***1. Yes, it still seems to be a puzzle as what exactly what the scanguage readout meaning is as relates to the rear drive coupling. Even the O'scope display is subject to differing interpretations. An electric solenoid might have FULL voltage applied initially and the reduced to a low holding voltage/current to simply hold the plunger in place. So even with the 25% duty cycle the solenoid plunger/actuator might be fully "deployed".

Absent a dynamometer I don't see how any of us could correlate voltage duty cycle % with the level of rear drive coupling.

***2. Mechanically the same does not necessarily correlate to firmware version be equal. It might be exacly the same revision or may be quite radically different. As a for instance what if, instead of reducing the regen capability as the OAT declines to freezing why not first begin engaging the rear drive coupling to help alleviate the potential for loss of control due to regen.

***3. Well, yes. We now know when the rear drive is pre-emptively engaged. That is, only when accelerating from a dead stop or low speed acceleration. Otherwise only the front wheels have "drive" at least primarily (95%..??).

The various materials I have been able to find indicate that when front wheelspin is detected three things will occur pretty much simultaneously. TC braking of the front wheels, BOTH front wheels, engine dethrottling, and engine torque coupling to the rear driveline.

The question becomes.."how long will the above "condition" persist..??"

 

Your saying the they send rear wheel torque, just incase or unknown to the driver, there is poor traction?

Your are forgetting one thing. As many times as I have tried, I can't leave a dead stop without getting rear wheel torque no matter how lightly I touch the throttle. Light, moderate or hard, I get the same results!

 

[quote=wwest;211827]Well, for one a <'09 FEH can't send power to a single wheel, no TC.

At a constant speed on a tight curve, I see no rear wheel torque.

"When increased handling or traction is required, the Intelligent 4WD System actively controls power" Driving perfectly straight and slow from a dead stop, do I need increased handling or traction???

"The majority of power is sent to the front wheels" I agree with that!

 

I'll take the percentage or whatever when needed but most of time it's unneeded.

The SG-II is nice but other the plugging in numbers, I'm clueless about it but have seen one guage setting affect a response from a command sent. That's why I question BillyKs statements of rear wheel torque at a steady speed. He has three SGs running at the same time and I think the 4WD PID is being skewed by something else or his vehicle has problems.

 

The SG-II shows rear wheel drop off slowly as you reach a steady speed but the scope shows a faster drop.

The workshop manual mentions using the 4WD ATC duty cycle for pinpoint tests. It's a valid PID. What I can deduct form the manual and the command, it is the 4WD module's address. I can only "assume" that it's the correct PID.

The only pinpoint test that I can reproduce is a tight turn <5MPH on dry had pavement. More the 20% is correct and I get that.

One test that I mentioned long time ago was to jack up the front end, one rear wheel and switch OFF the TC. You get all available torque to the one raised rear wheel.

 

"...light, moderate or hard..."

At the instant, the VERY instant, you begin depressing the gas pedal the engine/transaxle control ECU does not know what your end "target" might be, it cannot predict the future. So the safe thing for the firmware programmer to do is assume the worse case and engage the rear drive immediately upon even the slightest initial depression of the gas pedal provided the transaxle is, is soon to be, in a low gear range.

And keep in mind that with DBW the rising of engine torque can be delayed until the rear drive is engaged or even until an appropriate downshift has completed.

No harm done if the traction is high and/or light acceleration is the target, and just maybe a few less injuries or even deaths.

At least that's the direction I would give my programming staff given the HIGH level of torque these hybrids can produce if the "target" should be HARD acceleration. The LAST thing a manufacturer wants is a preventable inadvertent loss of control for this reason.

 

*** A compromise, maybe..??

Yet another presumption, pre-emptive "strike".

FWD vehicles are HIGHLY subject to plowing/understearing should you encounter a slippery surface. Are they moving some of the HIGH engine torque at low speeds in TIGHT turns to the rear in order to allocate more of the front wheel drive traction to directional control to alleviate, lower, the potential for plowing/understearing..??

That's most likely what is done with the SH-AWD system but in that case virtually ALL of the engine torque can be re-routed to the rear in this circumstance.

 

TC controls torque to a individual wheel and the 4WD system controls torque between the front and rear, so you would have rear torque with the TC OFF.

 

But then other than low speed acceleration, what event "triggers", causes, the ATC to engage...??

With the old Aerostar it was rear wheelspin/slip that caused it to go from 30/70 F/R to 50/50 F/R. In reality it was simply a difference in F/R driveline roation rate but with the majority of torque to the rear there was a presumption of rear wheelspin/slip.

The Aerostar 50/50 mode was only sustained for about 20 seconds and then automatically went back to 30/70 and then awaited the next "event".

The FE's original F/awd system, in automatic mode, was much the same, FWD "ONLY", front wheelspin/slip would get you about 20 seconds with the rear driveline fully engaged.

With the FE/FEH, assuming it went into 4WD for some reason, event, what would result, as well it MUST, in the rear driveline "uncoupling"..??

Time period expiration..??

 

I have no idea how it's programmed, the dealer doesn't know and neither does their Tech HotLine! If I was still an active Ford employee, I maybe could get some contact numbers to call from our engineering people.