LSD and Traction control.
#1
LSD and Traction control.
I understand both individualy.
I also know you can switch the TC off if you want (I assume it resets every time car is switched on/off).
What happens with TC on with a LSD? dont they kind of work against each other?
I also know you can switch the TC off if you want (I assume it resets every time car is switched on/off).
What happens with TC on with a LSD? dont they kind of work against each other?
#2
Registered User
Join Date: May 2002
Location: Houston
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
If the TCS simply detects slip of both rear wheels and then cuts power then a LSD and TCS will be happy mates.
If the TCS also applies differential braking if one rear wheel slips then I too see incompatibility issues.
The VDC must apply differential braking to accomplish its task. Of course the VDC will not be active until the yaw sensors trigger it.
So I am postulating that the TCS only cuts power if both rear wheels are turning faster than the front wheels. No differential braking is used. Once the yaw sensors detect a slide then VDC applies differential braking and possibly a power cut.
I do not like driver's aids so I am happy that the RX-8 TCS can be disabled. I just wish I could get an 8 without ABS. Yes, I know ABS does wonders but threshold braking is a fun thing to do. Isn't a sporty car intended to be fun!
If the TCS also applies differential braking if one rear wheel slips then I too see incompatibility issues.
The VDC must apply differential braking to accomplish its task. Of course the VDC will not be active until the yaw sensors trigger it.
So I am postulating that the TCS only cuts power if both rear wheels are turning faster than the front wheels. No differential braking is used. Once the yaw sensors detect a slide then VDC applies differential braking and possibly a power cut.
I do not like driver's aids so I am happy that the RX-8 TCS can be disabled. I just wish I could get an 8 without ABS. Yes, I know ABS does wonders but threshold braking is a fun thing to do. Isn't a sporty car intended to be fun!
#3
If you like to threshold brake, just pull out the ABS fuse when you're at the track. Not as simple as pushing a button on the dash, but it's not too difficult to disable ABS temporarily.
#4
Registered User
Join Date: Aug 2002
Location: Denver, CO, USA
Posts: 2,045
Likes: 0
Received 0 Likes
on
0 Posts
Before you do something like that, just remember that there are some cars which have a couple of things on one fuse. You might be disabling more than just the ABS...
---jps
---jps
#6
Registered User
Join Date: May 2002
Location: Houston
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by CharT
If you like to threshold brake, just pull out the ABS fuse when you're at the track. Not as simple as pushing a button on the dash, but it's not too difficult to disable ABS temporarily.
If you like to threshold brake, just pull out the ABS fuse when you're at the track. Not as simple as pushing a button on the dash, but it's not too difficult to disable ABS temporarily.
vipeRX7,
Yes, the RX-8 with 6 speed manual has LSD standard in the USA market. Availability may be different in other markets.
#7
Originally posted by babylou
vipeRX7,
Yes, the RX-8 with 6 speed manual has LSD standard in the USA market. Availability may be different in other markets.
vipeRX7,
Yes, the RX-8 with 6 speed manual has LSD standard in the USA market. Availability may be different in other markets.
#8
Originally posted by babylou
What about the brake force distribution? I am assuming that since the RX-8 has electronic brake force distribution that there is no proportioning valve. If so, disabling the ABS will mean that the brakes will not be biased correctly.
What about the brake force distribution? I am assuming that since the RX-8 has electronic brake force distribution that there is no proportioning valve. If so, disabling the ABS will mean that the brakes will not be biased correctly.
#9
Registered User
Join Date: May 2002
Location: Houston
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by CharT
It's possible, but I'm not sure how EBD works. I assume there is a default brake bias to work from since the brakes still need to work even if your electronics go out.
It's possible, but I'm not sure how EBD works. I assume there is a default brake bias to work from since the brakes still need to work even if your electronics go out.
#10
Registered
iTrader: (1)
Join Date: Mar 2003
Location: Pacifica
Posts: 280
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Sputnik
Before you do something like that, just remember that there are some cars which have a couple of things on one fuse. You might be disabling more than just the ABS...
---jps
Before you do something like that, just remember that there are some cars which have a couple of things on one fuse. You might be disabling more than just the ABS...
---jps
#11
Registered
Originally posted by babylou
Yes, I know ABS does wonders but threshold braking is a fun thing to do. Isn't a sporty car intended to be fun!
Yes, I know ABS does wonders but threshold braking is a fun thing to do. Isn't a sporty car intended to be fun!
Regards,
Gordon
#12
mostly harmless
Join Date: Jun 2002
Location: Greater Vancouver Area, BC
Posts: 3,440
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Gord96BRG
So instead of braking to the threshhold of wheel lockup, brake to the threshhold of ABS engagement. What's the big deal? It's still threshhold braking, only you don't get flatspots if you get it wrong!
Regards,
Gordon
So instead of braking to the threshhold of wheel lockup, brake to the threshhold of ABS engagement. What's the big deal? It's still threshhold braking, only you don't get flatspots if you get it wrong!
Regards,
Gordon
HA!! riiiight. "oh sweet!! now i have this killer vibration on my brand new $200 front-right tyre!!"
#13
Registered User
Join Date: May 2002
Location: Houston
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
You gotta be pretty damn ham footed to flat spot a street tire. If the tire locks up for a few feet the flat spot is neglible. Racing slicks are a completely different story since their abrasion resistance is way lower.
The problem I have experienced with braking to the limit of BAS is that when ABS has actuated you have to back way off the brakes before above takes a break on the brakes.
The problem I have experienced with braking to the limit of BAS is that when ABS has actuated you have to back way off the brakes before above takes a break on the brakes.
#15
Registered User
Join Date: Jan 2003
Location: Farmington Hills, MI
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by babylou
If the TCS simply detects slip of both rear wheels and then cuts power then a LSD and TCS will be happy mates.
If the TCS also applies differential braking if one rear wheel slips then I too see incompatibility issues.
If the TCS simply detects slip of both rear wheels and then cuts power then a LSD and TCS will be happy mates.
If the TCS also applies differential braking if one rear wheel slips then I too see incompatibility issues.
but depends on what kind of limited slip, and how limited it is. Viscous limited slip takes a second to tighten up. So long as the TCS isn't trying to correct a Major SNAFU, then differential braking could be used for a short time. I think with power limiting control it could be feasable. OEM's are going away from just differential braking because of the abuse the brakes take when drivers keep the power on.
"and how limited it is"
I say that because limited slip clutches can be tuned for a certain percent of lockup/torque transfer. I don't think OEM's really use anything other than 100%, however.
How would things work out with Torsen limited slip?
Tom
P.S. I was 'evaluating' several new 2003 Lincoln LS's with TCS, and in dirt the TCS wouldn't let the car get out of hand enough to take a long time to recover. It would kick in immediately, and quickly recover the vehicle. Didn't get opportunity to test it on snow.
Last edited by SlideWRX; 05-12-2003 at 02:46 PM.
#17
Administrator
after reading this thread it seems the question about how this works with the abs/ebd leaves out the fact that the abs/ebd is working the front brakes as well as the backs. or have i missed something?
#18
Registered User
Join Date: Jan 2003
Location: Farmington Hills, MI
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by zoom44
after reading this thread it seems the question about how this works with the abs/ebd leaves out the fact that the abs/ebd is working the front brakes as well as the backs. or have i missed something?
after reading this thread it seems the question about how this works with the abs/ebd leaves out the fact that the abs/ebd is working the front brakes as well as the backs. or have i missed something?
Tom
#20
Registered User
Join Date: May 2002
Location: Houston
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
Sideslip,
The RX-8 uses a Torsen type LSD so differential reaction is instantaneous.
I will not be getting an RX-8 with the TCS or DSC so I guess I do not have to worry about any interactions amongst these systems. I will leave it to the rest of you figure it out. Good luck.
The RX-8 uses a Torsen type LSD so differential reaction is instantaneous.
I will not be getting an RX-8 with the TCS or DSC so I guess I do not have to worry about any interactions amongst these systems. I will leave it to the rest of you figure it out. Good luck.
#21
I Just Can't STOP!
Join Date: Jul 2003
Location: The Big Apple
Posts: 210
Likes: 0
Received 0 Likes
on
0 Posts
Nice thread.
A couple of points. TC only works on the driver wheels, so in the RX case the rear wheels only.
TC's only job in life is to keep both drive wheels spinning at the same rate with each other and the fronts. It can do this through brake application and/or cutting the spark to the engine. USUALLY the system is designed to go to the brakes first as most customers find the engine suddenly dying a bit unrefined. With a manual it can, and has to me, stall the engine under very slippery conditions.
As far as the LSD and TC, the TC doesn't care or look at what the LSD does. It simply looks at the wheel speed of each rear wheel and the front wheels. If either the rear wheels aren't spinning at the same speed or the rears are spinning faster than the fronts it kicks in.
But, a smart development engineer will be sure to set the TC threshold to work best with the LSD so as not to give the car odd feeling handling. This is easy since once the diff does it's job the the rear wheels can no longer spin at different speeds. So all the TC needs to do is compare the rear to the front and it can then brake both rear wheels together.
However, like all else ------- junk in -----------> junk out!
A fellow engineer has a very good site on ABS and EBD which will explain both in laymen terms:
http://www.geocities.com/nosro/abs_faq/
An excerpt from the site on EBD:
What is Electronic Brake Distribution?
"EBD" is also sometimes called "Dynamic Rear Proportioning" or "DRP". When a vehicle brakes, weight shifts forward so that the front wheels are carrying more weight than the rear wheels. As weight is removed from a tire, its ability to grip is reduced. Under braking, since the rear wheels are carrying less weight, they are more prone to skidding (locking up under braking). This is bad. Very bad.
Some people expect that locking up the rear wheels should be preferable to locking up the front wheels. After all, at least with the front wheels unlocked, you'll be able to steer. This is true. However, locking the rear wheels causes the vehicle to become unstable. That is, with the rear wheels locked, the vehicle will tend to spin out in the same way that an upside-down broom balanced on the palm of your hand will tend to tip over. Sure, you can try keep the inverted broom balanced on the palm of your hand by moving your hand around, but you have to be quick. The same goes for steering when the rear wheels are locked. The vehicle will tend to spin out and you will be able to steer, but you must be extremely quick. As the vehicle speed increases, the tendency to spin out becomes even greater and you need to be even quicker to steer out of a spin. Eventually, you reach a speed where not even the best driver can react quickly enough. Therefore, it is always preferable to lock up the front wheels, or at least to lock up the front wheels before locking up the rear wheels.
So what is done about this? In the days before ABS, a "proportioning valve" was used to reduce rear braking as you braked more. For example, this mechanical device might reduce the rear braking force by 10% if you applied 50 pounds to the brake pedal and reduced the rear braking force by 20% if you applied 70 pounds to the brake pedal.
EBD uses the ABS hardware to take over this task. The mechanical proportioning valve is removed. Instead, ABS uses the wheel speed sensors to determine when the rear wheels are spinning minutely slower than the front wheels (we're talking about less than 1% here). This would be due to the rear wheels being comparatively over-braked relative to the weight on the tire. ABS uses this information to cap or reduce the brake pressure to the rear brakes, using the same hydraulic mechanisms as ABS. You won't hear this happening, however. When ABS is working, you hear a buzzing sound - this is the ABS motor which turns the pump. However, in EBD mode, not much fluid is being moved around, so the motor is not turned on to save you the annoyance. You also will not likely feel anything in the brake pedal since so little fluid is being moved.
EBD has become extremely popular for the reasons that it is inexpensive (after all, it is just some extra software) and actually does a better job than the old mechanical device. While the mechanical device worked in a fixed pre-determined way, EBD can adapt to any particular situation, including a loaded trunk, or tires with different stickiness.
A couple of points. TC only works on the driver wheels, so in the RX case the rear wheels only.
TC's only job in life is to keep both drive wheels spinning at the same rate with each other and the fronts. It can do this through brake application and/or cutting the spark to the engine. USUALLY the system is designed to go to the brakes first as most customers find the engine suddenly dying a bit unrefined. With a manual it can, and has to me, stall the engine under very slippery conditions.
As far as the LSD and TC, the TC doesn't care or look at what the LSD does. It simply looks at the wheel speed of each rear wheel and the front wheels. If either the rear wheels aren't spinning at the same speed or the rears are spinning faster than the fronts it kicks in.
But, a smart development engineer will be sure to set the TC threshold to work best with the LSD so as not to give the car odd feeling handling. This is easy since once the diff does it's job the the rear wheels can no longer spin at different speeds. So all the TC needs to do is compare the rear to the front and it can then brake both rear wheels together.
However, like all else ------- junk in -----------> junk out!
A fellow engineer has a very good site on ABS and EBD which will explain both in laymen terms:
http://www.geocities.com/nosro/abs_faq/
An excerpt from the site on EBD:
What is Electronic Brake Distribution?
"EBD" is also sometimes called "Dynamic Rear Proportioning" or "DRP". When a vehicle brakes, weight shifts forward so that the front wheels are carrying more weight than the rear wheels. As weight is removed from a tire, its ability to grip is reduced. Under braking, since the rear wheels are carrying less weight, they are more prone to skidding (locking up under braking). This is bad. Very bad.
Some people expect that locking up the rear wheels should be preferable to locking up the front wheels. After all, at least with the front wheels unlocked, you'll be able to steer. This is true. However, locking the rear wheels causes the vehicle to become unstable. That is, with the rear wheels locked, the vehicle will tend to spin out in the same way that an upside-down broom balanced on the palm of your hand will tend to tip over. Sure, you can try keep the inverted broom balanced on the palm of your hand by moving your hand around, but you have to be quick. The same goes for steering when the rear wheels are locked. The vehicle will tend to spin out and you will be able to steer, but you must be extremely quick. As the vehicle speed increases, the tendency to spin out becomes even greater and you need to be even quicker to steer out of a spin. Eventually, you reach a speed where not even the best driver can react quickly enough. Therefore, it is always preferable to lock up the front wheels, or at least to lock up the front wheels before locking up the rear wheels.
So what is done about this? In the days before ABS, a "proportioning valve" was used to reduce rear braking as you braked more. For example, this mechanical device might reduce the rear braking force by 10% if you applied 50 pounds to the brake pedal and reduced the rear braking force by 20% if you applied 70 pounds to the brake pedal.
EBD uses the ABS hardware to take over this task. The mechanical proportioning valve is removed. Instead, ABS uses the wheel speed sensors to determine when the rear wheels are spinning minutely slower than the front wheels (we're talking about less than 1% here). This would be due to the rear wheels being comparatively over-braked relative to the weight on the tire. ABS uses this information to cap or reduce the brake pressure to the rear brakes, using the same hydraulic mechanisms as ABS. You won't hear this happening, however. When ABS is working, you hear a buzzing sound - this is the ABS motor which turns the pump. However, in EBD mode, not much fluid is being moved around, so the motor is not turned on to save you the annoyance. You also will not likely feel anything in the brake pedal since so little fluid is being moved.
EBD has become extremely popular for the reasons that it is inexpensive (after all, it is just some extra software) and actually does a better job than the old mechanical device. While the mechanical device worked in a fixed pre-determined way, EBD can adapt to any particular situation, including a loaded trunk, or tires with different stickiness.
Last edited by RomanoM; 07-07-2003 at 05:38 AM.
Thread
Thread Starter
Forum
Replies
Last Post
garethleeds
Europe For Sale/Wanted
6
11-19-2015 06:32 AM