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[feeutfo]

...never noticed this before, but rear wheels spinning in the snow, the tc makes a rapid fire bobobobob noise, but lower pitched, like a rev limiter but it certainly isn't a rev limiter as the revs are cut quite aggressively as expected, plus the noise come from the back.

Could this be the rear brakes activating, as TB suspects with his....?

[Ian_D]

Im not sure what it is, but I dont like the sound of it! so I turn it off in weather like this 

Edit: Mines older than yours and I dont think it can apply the brakes? Anyway, it sounds like the engines run out of fuel and about to conk out!

[mrjimbo]

Definately sounds like a rev limiter but is it cutting the spark or fuel ?

[Mr Skrunts]

Mine sounds great at the moment since the back box fell off, there was a patch of ice on the end of the road, the TC flicks light on and off plus the exhaust starts to make a noise like an angry tank trying to chase after Jeremy Clarkson in a Range Rover on the shooting/test range.

Not sure that the brakes have anything to do with the TC, but am happy to be corrected, I thought it just cut the power to the engine hence making it feel like the brakes are active.

[Boditza]

from what i have learned, yesterday, in newer models the tc also aplies the brakes, on older ones just limits the revs

[Andy B]

from what i have learned, yesterday, in newer models the tc also aplies the brakes, on older ones just limits the revs

  Correct! 

[aaronjb]

from what i have learned, yesterday, in newer models the tc also aplies the brakes, on older ones just limits the revs

  Correct! 

ISTR reading someone (TB? Kevin?) saying that the later models actually do both - create a misfire and apply the rear brakes, depending on conditions (presumably the amount of detected slip).. but I've not exactly paid attention when the light is flashing

[Gaffers]

mine is definitely activating the brakes under certain conditions, quite disconcerting actually 

[feeutfo]

Only reason I paid attention is this 03 car makes a noise that my previous 52plate didn't.

Had to turn the radio and heater off to get a proper ear full. It's possible I just didn't hear it on the old car, as typically the car is on snow covered minor roads when it's warming up with heater on flat out demist etc. So some noises would have been drowned out. This car makes the noise just about audible over the demisting heater.

[PxMetro]

Only reason I paid attention is this 03 car makes a noise that my previous 52plate didn't.

Had to turn the radio and heater off to get a proper ear full. It's possible I just didn't hear it on the old car, as typically the car is on snow covered minor roads when it's warming up with heater on flat out demist etc. So some noises would have been drowned out. This car makes the noise just about audible over the demisting heater.

Sounds like you will have to turn the radio up a bit more then Chris, so you don't hear it 

[Marks DTM Calib]

Yup, it brakes the spinning wheel via the ABS module.

This is true of all cars with the 4 channel ABS from 1998 onwards

[Boditza]

Yup, it brakes the spinning wheel via the ABS module.

This is true of all cars with the 4 channel ABS from 1998 onwards

and it should have done this from the start on earlyer models too.. it helps the diff makeing it a sort of lsd by aplying brake on the wheel that spins fast and equalizing rotations

[Kevin Wood]

You can hear the ABS valves tapping if you listen carefully while TC is working. Have never noticed mine misfiring so power is probably cut by ignition retard and/or closing the throttle (as it's DBW).

Kevin

[TheBoy]

In this weather, you can have lots of braking effort from the TC system, without it starting to hit engine power, so you can hear the system working overtime on the rear brakes.

Kevin Wood - if you want to see engine cut in action (it pulses the engine power), get it in the snow, moving, then give it some large (though not flooring it) - once the system decides brakes alone won't solve it, you'll see the revs dance between 2 values, eg 3000rpm and 2250rpm.

You can do similar on greasy roads, but ime, you do need to give it a bootload, and the that tends to mean the revs will pulsate between much higher values.

If you do it from a standing start, giving it all 200bhp, and keep foot buried, it will bog down, so you won't see the effect.

[2woody]

I suspect that there are three different ABS types on Omega.

type 1 - introdces a misfire as the traction control method - truly agricultural.

type 2 - from mini-facelift, uses the brakes, too.

type 3 - not sure if from facelift or from DBW-on has the same ABS and TC, but also performs the front/rear split.