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Discussion Starter · #1 ·
AAM Ecotrac AWD Operation Testing & Data with Alfa OBD,Selec Terrain Modes Compared

Had some more time to play with my Fiat and test out the rear torque transfer with Alfa OBD and how it related to each selec terrain setting.

The first 4 videos are with the vehicle in each selec terrain position and me doing a brake torque to approx 2500rpm with my foot on the brake.

Auto

Snow

Sport

Sand/Mud

The common theme here is that the maximum torque being sent to the rear axle is the SAME regardless of selec terrain mode in this method of testing. These numbers are also the same when doing 0-100kms/h runs in each selec terrain mode (The max is always ~2500nm) Making the case that the vehicle only ever sends up to 50% of engine power to the rear axle and sport mode doesn't send more than 50% engine power to the rear.

The next set of videos show the same date but what i'm doing is shifting from Park into drive and keeping my foot on the brake but off the gas.

Auto

Snow

Sport

Sand/Mud

You will notice auto sends just a small amount of torque to the rear at idle.

Snow mode sends more than auto ~250nm

Sport mode sends THE SAME amount as snow mode ~250nm

Sand/Mud send the most amount @ ~500nm

It would appear that at idle without any throttle input both snow and sport mode are sending a portion of engine torque to the rear (not 50%)
and sand mud is sending %50 of engine power at idle.

Now some might say this wasn't realistic because all the wheels were on the ground and not slipping. I jacked up my 2 front tires again and ran the same method for idling in gear in each selec terrain mode and got the same values as mentioned above.
 

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Discussion Starter · #3 ·
So is the select-trac advertising false?
I"m not going to outright say its false but a more accurate statement would be that it varies the torque split from 0-50% of engine torque to the rear, I've got another follow up post coming with another interesting bit of info as well>:D
 

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Discussion Starter · #4 ·
I wanted to try and make another set of videos measuring the same data but more releastic. The best I could come up with in a somewhat controlled environment was putting down 2 ramps, 1 in front of the passenger front wheel and 1 in front of the driver side rear wheel. This would allow 1 front and 1 rear wheel to come up off the ground to pseudo simulate an offload obstacle.

My methodology (if you could call it that) was to only use as much throttle as necessary to keep the vehicle moving up the ramps, this was hard at times because one the wheels starting spinning I wanted to avoid the BLD's kicking in and launching me up and over the ramps >:D


Auto

Snow
Snow 1st Gaer (To see if being in 1st changed anything vs 2nd)

Sport

Sand/Mud

Observations. Ideally I was trying to keep the accelerator pedal position the same so that if there were any differences in torque split it would be easier to say "at 10% throttle auto mode sends more power to the rear than snow mode"


That was not very easy to do.

Between Auto and Snow mode (1st gear one) there really isn't much difference power is being sent to the rear but nothing drastically different between the 2 modes.

Auto and Snow mode (2nd gear) not much difference at all.

Sport mode functions very similar to auto and snow mode that nothing stands out as being drastically different.

Sand/Mud mode is where things get SUPER interesting.

I made mention of just using enough throttle to get the vehicle moving up the ramp, take a look at the throttle position, watch the throttle position on the sand/mud mode log. It immediately jumps to a higher value than the other modes even though i'm not pushing on the gas any harder. As a result the torque sent to the rear wheels spikes much higher and quicker and reaches the maximum of around ~2500nm where as the other modes don't.

It would appear than sand/mud mode has a pedal commander built in and actually makes the throttle response better than sport mode:surprise: Sand/Mud mode also send the power to the rear end quicker than other modes even sport mode. Now if I could find the sand/mud mode shift pattern and put the sport mode RPM limits in that would be awesome:laugh:

I can't make any concrete conclusions and i'm sure many will want to argue, but if the max torque being delivered to the rear axle is 2500nm, then we could assume that is 50% of the engine power being delivered rearward. In WOT situations each selec terrain mode will send up to 50% of engine power to the rear and no more.

The AWD system is good at varying the torque sent to the rear at varying rates up to 50% but the 60% send to the rear in sport mode is a load of BS and the "up to 100% to the rear in sand/Mud is also not accurate either.
 

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In your opinion do you think the system could support the maximum 348 ft-lbs of torque from the transaxle? I'm curious to know why FCA limited the torque. I would assume it could only be because there is a component downstream that would prematurely fail. That or the limiting factor is the engine. In the case of the 2.0T I would think that getting an extra 18% torque would be achievable. The Alfa Romeo Giulia has 280 hp and 306 lb-ft but we are talking a measly 3.7%. Also have you found anything to suggest that the driveline module limits torque similar to the transaxle/TCM?
 

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Discussion Starter · #7 ·
The PCM and TCM both limit torque to the engine and trans, the ZF8(Like the guilia, JL Wrangler and WK2 Grand Cherokee) equipped vehicles don't have that type of torque management tuned like the KL does. The trans isn't going to be the issue when it comes to power its going to be the PTU and RDM.
 

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The PCM and TCM both limit torque to the engine and trans, the ZF8(Like the guilia, JL Wrangler and WK2 Grand Cherokee) equipped vehicles don't have that type of torque management tuned like the KL does. The trans isn't going to be the issue when it comes to power its going to be the PTU and RDM.
I think I am starting to see a trend, anecdotally. It seems that PTU/transfer cases are one of the weakest points on a vehicle these days. My old vehicle was junked because the transfer case broke, and from what I have read the PTU fails fairly often on the cherokee. Why don't manufacturers just put in a more reliable part?
 
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