So we bought the AWD version of the RDX precisely because our previous FWD sedan would get stuck in snowed-in parking spots. Today I went out to move our car, that was snowed-in, but not terribly so, and it took an hour to get it out! I don't expect miracles, but what I didn't understand is why only one tire would spin, and not all four? It was of of course this one tire that stopped the car from pulling itself out, which I think it easily should have been able to do had all four wheels been powered (which I thought would occur with AWD).

I suppose I misunderstand what AWD is then?

Thanks!

 

My understanding is that it is a front wheel drive vehicle until it detects slippage to the front wheels, then the rears kick in. I think your problem is one you likely don't have snow tires and 2 you may not have taken off the VSA, which retards the acceleration and cuts the power. Have to shut it off when you are in this predicament. You also may have needed to dig it out bit as well.

 

^^ditto^^

 

Sure, but at no point did the rear tires spin or all four at once, which was surprising. Seemed to act just like a FWD vehicle. I tried to turn off VSC but didn't realize the buttons needed to be held down to disable it, will remember for next time!

 

^for all practical purposes it IS a FWD car until it needs to be AWD. Honda should have included a limited slip differential imho...

 

I think there is a constant split between the front and the rear (the rear gets some torque even under ideal conditions).

I would have expected two wheels to spin if it were stuck (one on each axle).

 

No, 100% power goes to the front wheels unless the system detects slippage. In an open diff, the power goes to the wheel with the least resistence, i.e., the wheel with the least amount of traction. It is then up to the traction control system to brake the wheel that's slipping to provide the other wheels with more power. I don't recall how much power can be directed to the rear axle (i.e. up to 50%).

 

The AWD system on the new RDX is full-time FWD until slippage triggers the differential to engage and transfer power to the rear. However, with traction control on, the system begins to try to modulate power to the front wheels, causing them to spin at varying rates and thus limiting the power transfer to the rear wheels. This means that the rear wheels seldom get consistent power that can be applied when it has traction.

This video does a good job demonstrating just that. It uses Honda's Real-Time AWD system on the CR-V, which is mechanically similar to the setup now used on the RDX.


Also, something to keep in mind is that the AWD system is only as good as the traction it is able to find through the tires. Your cold all-season tires are going to be hard as hockey pucks in the cold and will not be able to gain much traction. You can read more about this by clicking here.

 

I had to explain this to my mom when she got her element, in fwd when ur in a snowy turn you usually let off the gas if you slip.
with the honda/acura awd its the same BUT if you arent accelerating IN the during and OUT of the turn the rear wheels wont sense the slip and dont engage.

Its a great system, the SH-awd in mdx etc is way more advanced BUT
how many times are you going up a 60% incline with left side ice and right side dry or on a ice rink like they do when testing the car at the acura winter facility... Never.

Also with our AWD system if you're ever STUCK and not getting out at all, once the system hits a certain temp it will disengage so you dont damage it, at that point call your tow

 

Thanks for that link. I would not have expected those results and I'm wondering how the current RDX would perform - I tend to think it would be similar to the Highlander.

The manual recommends turning off the VSA if the vehicle is stuck. Would that have made a difference in the performance of the Highlander?

 

You're right. I should have checked before posting speculation.

I found this at http://www.acura.com/Features.aspx?m...ligent_control

All-Wheel Drive with Intelligent Control System™
In normal cruising, the system operates as an efficient FWD vehicle with 100% of engine torque being directed to the front wheels.
During moderate acceleration or when front wheel slip is detected in dry conditions, 25% of engine torque is transferred to the rear wheels.
On a wet or slippery surface, wheel slippage will cause a reduction in engine output to the front wheels possibly to a point where torque is distributed 50/50 between the front and rear wheels.

 

I think it's odd that no power went to the rear. Even with VSA on I dont think the system would brake both rear wheels when hitting the gas. You should have a dealer check that out.

Also, speaking from personal experience, if you just keep your foot on the gas and let the AWD system seek out the wheels with traction it helps. If you keep releasing the gas the system cannot do this.

I have not been stuck yet with my new RDX, but in my old one with SH-AWD this idea worked. I was parked on a pile of snow/ice on an uphill street. The tires sucked and the car wasnt going anywhere, but when I kept my foot on the gas for while, it eventually found a way out.

 

so the real question is, would the Rdx make it up that ramp?

 

Here's some notes on that FYI.

https://acurazine.com/forums/showthr...=904856&page=2

 

The VSA does not rely on the brakes to reduce power (it uses the brakes to induce yaw). It has the ability to adjust the throttle input electronically at the throttle body. Effectively, the situation you described about releasing the gas is exactly what the VSA would do.

Your old SH-AWD RDX did not rely on a purely mechanical differential to send power to the rear. It had the ability to induce the rear drive components to spin when the computer indicated it was necessary. This meant that slip was not even needed at the front for the RDX to send power to the rear.

In the situation the OP described, what might have worked was to turn off the VSA and stomp the gas to force the car to send power to the rear.

 

Yep, that video explained it all. Next time I'll shut the VSA off and I think I'll be OK. Given the weather in the northeast, the car is already buried, so I'll have another shot at it!

 

No.

 

it would if you had limited slip differentials...

 

I wonder if the video had a subaru bias. See this video between outback and venza.

 

It is a Subaru produced video, so there is bound to be some bias. However, it does a good job of illustrating the difference between full-time AWD systems, such as what the Subaru and Venza have and part time AWD systems like the one in the CR-V and 2G RDX. Cars that require slip to induce torque shift can be hampered by traction control systems that are overly aggressive in cutting power.

 

If you want a real all wheel drive system, get a subaru. The Acura system, same as the CRV is a front wheel drive system that only sends power to,the rear wheels when the front slip. You cant lock it where all 4 wheels go. It also depends on ypur tires.