Questionable AWD System

A

Airvtec

Member
Location
Hayward, CA
Car
2006 FX35
It was raining last weekend up here in Nor Cal. My wife and I were leaving the parking lot from grocery shopping. I decided to turn off the VDC, and waited until the coast was clear. Never mentioned to my wife what I'm about to do. I gassed hard from a dead stop coming out of the parking lot making a right turn onto the street. To my surprise, the rear spinned so hard that I almost did a 180. For a split second there, I thought we were going to face the wrong side of the road. I was able to spin the car back around. Scared the crap out of my wife, and lost my right hearing from wife screaming, but it was fun.

I then tried launching the car from a dead stop, still with the VDC off. This time just going in a straight line. It felt like the rear had continuous power/spin, while the fronts were just pulsing with engagement. I definitely felt the rear wheels spin, loss of traction. The front wheels just didn't felt like it was fully engaged, cuz the whole time when the car was moving forward the rears were busy trying to get traction. I just wonder how well does this electronically controlled AWD system works.

My previous car was a '00 Audi S4. When I launched the S4 from a dead stop, in the rain, going straight there was almost no loss of traction. I know the S4 is full time AWD. And I know the FX AWD is electronically controlled, and it becomes RWD at certain speed with AWD kicking in when slippage is sensed. At least, I expected the same kind of traction from a dead stop, straight line launch.

Do you guys feel the AWD in the FX is more show? Wasn't this AWD system adopted from the previous Skyline? What am I not understanding about this system? I expected more traction from this AWD system.
 
I’m guessing it has something to do with your tires. When I have my stock RSA’s driving in the snow or rain sometimes it gets very scary because they have low traction especially in the snow. Also It’s not a very good idea to turn the VDC off especially in the wet weather.
 
LaxmaN said:
I’m guessing it has something to do with your tires. When I have my stock RSA’s driving in the snow or rain sometimes it gets very scary because they have low traction especially in the snow. Also It’s not a very good idea to turn the VDC off especially in the wet weather.
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Under normal driving circumstances I wouldn't turn the VDC off, but I like it off when some "fun" driving is desired. I do have so called ultra high performance all-season tires. However, unless you have enough hp that will break traction on all 4 wheels I really don't see the tires making a big difference IN THIS SCENARIO. If I had summer tires, all-season tires, whatever tires. On an AWD car in the rain, dead stopped, WOT lauch, going straight, in an auto tranny. I just expected similar traction in the FX as in the Audi in this case.
 
Airvtec said:
Under normal driving circumstances I wouldn't turn the VDC off, but I like it off when some "fun" driving is desired. I do have so called ultra high performance all-season tires. However, unless you have enough hp that will break traction on all 4 wheels I really don't see the tires making a big difference IN THIS SCENARIO. If I had summer tires, all-season tires, whatever tires. On an AWD car in the rain, dead stopped, WOT lauch, going straight, in an auto tranny. I just expected similar traction in the FX as in the Audi in this case.
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Try to do this again this time with the VDC on. I bet you'll have different outcome.(Do this in a safe manner) by turning off the VDC your turning off your electronic traction control, EBD electronic brake distribution, ABS. Tires will still plays an important part.
 
LaxmaN said:
Tires will still plays an important part.
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Tires play THE important part in traction. How else can you explain the huge difference between the all season tires and snow tires in snow?

Also, as far as I know, the power distribution on our FX at the start is 25% front, 75% rear. It goes to 100% rear once past a certain speed (20 mph?) and introduces the AWD back with extra adjustments if it senses slip. If you hit the Snow button, it switches to 50% front & rear until 40 mph. I remember this from an FX catalogue but not 100% sure. But if true, by removing VDC from the equation, you're giving 3/4th of the power to the rear wheels in a slippery environment and without a chance to do adjustments.

In an Audi, it will be opposite. The car will be give the power to the front most of the time but adjust it when it senses slip. It's so natural that a front wheel drive car having have better traction at a slippery road AND on a turn AND with heavy throttle then a rear wheel drive car at the same situation.

Shortly: You're not comparing apples to apples. Do the same with a BMW X5 with similar tires and you'll get the same results.
 
I felt a big change in traction when I changed my tires from Goodyear to Kumho tires. Both were Temperature A and Traction A but my old ones were better in traction.
 
EG3 said:
Tires play THE important part in traction. How else can you explain the huge difference between the all season tires and snow tires in snow?

Also, as far as I know, the power distribution on our FX at the start is 25% front, 75% rear. It goes to 100% rear once past a certain speed (20 mph?) and introduces the AWD back with extra adjustments if it senses slip. If you hit the Snow button, it switches to 50% front & rear until 40 mph. I remember this from an FX catalogue but not 100% sure. But if true, by removing VDC from the equation, you're giving 3/4th of the power to the rear wheels in a slippery environment and without a chance to do adjustments.

In an Audi, it will be opposite. The car will be give the power to the front most of the time but adjust it when it senses slip. It's so natural that a front wheel drive car having have better traction at a slippery road AND on a turn AND with heavy throttle then a rear wheel drive car at the same situation.

Shortly: You're not comparing apples to apples. Do the same with a BMW X5 with similar tires and you'll get the same results.
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I agree tires are important, however in an AWD it is less important than if it were on a FWD or RWD as far as traction is concerned when launching from a dead stop. What I'm trying to say is given the road is wet, not flooded, not snow, not ice...just wet. And say I have these crappy tires on an AWD FX35, and I launch it from a dead stop. It shouldn't have that big of a difference as say a high end set of tires...in the wet. This stems from my thought that a 35 doesn't have enough power to break traction on all 4 wheels in the wet. If that's the case, I can deduce the tires that I have aren't really the problem. Given the road is just wet, not flooded, not snowed, nor iced.

Your explanation on how the power is distributed (25/75) makes more sense. I thought the AWD system is more 50/50 at dead stop....doh :tongue: The reason why I turned of the VDC is so the computer wouldn't cut power.

FYI, Audi's quattro is 50/50 slip full time. You're probably thinking of the VW 4motion, which is different.
 
Airvtec said:
I agree tires are important, however in an AWD it is less important than if it were on a FWD or RWD as far as traction is concerned when launching from a dead stop. What I'm trying to say is given the road is wet, not flooded, not snow, not ice...just wet. And say I have these crappy tires on an AWD FX35, and I launch it from a dead stop. It shouldn't have that big of a difference as say a high end set of tires...in the wet. This stems from my thought that a 35 doesn't have enough power to break traction on all 4 wheels in the wet. If that's the case, I can deduce the tires that I have aren't really the problem. Given the road is just wet, not flooded, not snowed, nor iced.
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Couple of points here:

1) When it first starts to rain after some dry weather, it is more dangerous than it would be after some half day of rain. The dust that settles down with the rain becomes a slippery thin layer of mud that can cause traction loss more than when it would be raining for a while
2) You're not going straight from stop. You're TURNING from a stop with no traction control system to apply brakes to the necessary tires and you're powering your rear wheels. If you have ever driven a FWD car, you'll know that it'll lose traction and tend to spin the rear end compared to either an AWD or FWD car.
3) If Audi is 50:50 all the time, it's so natural that it'll handle better than FX without traction control.
4) High end vs crappy is not the correct tire comparison. A tire can be very high end but still be focused much more on dry that it'll let you spin the rear end in wet. Here's a short story:
I recently changed a set of brand new Falken Ziex tires in 22" after almost sliding & crashing in a highway merge. Never had that problem before with stocks, a different set of Bridgestones in 20 or yoko geolandars in 20. Now Falken Ziex is not a bad tire and supposedly it's a very good all season tire BUT it wasn't good in 22 size and in a wide track. Changed to Yoko Paradas in 22 and it's good now.

My point is: I don't know what tires are you using but comparing FX to Audi is not a fair comparison. Compare it to an X5 in 22s with similar tires or compare it to a Merc ML in similar tires. The fact that FX will put more power to the rear wheels WITHOUT traction control and in a TURN in WET will make it spin. It's not a fault. It's how it's made.
 
LaxmaN said:
by turning off the VDC your turning off your electronic traction control, EBD electronic brake distribution, ABS.
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can anyone verify this statement? i always have VDC off, but i dont think i lose EBD or ABS. i thought it just took off traction and stability control?
 
StuLax18 said:
can anyone verify this statement? i always have VDC off, but i dont think i lose EBD or ABS. i thought it just took off traction and stability control?
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I know it that way as well. It shouldn't turn off any brake system, just traction systems.
 
I think it turns off EBD but not ABS, don't think you can turn the ABS off but I think the Electronic Brake Distribution is part of the Vehicle Dynamic Control system...
 
turbocad6 said:
I think it turns off EBD but not ABS, don't think you can turn the ABS off but I think the Electronic Brake Distribution is part of the Vehicle Dynamic Control system...
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Correct.

And yes, it is a rear-wheel biased AWD system, and yes it is from the same electronically controlled AWD system as the Skyline, called ATTESA-ETS.

I don't remember the numbers exactly, but I do know it uses the ABS sensors to detect rear-wheel slip and anything above 5% (rear wheels spinning 5% more than the front) is when it STARTS to send power/torque to the front wheels. It goes UP TO 50% to the front wheels, and I'm assuming that's in worst case situation (like a ton of rear wheel slip).
 
EG3 said:
Couple of points here:

1) When it first starts to rain after some dry weather, it is more dangerous than it would be after some half day of rain. The dust that settles down with the rain becomes a slippery thin layer of mud that can cause traction loss more than when it would be raining for a while
2) You're not going straight from stop. You're TURNING from a stop with no traction control system to apply brakes to the necessary tires and you're powering your rear wheels. If you have ever driven a FWD car, you'll know that it'll lose traction and tend to spin the rear end compared to either an AWD or FWD car.
3) If Audi is 50:50 all the time, it's so natural that it'll handle better than FX without traction control.
4) High end vs crappy is not the correct tire comparison. A tire can be very high end but still be focused much more on dry that it'll let you spin the rear end in wet. Here's a short story:
I recently changed a set of brand new Falken Ziex tires in 22" after almost sliding & crashing in a highway merge. Never had that problem before with stocks, a different set of Bridgestones in 20 or yoko geolandars in 20. Now Falken Ziex is not a bad tire and supposedly it's a very good all season tire BUT it wasn't good in 22 size and in a wide track. Changed to Yoko Paradas in 22 and it's good now.

My point is: I don't know what tires are you using but comparing FX to Audi is not a fair comparison. Compare it to an X5 in 22s with similar tires or compare it to a Merc ML in similar tires. The fact that FX will put more power to the rear wheels WITHOUT traction control and in a TURN in WET will make it spin. It's not a fault. It's how it's made.
Click to expand...

Actually, I was going straight on my 2nd try. Just wanted to see how the car reacted to launching in the wet going straight, cuz I was so surprised at the amount of power that went to the rear during my 1st try of making a turn. I expected the FX to launch with a lot more grip in the wet, of course this is without knowing the AWD didn't distribute 50/50 power. It's obvious now that the VDC & snow control plays a big role in how the AWD in the FX reacts (i.e., on/off, power distribution).

Guess what I was hoping is having the VDC off, so the computer won't slow down the car by applying throttle cut or electronic braking. Instead relying soley on the AWD to provide traction.
 
I love these electronic enhancements... some people think if there a good enough driver they don't need it. well, unless you have 4 seperate brake pedals & 4 seperate legs with spit second response times & extra sensatory perception I call bs...


I'm such a fan of this type of technology that I actually swapped my whole frame on my 83 caddy with a frame from a 91 just to add abs to that vehicle... no human control can possibally equal what the computers, sensors & individual solinoids can do
 
hooey phooey, my first car two cars didnt have any sort of these stability control programs and i got along fine. abs, however, i really enjoy. i liked that highway crash scene about 45 seconds into the first video. something just like happened to me about a week ago. i just slammed on the brakes, and luckily all the cars went to the right lane and outta my way. me and the pickup right in front of me just slowed way down until it cleared and then kept going. im not sure if the pickup that was involved rolled though, i think it just slid across the lanes.
 
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