will announce SUV of the year 2002 on October 10 at California Orange county Auto Show. My guess is CRV missed the deadline. That leaves Explorer, TrailblazerEnvoyBravada, Rendevous, Highlander, Liberty . Highlander wins of course.
My understanding, gained from years of reading car magazines, is that MT's Car of the Year award is something of a joke in the journalism profession. MT is supposedly heavily biased toward Detroit-based carmakers. Kind of a 'house organ'.
I recall that the same reviewer found that the same AWD system - isn't it? - that he appeared to criticize in the new CR-V - he found it the best AWD system in real world use when reviewing the Acura MDX. Isn't the CR-V's system the same? He implies there's a difference but I wonder if that's true.
...The design goal was "beat winter." Thus, the MDX has a type of four-wheel drive aimed at snowy, icy roads. In a comparison test, a prototype MDX kicked the goobers out of rivals on snow and slush in the Rocky Mountains.
Mercedes-Benz ML320 and BMW X5 fell on their faces in the slick stuff. Their traction-control systems tried to halt the vehicles by applying the brakes when wheels spun, instead of keeping them going through the tough stuff. Lexus RX 300 wound up bouncing off snowbanks. The rear-wheel-drive portion of its four-wheel drive doesn't kick in until the front wheels lose traction. By then, the Lexus was irretrievably headed for the ditch.
MDX could be slung around snowy corners with nary a shiver or slither. It could be accelerated viciously on slush without falling into the whimpering, thumb-sucking standstill of its German rivals.
SUVs get better motor running
The only vehicle on hand that could remotely match MDX on the snow and ice was Ford Explorer with Control Trac, a more traditional type of four-wheel drive. But Explorer rode stiffly and bounced violently when driven at MDX speeds.
MDX's slick-working 4x4 system is a front-drive arrangement that sends power to the back wheels only when needed. The key: Acura engineers think it's needed any time you accelerate. Front wheels needn't slip before back ones get power.
Steady cruising and braking are done in front-drive mode. But all four wheels clock in when you pass, leave the stop sign or race up a freeway ramp. That makes the vehicle more stable, even on dry pavement. The magic, though, is when you hit a slick spot in a corner. Skip the brakes and go for the gas, as a good driver would, and MDX hauls you around just fine....
If it's not the same system, then perhaps Honda should make it like the MDX, locking the wheels into AWD whenever there's acceleration. Maybe the difference lies in the fact that the MDX is so powerful that AWD is needed under acceleration and that's just not the case with the CR-V.
but the MDX is bigger and much more powerful, so I'm certain the MDX uses a much beefier version.
Also, the MDX is at a much higher pricepoint, which would allow it to incorporate some more "costly" upgrades, that the CRV wouldn't have.
For example: The reporter of the MDX indicated that slippage is not necessary for the rear wheels to engage. It (the MDX's AWD) apparently engages anytime that you accelerate. That's not true for the CRV.
Acura MDX uses a completely different AWD system (an electronic system versus mechanical system in CR-V).
The MDX system is called "VTM-4" (VTM: Variable Torque Management). This sounds like a good (and very light) AWD system most people will ever need. The nice part about VTM-4 is that it is a combination of pro-active and passive system.
Every time you stomp on the gas pedal, all wheels get power. Slippage is not required under these circumstances, it just sends power to all wheels. From then on, the amount of torque split between front and rear wheels can vary (continuously, instead of in 'fixed chunks' as in many other AWD systems) depending on traction requirements.
During cruising, the front wheels take over, and at that time it becomes a 'passive' system, waiting to detect slippage. If it does, then once again a gradual shift of power occurs to the rear wheels.
The VTM-4 also engages when the vehicle turns, without having to detect slippage (once again, a pro-active system).
There is a 'lock' feature that will keep the power supply to all wheels permanently, regardless of whether or not you depress the gas pedal, with maximum torque (40%?) to rear wheels upto 6 mph. Between 6-18 mph, the front wheels gradually get more power. This would help in getting out of snow/mud situations.
CR-Vs Real Time AWD system is a much simpler technology, but it is enough for most drivers. I've read people talking about the 'possibilities' of losing control of vehicle if the other set of wheels engage only when slip is detected. They probably will say the same about ABS, traction control and stability control systems as well, which are all passive systems. And these are designed to give control to drivers, not take it away from them.
CR-V's AWD system may take a fraction of a second to engage (like an ABS, TCS etc. would), but so does a Subaru AWD system. The only difference is that the Subaru AWD system has about 10% of the power delivered to the rear wheels at all times. 90% of the power is still at the front wheels! During cruising at 60 mph, the Subaru may be delivering about 60 HP at the front wheels, and about 6-7 HP at the rear wheels. When the front wheels lose traction, substantial amount of torque has to be sent to the rear wheels in this case as well, perhaps a meagre 6-7 HP less in this case.
A vehicle is more likely to lose traction on the wheels that have more power, and in either case, it would be the front wheels. And in either case, the mechanical system will have to engage to shift some power to the rear wheels.
Good post. It sounds like the MDX is closer to what Subaru offers, in that if you accelerate hard, more power is sent to the rear wheels.
I'm not sure I agree with you regarding the extra time it takes for the Subaru system to engage (you could be right, I'm just not sure). Also on Subarus, the 10% of power to the rear wheels is only for "most" automatics, and it too is electronically controlled. All Subaru manuals have 50/50 front-to-rear normal power split, and use a viscous coupling. All WRX models (manual & automatic) also have the the 50/50 power split; and the H-6 with VDC (automatic) has a 40/60 power split, with more power under normal conditions being sent to the rear. The VDC can also vary the power split between each wheel—not just front-to-rear. (NOTE: the power split for the WRX automatic and VDC automatic may be off 5% one way or the other, but what I've quoted is close enough to make my point)
Also I believe all Subarus can send 90% of the power to the rear wheels if need be. I don't know if the CRV or MDX can do that. Finally, all Subaru AWD systems are also more active in cornering (again like the MDX) and in hard braking too.
Difference is that the Subaru AWD systems have a centre differential, whereas the MDX does not. This means that the MDX's system reverts back to 2WD in turns. Additionally, as you pick up speed, VTM-4 switches back to FWD unlike the Subaru systems which still runs at 80/20 (not 90/10), 50/50, or 45/55, depending on the model and transmission. In emergency maneuver situations, you will be left with FWD unless you have wheel slippage.
There is a VTM-4 lock button that allows you to lock the power to the rear wheels at about a 50/50 split. However, this shuts down completely at 18 mph. Recently, one MDX owner was writing about how frustrated he was driving on sand because the vehicle would revert to FWD mode with or without the lock and he would get stuck nearly immediately (and had to get out with his wife and dig several times which made her extremely displeased!) even with deflated tires. He swore that he would never take it onto the beach again.
VTM-4 is actually quite similar to Isuzu's TOD 4WD in that which it is somewhat proactive, it switches off in certain situations since it doesn't have a centre differential (doesn't help you in turns on dry pavement). The big difference is that TOD can be locked into a 50/50 mode without turning off at a certain speed, and that it also has a low range.
In any case, I digress. Back to your regular CR-V discussion.
Interesting comment about the MDX and sand. I wonder how the CRV does on deep soft sand? We recently had our Forester out on the beach of the Outer Banks of North Carolina. This was the first time I've had it out on sand, and it did just fine. Although, I didn't experience any really "super-soft" sand, as it had just rained recently, thus packing the sand down somewhat. (I'm sure juice will chirp in here, as he's had some extensive sand driving with his Forester)
I agree that USA Today writer is being a bit harsh on the CR-V's RT4WD. It's plenty for a system that wasn't designed for heavy offroading and very demanding conditions.
However, I do believe he is being consistent. His criticism about the RX300 would apply to the CR-V RT4WD as well :
Lexus RX 300 wound up bouncing off snowbanks. The rear-wheel-drive portion of its four-wheel drive doesn't kick in until the front wheels lose traction. By then, the Lexus was irretrievably headed for the ditch.
As Drew pointed out Subaru 4EAT AWD can actively change torque split based on throttle inputs and transmission position. In a situation like climbing snowbanks, the torque split is closer to 50/50.
I kind of wonder why Honda keeps trying to develop it's own unique AWD systems when there are other proven systems on the market. For example, a VC based system (previous generation RT4WD) can be tuned to be made compatible with ABS.
There is a VTM-4 lock button that allows you to lock the power to the rear wheels at about a 50/50 split. However, this shuts down completely at 18 mph. VTM-4 in LOCK position would send 50-50 (or whatever) split to wheels upto a maximum speed of 6 mph, thereafter, the split gradually goes in favor of FWD to about 18 mph. At higher speeds (note: cruising), the rear wheels are disengaged unless slippage is detected.
Recently, one MDX owner was writing about how frustrated he was driving on sand because the vehicle would revert to FWD mode with or without the lock and he would get stuck nearly immediately (and had to get out with his wife and dig several times which made her extremely displeased!) even with deflated tires. Reminds me of my last trip to Padre Islands on the Texas Gulf Coast. The beach was crowded, and demands AWD vehicles. I was in a rented Taurus, believe me, I passed a stuck (in sand) Subaru Outback, with its wheels spinning in vain. I have seen Land Cruisers getting stuck in deserts (note: sand). AWD will give you advantages, but one has to understand the laws of Physics as well.
Difference is that the Subaru AWD systems have a centre differential, whereas the MDX does not. This means that the MDX's system reverts back to 2WD in turns. This does not mean anything to me. I remember reading about MDX's system engaging when taking turns. It would work in the same way as it does when accelerating (i.e. without waiting for a loss of traction, proactively).
I want to hear from someone that drives their CRV in the snow. I want to buy this car to drive up to the mountains to go skiing. Is the RT4WD good enough for this? I really don't want to get out of the car and put chains on.
I want to hear from someone that drives their CRV in the snow. I want to buy this car to drive up to the mountains to go skiing. Is the RT4WD good enough for this? I really don't want to get out of the car and put chains on.
in the photo. yet it is same size as current one and only 1 inch smaller than competitors. I never felt current CRV wheels are too small. Maybe its better in real life.
You have to realize that while the size of the wheels are the same as in the last generation model, the car itself grew a few inches bigger.
But just look at how clean the car looks without the black bladding and door handles. Although the tail lights, at least in this picture, look like sparkling candy canes.
Read the Car and Driver test today. Disapointed with the 192 ft stopping distance from 70mph. Tribute did 175 ft. Rav4 did 163 ft. Even the old CRV did 184. Only Grand Vitara did worse at 193 and Tracker 205 ft. Those small tires ?
Acceleration from 0 to 60 with 5 speed is 8.4 seconds. I'm guessing automatic will do 9.4 seconds. Tribute automatic did 8.2. Forester 9.7. Grand Vitara 10.2. So its middle of the pack.
All the hoopla about noise improvement to best in class turns out to be just noise. It is 42 dba at idle, 75 full throttle, 70 cruising and coasting at 70 mph. This is only about 1 dba better than EscapeTribute, on par with Grand Vitara, about 2 dba better than Rav4,Xterra. Much worse than Highlander which scored 68dba at 70mph.
But was the Tribute's 8.2 second for a 4-cylinder model or the V-6 one? I get the feeling that it's the V-6. And if so, I'd say the CR-V's acceleration number is quite good for a 4-banger hauling a ~1.5 ton vehicle.
But as for the braking numbers- that's really bad. Not only size- but what about the actual tires that were used?
I took a look at the new 2002 CR-V website and from what I see, I have to get an EX model, with all the extra trimmings, if I want ABS. Do you come to the same conclusion? (Going to www.honda.com will take you there)
Also, thanks for all of your posts! I have learned alot from what is written here.
Chriswei - Pretty good. Here's a story I wrote for the CR-V Information Xchange after a meet in Bradford, PA. We trekked for 2-3 hours on snowmobile paths in the Allegheny National Forest. We had about 3-6 inches of fresh snow on top of a packed base. There were a number of spots where we drove through ice ruts under the newly fallen powder.
I drive mine like it's a front wheel drive car (which it is). When I need power at the rear wheels, it's there. Most of the time it's not necessary.
Scname - C&D has published a full comparison? Or are you comparing numbers from different test?
I'm using March 2001 issue for data. Its got the 11 dwarf comparison, available at their website. Tested their snow driving ability. Those data itself came from past C&D tests in other issues.
New CRV numbers came from November issue.
Diplois, Tribute is a V6. Their 4 cylinder has only 130 hp, don't know why anyone would bother..
Kewl. Thanks. It's hard to compare things like braking and sound insulation unless the tests are done in the same conditions. Regardless, those braking numbers are not what I was expecting. The vehicle isn't much heavier and they've added rear disk brakes. With only a paper comparison available, I would have expected better from the new CR-V.
Illinoiscentra - You are correct. Honda has been funny about that since they introduced the CR-V. I was pleasantly surprized to read that they didn't make the same requirement for side airbags.
Hey, it's funny that y'all are talking about the CR-V's performance on sand. I just returned home after the Owners' Event on Galveston Island today. No disappointments -- and a full write-up to come in the next few weeks. :-)
scname -- Before you dismiss the noise reduction as insignificant, I want to make sure that you understand how sound is measured: An increase of 10 decibels represents a doubling of the intensity of sound. That means a drop of 1 dB is actually a drop of 10% in sound, 2dB is a drop of 20%, etc. That may be enough to matter to some people. Now, if you knew this already and still think it's insignificant, then feel free to ignore this. :-)
It doesn't take too much effort (or stupidity) to get stuck in sand, no matter what you drive. A couple of years ago, I was following someone in a Land Rover Discovery on the beaches of the Outer Banks or NC. He was clowning around, and got so stuck it wasn't funny. I've also seen a Jeep CJ-7 almost half submerged in sand.
What some people do when they get stuck, is spin the wheels, thus digging themselves a deeper hole. If you have tires with an aggressive tread, this is very easy to do, since they're designed to "dig" and not "float." Once the vehicle's frame is sitting on the sand, the tires spin freely, and you'll never get out without jacking the vehicle and shovel more sand under the tires.
Actually the best sand tire is a "bald" street tire, aired down to about 18 - 20 psi. This type of tire will "float" (stay on top of the sand, not dig into it) easily.
I guess the first 5-8 in, snow we get here in the midwest I will toss a snow shovel in and see what kind of traction I can get without getting stuck.
I am used to driveing 4x4's with a transfercase, locking front hubs and a positive traction rear axle, and aggressive tires that dig into the snow.
Don't get me wrong I don't want to go off road, as this not a off road vehicle.
What I do want to do, is get to work in the morning, before the snow plow makes thru the neighboor hood. Drifted in roads with this vehicle surely would be a no-no.
If you live where it snows, and drive a CR-V,I'de like to hear your story. Thanks Tom F.
I think you'll be fine with a CRV in the snow. Carrying a shovel is always a good idea when driving in deep snow. I carry one too, when I'm in those conditions.
Tomf11 - The troubles I've had are the result of the snow plows getting to my neighborhood before I get out. They have a tendency to leave piles of plowed snow at the end of side streets and in parking lots. This is where the CR-V's ground clearance, approach angles, and sill clearance come in handy.
I no longer have a job which requires me to get to work in the snow, so most of the time I simply stay put. With that said, I have been off-roading in the snow and I've taken the CR-V out into unplowed parking lots for fun. The V handles much like a FWD car, though when slippage does occur, the rear tires kick in and the car plows forward. This keeps you moving and prevents getting bogged down by maintaining momentum. In certain situations, it may also help keep you pointed forward rather than slipping into a spin.
I wrote "plows forward" above intentionally. Understeer is the basic trait for AWD vehicles (which is better than oversteer for our purposes). The often overlooked problem with AWD and 4X4 systems is that the rear wheels cannot steer. When they kick in, they will push the front tires forward. Even if those front tires are pointed to the side, in a turn. If the front tires have grip, AWD/4X4 forces the car into the turn. This is the dry weather benefit of AWD in sports cars. In slick conditions, it can force a loss of traction up front. So regardless of the type of system you have (AWD, part-time 4X4, or automatically engaged 4X4), you need to go slow and be careful.
On the new 2002 CRV, can you change the tire wider without having any problem with the road handling and specially turning sharp cover.Any information would greatly apprecaited. THANK YOU
Motorweek will be testing the '02 CR-V on their weekly TV show next week, so either Oct. 13th or 14th depending on where you are.
I lease a '00 Accord and can't wait for July '03 when I can rid of it. It's big, dull, and clumsy. Wish I could have my '95 Civic back! Might go back to a Civic in '03, but...
Wow the new CR-V is great looking. I drove by a Honda dealership today and noticed that they were PACKED. I mean, it looked like a convention in there. I was thinking that perhaps people were clamoring for the low Honda finance rates but it must have been them looking at the new Cr-V. Wish I had gone inside - o well maybe tomorrow I'll have a look-see.
I guess I'll discuss more of the VTM-4 over in the other topic, but here is how VTM-4 works (without a central differential),
"Its rear wheels are engaged when its wheel-speed sensors and electronic control unit anticipate or read front-wheel slippage.
When the sensors detect wheel slippage, the VTM-4 computer sends current to electromagnetic coils on the right and left sides of the rear-axle drive unit. These coils apply wet clutches that mechanically lock the halfshafts to the pinion-driven ring gear. The halfshafts then transfer the muscle out to the wheels."
I'm not sure what you meant by 3WD as opposed to 4WD, and the talk about stability control (which I know is not about traction, but correction). But we shall discuss it later (again!).
Yup, I know that's how it works. The text you quote is included in the press kit, which I have had since September 2000. The wheel speed sensors that are mentioned are actually the ABS wheel speed sensors. Due to the lack of a centre differential, all four wheels cannot be spun together at the same rate, as such, 4 wheel drive cannot be engaged on dry surfaces in turns or binding will occur. As a result, the system will either revert to FWD (2WD) in this situation, or it will only send the majority of power to one rear wheel (possible due to the clutch packed rear differential, hence making it 3WD.
The VTM-4 system does not know when a skid is about to occur since it doesn't have any yaw or steering angle sensors that can compare the vehicle's actual lateral rotation on its axis versus where the driver wants the vehicle to go. As such, it cannot help in this situation. Since it is a torque-on-demand system, in order to be work, the driver's foot must be on the MDX's throttle pedal causing the engine to send power to the system. In an emergency situation the AWD system is useless if and when the driver lifts his/her foot off the throttle pedal and shifts to the brake pedal. Since the system reverts to 2WD/FWD mode; the vehicle subsequently behaves like a front driver. The Isuzu TOD-system works in a similar fashion when in "auto" mode.
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In both the CRV and MDX, if you have to "rock" the vehicle to get it moving in deep snow, I'm assuming that it will revert to FWD (for an instant), each time you switch between forward and reverse.
Which raises another question: Does the CRV (and MDX) offer AWD capability in reverse? I ask this question, because I've read in the past that some so-called AWD systems only work (in AWD) in forward gears. I'm not sure which vehicles this article referred to.
Seems to me that whatever 4/AWD system you're talking about, none of them are going to increase your lateral grip at all in snow , right? I don't see how, once a tire starts to slide, applying driving force to it is going to re-establish its grip, or how its being driven would prevent it starting to slide in the first place, as compared to a tire that's "coasting". Maybe more likely the other way round? So the usefulness in terms of added grip in driving a wheel only applies to the forward component of motion, and is irrelevant to any lateral forces. Which seems seems to confirm my impression, that 4 or AWD vehicles are a great help in allowing you to climb steeper hills, to get started in deep snow, climb over snow plow berms, etc. - but don't help you go around turns any faster without sliding than 2wd, everything else being equal. Which brings me the USA Today guys statement about the Honda system kicking in "too late" to keep the vehicle from sliding off the outside of the turn. Doesn't make sense to me. I can see where a full time system like the Subie's could be a big advantage in dirt or gravel, because there you have all kinds of partial-traction conditions possible where the system would influence the handling (over/understeer) of the vehicle via the throttle. But in snow, once you start to slide you have essentially zero traction. And that's going to happen when you exceed the lateral adhesion capability of a wheel, regardless of whether its driven or not. If all that's true, then the Honda system should be about as good as anything else in snow. All bets off in dirt/gravel, though. Someone who really knows should tell me if I'm full of beans - I'm just making this up as I go along.
>>In an emergency situation the AWD system is useless if and when the driver lifts his/her foot off the throttle pedal and shifts to the brake pedal.
How is that different that real 4WD? Both the Durango and Montero I drive have both AWD and 4WD. They handle the same, i.e., there is no difference in deceleration ability when in different modes.
I have often read that 4WD vehicles, because of their extra weight, are actually worse at stopping in ice or snow than lighter weight vehicles. In that case, AWD only - being lighter - should have an marginal advantage.
One of the advantages Subaru promotes in their advertising is an AWD power shift in going around corners. I think they're referring to either dry pavement or wet pavement. I agree, once a vehicle has lost traction in a corner, snow for example, the benefit of AWD is somewhat questionable.
Sorry, I don't have a Subie brochure in front of me to give their exact wording on the subject.
Bob, if you look at the above calculations, the idea with a full-time or permanent system is not to lose traction in a curve in the first place ;-). If you lose traction, you will slide and by the time the AWD system kicks in, it may be too late. The sudden traction gain from the rear wheels may also cause understeer to change over to oversteer, catching the driver off guard. That is what the USA Today article was pointing out, which is why it seems quite reasonable to me (even though I'm not a fan of that writer, by far; but this is just my own personal opinion. YMMV, of course).
Click on "Shop@Subaru," then click on "All-Wheel-Driveing System." This gives a good explanation of how their system works, and the theories behind it.
Since there seem to be more detailed comparisons going on in here, I suggest that we take this over to the existing Subaru Forester vs Honda CR-V discussion topic so as to help direct this topic back to more CR-V related matters.
Thanks!
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Thanks for the links. I was looking at the forward going and lateral traction capabilities of a given tire as separate numbers - but if they're both drawn from the same "account", I take the author's point. But are you sure he's right about that? Consider this - given his mathematical scenario, a FWDcar accelerating through a corner should have a LOT more traction available at the rear wheels than the fronts. So if you suddenly hit a patch of sand, the front end should wash out before the rear end, resulting in a clockwise spin, for example, in a left hand turn. Is this what actually happens? Doesn't seem right to me, but I could certainly be wrong. Come to think of it, a RWD car does spin the other way, so he's probably right.
Excuse me for continuing this discussion in the CRV thread, but I think it makes sense here, as part of the logic also applies to the vehicle.
it will only send the majority of power to one rear wheel (possible due to the clutch packed rear differential, hence making it 3WD. Wouldn't that be something similar to a stability control system? I.e. taking power away from a wheel ( a stability system would do so by applying brakes).
The VTM-4 system does not know when a skid is about to occur since it doesn't have any yaw or steering angle sensors that can compare the vehicle's actual lateral rotation on its axis versus where the driver wants the vehicle to go. If Honda had used VSA on MDX (it did offer VSA with RT4WD on CRV in Japan), it would have yaw sensors. But that would be more about stability control than transfer of power to the other set of wheels. During cornering, the wheel speeds aren't the same anyway, and that would be enough to trigger a transfer of power, however small or large, electronically (instead of mechanically, as with a central differential).
Since it is a torque-on-demand system, in order to be work, the driver's foot must be on the MDX's throttle pedal causing the engine to send power to the system. In an emergency situation the AWD system is useless if and when the driver lifts his/her foot off the throttle pedal and shifts to the brake pedal. I'd like to see where you got the information that lifting off the gas pedal would not 'initiate' rear wheel engagement even upon detecting slippage (loss of traction, not stability). As far as I understand (from what I have read thus far), the on-demand refers to proactive engagement (during acceleration/cornering) and reactive engagement (upon detection of slippage). With the LOCK mode, it doesn't need the driver's foot on the pedal anyway (upto 18 mph, after which it becomes a reactive system).
BTW, do you remember my post about a trip to Padre islands, and driving the Taurus on sand? I didn't need a lot of 'momentum' to get going, just enough, and it definitely wasn't more than 10-15 mph (on a crowded beach). But I did use the steering to grab as much traction as possible, without having to slow down, and avoiding excessive use of the gas pedal. So I wonder why 18 mph would be 'too slow' to get out of snow/sand banks (the purpose of having LOCK on the MDX).
The author of that website, Harold P., is a professional 4WD instructor and extremely well known in the business. He is such an expert in these matters (having to do with 4WD vehicles, etc.) that even vehicle manufacturers consult with him. For example, he has done work with both Mercedes-Benz and Jeep in the past, and has even written books about those vehicles. Additionally, he is also a professional photographer who covers the Baja rally races, etc.
When accelerating from a standstill, the weight transfers to the rear of the vehicle. That's why sports cars are rear wheel drive. The weight transfers to the rear, pressing on the rear drive wheels and contributing to the traction. Most FWD'ers do better in the snow because the weight of the engine is on the drive wheels. However, this front wheel bias also contributes to poorer handling due to a less balanced chassis. This effect of weight transfer to the rear is exacerbated when climbing uphill, which is why FWD vehicles can lose their tractive advantages when climbing uphill in the snow. As the slope gets steeper, more weight shifts to the rear, away from the front drive wheels.
"Consider this - given his mathematical scenario, a FWDcar accelerating through a corner should have a LOT more traction available at the rear wheels than the fronts."
What you have to remember is that FWD cars can have significantly more weight in front (ex. 60% of the vehicle's weight on the front half of the car). As such, even though when accelerating, the weight distribution shifts to the rear, there may still be a lot of weight over the front wheels. Too much weight will burden the front wheels, since not only do they steer the car, but they also propel the car. Again another performance and handling benefit of RWD.
"So if you suddenly hit a patch of sand, the front end should wash out before the rear end, resulting in a clockwise spin, for example, in a left hand turn. Is this what actually happens? Doesn't seem right to me, but I could certainly be wrong."
If the front tires lose traction, this will probably result in understeer. The car will run wide to the outside of the curve but will not spin around. This is the "safe" route, and most manufacturers tweak their cars so as to safely understeer when they exceed their limits. In an understeer situation, transfer of power to the rear wheels will help marginally, but the rear wheels having more traction may simply push the vehicle to an even wider arc. As soon as tires spin, they start to lose their directional ability.
However, in some circumstances (which are too detailed to get into for this context), because of the front bias weight distribution of the FWD vehicle, oversteer can also occur (because of the lighter rear end) resulting in a spin, even for a front wheel driver.
In any case, you see how weight distribution is a very complex matter to handle; this is why the professional drivers get paid the big bucks.
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Comments
...The design goal was "beat winter." Thus, the MDX has a type of four-wheel drive aimed at snowy, icy roads. In a comparison test, a prototype MDX kicked the goobers out of rivals on snow and slush in the Rocky Mountains.
Mercedes-Benz ML320 and BMW X5 fell on their faces in the slick stuff. Their traction-control systems tried to halt the vehicles by applying the brakes when wheels spun, instead of keeping them going through the tough stuff. Lexus RX 300 wound up bouncing off snowbanks. The rear-wheel-drive portion of its four-wheel drive doesn't kick in until the front wheels lose traction. By then, the Lexus was irretrievably headed for the ditch.
MDX could be slung around snowy corners with nary a shiver or slither. It could be accelerated viciously on slush without falling into the whimpering, thumb-sucking standstill of its German rivals.
SUVs get better motor running
The only vehicle on hand that could remotely match MDX on the snow and ice was Ford Explorer with Control Trac, a more traditional type of four-wheel drive. But Explorer rode stiffly and bounced violently when driven at MDX speeds.
MDX's slick-working 4x4 system is a front-drive arrangement that sends power to the back wheels only when needed. The key: Acura engineers think it's needed any time you accelerate. Front wheels needn't slip before back ones get power.
Steady cruising and braking are done in front-drive mode. But all four wheels clock in when you pass, leave the stop sign or race up a freeway ramp. That makes the vehicle more stable, even on dry pavement. The magic, though, is when you hit a slick spot in a corner. Skip the brakes and go for the gas, as a good driver would, and MDX hauls you around just fine....
http://www.usatoday.com/money/columns/healey/0029.htm
If it's not the same system, then perhaps Honda should make it like the MDX, locking the wheels into AWD whenever there's acceleration. Maybe the difference lies in the fact that the MDX is so powerful that AWD is needed under acceleration and that's just not the case with the CR-V.
Comments.
Also, the MDX is at a much higher pricepoint, which would allow it to incorporate some more "costly" upgrades, that the CRV wouldn't have.
For example: The reporter of the MDX indicated that slippage is not necessary for the rear wheels to engage. It (the MDX's AWD) apparently engages anytime that you accelerate. That's not true for the CRV.
Bob
The MDX system is called "VTM-4" (VTM: Variable Torque Management). This sounds like a good (and very light) AWD system most people will ever need. The nice part about VTM-4 is that it is a combination of pro-active and passive system.
Every time you stomp on the gas pedal, all wheels get power. Slippage is not required under these circumstances, it just sends power to all wheels. From then on, the amount of torque split between front and rear wheels can vary (continuously, instead of in 'fixed chunks' as in many other AWD systems) depending on traction requirements.
During cruising, the front wheels take over, and at that time it becomes a 'passive' system, waiting to detect slippage. If it does, then once again a gradual shift of power occurs to the rear wheels.
The VTM-4 also engages when the vehicle turns, without having to detect slippage (once again, a pro-active system).
There is a 'lock' feature that will keep the power supply to all wheels permanently, regardless of whether or not you depress the gas pedal, with maximum torque (40%?) to rear wheels upto 6 mph. Between 6-18 mph, the front wheels gradually get more power. This would help in getting out of snow/mud situations.
CR-Vs Real Time AWD system is a much simpler technology, but it is enough for most drivers. I've read people talking about the 'possibilities' of losing control of vehicle if the other set of wheels engage only when slip is detected. They probably will say the same about ABS, traction control and stability control systems as well, which are all passive systems. And these are designed to give control to drivers, not take it away from them.
CR-V's AWD system may take a fraction of a second to engage (like an ABS, TCS etc. would), but so does a Subaru AWD system. The only difference is that the Subaru AWD system has about 10% of the power delivered to the rear wheels at all times. 90% of the power is still at the front wheels! During cruising at 60 mph, the Subaru may be delivering about 60 HP at the front wheels, and about 6-7 HP at the rear wheels. When the front wheels lose traction, substantial amount of torque has to be sent to the rear wheels in this case as well, perhaps a meagre 6-7 HP less in this case.
A vehicle is more likely to lose traction on the wheels that have more power, and in either case, it would be the front wheels. And in either case, the mechanical system will have to engage to shift some power to the rear wheels.
I'm not sure I agree with you regarding the extra time it takes for the Subaru system to engage (you could be right, I'm just not sure). Also on Subarus, the 10% of power to the rear wheels is only for "most" automatics, and it too is electronically controlled. All Subaru manuals have 50/50 front-to-rear normal power split, and use a viscous coupling. All WRX models (manual & automatic) also have the the 50/50 power split; and the H-6 with VDC (automatic) has a 40/60 power split, with more power under normal conditions being sent to the rear. The VDC can also vary the power split between each wheel—not just front-to-rear. (NOTE: the power split for the WRX automatic and VDC automatic may be off 5% one way or the other, but what I've quoted is close enough to make my point)
Also I believe all Subarus can send 90% of the power to the rear wheels if need be. I don't know if the CRV or MDX can do that. Finally, all Subaru AWD systems are also more active in cornering (again like the MDX) and in hard braking too.
Bob
There is a VTM-4 lock button that allows you to lock the power to the rear wheels at about a 50/50 split. However, this shuts down completely at 18 mph. Recently, one MDX owner was writing about how frustrated he was driving on sand because the vehicle would revert to FWD mode with or without the lock and he would get stuck nearly immediately (and had to get out with his wife and dig several times which made her extremely displeased!) even with deflated tires. He swore that he would never take it onto the beach again.
VTM-4 is actually quite similar to Isuzu's TOD 4WD in that which it is somewhat proactive, it switches off in certain situations since it doesn't have a centre differential (doesn't help you in turns on dry pavement). The big difference is that TOD can be locked into a 50/50 mode without turning off at a certain speed, and that it also has a low range.
In any case, I digress. Back to your regular CR-V discussion.
Thanks,
Drew
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Interesting comment about the MDX and sand. I wonder how the CRV does on deep soft sand? We recently had our Forester out on the beach of the Outer Banks of North Carolina. This was the first time I've had it out on sand, and it did just fine. Although, I didn't experience any really "super-soft" sand, as it had just rained recently, thus packing the sand down somewhat. (I'm sure juice will chirp in here, as he's had some extensive sand driving with his Forester)
But, as you said, back to CRVs...
Bob
However, I do believe he is being consistent. His criticism about the RX300 would apply to the CR-V RT4WD as well :
Lexus RX 300 wound up bouncing off snowbanks. The rear-wheel-drive portion of its four-wheel drive doesn't kick in until the front wheels lose traction. By then, the Lexus was irretrievably headed for the ditch.
As Drew pointed out Subaru 4EAT AWD can actively change torque split based on throttle inputs and transmission position. In a situation like climbing snowbanks, the torque split is closer to 50/50.
I kind of wonder why Honda keeps trying to develop it's own unique AWD systems when there are other proven systems on the market. For example, a VC based system (previous generation RT4WD) can be tuned to be made compatible with ABS.
Ken
VTM-4 in LOCK position would send 50-50 (or whatever) split to wheels upto a maximum speed of 6 mph, thereafter, the split gradually goes in favor of FWD to about 18 mph. At higher speeds (note: cruising), the rear wheels are disengaged unless slippage is detected.
Recently, one MDX owner was writing about how frustrated he was driving on sand because the vehicle would revert to FWD mode with or without the lock and he would get stuck nearly immediately (and had to get out with his wife and dig several times which made her extremely displeased!) even with deflated tires.
Reminds me of my last trip to Padre Islands on the Texas Gulf Coast. The beach was crowded, and demands AWD vehicles. I was in a rented Taurus, believe me, I passed a stuck (in sand) Subaru Outback, with its wheels spinning in vain. I have seen Land Cruisers getting stuck in deserts (note: sand).
AWD will give you advantages, but one has to understand the laws of Physics as well.
Difference is that the Subaru AWD systems have a centre differential, whereas the MDX does not. This means that the MDX's system reverts back to 2WD in turns.
This does not mean anything to me. I remember reading about MDX's system engaging when taking turns. It would work in the same way as it does when accelerating (i.e. without waiting for a loss of traction, proactively).
You have to realize that while the size of the wheels are the same as in the last generation model, the car itself grew a few inches bigger.
But just look at how clean the car looks without the black bladding and door handles. Although the tail lights, at least in this picture, look like sparkling candy canes.
Acceleration from 0 to 60 with 5 speed is 8.4 seconds. I'm guessing automatic will do 9.4 seconds. Tribute automatic did 8.2. Forester 9.7. Grand Vitara 10.2. So its middle of the pack.
All the hoopla about noise improvement to best in class turns out to be just noise. It is 42 dba at idle, 75 full throttle, 70 cruising and coasting at 70 mph. This is only about 1 dba better than EscapeTribute, on par with Grand Vitara, about 2 dba better than Rav4,Xterra. Much worse than Highlander which scored 68dba at 70mph.
But as for the braking numbers- that's really bad. Not only size- but what about the actual tires that were used?
Also, thanks for all of your posts! I have learned alot from what is written here.
M Tanquary
Tail lamps do appear more transparent in the Japanese photos. Hope they are not saving those for themselves like so much else.
http://auto.ascii24.com/auto24/issue/2001/0918/32npr_kt0918_09.html?kr04
I drive mine like it's a front wheel drive car (which it is). When I need power at the rear wheels, it's there. Most of the time it's not necessary.
Scname - C&D has published a full comparison? Or are you comparing numbers from different test?
New CRV numbers came from November issue.
Diplois, Tribute is a V6. Their 4 cylinder has only 130 hp, don't know why anyone would bother..
scname -- Before you dismiss the noise reduction as insignificant, I want to make sure that you understand how sound is measured: An increase of 10 decibels represents a doubling of the intensity of sound. That means a drop of 1 dB is actually a drop of 10% in sound, 2dB is a drop of 20%, etc. That may be enough to matter to some people. Now, if you knew this already and still think it's insignificant, then feel free to ignore this. :-)
What some people do when they get stuck, is spin the wheels, thus digging themselves a deeper hole. If you have tires with an aggressive tread, this is very easy to do, since they're designed to "dig" and not "float." Once the vehicle's frame is sitting on the sand, the tires spin freely, and you'll never get out without jacking the vehicle and shovel more sand under the tires.
Actually the best sand tire is a "bald" street tire, aired down to about 18 - 20 psi. This type of tire will "float" (stay on top of the sand, not dig into it) easily.
Bob
While we're on the subject of meets, I'll spread some spam for GatorGreg. I will be attending this one.
St. Augustine Scrub
I am used to driveing 4x4's with a transfercase, locking front hubs and a positive traction rear axle, and aggressive tires that dig into the snow.
Don't get me wrong I don't want to go off road, as this not a off road vehicle.
What I do want to do, is get to work in the morning, before the snow plow makes thru the neighboor hood. Drifted in roads with this vehicle surely would be a no-no.
If you live where it snows, and drive a CR-V,I'de like to hear your story. Thanks Tom F.
Bob
I no longer have a job which requires me to get to work in the snow, so most of the time I simply stay put. With that said, I have been off-roading in the snow and I've taken the CR-V out into unplowed parking lots for fun. The V handles much like a FWD car, though when slippage does occur, the rear tires kick in and the car plows forward. This keeps you moving and prevents getting bogged down by maintaining momentum. In certain situations, it may also help keep you pointed forward rather than slipping into a spin.
I wrote "plows forward" above intentionally. Understeer is the basic trait for AWD vehicles (which is better than oversteer for our purposes). The often overlooked problem with AWD and 4X4 systems is that the rear wheels cannot steer. When they kick in, they will push the front tires forward. Even if those front tires are pointed to the side, in a turn. If the front tires have grip, AWD/4X4 forces the car into the turn. This is the dry weather benefit of AWD in sports cars. In slick conditions, it can force a loss of traction up front. So regardless of the type of system you have (AWD, part-time 4X4, or automatically engaged 4X4), you need to go slow and be careful.
Bob
I lease a '00 Accord and can't wait for July '03 when I can rid of it. It's big, dull, and clumsy. Wish I could have my '95 Civic back! Might go back to a Civic in '03, but...
Keeping my eyes on the new CR-V...
"Its rear wheels are engaged when its wheel-speed sensors and electronic control unit anticipate or read front-wheel slippage.
When the sensors detect wheel slippage, the VTM-4 computer sends current to electromagnetic coils on the right and left sides of the rear-axle drive unit. These coils apply wet clutches that mechanically lock the halfshafts to the pinion-driven ring gear. The halfshafts then transfer the muscle out to the wheels."
I'm not sure what you meant by 3WD as opposed to 4WD, and the talk about stability control (which I know is not about traction, but correction). But we shall discuss it later (again!).
The VTM-4 system does not know when a skid is about to occur since it doesn't have any yaw or steering angle sensors that can compare the vehicle's actual lateral rotation on its axis versus where the driver wants the vehicle to go. As such, it cannot help in this situation. Since it is a torque-on-demand system, in order to be work, the driver's foot must be on the MDX's throttle pedal causing the engine to send power to the system. In an emergency situation the AWD system is useless if and when the driver lifts his/her foot off the throttle pedal and shifts to the brake pedal. Since the system reverts to 2WD/FWD mode; the vehicle subsequently behaves like a front driver. The Isuzu TOD-system works in a similar fashion when in "auto" mode.
Drew
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Which raises another question: Does the CRV (and MDX) offer AWD capability in reverse? I ask this question, because I've read in the past that some so-called AWD systems only work (in AWD) in forward gears. I'm not sure which vehicles this article referred to.
Bob
So the usefulness in terms of added grip in driving a wheel only applies to the forward component of motion, and is irrelevant to any lateral forces. Which seems seems to confirm my impression, that 4 or AWD vehicles are a great help in allowing you to climb steeper hills, to get started in deep snow, climb over snow plow berms, etc. - but don't help you go around turns any faster without sliding than 2wd, everything else being equal.
Which brings me the USA Today guys statement about the Honda system kicking in "too late" to keep the vehicle from sliding off the outside of the turn. Doesn't make sense to me.
I can see where a full time system like the Subie's could be a big advantage in dirt or gravel, because there you have all kinds of partial-traction conditions possible where the system would influence the handling (over/understeer) of the vehicle via the throttle. But in snow, once you start to slide you have essentially zero traction. And that's going to happen when you exceed the lateral adhesion capability of a wheel, regardless of whether its driven or not.
If all that's true, then the Honda system should be about as good as anything else in snow. All bets off in dirt/gravel, though.
Someone who really knows should tell me if I'm full of beans - I'm just making this up as I go along.
How is that different that real 4WD? Both the Durango and Montero I drive have both AWD and 4WD. They handle the same, i.e., there is no difference in deceleration ability when in different modes.
I have often read that 4WD vehicles, because of their extra weight, are actually worse at stopping in ice or snow than lighter weight vehicles. In that case, AWD only - being lighter - should have an marginal advantage.
Sorry, I don't have a Subie brochure in front of me to give their exact wording on the subject.
Bob
http://www.4x4abc.com/4WD101/need.html
http://www.4x4abc.com/4WD101/tractionturn2.html
http://www.4x4abc.com/4WD101/tractionturn4.html
Bob, if you look at the above calculations, the idea with a full-time or permanent system is not to lose traction in a curve in the first place ;-). If you lose traction, you will slide and by the time the AWD system kicks in, it may be too late. The sudden traction gain from the rear wheels may also cause understeer to change over to oversteer, catching the driver off guard. That is what the USA Today article was pointing out, which is why it seems quite reasonable to me (even though I'm not a fan of that writer, by far; but this is just my own personal opinion. YMMV, of course).
http://www.subaru.com/news.html
Bob
Thanks!
Drew
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But are you sure he's right about that? Consider this - given his mathematical scenario, a FWDcar accelerating through a corner should have a LOT more traction available at the rear wheels than the fronts. So if you suddenly hit a patch of sand, the front end should wash out before the rear end, resulting in a clockwise spin, for example, in a left hand turn. Is this what actually happens? Doesn't seem right to me, but I could certainly be wrong.
Come to think of it, a RWD car does spin the other way, so he's probably right.
it will only send the majority of power to one rear wheel (possible due to the clutch packed rear differential, hence making it 3WD.
Wouldn't that be something similar to a stability control system? I.e. taking power away from a wheel ( a stability system would do so by applying brakes).
The VTM-4 system does not know when a skid is about to occur since it doesn't have any yaw or steering angle sensors that can compare the vehicle's actual lateral rotation on its axis versus where the driver wants the vehicle to go.
If Honda had used VSA on MDX (it did offer VSA with RT4WD on CRV in Japan), it would have yaw sensors. But that would be more about stability control than transfer of power to the other set of wheels. During cornering, the wheel speeds aren't the same anyway, and that would be enough to trigger a transfer of power, however small or large, electronically (instead of mechanically, as with a central differential).
Since it is a torque-on-demand system, in order to be work, the driver's foot must be on the MDX's throttle pedal causing the engine to send power to the system. In an emergency situation the AWD system is useless if and when the driver lifts his/her foot off the throttle pedal and shifts to the brake pedal.
I'd like to see where you got the information that lifting off the gas pedal would not 'initiate' rear wheel engagement even upon detecting slippage (loss of traction, not stability). As far as I understand (from what I have read thus far), the on-demand refers to proactive engagement (during acceleration/cornering) and reactive engagement (upon detection of slippage). With the LOCK mode, it doesn't need the driver's foot on the pedal anyway (upto 18 mph, after which it becomes a reactive system).
BTW, do you remember my post about a trip to Padre islands, and driving the Taurus on sand? I didn't need a lot of 'momentum' to get going, just enough, and it definitely wasn't more than 10-15 mph (on a crowded beach). But I did use the steering to grab as much traction as possible, without having to slow down, and avoiding excessive use of the gas pedal. So I wonder why 18 mph would be 'too slow' to get out of snow/sand banks (the purpose of having LOCK on the MDX).
When accelerating from a standstill, the weight transfers to the rear of the vehicle. That's why sports cars are rear wheel drive. The weight transfers to the rear, pressing on the rear drive wheels and contributing to the traction. Most FWD'ers do better in the snow because the weight of the engine is on the drive wheels. However, this front wheel bias also contributes to poorer handling due to a less balanced chassis. This effect of weight transfer to the rear is exacerbated when climbing uphill, which is why FWD vehicles can lose their tractive advantages when climbing uphill in the snow. As the slope gets steeper, more weight shifts to the rear, away from the front drive wheels.
"Consider this - given his mathematical scenario, a FWDcar accelerating through a corner should have a LOT more traction available at the rear wheels than the fronts."
What you have to remember is that FWD cars can have significantly more weight in front (ex. 60% of the vehicle's weight on the front half of the car). As such, even though when accelerating, the weight distribution shifts to the rear, there may still be a lot of weight over the front wheels. Too much weight will burden the front wheels, since not only do they steer the car, but they also propel the car. Again another performance and handling benefit of RWD.
"So if you suddenly hit a patch of sand, the front end should wash out before the rear end, resulting in a clockwise spin, for example, in a left hand turn. Is this what actually happens? Doesn't seem right to me, but I could certainly be wrong."
If the front tires lose traction, this will probably result in understeer. The car will run wide to the outside of the curve but will not spin around. This is the "safe" route, and most manufacturers tweak their cars so as to safely understeer when they exceed their limits. In an understeer situation, transfer of power to the rear wheels will help marginally, but the rear wheels having more traction may simply push the vehicle to an even wider arc. As soon as tires spin, they start to lose their directional ability.
However, in some circumstances (which are too detailed to get into for this context), because of the front bias weight distribution of the FWD vehicle, oversteer can also occur (because of the lighter rear end) resulting in a spin, even for a front wheel driver.
In any case, you see how weight distribution is a very complex matter to handle; this is why the professional drivers get paid the big bucks.
Good luck,
Drew
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