Launch Control using ABS?
03-05-2012, 12:56 PM
#1
Launch Control using ABS?
Maybe I am completely crazy, but it seems to me that it would be possible to use the factory supplied ABS actuator and an aftermarket controller to create a launch control system. Using the ABS sensors as inputs, the controller would modulate the hydraulic pressure via the ABS actuator to apply the brake to the slipping wheel, effectively sending more torque to the wheel with more traction.
It is a common practice when stuck in mud or snow to use the brakes in a vehicle with open differentials when one of the drive wheels is slipping. As the braking force increases on the drive axle, the difference in the traction of the two drive wheels becomes negligible and the torque is split in a ratio that approaches 50/50 even with an open differential. This is because the open diff doesn't care where the resistive force is coming from, be it from traction or from the brake, when the resistive force is equal to both wheels, the torque will be evenly split.
The controller would basically be a piggy back to the stock ABS control module. It would monitor the wheel speed of all four wheels, and if one of the drive wheels was rotating significantly faster then the other drive wheel, the brake would be applied to the slipping wheel.
Using some math and assuming the rear wheels are not slipping, this system should even work when going around a turn, like when accelerating out of a corner.
What I really lack is a fundamental understanding of Nissan's ABS system. With PWM you should be able to modulate the pressure created by the ABS pump. If you had the right solenoids open and closed, it looks like you could send this modulated hydraulic pressure to a wheel of your choosing.
Does this sounds feasible? Is there anyone out there with a very good understanding of how the ABS system works? Can the ABS pump be used to generate pressure like I am describing above?
It is a common practice when stuck in mud or snow to use the brakes in a vehicle with open differentials when one of the drive wheels is slipping. As the braking force increases on the drive axle, the difference in the traction of the two drive wheels becomes negligible and the torque is split in a ratio that approaches 50/50 even with an open differential. This is because the open diff doesn't care where the resistive force is coming from, be it from traction or from the brake, when the resistive force is equal to both wheels, the torque will be evenly split.
The controller would basically be a piggy back to the stock ABS control module. It would monitor the wheel speed of all four wheels, and if one of the drive wheels was rotating significantly faster then the other drive wheel, the brake would be applied to the slipping wheel.
Using some math and assuming the rear wheels are not slipping, this system should even work when going around a turn, like when accelerating out of a corner.
What I really lack is a fundamental understanding of Nissan's ABS system. With PWM you should be able to modulate the pressure created by the ABS pump. If you had the right solenoids open and closed, it looks like you could send this modulated hydraulic pressure to a wheel of your choosing.
Does this sounds feasible? Is there anyone out there with a very good understanding of how the ABS system works? Can the ABS pump be used to generate pressure like I am describing above?
03-05-2012, 03:28 PM
#2
Steal the ABS system and ECU from a 350Z or a G35. That's how they do their VSC. It's annoying as sheit since every time you touch the gas in a turn on a wet road, it clamps down the brakes and cuts the throttle.
or you could do it yourself and try to make something better... but I'd say you're better off just getting a better differential and learning to drive.
or you could do it yourself and try to make something better... but I'd say you're better off just getting a better differential and learning to drive.
03-05-2012, 04:37 PM
#3
Maybe I am completely crazy, but it seems to me that it would be possible to use the factory supplied ABS actuator and an aftermarket controller to create a launch control system. Using the ABS sensors as inputs, the controller would modulate the hydraulic pressure via the ABS actuator to apply the brake to the slipping wheel, effectively sending more torque to the wheel with more traction.
It is a common practice when stuck in mud or snow to use the brakes in a vehicle with open differentials when one of the drive wheels is slipping. As the braking force increases on the drive axle, the difference in the traction of the two drive wheels becomes negligible and the torque is split in a ratio that approaches 50/50 even with an open differential. This is because the open diff doesn't care where the resistive force is coming from, be it from traction or from the brake, when the resistive force is equal to both wheels, the torque will be evenly split.
The controller would basically be a piggy back to the stock ABS control module. It would monitor the wheel speed of all four wheels, and if one of the drive wheels was rotating significantly faster then the other drive wheel, the brake would be applied to the slipping wheel.
Using some math and assuming the rear wheels are not slipping, this system should even work when going around a turn, like when accelerating out of a corner.
What I really lack is a fundamental understanding of Nissan's ABS system. With PWM you should be able to modulate the pressure created by the ABS pump. If you had the right solenoids open and closed, it looks like you could send this modulated hydraulic pressure to a wheel of your choosing.
Does this sounds feasible? Is there anyone out there with a very good understanding of how the ABS system works? Can the ABS pump be used to generate pressure like I am describing above?
It is a common practice when stuck in mud or snow to use the brakes in a vehicle with open differentials when one of the drive wheels is slipping. As the braking force increases on the drive axle, the difference in the traction of the two drive wheels becomes negligible and the torque is split in a ratio that approaches 50/50 even with an open differential. This is because the open diff doesn't care where the resistive force is coming from, be it from traction or from the brake, when the resistive force is equal to both wheels, the torque will be evenly split.
The controller would basically be a piggy back to the stock ABS control module. It would monitor the wheel speed of all four wheels, and if one of the drive wheels was rotating significantly faster then the other drive wheel, the brake would be applied to the slipping wheel.
Using some math and assuming the rear wheels are not slipping, this system should even work when going around a turn, like when accelerating out of a corner.
What I really lack is a fundamental understanding of Nissan's ABS system. With PWM you should be able to modulate the pressure created by the ABS pump. If you had the right solenoids open and closed, it looks like you could send this modulated hydraulic pressure to a wheel of your choosing.
Does this sounds feasible? Is there anyone out there with a very good understanding of how the ABS system works? Can the ABS pump be used to generate pressure like I am describing above?
03-05-2012, 04:58 PM
#4
I am thinking, we would need to figure out how to electronically apply brakes, perhaps adding some kind of solenoid.
We would adjust the pressure to the brakes, such as 50% or so pressure (when the solenoid applies the brake), then we could do some logic with electronics. We read the input from the wheel speed sensors (is it resistance we get back?), if left wheel sensor shows higher rate then this circuit board will activate the solenoid. Not too experienced with circuitry but this is def possible. Now,.... how would a solenoid apply brakes? I know they can be used "line lock" but thats after you apply the brakes then hold the pressure by closing the solenoid right? we need something to mimic someone pushing the pedal
We would adjust the pressure to the brakes, such as 50% or so pressure (when the solenoid applies the brake), then we could do some logic with electronics. We read the input from the wheel speed sensors (is it resistance we get back?), if left wheel sensor shows higher rate then this circuit board will activate the solenoid. Not too experienced with circuitry but this is def possible. Now,.... how would a solenoid apply brakes? I know they can be used "line lock" but thats after you apply the brakes then hold the pressure by closing the solenoid right? we need something to mimic someone pushing the pedal
03-05-2012, 05:05 PM
#5
This is more of a theory. I don't know if this will ever make it off the drawing board. I tend to have a lot of interesting ideas but not enough time. I'll put this on my list after rebuild engine (mostly done), make SFCs, build panhard bar conversion, design acoustic resonance tuned intake.
Matt, you give me an idea though. I'm going to check out the FSMs for the G35 and 350z.
03-05-2012, 05:47 PM
#6
http://papers.sae.org/910700/
Is anyone a member of SAE?
Streetz,
There is a motor that dirves a pump in the acutuaor that does most of the work. There are eight soleniods but they are just valves.
Best as I can tell, when the ABS activates on a wheel, the inlet solenoid closes and the outlet solenoid opens for that corner. The pump runs to return the brake fluid to the side of the system where the MC connects to the actuator. That is the pulsing pedal feel. Of course this happens in the blink of an eye.
There is something I am missing, though. I say this because I've had a look at the 350z FSM (BRC section) and the actuator is very similar to the A32. There is a mysterious reservoir in the actuator. I wonder what would happen if you closed all of the outlet solenoids, and opened the inlet solenoid only for the wheel that was spinning. I think you might be able to pump fluid into that caliper. This is as long as you didn't pump it back into the MC.
What you would need is some valve between the MC and ABS actuator to prevent the fluid from being forced into the MC. Under normal operating conditions, when the ABS activates, you are panic braking (or maybe the road are slippery), so the hydraulic pressure from your foot keeps the fluid in the ABS actuator. But this is also why you feel the pedal pulsate. If the same system were to be used as I've described, you would need to stop this flow of fluid. That is where one of the "line lock" solenoids you mention would come into play.
There is also a "gradient switch" in the a32 system. It looks like it switches the line from the MC from wide open to a small orifice. I don't know how it is controlled though.
Is anyone a member of SAE?
Streetz,
There is a motor that dirves a pump in the acutuaor that does most of the work. There are eight soleniods but they are just valves.
Best as I can tell, when the ABS activates on a wheel, the inlet solenoid closes and the outlet solenoid opens for that corner. The pump runs to return the brake fluid to the side of the system where the MC connects to the actuator. That is the pulsing pedal feel. Of course this happens in the blink of an eye.
There is something I am missing, though. I say this because I've had a look at the 350z FSM (BRC section) and the actuator is very similar to the A32. There is a mysterious reservoir in the actuator. I wonder what would happen if you closed all of the outlet solenoids, and opened the inlet solenoid only for the wheel that was spinning. I think you might be able to pump fluid into that caliper. This is as long as you didn't pump it back into the MC.
What you would need is some valve between the MC and ABS actuator to prevent the fluid from being forced into the MC. Under normal operating conditions, when the ABS activates, you are panic braking (or maybe the road are slippery), so the hydraulic pressure from your foot keeps the fluid in the ABS actuator. But this is also why you feel the pedal pulsate. If the same system were to be used as I've described, you would need to stop this flow of fluid. That is where one of the "line lock" solenoids you mention would come into play.
There is also a "gradient switch" in the a32 system. It looks like it switches the line from the MC from wide open to a small orifice. I don't know how it is controlled though.
03-05-2012, 08:49 PM
#7
You can do this for pretty cheap with some creativity...
1. just get yourself a set of electric trailer brakes. mount them as secondary brake calipers.
2. write a program that watches the wheel speeds of both front wheels and compares them to the rears..
3. If the fronts are significantly higher, then determine which corner has the highest wheel speed.
4. fire a PWM or a graduated output to a power transistor that feeds the trailer brakes to slow down the fastest wheel.
profit.
OR....
get a better differential and learn to feather the throttle.
1. just get yourself a set of electric trailer brakes. mount them as secondary brake calipers.
2. write a program that watches the wheel speeds of both front wheels and compares them to the rears..
3. If the fronts are significantly higher, then determine which corner has the highest wheel speed.
4. fire a PWM or a graduated output to a power transistor that feeds the trailer brakes to slow down the fastest wheel.
profit.
OR....
get a better differential and learn to feather the throttle.
03-08-2012, 04:31 PM
#8
Matt I know I can buy a HLSD and call it a day. That's not what this tread is about though. I like the idea of taking original equipment and re-purposing it with some ingenuity. Honestly, I don't even drag race. I'm just the curious type, trying to make something I have better.
03-17-2012, 04:16 PM
#11
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