rob-2 Posted August 26, 2011 Author Share Posted August 26, 2011 My observation of having two wheels on the ice and the other two on dry pavement is the iced ones spin on my former 04 WRX 5mt and current LGT. Occasionally power is kicked to the dry ones and the car moves a bit. However always one rear and one front spins. I am curious how well our new to us 07 Acura MDX works with SH-AWD. Apparently it kicks power not only front to back but can go to a single wheel(rear) or one side full side. I noticed in hard turns when really pushing it actually puts power to a single rear wheel with the AWD display. What will happen on the SH-AWD when a wheel spins the system kicks more power to the wheels via the electronically controlled diffs that have traction and applies brake to the spinning wheel to stop it from spinning. You get about 1-2 full wheel spins, traction controlled light flickers and you move away. If it's really bad it will reduce throttle. Link to comment Share on other sites More sharing options...
rob-2 Posted August 26, 2011 Author Share Posted August 26, 2011 07 first year for I-drive and for traction control. That would explain why I don't have traction control button anywhere in the car. Link to comment Share on other sites More sharing options...
frank_ster Posted August 27, 2011 Share Posted August 27, 2011 the sh awd system is pretty cool its like a 4 eat and the rear diff is not a diff anymore. it has the ring and pinion and then a clutch for each wheel. so normal driving the car is front wheel drive when you loose traction the clutches in the back tighten. when they are fully engaged it acts like a locked rear axle. "Would you care to explain the mechanics? Say, for a 5mt 05 lgt." well the car has 3 differentials. the 5mt the center differential has some clutches that are compressed with a spring. this gives a constant resistance to different speeds of front and rear axle. ( just like a limited slip or posi) the resistance could be measured as foot pounds if you will. its not that much actually maybe 20 or 30 ft/lbs. so jsut to make things simple out of the tranny you have 500 ft lbs torque this is split evenly to front and rear wheels so 250 -250 . the center diff clutches will add this 30 ft lbs to the wheels that are spinning slower. so you could have 280 ft lbs front and 220 rear or vise versa. where it gets kinda dumb is well its 50% 50% correct ? well if you have one wheel in the air the 50% of nothing is nothing .. so you have your front wheels on ice and rear on pavement and you try to move the front wheels have almost no traction, so 50% of nothing is zero so the rear wheels have the same 50% of nothing. but you have that 30 ft lbs ! witch will go to the rear! its not much but its some thing. and it usually allows you to at least rock your car back and forth. but in the case of one front wheel and one rear wheel in the air ( twist) each wheel has the 25% of power. but again if 25% of nothing is nothing so the other wheels have nothing either. if you have a rear or front or both limited slip each limited slip would provide 30 ft lbs to the wheel that is turning slower. so if you had 1 rear limtied slip you would have a total of 30 ftlbs moving your car ( again just made up numbers ) if you have two limited slip diffrentials you would have 60 ftlbs moving you car. in the case of 1 wheel with traction you have the 30 ft lbs trans mitted to the axle thats turning slower then the limited slip rear or front diff will trans mit the 30 ftlbs to the wheel that is turning slower. the advantage of 4 speed auto 5 speed auto or the 6mt with the dccd they can have way more than 30 ftlbs trans mitted to the axle that is turning slower. more like 200 -300 ftlbs if not more to the axle that is turning slower. so in the case of front wheels on ice and rear on pavement you have 300 footlbs going to the rear wheels instead of 30! but in the case of one front wheel and 1 rear wheel with no traction your still limited to the limited slip diffrential 30 foot lbs to keep you moving. but in the case of the sh awd they can probably transmit 200 foot lbs to one rear wheel witch is awesome. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
dmanaenk Posted August 27, 2011 Share Posted August 27, 2011 the 5mt the center differential has some clutches that are compressed with a spring. Huh? I though LGT center diff was viscous coupling. whitetiger on the last page claims center VLSD will transmit 4kgf-m/100rpm to the back of the front is completely free (which isn't even accurate since there was just a bit of friction between the front unloaded tire and pavement). Which should be plenty to move the car with both rear wheels on the ground. I don't know what rear VLSD is rated at, and this is probably needed to calculate how much torque the rear wheel on the ground will get if front and one rear are spinning. 666 Link to comment Share on other sites More sharing options...
frank_ster Posted August 27, 2011 Share Posted August 27, 2011 define viscous coupling and if a front wheel is in the air the opposite rear wheel is in the air or has very little weight on it. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted August 27, 2011 Share Posted August 27, 2011 http://en.wikipedia.org/wiki/Viscous_coupling_unit Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
dmanaenk Posted August 27, 2011 Share Posted August 27, 2011 And by linking to wikipedia you're trying to say that your 'clutches with a spring' is somehow accurate? Anyway, if "front wheel is in the air the opposite rear wheel is in the air or has very little weight on it" the rear LSD will transfer some torque to the rear wheel with traction. How much - is the question. I personally tested this and was able to move, so in my car is a 3-wheel drive, requiring both rears and one front to have no/little grip. Maybe spec.b rear lsd can transfer more grip to the rear wheel than regular LGT rear VLSD. 666 Link to comment Share on other sites More sharing options...
SSpeed Posted August 27, 2011 Share Posted August 27, 2011 What will happen on the SH-AWD when a wheel spins the system kicks more power to the wheels via the electronically controlled diffs that have traction and applies brake to the spinning wheel to stop it from spinning. You get about 1-2 full wheel spins, traction controlled light flickers and you move away. If it's really bad it will reduce throttle. Looks like other Acura owners have less faith than you... http://rdx.acurazine.com/forums/showthread.php?t=763869 What happened here then? [ame=http://www.youtube.com/watch?v=Nos7cfy4ChA]2009 Acura RL SH-AWD vs Snow - AcuraZine Exclusive - YouTube[/ame] Link to comment Share on other sites More sharing options...
frank_ster Posted August 27, 2011 Share Posted August 27, 2011 uh .. did you look at the wiki .. viscous cupling is clutches in oil ... wtf ? the acura got out ? whats the problem ? probably had summer tires and that snow looked stupid heavy. edit: the in the video i saw the rears turning well. from the looks of it he jsut didn't want to simply drive out through the pushed up snow bank and decided to go around. he simply had a hard time climbing on to the curb. but other than that i didn't see very much front wheels spining. also the principal of the sh awd is what i was talking about the actual effectiveness of the system on the actual cars i don't know because i never driven one nor taken one apart. from the link yes it seams the clutches are weak or the control of them doesn't apply enough pressure. but with modification it would be a good system i guess. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
rob-2 Posted August 27, 2011 Author Share Posted August 27, 2011 Looks like other Acura owners have less faith than you... http://rdx.acurazine.com/forums/showthread.php?t=763869 What happened here then? 2009 Acura RL SH-AWD vs Snow - AcuraZine Exclusive - YouTube Having driven an 05 RL with SH-AWD in 6inches of heavy snow I can tell you the driver here is doing something odd. I'm not sure exactly what but I've driven out of this situation myself. I however turned off traction control and drove away. In my situation I was spinning all four wheels and easily drove away. I was on some POS michelin all season that came with the car that are piss poor in snow. Watch SH-AWD in action here [ame=http://www.youtube.com/watch?v=FJZxVefta68]Lexus ATC vs. Audi Quattro vs. Acura SH-AWD - YouTube[/ame] Link to comment Share on other sites More sharing options...
frank_ster Posted August 28, 2011 Share Posted August 28, 2011 yea thats more of what i was talking about. there able to transfer a lot of power to one rear wheel. but would i get sh awd .. nah why ? well makes it super hard to kick the ass end out on dry pavement, like we can on 5mt and i can in my 5 eat Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
ShadowImg Posted August 28, 2011 Share Posted August 28, 2011 I could be wrong, but don't those clutches stop functioning after a certain (low) speed? I thought I remembered that most of the e-LSDs like that disengaged after like 10mph and only worked below that. Could be entirely false though. I have no first hand knowledge. Link to comment Share on other sites More sharing options...
SSpeed Posted August 28, 2011 Share Posted August 28, 2011 Having driven an 05 RL with SH-AWD in 6inches of heavy snow I can tell you the driver here is doing something odd. I'm not sure exactly what but I've driven out of this situation myself. I however turned off traction control and drove away. In my situation I was spinning all four wheels and easily drove away. I was on some POS michelin all season that came with the car that are piss poor in snow. Exactly... so I question anytime someone who has ripped on a car non-stop, while extolling the virtues of another, posts about something wrong with their car again... Link to comment Share on other sites More sharing options...
iNVAR Posted August 28, 2011 Share Posted August 28, 2011 Snow in NYC can be packed very tightly after plowing. In fact, it's more like packed ice. If you (or anyone else) have tried to pull in or out of a parking spot there before, you would't know. I've gotten my car stuck in it numerous times before. Plenty of ways to do that apart from high centering it. You can even see in the video when he gets one of his wheels on the curb that the other wheel is on TOP of the snow, not cutting through it at all. Link to comment Share on other sites More sharing options...
dmanaenk Posted August 28, 2011 Share Posted August 28, 2011 uh .. did you look at the wiki .. viscous cupling is clutches in oil ... wtf ? Next you're gonna say that 'oil' and 'spring' is the same thing.... I dont call a bunch of circular plates clutches when they don't contact each other. But whatever works for you as a definition of a clutch. The question is how much torque will go to the rear wheel with traction. You made-up some numbers to claim 'very little'. And one of those numbers seems 20 times too low based on what whitetiger said about stock center diff. So your explanation for your original claim " an 05 lgt will spin 1 rear wheel and one front wheel. if neither of those have traction the car isn't gonna move" does not add up. 666 Link to comment Share on other sites More sharing options...
rob-2 Posted August 28, 2011 Author Share Posted August 28, 2011 Exactly... so I question anytime someone who has ripped on a car non-stop, while extolling the virtues of another, posts about something wrong with their car again... Sh-awd acts differently with tcs on or off. I think in my case better tires would have made a huge difference. Link to comment Share on other sites More sharing options...
rob-2 Posted August 28, 2011 Author Share Posted August 28, 2011 Exactly... so I question anytime someone who has ripped on a car non-stop, while extolling the virtues of another, posts about something wrong with their car again... Snow in NYC can be packed very tightly after plowing. In fact, it's more like packed ice. If you (or anyone else) have tried to pull in or out of a parking spot there before, you would't know. I've gotten my car stuck in it numerous times before. Plenty of ways to do that apart from high centering it. You can even see in the video when he gets one of his wheels on the curb that the other wheel is on TOP of the snow, not cutting through it at all. Drove 10 years out east with fwd and never got stuck. Your point is valid about snow pack but you and know you work a path out. Link to comment Share on other sites More sharing options...
frank_ster Posted August 28, 2011 Share Posted August 28, 2011 Next you're gonna say that 'oil' and 'spring' is the same thing.... I dont call a bunch of circular plates clutches when they don't contact each other. But whatever works for you as a definition of a clutch. The question is how much torque will go to the rear wheel with traction. You made-up some numbers to claim 'very little'. And one of those numbers seems 20 times too low based on what whitetiger said about stock center diff. So your explanation for your original claim " an 05 lgt will spin 1 rear wheel and one front wheel. if neither of those have traction the car isn't gonna move" does not add up. its the same idea as an automatic tranny, bunch of clutches ( wear clutches and frictions ) one has splines or what ever on the out side and the other splines on the inside, they are pre loaded . as seen is the diagram i posted earlyier. the torque numbers i made up the exact numbers i don't know. but i have played with it on my 2.5 i 5 mt and my neighbors wrx. the amount of torque that the center diff will pass to the slower turning axle is not very much. its why the cars don't bind when your turn. you can tie down or lock 3 wheels on a wrx and have 1 tire spining. when you try to move ( very hard abusive on the center diff clutches) and much worse at higher rpm's. the rate for the center diff clutches to tighten up takes some time. seconds i'm not sure. eventually the heat build up will cause the slower turning axle to turn. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
frank_ster Posted August 28, 2011 Share Posted August 28, 2011 sorry i did some more reading into the center diff, its stlightly different than what i thought originally. your correct its not exactly like clutches and a spring. this way it allows some change in center diff tightness. Now that's thinking out of the boxer! fyi all 05 + legacy's have built in code reader Link to comment Share on other sites More sharing options...
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