Fuel economy and iAWD - let the fun begin!

[LPSISRL]

I've been having an off-line chat about fuel economy so I thought I'd open some of it up to the group.

I had an SX4 with iAWD. I'm assuming that the Kizashi iAWD is the same system. From all descriptions it sounds like it works the same. There is no mileage gain by running in only FWD if the iAWD never needs to be engaged, such as under normal driving conditions.

Here's the reason: the engine has to turn the transfer case and the drive shaft regardless of whether or not iAWD is engaged. The rear wheels also still turn the axles into the differential. This causes drive train drag all the time effecting fuel economy. So, the little time that the AWD may be actually sending power to the rear wheels through the iAWD controlled clutches is insignificant as far as fuel economy is concerned. If turning off the iAWD actually prevented the transfer case and drive shaft from spinning, then using FWD only would save fuel. But since the Kizashi doesn't work that way, no fuel savings buy turning the iAWD off. Again, this is under normal driving conditions when power would not normally be sent to the rear wheels.

BTW - many owners on the SX4 forum experimented on trips and such with and without iAWD turned on and there was no difference in fuel economy.

[Kiz224]

Yep LPSISRL, I agree. I always have the AWD engaged, no matter the season here in MN. I like the way the Kizzy drives and am not going to fret too much about MPG anyhow.

[Firefly]

Makes sense. I noticed no difference in fuel economy between FWD and AWD. I leave it in AWD for a better driving experience.

[KuroNekko]

The Kizashi's AWD system is full-time AWD which means the AWD system sends power to the rear wheels on a need basis. Most of the time, it's 2WD even when the AWD button is engaged. This only begs to question why Suzuki bothered with an AWD button at all. Personally, I think it was a gimmick to try make the car seem more fuel efficient. You guys with AWD obviously have tested it out and see no fuel economy benefit by leaving it off. This observation supports the fact that the car is almost always in 2WD anyways except for when you are in snow and/or slip is detected.

It also supports the explanation of why most other cars and SUVs with AWD don't have a button to engage it or not. For full-time systems like that found in a Honda CR-V, it simply kicks in when needed. For a Subaru with permanent AWD, all the wheels always have some level of power going to them at all times. Neither of these cars have a button for AWD, it's simply available all the time.

Despite the questionable use of a button to override the AWD, I wish the manual transmission Kizashis were available with AWD.

[Pyramid1]

Shouldn't it be fairly easy to see if the AWD button is really doing anything other than turning a tiny led light on and off? What I mean is, can you guys with AWD tell any difference between on/off driving on a wet, snowy or icy road?

[murcod]

To see any fuel usage change you'd need something like the "free wheeling hubs" that are fitted to proper off road vehicles (or at least they were in the past....) Back when a 4WD was RWD on road and a transfer case was used to manually select 4WD in slippery conditions.

The free wheeling hubs enable you to disconnect the hub from the CV shaft/ drive shaft on the non driven wheels (ie. when in 2WD.) This would disconnect the CV shafts, diff and tailshaft (in the FWD Kizashi's case) and stop them from continually causing drag by being rotated by the direct connection to the rear wheels.

[Woodie]

That's exactly why I don't have it. Not going to carry around all that weight, drag, and moving parts which require maintenance so that they'll be there on the twice a year when they might come in handy. FWD and all weather tires are light years better than anything we had back in the 60's, yet somehow we managed to survive. Add some genuine snow tires and most FWD cars will climb trees. This car's too low to really go through the deep stuff anyway.

[LPSISRL]

The couple times I had my SX4 iAWD out in the snow it was fun. The AWD, ESP and traction control made it just about impossible to lose control of as long as I wasn't doing something stupid. (like entering a turn way too fast but even then it was controllable) But I can see in the northern climates how nice it would be. Especially for the wife and kids. It could, however, give them a false sense of security when driving in slippery conditions. What I mean is being able to control the AWD car in adverse weather with ease but when they drive another vehicle, it might not be such a nice experience.

[KuroNekko]

Shouldn't it be fairly easy to see if the AWD button is really doing anything other than turning a tiny led light on and off? What I mean is, can you guys with AWD tell any difference between on/off driving on a wet, snowy or icy road?

I have no doubt the AWD is a huge advantage in the snow, ice, and poor road conditions. The question here is whether disengaging AWD for cars that have it is beneficial for fuel economy. The reason why people are discussing it is because there has been no noticeable fuel economy difference between AWD on and AWD off for normal driving conditions. When you then consider that nearly all other full-time AWD systems don't have an AWD On/Off button, you start questioning why Suzuki even bothered with it at all.

I am not questioning the advantage of AWD in foul weather. I drove a Subaru Impreza for several years when I lived in the California mountains which got at least several feet of snow every year. While tire type and more importantly, tread condition are very important, the AWD system helps greatly.
While I agree that ground clearance issues may stop a car like the Impreza or the Kizashi in very deep snow, AWD sedans actually do very well in the snow. I have confidently driven past many Ford F250s and Chevy Tahoes with 4x4 that were stuck in the snow.
How is it that a car like the Impreza was better? Vehicle weight and tire size.
While weight on the snow is important, you also don't want too much weight. Being too heavy on the snow can get you stuck and spinning. Not to mention many trucks have horrible weight distribution. There is little point in having 4x4 on the snow in a heavy truck if there is no weight over the rear wheels. In comparison, a smaller car like the Impreza or Kizashi has far better weight distribution and puts down a good amount of weight over all wheels without being too heavy overall.

The other factor is tire size. It is well known that thinner tires grip and handle better in the snow than large wide tires. You want tires that can get into the snow, not blanket over on top of it. There have been successful rally drivers who won their winter rallies by opting for thinner tires in the snow.
Now think of how large a tire from a huge truck or SUV is compared to that of an Impreza or Kizashi. The tires of these small cars grip into the snow better and offer greater traction, stability, and cornering ability.

There have been countless times when I have zipped right by huge trucks and SUVs stuck in the snow with traction problems. Having an AWD sedan is actually advantageous unless you live in a place where the roads aren't plowed much.

Honestly, in my opinion, there is something better than AWD or snow tires. It's chains. I have tried all of the above and can say that chains will get you through the roughest stuff. Personally, I have used all of the above before. I once even put chains over my snow tires on my former Suzuki Sidekick engaged in 4WD Low. The result? Alpine offroading in 2 feet of snow.

[Ronzuki]

Shouldn't it be fairly easy to see if the AWD button is really doing anything other than turning a tiny led light on and off? What I mean is, can you guys with AWD tell any difference between on/off driving on a wet, snowy or icy road?

Snow and wet you can definitely tell the difference. Ice...well, ice is ice, and I don't ef -around on ice. All bets are off and you're just along for the ride. On dry pavement the AWD is far less noticeable (non-existent) unless you're really banging on the car in the curves. It assists in pushing the car around and through the corners more smoothly and predictably under hard acceleration w/ the AWD activated. Not nearly as nice and controlled w/o it on in those instances. Could be my imagination, but my butt tells me it's not. The most noticeable, and beneficial use in my opinion, is the rainy weather. I've stated before that w/ a good set of tires and normal to spirited driving, it's as if the road were dry. Hard driving, and the car has drifted in the wet, but has never 'spun' with the new tires. Never really pushed the car as hard with the old Dunlops as I never felt confident in them. Quite the combination of all the technologies coming together keeping the car planted and moving in the direction intended. I've had the car get away from me in the snow once. I pushed it hard in a turn past where all the technology could no longer maintain my directional input. That's a scary line to cross, unlike a typical car that you will gradually feel (wheels spinning, steering ineffective) and realize you've gone past your limits, this car will go way past your limits and then give up. It was abrupt and, for the most part, w/o warning.