The PTU Fuse Drill
#13
09-03-2010, 01:34 PM
Re: The PTU Fuse Drill
It needs to dissable the clutches when more than a 3% radius wheel difference between front and rear is found because the awd control module could interpret that as a slippage condition, and engage the clutches permanently, resulting on stress to drive train and overheating of the unit.
There is one thing that we do need to find exactly: Do the clutches engage only when a difference in rotation between front and rear is found (slippage) or does it also provide some torque when starting to move, for example? I dont think any torque is provided to the rear at all at any time other than when slippage is detected. Slippage is detected in miliseconds, I dont think they need to put torque on the rear before it is detected.
The MPG difference must come from added weight and friction of all the freewheeling components that the 2wd doesnt have to turn. it's allways been the same, 2wd versions always had better mpg than 4wd versions of the same car or truck. Even on trucks where you had to manually couple the second traction axle, and even if you had the free hubs... being free hubs engaged better for mpg than hubs locked.
2WD 2010 FEH, 4860Lbs, 4Wd, 5020Lbs, 160 pounds difference due to the extra components on the 4WD. That's like carrying an extra adult on the car, every mile you drive, and you need to add the friction loses too.
I'm not sure if there is any torque, at all, sent to the rear wheels at any other time that when slippage is detected. What I have read on the manuals does not seem to indicate so. And if there was some, it should not make any difference since in asphalt both axles move at the same speed anyway. This is not a central differential based system, where torque is sent where it's needed, as used on Land Rovers, Subarus... looks like they can pulse the clutches, wich would allow for the release of some of the stress (and stress only comes when doing sharp turns if it was engaged solid)
Even on the light and short Suzuki adding the front free hubs it made a big impact on driveability and fuel economy, just for not having the front differential turning with the car. That is probably the biggest cause of the mgp loss.
If such a thing existed aftermarket, free hubs for our rear axle, perhaps a limited slip differential on the rear and being able to disable or enable the auto 4wd capability would be great. We would get some of the MPG's back and gain a bit more 4wd performance. But since the escape is not a real 4wd vehicle that could attract buyers, such a thing would have no market. There are plenty of other cars far more capable for that already.
http://en.wikipedia.org/wiki/Locking_hubs
Juan Fernandez
06 FEH, 06 HCH
Los Angeles, CA
There is one thing that we do need to find exactly: Do the clutches engage only when a difference in rotation between front and rear is found (slippage) or does it also provide some torque when starting to move, for example? I dont think any torque is provided to the rear at all at any time other than when slippage is detected. Slippage is detected in miliseconds, I dont think they need to put torque on the rear before it is detected.
The MPG difference must come from added weight and friction of all the freewheeling components that the 2wd doesnt have to turn. it's allways been the same, 2wd versions always had better mpg than 4wd versions of the same car or truck. Even on trucks where you had to manually couple the second traction axle, and even if you had the free hubs... being free hubs engaged better for mpg than hubs locked.
2WD 2010 FEH, 4860Lbs, 4Wd, 5020Lbs, 160 pounds difference due to the extra components on the 4WD. That's like carrying an extra adult on the car, every mile you drive, and you need to add the friction loses too.
I'm not sure if there is any torque, at all, sent to the rear wheels at any other time that when slippage is detected. What I have read on the manuals does not seem to indicate so. And if there was some, it should not make any difference since in asphalt both axles move at the same speed anyway. This is not a central differential based system, where torque is sent where it's needed, as used on Land Rovers, Subarus... looks like they can pulse the clutches, wich would allow for the release of some of the stress (and stress only comes when doing sharp turns if it was engaged solid)
Even on the light and short Suzuki adding the front free hubs it made a big impact on driveability and fuel economy, just for not having the front differential turning with the car. That is probably the biggest cause of the mgp loss.
If such a thing existed aftermarket, free hubs for our rear axle, perhaps a limited slip differential on the rear and being able to disable or enable the auto 4wd capability would be great. We would get some of the MPG's back and gain a bit more 4wd performance. But since the escape is not a real 4wd vehicle that could attract buyers, such a thing would have no market. There are plenty of other cars far more capable for that already.
http://en.wikipedia.org/wiki/Locking_hubs
Juan Fernandez
06 FEH, 06 HCH
Los Angeles, CA
#14
09-03-2010, 05:33 PM
Re: The PTU Fuse Drill
Juan:
Torque is sent to the rear wheels "every" time you leave from a dead stop "no matter" what the driving conditions are. It slowly drops off till you reach a constant speed.
I have a Scanguage-II setup to monitor rear wheel torque. I've tried to force extra rear wheel torque on snow but really didn't see any increase. There's supposed to be more rear wheel torque on heavy acceleration also but I've never seen more than 33-35% even with a full throttle take off from a dead stop.
To me, so far this Intelligent 4WD seems rather unintelligent and more hype than fact. Come next winter, I'll try to test it a bit more to see if it can change my mind.
I might add that as of of right now the online version of the '11 FE/FEH Ford Worlshop Manual doesn't even include a 4WD section.
Torque is sent to the rear wheels "every" time you leave from a dead stop "no matter" what the driving conditions are. It slowly drops off till you reach a constant speed.
I have a Scanguage-II setup to monitor rear wheel torque. I've tried to force extra rear wheel torque on snow but really didn't see any increase. There's supposed to be more rear wheel torque on heavy acceleration also but I've never seen more than 33-35% even with a full throttle take off from a dead stop.
To me, so far this Intelligent 4WD seems rather unintelligent and more hype than fact. Come next winter, I'll try to test it a bit more to see if it can change my mind.
I might add that as of of right now the online version of the '11 FE/FEH Ford Worlshop Manual doesn't even include a 4WD section.
#15
09-03-2010, 07:17 PM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: The PTU Fuse Drill
It needs to dissable the clutches when more than a 3% radius wheel difference between front and rear is found because the awd control module could interpret that as a slippage condition, and engage the clutches permanently, resulting on stress to drive train and overheating of the unit.
Sorry, no. If the computer can detect the disparaty then it should be able to correct/adjust for it. The disabling is purely because 3% or more would result in 'way too much driveline windup and/or tire scrubbing if the 4WD system were to be engaged.
There is one thing that we do need to find exactly: Do the clutches engage only when a difference in rotation between front and rear is found (slippage) or does it also provide some torque when starting to move, for example? I dont think any torque is provided to the rear at all at any time other than when slippage is detected. Slippage is detected in miliseconds, I dont think they need to put torque on the rear before it is detected.
The rear drive is ONLY engaged during acceleration. During acceleration is the time wheelspin/slip is most likely to develop so this is simply a pre-emptive measure to spread the engine torque over a larger tire/roadbed surface area.
The MPG difference must come from added weight and friction of all the freewheeling components that the 2wd doesnt have to turn. it's allways been the same, 2wd versions always had better mpg than 4wd versions of the same car or truck. Even on trucks where you had to manually couple the second traction axle, and even if you had the free hubs... being free hubs engaged better for mpg than hubs locked.
Both of my Jeeps, '85 & '92, would get better highway MPG in 2WD rather than 4WD (no locked diff'l).
2WD 2010 FEH, 4860Lbs, 4Wd, 5020Lbs, 160 pounds difference due to the extra components on the 4WD. That's like carrying an extra adult on the car, every mile you drive, and you need to add the friction loses too.
I'm not sure if there is any torque, at all, sent to the rear wheels at any other time that when slippage is detected. What I have read on the manuals does not seem to indicate so. And if there was some, it should not make any difference since in asphalt both axles move at the same speed anyway. This is not a central differential based system, where torque is sent where it's needed, as used on Land Rovers, Subarus... looks like they can pulse the clutches, wich would allow for the release of some of the stress (and stress only comes when doing sharp turns if it was engaged solid)
What's the sense in sending any level of torque to the rear wheels if that torque doesn't arrive at the tire/roadbed "interface" and thereby "stress", increase friction, on all components in between.
Even on the light and short Suzuki adding the front free hubs it made a big impact on driveability and fuel economy, just for not having the front differential turning with the car. That is probably the biggest cause of the mgp loss.
If such a thing existed aftermarket, free hubs for our rear axle, perhaps a limited slip differential on the rear and being able to disable or enable the auto 4wd capability would be great. We would get some of the MPG's back and gain a bit more 4wd performance. But since the escape is not a real 4wd vehicle that could attract buyers, such a thing would have no market. There are plenty of other cars far more capable for that already.
http://en.wikipedia.org/wiki/Locking_hubs
Juan Fernandez
06 FEH, 06 HCH
Los Angeles, CA
Sorry, no. If the computer can detect the disparaty then it should be able to correct/adjust for it. The disabling is purely because 3% or more would result in 'way too much driveline windup and/or tire scrubbing if the 4WD system were to be engaged.
There is one thing that we do need to find exactly: Do the clutches engage only when a difference in rotation between front and rear is found (slippage) or does it also provide some torque when starting to move, for example? I dont think any torque is provided to the rear at all at any time other than when slippage is detected. Slippage is detected in miliseconds, I dont think they need to put torque on the rear before it is detected.
The rear drive is ONLY engaged during acceleration. During acceleration is the time wheelspin/slip is most likely to develop so this is simply a pre-emptive measure to spread the engine torque over a larger tire/roadbed surface area.
The MPG difference must come from added weight and friction of all the freewheeling components that the 2wd doesnt have to turn. it's allways been the same, 2wd versions always had better mpg than 4wd versions of the same car or truck. Even on trucks where you had to manually couple the second traction axle, and even if you had the free hubs... being free hubs engaged better for mpg than hubs locked.
Both of my Jeeps, '85 & '92, would get better highway MPG in 2WD rather than 4WD (no locked diff'l).
2WD 2010 FEH, 4860Lbs, 4Wd, 5020Lbs, 160 pounds difference due to the extra components on the 4WD. That's like carrying an extra adult on the car, every mile you drive, and you need to add the friction loses too.
I'm not sure if there is any torque, at all, sent to the rear wheels at any other time that when slippage is detected. What I have read on the manuals does not seem to indicate so. And if there was some, it should not make any difference since in asphalt both axles move at the same speed anyway. This is not a central differential based system, where torque is sent where it's needed, as used on Land Rovers, Subarus... looks like they can pulse the clutches, wich would allow for the release of some of the stress (and stress only comes when doing sharp turns if it was engaged solid)
What's the sense in sending any level of torque to the rear wheels if that torque doesn't arrive at the tire/roadbed "interface" and thereby "stress", increase friction, on all components in between.
Even on the light and short Suzuki adding the front free hubs it made a big impact on driveability and fuel economy, just for not having the front differential turning with the car. That is probably the biggest cause of the mgp loss.
If such a thing existed aftermarket, free hubs for our rear axle, perhaps a limited slip differential on the rear and being able to disable or enable the auto 4wd capability would be great. We would get some of the MPG's back and gain a bit more 4wd performance. But since the escape is not a real 4wd vehicle that could attract buyers, such a thing would have no market. There are plenty of other cars far more capable for that already.
http://en.wikipedia.org/wiki/Locking_hubs
Juan Fernandez
06 FEH, 06 HCH
Los Angeles, CA
#16
09-03-2010, 07:29 PM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: The PTU Fuse Drill
Juan:
Torque is sent to the rear wheels "every" time you leave from a dead stop "no matter" what the driving conditions are. It slowly drops off till you reach a constant speed.
I have a Scanguage-II setup to monitor rear wheel torque. I've tried to force extra rear wheel torque on snow but really didn't see any increase. There's supposed to be more rear wheel torque on heavy acceleration also but I've never seen more than 33-35% even with a full throttle take off from a dead stop.
To me, so far this Intelligent 4WD seems rather unintelligent and more hype than fact. Come next winter, I'll try to test it a bit more to see if it can change my mind.
I might add that as of of right now the online version of the '11 FE/FEH Ford Worlshop Manual doesn't even include a 4WD section.
Torque is sent to the rear wheels "every" time you leave from a dead stop "no matter" what the driving conditions are. It slowly drops off till you reach a constant speed.
I have a Scanguage-II setup to monitor rear wheel torque. I've tried to force extra rear wheel torque on snow but really didn't see any increase. There's supposed to be more rear wheel torque on heavy acceleration also but I've never seen more than 33-35% even with a full throttle take off from a dead stop.
To me, so far this Intelligent 4WD seems rather unintelligent and more hype than fact. Come next winter, I'll try to test it a bit more to see if it can change my mind.
I might add that as of of right now the online version of the '11 FE/FEH Ford Worlshop Manual doesn't even include a 4WD section.
"...more hype than fact..."
Exactly....!!
What is needed is a replication of the old AeroStar 4WD system. The AeroStar runs in 30/70 F/R torque distribution mode and if (rear...) wheelspin/slip is detected it switches to 50/50 for the next "period" (3-4 minutes..??). If it drops back into 30/70 and wheelspin/slip occurs again then....repeat as required.
The problem with the FE/FEH, 2011 Explorer, RX350, etc, is that any wheelspin/slip that develops will more than likely be on the front. Front wheelspin/slip must be addressed, abated, with the utmost urgency otherwise loss of directional control becomes a REAL threat. So these vehicles MUST instantly dethrottle the engine while using braking to return to traction mode.
If a way could be found to couple more than 50%, say 80%, of the engine torque to the rear upon detection of front wheelspin/slip.....
Oh, sorry, that's what the SH-AWD system does via having a slight overdrive ratio, 13%(?), to the rear diff'l.
Last edited by wwest; 09-03-2010 at 07:37 PM.
#17
09-03-2010, 08:06 PM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: The PTU Fuse Drill
Juan:
Torque is sent to the rear wheels "every" time you leave from a dead stop "no matter" what the driving conditions are. It slowly drops off till you reach a constant speed.
I have a Scanguage-II setup to monitor rear wheel torque. I've tried to force extra rear wheel torque on snow but really didn't see any increase. There's supposed to be more rear wheel torque on heavy acceleration also but I've never seen more than 33-35% even with a full throttle take off from a dead stop.
To me, so far this Intelligent 4WD seems rather unintelligent and more hype than fact. Come next winter, I'll try to test it a bit more to see if it can change my mind.
I might add that as of of right now the online version of the '11 FE/FEH Ford Worlshop Manual doesn't even include a 4WD section.
Torque is sent to the rear wheels "every" time you leave from a dead stop "no matter" what the driving conditions are. It slowly drops off till you reach a constant speed.
I have a Scanguage-II setup to monitor rear wheel torque. I've tried to force extra rear wheel torque on snow but really didn't see any increase. There's supposed to be more rear wheel torque on heavy acceleration also but I've never seen more than 33-35% even with a full throttle take off from a dead stop.
To me, so far this Intelligent 4WD seems rather unintelligent and more hype than fact. Come next winter, I'll try to test it a bit more to see if it can change my mind.
I might add that as of of right now the online version of the '11 FE/FEH Ford Worlshop Manual doesn't even include a 4WD section.
Did you look under Traction Control...?
Since it isn't really/truly a 4WD system.
#18
09-03-2010, 08:46 PM
Re: The PTU Fuse Drill
A keyword search for 4WD, AWD and Four Wheel Drive all comes up nada. They just haven't added that section to the manual yet.
