Traction control or not?

[xc70fin]

Hi

I have quite stupid question. I have new for me (1 month) 2002 xc70 and I am just wondering what kind of traction control I have or do I have it?

I do not have button to switch it off but sometimes I can notice orange triangle warning light to come on in lower right corner!

Now when we have some snow here in Wisconsin, I have been testing my car but I have not understood how this "traction control" works. If I asselerate straight in snow with full trottle it just goes without light flashing and I bet wheels are spinning. Or in corner I can feel that car is under steering and wheels ...

SO, do I have it or .... and how it should work?

Thanks

[littlewaywelt]

Hi

I have quite stupid question. I have new for me (1 month) 2002 xc70 and I am just wondering what kind of traction control I have or do I have it?

I do not have button to switch it off but sometimes I can notice orange triangle warning light to come on in lower right corner!

Now when we have some snow here in Wisconsin, I have been testing my car but I have not understood how this "traction control" works. If I asselerate straight in snow with full trottle it just goes without light flashing and I bet wheels are spinning. Or in corner I can feel that car is under steering and wheels ...

SO, do I have it or .... and how it should work?

Thanks
You have STC and TRACS. It works by applying a brake to a spinning wheel so the torque can be redistributed to another wheel. Alls XCs have it. As an option one can order DSTC which is a dynamic system that also includes emergency braking assistance (EBA).

[xc70fin]

Why that light comes on so rarely? I would imagine that it come on when ever system works. When I was driving in snow and trying to get it activated (light on) it hardly ever hapend!

[skibo]

I'm glad this topic came up - I've been wondering about the difference between TRACS and STC. The manual to my MY04 goes on and on about the STC, but makes no mention of the TRACS, and I believe the brochure does the opposite - talks about TRACS but not STC.

I gather from various posts that the TRACS will brake a slipping wheel on an 'axle' to force power to the other side, and I understand that the DSTC uses some combination of brake application to eliminate spin-outs on curves, but what about plain-old STC?

And while I'm at it, the manual shows a button under the climate control panel to turn off STC, but I don't have it. In general, I'm kind of dissapointed in the manual - it is supposed to be XC specific, but it is full of stuff for the V70 and V70R as well - maybe this is one more thing that is only on a 'sister' model.

[gibbons]

From my experience, not from any literature, I have noticed the following. The triangle light flashes if the two wheels on the same end of the car spin at different rates. I think the light means the control system is braking the spinning wheel to force more power to the other side through the differential. For example, if I have one wheel on ice, and the other on dry, and give it the gas, the ice wheel spins for a fraction of a second, I hear some mechanicals, and then the car starts to go as I assume the other wheel with traction is getting the power. If all fours are on an equally slick surface and I punch it, they all spin (a bit, WRs are good but not perfect), but the yellow light doesn't flash.

By the way, when I had my car on jack stands, I started the motor and put it in gear with the brake on. When I let the brake off, all four wheels started turning at the same time. I have a Haldex on my 04, and I swear, it looked like all four wheels were hooked together. I didn't see any hesitation or delay at all!

[TrueBlue]

Skibo;

TRACS and STC are essentially the same system but function differently. TRACS is for the FWD models (V70s and XC90 - if anyone has bought that type?). The button - certainly in NA and European markets is for DSTC, whether the old Traction Control
button (which disappeared over here at the end of the Classic V70) is for other markets or is just the case of technical writers not being told how production has changed.... I wouldn't know!
The adoption of more electronic control (as opposed to the mechanical VC) has opened up loads of opportunities to connect features together. Some are included in the basic XC package and the rest are extras; DSTC, 4C, EBA, who knows what else. The manual and brochure descriptions are so imprecise that it's impossible for the potential owner to guess as to what he is getting.
Dealers are no help because their sources of information are much the same as ours.
In any event, I was horrified to see Volvo appointed demonstrators hooking up a '90 to a platform with rollers on one side (ground on the other) and then running the vehicle until the system stopped the spinning wheels - and the car ran off the ramp. This was heralded as a demo of DSTC. It wasn't, it merely the AWD system doing what it oughta'. When challenged they flanneled. AArrghh
Gibbons,
I'd go along with your assertion that all four wheels were hooked together. The older VC would probably not have done it.

Everyone,

The owner's manual explains the amber light; but not as well as Gibbons did above.

[Big]

Volvo would do the consumer a big service by better explaining what the various systems do and by making the DSTC standard. Yes, it costs extra, but many competitors provide similar systems as standard equipment. Plus, the dealers and consumers are often under the false impression that DSTC is not needed with AWD and STC. It's really hard to even find an XC70 on a lot with DSTC.

When I was researching our XC90 purchase (it comes standard with DSTC) in 2002, the literature said the following:

Stability and Traction Control (STC) is a combination of two existing Volvo systems, the low-speed, brake-activating TRACS (TRAction Control System) and the speed-independent, torque-limiting DSA (Dynamic Stability Assistance) system. STC is designed to prevent the driving wheels from spinning when starting and accelerating, as well as counteracting wheel spin if the driving wheels hit slippery patches when driving. The traction function works at lower speeds, up to 25 mph, by transferring the engine power to the wheel with the best grip from the one with the least grip. This is done using the ABS sensors and the brake system.

The stability function reduces engine torque, by cutting down on the fuel supply, if one of the driving wheels starts to lose its grip on the road, both during acceleration and when driving on a slippery road. This minimizes wheel spin and helps bring the car back to full stability.

The system reacts and is activated within milliseconds. An indicator lamp on the dashboard flashes when STC is engaged.

Dynamic Stability and Traction Control (DSTC) is an even more sophisticated stability system to improve active safety by also intervening and counteracting any tendency to skid. If the car makes a sudden movement and loses its directional line, or enters a corner too fast and the rear end starts to turn the car around, DSTC gently returns it to the right line by applying the brakes on one or more wheels.

DSTC works through the ABS system which has been further developed. In addition to more relief valves and a more powerful microprocessor, a brake reinforcement unit with electronic activation, sensors for side acceleration, yaw rate and steering wheel angle has been added.

The DSTC processor receives the signals and compares the actual behavior of the car with the desired behavior. Any deviation from the norm, such as the rear wheels starting to break away, and the system intervenes and makes corrections, activating the brakes on the wheel that will bring the car back in line. If necessary, the system also reduces engine torque, like STC.

DSTC is able to partially compensate for the driver's mistakes up to a certain point, as it counteracts and prevents skidding when the driver has already started to lose control. The system is particularly effective if the driver has to brake hard and steer away at the same time. The system counteracts any tendencies to skid and returns the car to its original course.

[ifnt420]

By the way, when I had my car on jack stands, I started the motor and put it in gear with the brake on. When I let the brake off, all four wheels started turning at the same time. I have a Haldex on my 04, and I swear, it looked like all four wheels were hooked together. I didn't see any hesitation or delay at all!FYI.
When the dealer was investigating the High Pitch metallic noise caused by the exhaust bracket scrapping against the drive shaft; they had my XC on the lift.
They started the car and put it into D, all 4 wheels started to spin at the same time/rate also. My XC is equipped with V.C. AWD.
I assume the big difference will be when the car is on the ground with more resistance, in which case the Haldex will hook right up, versus V.C. needs the oil to heat up to become sticky enough for it to hook up? Thoughts on this anyone?

[xc70fin]

I'm happy to hear that I really have stc and tracs to help in slippery surface. It is just so difficult to notice if it is electronics which helps or just AWD system.


Thank you about explanation!

[TrueBlue]

I assume the big difference will be when the car is on the ground with more resistance, in which case the Haldex will hook right up, versus V.C. needs the oil to heat up to become sticky enough for it to hook up? Thoughts on this anyone?
I agree; when I first complained about the VC on my 2002, the dealer did the same. However, when I did some static tests - as best I could - the rear wheels did not engage at all up to about 2,000 rpm, when I chickened out as the fronts were steaming (a bit).

I tested a 2003 with Haldex, and the rears revolved "pretty quickly".

The whole process confirmed the test done by Mr. Westlake and others a while ago.

[Len]

This is to make you sure that your XC has STC, read this –
http://apps.volvocars.us/ownersdocs/2005/2005_XC70/05xc70_01b.htm#pg22

[dlr97]

More confusion here due to Volvo documentation.

According to the specs at VolvoUSA web site (http://www.volvocars.us/Showroom/XC70/Specifications/Features/) under Roadholding, the 2005 (and my 2004) have TRACS standard, with DSTC optional.

Volvo FWD models, like the V70, have STC standard with DSTC optional. The other AWD models (R and XC90) have DSTC standard.

The TRACS equipped cars have no OFF button, as there is no reason to turn off TRACS. The STC and DTSC cars have an OFF button to defeat the throttle control feature that these cars have. Without the OFF button, these cars can become stranded when trying to move off of loose surfaces, because the system will essentially close the throttle too much while trying to control wheel spin. The OFF button also allows competent drivers to extract maximum performance from the car.

TRACS acts like a conventional limited slip differential at lower speeds, by braking a spinning wheel, sending torque to the non-spinning side. It does NOT control the throttle. With the Haldex-equipped XC70, a spinning wheel will send torque to the rear axle before TRACS even has time to turn on. I believe TRACS will also work on the rear two wheels.

STC (which includes both brake and throttle control) is much more important for FWD cars, which do not have the option of sending torque to the rear axle.

DSTC includes the yaw and steering sensors along with the functions of STC, and gives the system the option of manipulating individual brakes and the throttle to keep the car pointed about where the driver is trying to steer. It also must have an OFF switch to prevent the car being stuck.

Not to clear, I'm afraid. Wish Volvo would just make DSTC standard and clear up all the confusion.

Dave