That gave me a better understanding on how AWD works, thanks. I eventually will get winter tires, but up to now I haven't had big issues with the current tires they have work well in snow storms (of course with winter tires will be better). But unless I misunderstood you, you are just enforcing my point, unless the car starts to slip you won't get the extra power of full drive (over 40km/h at least). I haven't had issues with the car not responding well or not adjusting to the road conditions, my main complain was with the lack of full drive power that I was used to with the all time locked 4WD.
AWD or not really
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a real 4X4 only gets stuck deeper in the ditch IMO, there is a pdf about how the awd system works, it basicly takes into consideration if you are accellerating, the traction of each wheel and then decides how much power to send to the rear. saying that it's only FWD after 40km/h is totally false. Heck I went up the 25degree driveway at the cottage today with a fresh 15cm of snow, not a problem with good winter tires, didn't even have the lock on!
even on real 4X4s, they specify that you should not use the 4x4 system at high speeds for extended periods or you will put excesive wear on the components
even on real 4X4s, they specify that you should not use the 4x4 system at high speeds for extended periods or you will put excesive wear on the components
If your tires are not slipping then why would you need awd? Awd is not going to give you extra power, it just going to divide what power you have between the front wheels and rear wheels. However if your front tires are not spinning then the extra traction the rear wheels will provide is pointless.
If your tires do start to slip the computer controls the center differential and sends power to the rear wheels. The computer will determine how much power gets diverted to the rear wheels based on the difference between front and rear wheels speeds. The computer will send up to 45% of the engines power to the rear wheels.
The computer will also use individual brakes to prevent a wheel from spinning. If that happens you will notice a loss of power. But all cars and light trucks sold in the US must include this feature. The basic names are traction control (using brakes to prevent the wheel with the least amount of grip from spinning) and stability control (using brakes to prevent the vehicle from spinning out sideways).
When you push in the diff lock button it will send a full 50% to the rear wheels. The main advantage of the diff lock is if you are stopped and need the traction (say stuck in snow) and you do not push the difflock button the computer will start out in front wheel drive and then increase the power to the rear wheels. This may only take less than a second but it also isn't instant. Pushing the button avoids any delay and will provide a small amount more (5%) power to the rear wheels.
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Interesting discussion on AWD vs FWD and winter tires vs all-seasons. You folks have summarized the issues and considerations very well, with a dose of evolving experience thrown in for good measure. Here in Cincinnati we don't have true ice/snow conditions very often during the year, but I may look into getting a dedicated set of winter wheels and tires. After all, the RAV4 is supposed to be our 'foul weather' vehicle, yet I have dedicated winter wheels and tires on my daily driver.
So last Friday we had our first winter storm with significant snow and icing here is SW Ohio and I had the chance to see how the RAV4 behaves in winter conditions. To note, this is not my first AWD vehicle, the other two being a 4WD Highlander and an FJ Cruiser (manual, with full-time 4WD). The FJ has one of the best 4WD systems money can buy and an excellent benchmark. Also, both are equipped with substantially better tires than the RAV4's OEM Yokohamas.
I can report that, compared to the other two vehicles, the RAV4 performed very well. Here are my observations:
- The transition from FWD to AWD is very fast, smooth and barely noticeable. It takes less than half second for the car to realize that that front wheel are spinning and engage the rear axle. It is actually so quick and smooth that most people probably won't even notice and think that they are still in FWD. The only time when you can feel a perceptible "kick" when the rear axle engages is if you start on a steep incline, with the front wheel on a slippery spot, and rear wheels on clean pavement. My driveway is somewhat steep and impossible to climb with two-wheel drive only. The RAV4 did equally well as the other two 4WD cars. A friend's FWD Escape was dead-in-the-tracks. Even with substantial momentum, it could only make it half-way up the driveway, and once stopped would not start, but only slide backwards.
- The VSC performance is quick, predictable and effective. RAV4's VSC acts both to correct understeer and oversteer. In the FJ, VSC only corrects oversteer, but does not detect or correct understeer. In the HL is acts on both. That said, the RAV4 has substantially higher tendency to understeer than the other two vehicles. I am not sure if this is because of the lousy tires, or the fact that under normal driving conditions the RAV4 is basically FWD. Both the HL and the FJ are full-time 4WD and essentially understeer-free (unless you push them really hard). Unlike the FJ and the HL, RAV4's VSC is "silent", i.e. does not give you an audible warning that the system is active and the only way to detect it is through faint noise / vibration from the wheels. You actually need to know what you are looking for to detect that it is working. But it works nicely, and if you loose control, it's not because VSC is not doing its job, but because you are trying to defy the laws of physics (and remember, physics always wins). Overall, I would rate the RAV4's VSC to be the best of the three - it's the quickest to act, kicks-in even at the slightest skid, does exactly what it should to bring you back on the intended track, and is very "subtle" unlike some other systems I have experienced which can be quite disconcerting. Again, most people in a RAV4 probably won't even notice that the VSC has just saved their butt, it is so "gentle" and unobtrusive.
- The ABS is quick to act and performs as expected, withing the constraints of the car (stiff, long travel suspension, high center of gravity). It won't "hug the road" like a BWM Series-5, but you can't take an BMW5 off-road - the suspensions are designed for very different performance.
- Traction control also works as intended, minimizing slippage without "killing" engine traction completely. It does a very good job when starting on icy spots, when you want the tires to remain in "static" friction regime. I tested starting with traction control ON and OFF on the same inclined road several times, and traction control ON always resulted in more controlled start with less lateral "wobbling", with no loss in effective acceleration.
Net, I am very positively impressed by the new RAV4's snow performance. I am sure that once I upgrade to better tires, it will be my vehicle of choice for winter driving. It is more nimble than the HL and handles much better than the FJ.
I can report that, compared to the other two vehicles, the RAV4 performed very well. Here are my observations:
- The transition from FWD to AWD is very fast, smooth and barely noticeable. It takes less than half second for the car to realize that that front wheel are spinning and engage the rear axle. It is actually so quick and smooth that most people probably won't even notice and think that they are still in FWD. The only time when you can feel a perceptible "kick" when the rear axle engages is if you start on a steep incline, with the front wheel on a slippery spot, and rear wheels on clean pavement. My driveway is somewhat steep and impossible to climb with two-wheel drive only. The RAV4 did equally well as the other two 4WD cars. A friend's FWD Escape was dead-in-the-tracks. Even with substantial momentum, it could only make it half-way up the driveway, and once stopped would not start, but only slide backwards.
- The VSC performance is quick, predictable and effective. RAV4's VSC acts both to correct understeer and oversteer. In the FJ, VSC only corrects oversteer, but does not detect or correct understeer. In the HL is acts on both. That said, the RAV4 has substantially higher tendency to understeer than the other two vehicles. I am not sure if this is because of the lousy tires, or the fact that under normal driving conditions the RAV4 is basically FWD. Both the HL and the FJ are full-time 4WD and essentially understeer-free (unless you push them really hard). Unlike the FJ and the HL, RAV4's VSC is "silent", i.e. does not give you an audible warning that the system is active and the only way to detect it is through faint noise / vibration from the wheels. You actually need to know what you are looking for to detect that it is working. But it works nicely, and if you loose control, it's not because VSC is not doing its job, but because you are trying to defy the laws of physics (and remember, physics always wins). Overall, I would rate the RAV4's VSC to be the best of the three - it's the quickest to act, kicks-in even at the slightest skid, does exactly what it should to bring you back on the intended track, and is very "subtle" unlike some other systems I have experienced which can be quite disconcerting. Again, most people in a RAV4 probably won't even notice that the VSC has just saved their butt, it is so "gentle" and unobtrusive.
- The ABS is quick to act and performs as expected, withing the constraints of the car (stiff, long travel suspension, high center of gravity). It won't "hug the road" like a BWM Series-5, but you can't take an BMW5 off-road - the suspensions are designed for very different performance.
- Traction control also works as intended, minimizing slippage without "killing" engine traction completely. It does a very good job when starting on icy spots, when you want the tires to remain in "static" friction regime. I tested starting with traction control ON and OFF on the same inclined road several times, and traction control ON always resulted in more controlled start with less lateral "wobbling", with no loss in effective acceleration.
Net, I am very positively impressed by the new RAV4's snow performance. I am sure that once I upgrade to better tires, it will be my vehicle of choice for winter driving. It is more nimble than the HL and handles much better than the FJ.
Excellent write-up! Especially with the experience with the FJ & HL. My only complaint is it took me two extra clicks to verify you had a 4.4 model. And yes I know I'm on the 4.4 forum. I just like seeing it in the signature.
The only difference I see from my 4.3 is that when VSC activates the "skidding car" indicator on the dash lights and is accompanied by a beeping.
I must say
The only difference I see from my 4.3 is that when VSC activates the "skidding car" indicator on the dash lights and is accompanied by a beeping.
I must say
has to be the best to-the-point phrase I've EVER seen on this forum. :!: :idea: :thumbs_up:
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