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Unread 11-17-2009, 10:32 PM   #1
Tyler-98-W68
Registered User
2012 MK Compass 
 
Join Date: May 2009
Location: Canada
Posts: 82
Patriot 4WD System Testing With Videos

I love to tinker around with different things on the Patriot and one of the largely debated topics is how the 4WD system really works. I"ve mentioned before I would love to see how a Patriot would function in one of those Subaru Style tests.

What I decided to do was jack up the front of the vehicle so the front tires were just barely off the ground. I would then try the 3 different modes of the Patriots 4x4 system and see how it behaved. Now of course this isn't totally realistic but it gives a better understanding how everything works.

First video is with ESP Full Off Gear selector in [D] with 4x4 Unlocked
I put the Pat in drive and then slowly let of the brake waited a few seconds and slowly eased onto the accelerator

0:18-0:24 seconds is just idling

0:24s+ start applying throttle

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As you can see the drivers front wheel does not spin (it is off the ground) and the passenger front wheel starts spinning fast and then slows down, which I belive is due to the ecc sending torque to the rear wheels, you'll notice once the front wheel stops spinning the Patriot lurches forward (indicating torque going to the rear wheels although it is hard to see in the video, I could feel it while in the Pat). The front wheel continues to spin at timed intervals (When my foot was off the gas). Indiciating the ECC was locking and unlocking. As I increase pressure on the gas pedal the front wheel slows and it seems the ecc is progressing to what seems almost full lockup before I let off the gas. My guess as to why the passenger wheel isn't spinning is because there isn't enough difference in the wheel speeds to make the BLD kick in. Had i given it more gas the Patriot would have driven forward off the jack.

Second video is with ESP Full Off Gear selector in [D] with 4x4 Locked.
I put the Pat in drive and then slowly let of the brake waited a few seconds and slowly eased onto the accelerator

0:16-0:21 idling
0:21+ start applying throttle

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Whats interesting right off the bat is the behavior while in the locked mode when idling, it behaves exactly the same way as when the 4x4 was unlocked, lurching forward at intervals, once I touch the gas pedal everything locks up and unlike the AWD mode there is no progression with the ECC it's locked up until i release the gas pedal. In this mode if I would have used more gas I would have been able to drive off the jack.

Third video is with ESP Full Off Gear selector in [L] with 4x4 Locked. This is the FDII mode

I put the Pat in drive and then slowly let of the brake waited a few seconds and slowly eased onto the accelerator

0:16-0:21 idling, foot off the gas
0:21+ start applying throttle

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In the FDII mode everything is the same as the 2nd video, rpms are higher and the Patriot seemed to be more eager to jump off the jacks (increased torque i'm guessing) The sound you hear at the end the the Pat shifting on the blocks (nothing broke)

I think that in all cases when the patriot operates in the AWD mode when there is no throttle is probably to prevent binding in the drivetrain at low speeds, i'm really intrigued how it works because the second there is any throttle input everything locks up (depending on the mode you are in)

In all cases above the patriot was able to transmit enough torque to move the vehicle forward, now whether or not it would be enough to drive over a small bump i'm not sure. Another thing to recognize is that the front wheels had ZERO traction, if your front wheels are on ice there is going to be at least some resistance so this isn't a 100% realistic test.

Here is a quote from part of the explanation of the 4WD system from jeep:

Quote:
OPERATION

The all-wheel-drive system requires no driver input or control. Under most driving conditions, it is passive and power is transmitted to the front wheels alone. Unlike all-wheel drive systems that rely on pumps or viscous fluids to transfer torque, this system requires no front-to-rear slippage for activation. This allows the system to transfer torque solely in response to accelerator pedal position. If the driver is asking for a lot of power, the system immediately starts clamping the electronically controlled coupling (ECC), transferring a high percentage of power to the rear wheels. This avoids front wheel slippage, as power to propel the car is transmitted through all four tires. This mode of operation is called open-loop operation in that there is no feedback to affect the torque transfer.

A second, closed loop, operating mode uses feedback from the wheel-speed sensors to determine the appropriate torque transfer. When the front wheels slip, the All Wheel Drive (AWD) Control Module tells the ECC to start clamping, sending power to the rear wheels. Attempting the same aggressive launch described above with the front wheels on ice and the rear wheels on dry pavement, the ECC sends even more torque to the rear wheels to minimize slippage and launch the vehicle. Both modes are always active with the closed loop mode layered on top of open loop mode to increase torque to the rear wheels when needed to maintain traction in extreme cases.
The AWD mode acts exactly as Jeep States and it appears the ECC is able to vary the amount of tourque going to the rear wheels. When the patriot is idling it appears to be in the "closed loop mode". Once you start giving it some gas then the open loop system also comes in and starts working. It also in my opinion shows that the isn't a whole lot of difference between the 4x4 locked (in D) and unlocked (in D) as the ECC nearly locks up in the AWD mode if you give it enough throttle.

I hope to make more videos in different situations in the near future, I was by myself today so I had to really be careful what I was doing.

If anyone has requests as to what sort of things i should try I would be more than happy to test them out.

Last video has a stupid watermark because my neighbor came over and asked what the hell i was doing so I cut that out

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Unread 11-18-2009, 01:28 PM   #2
miketmx
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2008 MK Patriot 
 
Join Date: Mar 2009
Location: Canada
Posts: 257
Tyler, Thanks for the awesome videos.
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Unread 11-19-2009, 10:53 AM   #3
miketmx
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2008 MK Patriot 
 
Join Date: Mar 2009
Location: Canada
Posts: 257
Seeing the videos of the Patriot in the wet snow, I wonder again what would be wrong with using cable chains as long as you have ESP Off ?? Front wheels only or rear wheels only with 4X4 locked ??
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