As pretty much anyone who offroads knows, AWD vehicles absolutely tear up the trails vs a proper 4wd with lockers, since AWD relies on detecting tirespin (ie, destroying trail) to determine when it needs to activate.
AWD can theoretically work far better than a 4WD with diff locks, because it can simulate, based on the steering wheel angle, the exact speed each wheel should turn, and 'lock' each wheel to that speed giving zero slippage.
Just a shame that the sensor -> computer -> actuator feedback loop seems to be 200 milliseconds or more, so AWD vehicles just end up having different wheels slip semi-at-random till that wheel gets the brakes activated 200ms later.
It’s not just sensors. It’s mainly to avoid it falsely applying itself. In my opinion, that is far more dangerous because it’s wildly unpredictable when it will work as expected vs when it toque vector.
I can get the torque vectoring to do some weird things, kind the right conditions on my car. It’s okay because I’m intentionally pushing the limits, but I absolutely would not want the vectoring to kick in when I’m not expecting it. Towing on packed snow/ice is not the place you want to learn your wheels suddenly decided to react dramatically differently.
Most AWD systems do not have the ability to vector torque like that. They're usually based on mechanical limited-slip differentials that require some amount of slip before they partially lock, and sometimes the limited slip is only between front and rear, not left and right. There are different types, with some requiring a lot of slip before they lock up and others requiring little.
Limited slip differentials cost more than open differentials. Limited-slip differentials that lock up quickly cost more than those that allow a lot of wheelspin. Electronically-controlled torque-vectoring differentials cost yet more.
The system you describe seems to meet the NPS definition of 4WD someone linked elsewhere: "a means to mechanically power both front and rear wheels at the same time", though I wonder if there might be some more technical regulation with specific requirements. I agree that sort of thing could work well for off-road use.
AWD has come a long way in that regard in the last few years. It's still highly variable from manufacturer to manufacturer, but systems that use internal clutches alongside brakes (and not only brakes) to control wheel movement + tight feedback loops can really do a great job of minimizing wheel spin.
They get a lot of hate, but the bronco sport has the best AWD system I've driven to date in that regard.
And with that said, it is still the type of thing the Park Service would rightfully cite as not a proper 4wd. 9ish inches of clearance is not much, and the lack of a low range will bite you. I've taken mine on plenty of milder 4wd only trails in parks (e.g. black gap in big bend plus tons and tons of forest service roads), but I'm certainly not going to do elephant hill in canyonlands with it. That's what the dedicated off-road rig is for.
There are "4wd only" trails in national parks that high clearance AWD is fine on. The rangers will tell you which ones those are.
Canyonlands is a different beast than most national parks. Canyonlands has some very gnarly trails open if you have a permit. Lookup dollhouse sometime. Beautiful, but insanely technical. Elephant hill is better known and a bit milder.
londons_explore|1 year ago
AWD can theoretically work far better than a 4WD with diff locks, because it can simulate, based on the steering wheel angle, the exact speed each wheel should turn, and 'lock' each wheel to that speed giving zero slippage.
Just a shame that the sensor -> computer -> actuator feedback loop seems to be 200 milliseconds or more, so AWD vehicles just end up having different wheels slip semi-at-random till that wheel gets the brakes activated 200ms later.
SkyPuncher|1 year ago
I can get the torque vectoring to do some weird things, kind the right conditions on my car. It’s okay because I’m intentionally pushing the limits, but I absolutely would not want the vectoring to kick in when I’m not expecting it. Towing on packed snow/ice is not the place you want to learn your wheels suddenly decided to react dramatically differently.
Zak|1 year ago
Limited slip differentials cost more than open differentials. Limited-slip differentials that lock up quickly cost more than those that allow a lot of wheelspin. Electronically-controlled torque-vectoring differentials cost yet more.
The system you describe seems to meet the NPS definition of 4WD someone linked elsewhere: "a means to mechanically power both front and rear wheels at the same time", though I wonder if there might be some more technical regulation with specific requirements. I agree that sort of thing could work well for off-road use.
jofer|1 year ago
They get a lot of hate, but the bronco sport has the best AWD system I've driven to date in that regard.
And with that said, it is still the type of thing the Park Service would rightfully cite as not a proper 4wd. 9ish inches of clearance is not much, and the lack of a low range will bite you. I've taken mine on plenty of milder 4wd only trails in parks (e.g. black gap in big bend plus tons and tons of forest service roads), but I'm certainly not going to do elephant hill in canyonlands with it. That's what the dedicated off-road rig is for.
There are "4wd only" trails in national parks that high clearance AWD is fine on. The rangers will tell you which ones those are.
Canyonlands is a different beast than most national parks. Canyonlands has some very gnarly trails open if you have a permit. Lookup dollhouse sometime. Beautiful, but insanely technical. Elephant hill is better known and a bit milder.
alamortsubite|1 year ago
throwaway984393|1 year ago
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