Mazda 6 Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
272 Posts
Discussion Starter #1
I'm making a left hand turn and I'm at around 3500 in 2nd (still through the wide left) and I punch it. The drivers side rear tire chrips and I launch around the corner. No DSC light.

So my question is, if DSC detects slipage of tires, how did the AWD kick in with enough force to break loose the rear if the front tires don't slip at all, and the DSC didn't detect anything? I'm starting to think that the AWD is not 100/0 all the time.
 

·
Registered
Joined
·
440 Posts
I'm making a left hand turn and I'm at around 3500 in 2nd (still through the wide left) and I punch it. The drivers side rear tire chrips and I launch around the corner. No DSC light.

So my question is, if DSC detects slipage of tires, how did the AWD kick in with enough force to break loose the rear if the front tires don't slip at all, and the DSC didn't detect anything? I'm starting to think that the AWD is not 100/0 all the time.
[/b]
it reads more than just tire slip.
 

·
Registered
Joined
·
489 Posts
Plus, it's tuned to allow somewhat more agressive driving before it kicks in. AWD should activate before DSC.
 

·
Registered
Joined
·
123 Posts
i was driving home from work my drive is about 45 min. i get to my block down shift to third to make a left turn and then down to second gear. i get on it about half ot hit a couple of bumps the ones they fill after doing work in front of houses and the dsc lights starts blinking i was like wtf omg this is bad i hit a bump and the car thinks the wheels are slipping. so now not only the car bog when i hit a bump but now i get to see the 4 wheel light come on. mazda?
 

·
Registered
Joined
·
391 Posts
In my 2003 6S, the TCS (DSC) would activate for about 2 seconds before the light would come on. Just because you don't see the light doesn't mean it's not doing anything. ;)
 

·
Registered
Joined
·
353 Posts
I've only got the light maybe twice. Once because I went into a turn and hit the brakes going around it andwe felt it kick in. Another time because i launched with with it on... felt weird and liek the car just said no.

Under hard driving I dont get the light to come on and I ahve slid the rear around a few times. Seems it works more when your on the brakes than on the gas.
 

·
Registered
Joined
·
566 Posts
I've had it kick in sliding on gravel. The car definitely started to slip and rotate before the machinery caught it. Actually made control worse because I wasn't sure what the car was trying to do (besides pull power-not necessarily helpful partway thru a corner). I'm not sure this DSC is the smartest tool in the drawer :) Anyway, it does seem to let quite a bit happen before it kicks in. Snow tests will determine if it's any use for me at all. BTW, does the DSC calibration change with speed? Will it allow more aggressive slip at low speeds?
 

·
Registered
Joined
·
353 Posts
I believe I know hwo to make the car full time awd. I looked at some of the pictures of the rear diff and what not. If I can find one from a car that was wrecked and get it then I can work on making a piece so it would be 4wd all the time. There would still be no center diff though from the looks, at least in the pic, its something that could be possible. THough making it 4wd would be easier then putting a diff in. Liek I said if I an find a junkied MS6 (i know there are a couple) and I can get the rear diff I can work on making a piece for it.
 

·
Registered
Joined
·
259 Posts
I believe I know hwo to make the car full time awd. I looked at some of the pictures of the rear diff and what not. If I can find one from a car that was wrecked and get it then I can work on making a piece so it would be 4wd all the time. There would still be no center diff though from the looks, at least in the pic, its something that could be possible. THough making it 4wd would be easier then putting a diff in. Liek I said if I an find a junkied MS6 (i know there are a couple) and I can get the rear diff I can work on making a piece for it.
[/b]

I hope you like drivetrain binding. You need a center diff otherwise the car will not turn very well.
 

·
Registered
Joined
·
272 Posts
Discussion Starter #10
I think we are all encountering the same thing, the rear tires get a fair amount of torque before the front tires slip. Which means the AWD is not 100% FWD until it slips. If the AWD only kicks in when the front tires slip, the DSC should also kick in when the AWD does. But whenever I get the car into a 4-wheel drift (long left turn from a stop on a very slippery surface), the rears are breaking loose at the same time as the front, then a tenth of a second later the DSC kicks in. I think that snow will only cause the fronts to break loose easily and not prove much, but make testing the AWD easier.
 

·
Registered
Joined
·
272 Posts
Discussion Starter #11
Not sure where the 100% FWD information came from, but it's wrong. I thought the AWD system was fully activated when the front tires slip, not so....

http://forum.mazda6tech.com/about4221.html

It is controlled by the AWD CM (control module)
Some snipets from the docs:
  • Based on a signal from the AWD CM, it operates the electromagnetic clutch and transmits drive torque to the rear wheels.
  • When the AWD solenoid control current is OFF, no torque is generated in the pilot clutch because there is no current folowing to the AWD solenoid.
  • When starting off or accelerating during straight-ahead driving, torque transmitted to the rear wheels is optimally controlled to ensure sufficient acceleration performance.
  • If a parking brake signal input to the AWD CM indicates, the module controls the torque transmitted to the rear wheels.
  • When the AWD CM determines, based on the four-wheel signal and steering wheel angle signal, that the vehicle is in tight cornering, it reduces the torque transmitted to the rear wheels to avoid tigh corner braking characteristics.
So, I must conclude that the AWD is 50/50 under most conditions, since it reduces torque to rear wheels when tight cornering.
 

·
Registered
Joined
·
375 Posts
you guys are lucky, my gm tcs on the TA would retard timing so much the car would litterally stall out when you were going up a small slippery hill.

it was funny though cause people wouldnt know how to turn it off and would take my car for a joy ride and not even be able to spin tire.

and it made my dyno guys look like dicks cause they would stall the car out on the dynos
 

·
Registered
Joined
·
259 Posts
Not sure where the 100% FWD information came from, but it's wrong. I thought the AWD system was fully activated when the front tires slip, not so....

http://forum.mazda6tech.com/about4221.html

It is controlled by the AWD CM (control module)
Some snipets from the docs:
  • Based on a signal from the AWD CM, it operates the electromagnetic clutch and transmits drive torque to the rear wheels.
  • When the AWD solenoid control current is OFF, no torque is generated in the pilot clutch because there is no current folowing to the AWD solenoid.
  • When starting off or accelerating during straight-ahead driving, torque transmitted to the rear wheels is optimally controlled to ensure sufficient acceleration performance.
  • If a parking brake signal input to the AWD CM indicates, the module controls the torque transmitted to the rear wheels.
  • When the AWD CM determines, based on the four-wheel signal and steering wheel angle signal, that the vehicle is in tight cornering, it reduces the torque transmitted to the rear wheels to avoid tigh corner braking characteristics.
So, I must conclude that the AWD is 50/50 under most conditions, since it reduces torque to rear wheels when tight cornering.
[/b]

This is a rather far fetched conclusion from the given information. If the torque distro was 50/50 most of the time you would not be able to steer the car. The only way you can have 50/50 distribution all the time while still retaining independent wheel rotation is with a center diff. An electromagnetic coupling is unable to produce this torque distribution under normal driving conditions without drivetrain binding.

This is the reason why it must reduce torque to the rear wheels, in order to steer.

http://forum.mazda6club.com/index.php?showtopic=53530#7

previous explaination here...

It would take me forever to explain but it has been discussed before. I am well aware and have researched the basics of how a haldex system works and its shortcomings. If you have time to read the entire thread...

You will find that what I have stated is 100 percent true in order for a haldex system to work.


The basic shortcoming of haldex comes from the reason why cars need differentials in the first place...



http://forum.mazda6club.com/index.php?show...=50136&st=0




If all the tyres are the same diameter, how can the rear's possibly be moving (assume you mean rotating) slower than the front's?

When a car is turning the outside wheels have farther to travel and rotate faster than the inside wheels. Thats the only time wheels of the same diameter on the same car rotate at different rates, with the exception of power spin/brake slip.

And where do you get "the sharper the turn the less AWD"? Do you own a speed6, have you even driven one through all configurations? Or do you just read too much?

Lets get something straight, front wheel spin is not a prerequisite for transfering torque to the rear wheels. The system is active, not reactive. Given the type of driving I do my rear wheels are alive almost all of the time.
[/b]

Powering out of a turn if the haldex ever attempts to go full lock you will loop the car because it tries to sync the front and rear wheels together. Without diffrerentials the wheels cannot spin independently while still delivering power. Any amount of haldex lock will impart a syncing effect on the front and rear set of wheels which are spinning at diffrent rates.

All this more agressive haldex software is great... but the last place I want the haldex to lock up is when agressively powering out of an increasing radius turn causing me to completely loose it when my rear wheels which are spinning slower than the front wheels mid turn decide to match each other in speed at the limits of adhesion.

The more it locks the more it tries to sync the drivetrain together and force wheels spinning at diffrent rates to spin at the same rate. To prevent this it has to decouple partially if the computer detects a change in steering input. In performance situations, ie corner exit, hairpins, sweepers, it takes away AWD when you need it the most.

By definitition it can never be rear biased its just a clutchpack that takes power from the front and attempts to couple the front and rear wheels together.

Haldex can be defined as an automaticly acting part-time AWD system since it lacks a center diffrential.

To answer your question....

Visual aids...





Only when going straight all four wheels are turning at the same speed rate.

As soon as a turn is initiated all four wheels will rotate at different rates since each of them follows a different imaginary circle.
This is what happens during a turn:

The inside wheels will rotate with less rpm than the outside wheels.

The differential on the rear axle guarantees that the rpm delivered via drive shaft from the transfer case are distributed to the left and right wheel as needed. Meaning equal rpm when traveling straight - less rpm to the inside wheel and more rpm to the outside wheel when in a turn.

The differential of the front axle does exactly the same thing.

The axle differentials take care of the need for different wheel rpm.

Interestingly enough during a turn the front axle needs more rpm than the rear axle. Here is why:

The front inside wheel will need more rpm than the rear inside wheel.

The front outside wheel will need more rpm than the rear outside wheel.

This means that the front wheels need more rpm than the rear wheels in a turn

When you add the rpm of front wheels (A+B) you will find that the number is higher than the combined rpm of the rear wheels (C+D).

Unlike full time AWD with a differential - Part time "active" AWD is not able to accomodate the need for different axle speeds because it uses a Coupling or a PTU. To allow rotation the PTU must DECOUPLE reducing the amount of power delivered to the rear wheels.

Full time systems allow all 4 tires to push or pull at maximum rate. In part time active AWD this is not the case.
 

·
Registered
Joined
·
566 Posts
But since the Haldex system acts by pulsing the locking unit anyway, you get the effect of seemless torque transfer (as long as the pulses are rapid enough not to destabilize the car). I've seen calculations about how much/little wheel travel goes by during each lock cycle but that's information in a vacuum since no one knows the cycling rate of OUR Haldex system. Has anyone ever felt the AWD system destabilizing their car pulling out of a turn? The video I've seen of track work seems to indicate that the car is quite easily controlled in slides and 4 wheel drifts. I haven't seen video of anyone going for maximum controlled speed but the track testing Edmunds did vs the Spec.B (which does have a diff between front and back) didn't indicate any decreased capability. Bottom line, it's not an Evo or an STI, but for anything you can throw at it on the street and probably anything you could find on the track, it does the job very nicely. Shall we get over the "diff envy"?
 

·
Registered
Joined
·
561 Posts
the complexity of all wheel drive....
thats some good info. although for the average joe its a bit much. most people just want to know how they can do rear drive burnouts.... basically, if you suck at driving, leave the dsc on. its probably smarter than you. if you want to have some fun and can handle power slides well, turn it off.
 

·
Registered
Joined
·
272 Posts
Discussion Starter #17
This is a rather far fetched conclusion from the given information. If the torque distro was 50/50 most of the time you would not be able to steer the car. The only way you can have 50/50 distribution all the time while still retaining independent wheel rotation is with a center diff. An electromagnetic coupling is unable to produce this torque distribution under normal driving conditions without drivetrain binding.

Snip...

Only when going straight all four wheels are turning at the same speed rate.

Snip...

Full time systems allow all 4 tires to push or pull at maximum rate. In part time active AWD this is not the case.
[/b]
I understood your post the first time I read it before I owned a speed 6.

But, you also just admitted that it is not 100% FWD until the car slips, as I have been lead to believe. Most of the time (ie going straight) the car is 50/50. Also, it is not 100/0 if I can power oversteer the car, which I can. I am also assuming that the computer can ON/OFF the clutches such that it will allow for the difference in tire speeds when you are not in a tight turn (as stated in the spec sheets posted).
 
1 - 17 of 17 Posts
Top