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2017 Lexus IS350, 2007 Toyota Camry, 1995 Toyota MR2, 1996 Honda Acty
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The GR-Four system determines torque split via clutch packs on the driveshaft. The rear is geared shorter and therefore is overdriven. By slipping the clutch packs, the system adjusts the torque split.

It isn't clear to me how much slip occurs at the 30:70 mode, but in theory by slipping less, you could send more torque rearward. This would be at the cost of heat and wear.

In terms of controlling how the clutchpack operates, there are aftermarket controllers already available. Revolution mentioned on Best Motoring that they used the Syvecs AWD controller to bypass factory protection measures.

Here's a video from Syvecs.

 

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Not possible. Engeering Explained has a great video on the topic.
I actually interpreted his video differently. My understanding was that the wet clutch pack has different "settings" depending on the torque distribution you are looking for (and also your current gear, I think).

So in theory, you probably could adjust the pack settings to transfer more torque to the rear diff. The issue with this is that the clutch pack acts as a "brake" in the way it transfers torque, so the more torque you try to force to the rear diff, the more heat and wear you put on the clutch pack.

Going off this logic, I would expect that driving in "sport" mode all the time would cause your clutch pack to wear out quicker than driving in the standard mode, as your clutch pack would be taking on more load.

Also, something that just occurred to me is that you'd probably see HP losses as you transfer more power to the rear, as some energy is being consumed as heat in the clutch pack. Probably insignificant but I'm not sure (maybe that's why track mode is 50:50?)

Oh and if someone more knowledgeable on the subject would like to correct me, please do! My understanding is obviously pretty shallow.

anyway, here is the video if anyone is interested:
 

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Suzuki GSXR750L7 Legacy 3.0R 6MT
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Unfortunaly due to the location of the clutch pack, overheating could always be a problem. Its not the hot exhaust so much or even the poor airflow if there are undercovers its the slipping that causes massive heat to be generated in the first place. Quite high drivetrain losses in AWD, that's just the nature of the beast. AWD so much easier to implement in my old 1/8th scale gas racing cars but the way they do it there is easy due to the level of power transfer involved. If it overheats you have no other option but to disengage it.
 

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I'm just curious about the future ability to mod it for cooling / durability. I think the GRY has a high capacity rear diff cover available, but thats for the diff... not the drive coupling. Looking at images of it I'm not sure exactly what could be done to increase fluid capacity or improve cooling but we'll need to wait and see. I wonder what Toyota does for its racecars running this system?

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