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Discussion Starter · #1 · (Edited)
Hi all!
I have a 2015 2.4 Patriot Sport with Automatic transmission (not CVT variator).
Near the top of each not small hill,
When Jeep loses speed inertia/momentum, it always happens exactly what at the end of video (not mine video) :
4wd is on.

Manual mode gear D = 1
ESP full off (5-7 second push)
Pedal is pushed to the metal.
No errors / lights on the panel.
Looks like engine revs are limited and cant go over 2000 rpms.

The same happens when you stuck BOTH front wheels 90° to a curb Forward or backward (See pics).

Patriot does not want to perform a burnout (I need it right now!) when feels hard obstacles....

What are possible reasons and how to deal with it?
1. Does TCS thinks that all wheels are spinning - so it blocks all wheels?

2. Rev/rpm limit does not allow to overcome TCS's brake pressure + hill angle gravity force ?

Tried to make all differentials free (brakes unlocked) by taking out ABS fuse #35.
It does not give a result - rpms are limited to 2000 with pedal to the metal = wheels dont slip/dont move...

I dont beleive that 2.4 cant overcome TCS brakes - it have to perform a burnout in this conditions, but it cant.....

Any suggestions how to remove this 2000rpm restriction at hard situations?

Thanks for any ideas! 20210428_145253.jpg 20210428_142600.jpg
 

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Hi all!
I have a 2015 2.4 Patriot Sport with Automatic transmission (not CVT variator).
Near the top of each not small hill,
When Jeep loses speed inertia/momentum, it always happens exactly what at the end of video (not mine video) :
4wd is on.

Manual mode gear D = 1
ESP full off (5-7 second push)
Pedal is pushed to the metal.
No errors / lights on the panel.
Looks like engine revs are limited and cant go over 2000 rpms.

The same happens when you stuck BOTH front wheels 90° to a curb Forward or backward (See pics).

Patriot does not want to perform a burnout (I need it right now!) when feels hard obstacles....

What are possible reasons and how to deal with it?
1. Does TCS thinks that all wheels are spinning - so it blocks all wheels?

2. Rev/rpm limit does not allow to overcome TCS's brake pressure + hill angle gravity force ?

Tried to make all differentials free (brakes unlocked) by taking out ABS fuse #35.
It does not give a result - rpms are limited to 2000 with pedal to the metal = wheels dont slip/dont move...

I dont beleive that 2.4 cant overcome TCS brakes - it have to perform a burnout in this conditions, but it cant.....

Any suggestions how to remove this 2000rpm restriction at hard situations?

Thanks for any ideas!
Maybe to protect the transmission? It is pretty lame though, it should be able to drive up a curb with a 4x4 badge on the back.
 

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Discussion Starter · #3 ·
Maybe to protect the transmission? It is pretty lame though, it should be able to drive up a curb with a 4x4 badge on the back.
It performs well 95% of middle-hard offroad but this 5% situations stress me up, having 4x4 Jeep badge :)

It can be a 'safe mode' by engineers not to brake transmission or engine, but in critical situation I have to accept this risks - just not to stuck and freeze somewhere far away...
 

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Fiat Cherokar
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Thats my video, its easy to explain lack of engine torque, no low range so you don't get the torque multiplication factor a vehicle with low range has, notice how it has no problem spinning 1 front and 1 rear wheel, its only the the brake lock differentials clamp down on the spinning wheels to send power to the wheels that aren't spinning. This is effective but takes twice as much torque to get meaningful movement out of the tires with traction.

It's not a safe mode I could recreate it many many times, FDII vehicles (which mine was) are affected to less of an extent due to the higher crawl ratio
 

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Discussion Starter · #5 ·
Thats my video, its easy to explain lack of engine torque, no low range so you don't get the torque multiplication factor a vehicle with low range has, notice how it has no problem spinning 1 front and 1 rear wheel, its only the the brake lock differentials clamp down on the spinning wheels to send power to the wheels that aren't spinning. This is effective but takes twice as much torque to get meaningful movement out of the tires with traction.

It's not a safe mode I could recreate it many many times, FDII vehicles (which mine was) are affected to less of an extent due to the higher crawl ratio
But why ECU cant allow to increase rpms (by pedal) to increase torque?
Engine is not defenetly stalling, Im sure- i hear it and feel no vibrations !
just electronics do not allow to go higher than 2000rpms....
 

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Discussion Starter · #6 ·
Thats my video, its easy to explain lack of engine torque, no low range so you don't get the torque multiplication factor a vehicle with low range has, notice how it has no problem spinning 1 front and 1 rear wheel, its only the the brake lock differentials clamp down on the spinning wheels to send power to the wheels that aren't spinning. This is effective but takes twice as much torque to get meaningful movement out of the tires with traction.

It's not a safe mode I could recreate it many many times, FDII vehicles (which mine was) are affected to less of an extent due to the higher crawl ratio
I also have found on forum threads that this **** happens with all types of trasmissions:
Mechanical
Variator
Conventional auto...

I think that it is ECU-TCS logic failure.
Something sets the rpm limit over all ttansmissions in hard scenario....
 

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Fiat Cherokar
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But why ECU cant allow to increase rpms (by pedal) to increase torque?
Engine is not defenetly stalling, Im sure- i hear it and feel no vibrations !
just electronics do not allow to go higher than 2000rpms....
Its a limitation of the engine not creating enough torque, plain and simple the engine can't make enough power at low engine speeds to overcome the force needed to move the vehicle.
 

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Fiat Cherokar
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Any vehicle can run into the same problem. My Cherokee Trailhawk with the 3.2 gets bogged down in the exact same way if I don't use low range, even my 5.7 Grand Cherokee does the same, it's all about engine power and lack of low range.
 

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Its a limitation of the engine not creating enough torque, plain and simple the engine can't make enough power at low engine speeds to overcome the force needed to move the vehicle.
I think OP is asking If the engine doesn't have enough power at low speeds, why is the engine prevented from going higher? Reducing the RPMs is like telling a weightlifter, "If you can't lift it with two arms, try it with one."
 

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Discussion Starter · #10 ·
I think OP is asking If the engine doesn't have enough power at low speeds, why is the engine prevented from going higher? Reducing the RPMs is like telling a weightlifter, "If you can't lift it with two arms, try it with one."
Exactly!
If engine do not die at 2000rpm staying on a hill with gas pedal (it runs smoothly), why not to open electro-throttle more to reach 2500, 3000 - 4000 rpm to get more torque?

I have an idea to connect to ECU with HPtuners software and find this limiter or throttle logic...
 

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Fiat Cherokar
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I think OP is asking If the engine doesn't have enough power at low speeds, why is the engine prevented from going higher? Reducing the RPMs is like telling a weightlifter, "If you can't lift it with two arms, try it with one."
Yes and i've said over and over, yes it doesn't have enough torque at low speeds, and again it happens to lots of other vehicles in offroad situations that don't have low range. There is no way around it.

This is a great example. FDII vehicle vs non FDII vehicle. FDII vehicle can crawl up. The FDI needs momentum and can't crawl



Different vehicle same thing A cherokee Trailhawk not using 4-low bogs down, but putting it in 4-low and the problem goes away



Now a 5.7 Grand Cherokee going up a steep incline, no 4 low and it struggles see the same trend happening over and over?

 

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Discussion Starter · #12 · (Edited)
Yes and i've said over and over, yes it doesn't have enough torque at low speeds, and again it happens to lots of other vehicles in offroad situations that don't have low range. There is no way around it.

This is a great example. FDII vehicle vs non FDII vehicle. FDII vehicle can crawl up. The FDI needs momentum and can't crawl



Different vehicle same thing A cherokee Trailhawk not using 4-low bogs down, but putting it in 4-low and the problem goes away



Now a 5.7 Grand Cherokee going up a steep incline, no 4 low and it struggles see the same trend happening over and over?

Thanks for great explanation and samples!

Now we mostly understand what happens.

But no answer why we cant increase rpms to dig on the top the hill.

If engine will stall - OK thats the torgue limit.
But it will not stall because of AT transmission:)

The core of a problem is inside torque converter.
Why AT hydraulic torque converter cannot spin more than 2000rpm?
Will it be destructed?
99% NO!

Before Pat, I had a classic Part Time with open differentials Kia sportage 1993 with 2.0 litres. Mechanical transmission.
Mechanical Throttle.
I could rev it up to 4000-5000 here, wheels spinning adding momentum....
It will dig here as crazy or stall IF REVS DROP less than 900rpm (mechanical transmission)...



Question is:
How to update AT Jeep to dig like a crasy pig to overcome this 2000rpm limits?
Fuses?
Cut /make a switch for some wires?
Software update?
Mechanical throttle?
 

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Fiat Cherokar
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You can't increase the rpms due to the torque converter, as such the stall speed is around 2000rpm. Its quite normal for small naturally aspirated engines to have very little torque a low RPMS. You will also notice in the very first video you posted, the vehicle had no problems spinning 1 front and 1 rear tire but again it didn't provide any useable traction, when forced (by the abs system) to transfer power to the wheels with traction it simply didn't have enough engine torque to do so.
 
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Discussion Starter · #15 · (Edited)
You can't increase the rpms due to the torque converter, as such the stall speed is around 2000rpm. Its quite normal for small naturally aspirated engines to have very little torque a low RPMS. You will also notice in the very first video you posted, the vehicle had no problems spinning 1 front and 1 rear tire but again it didn't provide any useable traction, when forced (by the abs system) to transfer power to the wheels with traction it simply didn't have enough engine torque to do so.
You are also right.
But! :)
I had a talk with auto-mechanics today:
Inside Torque Convertor there are only
Oil & two turbines on the shafts:
One shaft is from Transmission
Another shaft is from Engine.

Even if shaft from transmission is blocked by standing wheels (curb/hill/etc)-
Shaft from Engine will be rotate-able anyway( turbine is inside liguid).

The worst case - engine shaft will slip against transmission shaft. But that mean that rpms are increasing when wheels are static.

In our case there is no torque convertor's slip - rpms are limited electronicaly!
 

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Patriot does not want to perform a burnout (I need it right now!) when feels hard obstacles....

Any suggestions how to remove this 2000rpm restriction at hard situations?

Thanks for any ideas! View attachment 93988 View attachment 93989

On the trail here's some things to try:

When climbing a hill, try leaving it in Drive, and 2WD. Remember that it's a FWD vehicle first with most of the weight over the front wheels.
Send all the power to the front wheels and when the front wheels slip/spin, the RPM's will increase (higher up the torque curve) just before the computer kicks in the rear wheels.

Remember too, that adding a taller tire will change the final drive ratio. A significantly taller the tire will make it harder to climb a hill (increased radius / leverage against the engine). I noticed a decrease in acceleration / low end power going from a stock 215/65/17 (28") to a 30x9.5 (29.5"). I settled on a 235/75/15 (29") which gave extra clearance with no noticeable difference in acceleration over the stock tire.

Try airing down the tires. Airing down gives better traction with a longer contact patch, and will go over obstacles easier, "wraps around" the obstacle instead of climbing it.

Consider adding front sway bar disconnects. The sway bar tries to keep both wheels at the same level, which is good on the road but wastes torque/power out on the trail since engine power has to be used to overcome the resistance of the sway bar in addition to obstacle.

Disconnecting the sway bar takes the resistance of the bar out of the equation.

As always, YMMV.

Hope this helps / makes sense.
 

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Discussion Starter · #17 ·
On the trail here's some things to try:

When climbing a hill, try leaving it in Drive, and 2WD. Remember that it's a FWD vehicle first with most of the weight over the front wheels.
Send all the power to the front wheels and when the front wheels slip/spin, the RPM's will increase (higher up the torque curve) just before the computer kicks in the rear wheels.

Remember too, that adding a taller tire will change the final drive ratio. A significantly taller the tire will make it harder to climb a hill (increased radius / leverage against the engine). I noticed a decrease in acceleration / low end power going from a stock 215/65/17 (28") to a 30x9.5 (29.5"). I settled on a 235/75/15 (29") which gave extra clearance with no noticeable difference in acceleration over the stock tire.

Try airing down the tires. Airing down gives better traction with a longer contact patch, and will go over obstacles easier, "wraps around" the obstacle instead of climbing it.

Consider adding front sway bar disconnects. The sway bar tries to keep both wheels at the same level, which is good on the road but wastes torque/power out on the trail since engine power has to be used to overcome the resistance of the sway bar in addition to obstacle.

Disconnecting the sway bar takes the resistance of the bar out of the equation.

As always, YMMV.

Hope this helps / makes sense.
Nice idea to leave in 2wd :)) sounds reasonable for the first kick/slip :))
Tires and traction are out of discussion here because

Jeep do not deliver all torque it has above 2000rpms to wheels :(
 

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It delivers whatever torque it does @ 2000 rpm, which isn't much, and because of that tires / traction and sway bar resistance become more important.

Like Tyler, I've done a lot of wheeling in the Patriot and this is what's made a difference for me. As I said, YMMV.

Try dropping air in the front tires to 15 lbs, then try going over the curb. Maybe it will help you.
 

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this happens in my fwd. problem is the traction control never really shuts completely off. stability control does when you push the button. you are probably breaking traction and the brakes are being applied to keep from slipping. then the ecu says hell no to your right foot input to avoid motor or trans damage. its just a 4 cylinder :) if you want to drive up ice covered hills i would recommend a sno cat :) also revving it up in these newer cars is never the answer.
 

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this happens in my fwd. problem is the traction control never really shuts completely off. stability control does when you push the button. you are probably breaking traction and the brakes are being applied to keep from slipping. then the ecu says hell no to your right foot input to avoid motor or trans damage. its just a 4 cylinder :) if you want to drive up ice covered hills i would recommend a sno cat :) also revving it up in these newer cars is never the answer.
I respectfully disagree on the traction control. I think hitting the "ESC off" button does kill the traction control, while the ESC function remains partially in operation.

IMO, traction control is a pretty useless invention. As you noted, when climbing a hill it applies the brakes and you lose momentum. When climbing hills in slippery conditions power is an enemy and momentum is a friend. You can control the power, but ESC kicks your friend in the knee.
 
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