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SUVs Suzuki Grand Vitara/Vitara Suzuki Grand Vitara vs Subaru Forester vs Hyundai Santa Fe vs Jeep Liberty vs Ford Escape vs Saturn Vue
4940 messages, Last post on Sep 24, 2009 at 9:33 AM
You are in the Suzuki Grand Vitara/Vitara Forum. Your Hosts are steve_ & tidester
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Anyone sweating the details of fwd/awd slip&grip systems should also bear in mind the Grand Vitara's full-time AWD. With a low range commonly installed. I'd be interested in hearing how a pro-active traction control system works. |
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Replying to: xostnot (Sep 02, 2009 9:28 am) Happy to... Subaru has several AWD systems, at least 4 I can think of off the top of my head, so let me first specify that I am talking about their VTD (variable torque distribution). How is it proactive? VTD takes several inputs, including throttle position, for starters. So when you hit the throttle, the VTD can adjust the torque spread pro-actively, even while the engine revs up, well before tire spin occurs. Borg Warner's web site stated pretty clearly that after slippage occurs, it can react instantly, but that's still reactive, after you've lost traction. The coefficient of friction of a slipping tire is much lower than a tire that has not yet slipped. Subaru's VTD can spread power evenly and potentially prevent that traction loss before it ever happens. Another example: VTD also uses all the inputs from the stability control system, including yaw sensors, steering angle sensors, wheel speed sensor, steering position sensor, lateral G sensor, longitudinal G sensor, and brake pressure sensor. So let's look at a fairly common occurence: drop-throttle oversteer. You enter a turn a bit too fast in a reactive AWD crossover, which is in 100% FWD mode because you have traction (for now). Suddenly you let off the gas to slow down, and all of the engine braking is being done by the front wheels alone. VTD wouldn't be in FWD to begin with, but the throttle position sensor would let it know you let off the gas abruptly. The longitudinal G sensor tells it you are slowing down, and the lateral G sensor tells it your are turning. To top that off, the steering position sensor tells it your intended path, so it would have shifted power to the rear so the engine braking would not compromise your stability. If all that fails, only then does the stability control kick in and apply the brakes. Subaru's philosophy is that the AWD should act first. Similarly, if you're going down a steep hill, it would know most of the weight is on the front tires and could shift power bias to the front. Going up that same hill, power would go to the rear axle. The Borg Warner system would try to climb that hill in FWD first, and once it failed, the rear axle would kick in and try to save it. The Subaru is smarter and would have known that already. *** That's VTD, if we look at Viscous Couplings they default to 50/50 and react from there. So while they are reactive, at least the power split starts out balanced. Still better than 100% FWD reacting and sending some power to the rear axle. |
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Replying to: xostnot (Sep 02, 2009 9:28 am) Plus you could get a V6+manual trans combination. Very nice. I test drove one a while back, before they updated the engines. I think back then it was on-demand part-time 4WD, I don't recall.
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Replying to: ateixeira (Sep 02, 2009 10:27 am) Bob
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Replying to: rsholland (Sep 02, 2009 10:32 am) Any excuse to go look at new vehicles. 
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ateixeira, thanks for the sensible explanation. I don't know if the GV's system is that sophisticated. Seems to me it would be cheap to do, since all it takes is some extra software. Suzuki does license the traction/stability control system from Mercedes. But the Subaru system can't bias power side-to-side on the same axle, can it? I know some high end suv's/cars can do that. There is another cuv that has a low range. The Patriot can be spec'd with a single low gear on a cvt, plus raised suspension and skidplates. Were it not a generally inferior vehicle, it would make a serious alternative to the GV. The GV's 2.7L V6 engine may be underrated, or biased more for durability than power. On a recent trip over the major highway with the biggest climbs in North America, and in over an hour's driving over many climbs, it gradually became clear our GV, even with 3 people and full load of cargo, could outclimb a brand new Highlander. Hill after hill, it became obvious they were racing us uphill. On the last big one we left them behind at 120kph, and I still didn't have it floored. That's enough power for me. On that same highway and similar ones in winter conditions so bad most people are either down to 50kph or stopped, the GV can travel in control far faster than virtually every other type of vehicle. Much of this is due to having a perfect weight distribution of 25% on each tire. The Rav4's, CRV's, and frankly, the Subarus, creep along with the fwd sedans. |
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Replying to: xostnot (Sep 03, 2009 2:32 pm) |
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Replying to: xostnot (Sep 03, 2009 2:32 pm) No, as far as I know only Acura and BMW do that as of yet. Acura's SH-AWD does that, but only on the rear axle, and only part-time. The basic system is still FWD-based. So it has pros and cons. BMW's active differential works on the rear axle but I think it works full-time. It's the front axle that is only engaged part of the time, when needed. The 185hp V6 felt adequate when I test drove it, but not quick. It may be tuned more for torque than horsepower (edit: 184 lb-ft, so not really), but Toyota's V6 makes 269hp. The Highlander is bigger and heavier, so I woudn't really compare those. Suzuki updated it, though, right? Isn't it over 200 now? (edit: per Wiki it's 164hp for the 4 banger and 221 for the V6, a little less than each Subaru engine offers) Plus with the low range the mechanical advantage will let it climb just about anything it's ground clearance will allow it to. Subaru engines vary a lot. Our PZEV Forester makes 175hp, but it's light for its class. You can get a turbo Forester or an H6 Outback if you want more power, both well over 200hp. To me the Liberty is too trucky to be considered a CUV, it's a regular SUV IMHO. GV stands alone as a car-like CUV with a low-range. |
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Replying to: explorerx4 (Sep 03, 2009 4:37 pm) But for those like us who do use the low range regularly, it allows us to go places where only a low range will get you. In places not quite so difficult, using the low range reduces wear and tear and damage. In some cases, like descending dangerous slippery mountainous logging roads in the winter, using engine braking in low range, as opposed to using the brakes, has proven to be an important safety advantage. For those who may occasionally find low range useful, like going to cottage country, the low range may be worth having for the small increase in cost and weight to have it. |
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Replying to: xostnot (Sep 04, 2009 10:24 am) We used to vacation a lot at the Outer Banks of North Carolina. If I lived there or near there, a low-range equipped SUV or pickup would be a must-have for me, as beach driving is done by the "natives" all the time. Also remember that the Grand Vitara is a world-car, so in other markets (Australia, Africa, Mid-East, Asia, South America, Polynesia, etc.), where roads are often non-existent or miserable at best, low range is often used. Bob |
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