25, 50, and 75 miles per hour respectively, very few valves will regulate pressure or flow in the same way.
I think that oab_au and I both appreciate that the select monitor only shows what the TCU is trying to achieve, but not what is actually happening. Regarding the information provided by Road & Track, what is their source? Did they test it? If so, how? (Personally, I detest the media because it is so chronically full of misinformation.) If you
reeeally want to know what's happening, a pressure gauge will give you the best data. What it tells you is far,
far more meaningful than the select monitor.