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SUVs 4WD & AWD systems explained
1376 messages, Last post on Nov 23, 2009 at 9:11 AM
You are in the SUVs Forum. Your Hosts are steve_ & tidester
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Replying to: paisan (May 19, 2008 6:30 pm) Actually the DCCD is at least 16 years old: http://en.wikipedia.org/wiki/Subaru_Impreza_WRX_STI . >> Anyway, let's just let it drop cause these are all very good AWD systems, both the Mitsu and the Subie. We are splicing hairs arguing over them, not to mention wasting time and space on here.... Agreed. The Tidester was the one, who got this thing going again :--)
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Replying to: chelentano (May 19, 2008 6:39 pm) I'm done. -mike |
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Replying to: chelentano (May 19, 2008 6:39 pm) Oh, sure, blame it on ME! And you can pin rising gas prices on me too while you're at it!  tidester, host SUVs and Smart Shopper |
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Replying to: chelentano (May 19, 2008 2:55 pm) What's that saying, never say never? The FWD mode is 100% FWD so we know it's possible. The existence of “fuse” interface is not a prove, it’s your wishful thinking. They might just left it for future development. It's also documented in the owner's manual. |
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Replying to: chelentano (May 19, 2008 6:23 pm) That's great ... for Pajero owners. Mitsubishi probably won by using the entire safety recall budget for racing instead. When you don't have to fix safety recalls for 24 years (1977 to 2004) that leaves a LOT of money left over for your racing program. I'm sure the racing Pajeros cost them MILLIONS, which they had due to neglecting their street cars and the safety of their customers. 
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If you can't explain how a 4WD or AWD system works, go over to Off Topic Chatter and play in that sand box for a while. thanks!
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Replying to: steve_ (May 20, 2008 6:41 am) When I take delivery, I'll put mine up on jack stands and test out the FWD mode. Since it also turns off VDC, it should be very simple: * if only the front axle spins, it's 100% FWD * if both axles spin, the FWD mode does not work Anyone want to bet on the result? It will be very easy to prove that all those sources are indeed wrong. I'll be happy to prove it.
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One thing I'd enjoy reading here is info as to how responsive these AWD systems are. How long do they really take to detect wheel spin? Or to transfer power where needed? Also, othe than the center transfer clutches, what mechanisms do they use to pro-actively transfer or manage power to all 4 wheels? Do they rely on the wheel brakes? Extra clutches in the differentials or on the Axle shafts? Examples: VW commented once that their Haldex AWD systems respond within 1/4 of a wheel turn. Does that mean their systems, if faced with wheels on ice or in air, will transfer power almost instantly from those wheels? The '09 Subaru Forester videos clearly show some of the Foresters taking many seconds for their system to lock the spinning wheels and transfer power. That's not exactly a reactive, let alone pro-active system. Were those Subarus test mules, or the same as what we Customers buy / bought?
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Replying to: kurtamaxxxguy (May 20, 2008 7:28 am) That's marketing-speak, but translated it means they claim the driver can influence the distribution with the throttle and brake pedals. The video you refer to was the one on that island, correct? Where the press drove the new 09s? Do you have jack stands? If you have the time, jack up the front of the car and put both sides on jack stands at the jack point recommended in the owner's manual. Then use the rear differential to jack up the rear axle. If you have 4 jack stands it's better and safer, but you don't need to get under the vehicle for this. Then, quite simply, test it out. This is a simple way to test all the theory. Like paisan said this is all bench racing until we put it to the test. If the front wheels spin first, that means the rear axle is not getting enough power by default to turn them. It shouldn't take much to spin wheels that are in the air - the only resistance is the weight of the wheels themselves. If all 4 wheels spin, the AWD is defaulting to a mode that indeed sends power to both axles. This is what I predict will happen initially. After that, who knows what will happen, the AWD and VDC systems will try and fail to get traction since none of the wheels have any. I predict they will cycle, one or two at a time, searching for traction that isn't there. This method cannot test if enough power is sent to move the vehicle, but it can determine if some power is being sent to each individual wheel. If you do it, please video tape it. |
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