The Next Step in Tuning Your EVO - EBD
Jan 22, 2007, 07:54 PM
#1
The Next Step in Tuning Your EVO - EBD
Electronic Brakeforce Distribution
A quick refresher:
"Electronic brakeforce distribution (EBD) is an automobilebrake technology that automatically varies the amount of force applied to each of a vehicle's brakes, based on road conditions, speed, loading, etc. Often coupled with anti-lock braking systems, EBD can apply more or less braking pressure to each wheel in order to maximize stopping power.
In a hydraulic brake system not equipped with EBD, there is a fixed front-to-rear brake force bias which is determined by the hydraulic components (for example, caliper piston diameter). This bias may be shifted under heavy braking, by means of a mechanical proportioning valve, to prevent rear-wheel lockup. EBD instead applies brake force precisely through electronic control. It recognises that driving conditions, braking situations and vehicle weight distributions are unique and constantly changing. Working together with Anti-lock Braking System (ABS), EBD uses sensors to determine which wheels would provide maximum braking for the conditions – whether that's the front or rear wheels, the left or right. The final result is more precise and effective braking under all conditions. "
The EBD program from the factory is optimized for a stock EVO running stock suspension, wheels, tires, differentials, etc. on the average road conditions. As you change some of these systems, I would think that the optimal braking strategy would also change.
So, is the EBD controlled by the ABS computer? The ACD controller is beginning to be explored and exploited to improve performance. Do you think there are some gains to be made on the racetrack by tweeking the EBD setting of the EVO??
EVOlutionary
A quick refresher:
"Electronic brakeforce distribution (EBD) is an automobilebrake technology that automatically varies the amount of force applied to each of a vehicle's brakes, based on road conditions, speed, loading, etc. Often coupled with anti-lock braking systems, EBD can apply more or less braking pressure to each wheel in order to maximize stopping power.
In a hydraulic brake system not equipped with EBD, there is a fixed front-to-rear brake force bias which is determined by the hydraulic components (for example, caliper piston diameter). This bias may be shifted under heavy braking, by means of a mechanical proportioning valve, to prevent rear-wheel lockup. EBD instead applies brake force precisely through electronic control. It recognises that driving conditions, braking situations and vehicle weight distributions are unique and constantly changing. Working together with Anti-lock Braking System (ABS), EBD uses sensors to determine which wheels would provide maximum braking for the conditions – whether that's the front or rear wheels, the left or right. The final result is more precise and effective braking under all conditions. "
The EBD program from the factory is optimized for a stock EVO running stock suspension, wheels, tires, differentials, etc. on the average road conditions. As you change some of these systems, I would think that the optimal braking strategy would also change.
So, is the EBD controlled by the ABS computer? The ACD controller is beginning to be explored and exploited to improve performance. Do you think there are some gains to be made on the racetrack by tweeking the EBD setting of the EVO??
EVOlutionary
Jan 23, 2007, 05:22 AM
#2
Hmm The EBD/EBC (electronic Brake Force control) I think just directs the brake force away from locked wheels. But My braking system is completely stock and locking a wheel is rather difficult. Even though those gigantic brembos are clamping down on the rotor so hard, the car just stops and doesn't skid. I have compley stock suspesnsion and Wheels and BRakes. But I suppose it could very well be throw off alittle by biger wheels or something. I guess we have to wait for a reply from someone with after market wheels to see if they see a difference with the stock braking system.
Jan 23, 2007, 06:10 AM
#3
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From reading the mitsu website I took it that EBD was in fact a glorified system of ABS in that it not only tells the binders to be on or off but how hard. For this reason we should not have quite the same angry chatter that we get from other ABS systems as they modulate on/off/on/off/on/off.
As for how it would respond to mods, it only makes sense that this system may be more sensitive to change in that they take more factors into account than just wheel speed. With that said I would also think that like most OEM systems there would be a decent margin for error.
As for performance applications, it seems that the same system could be used in the same way ABS systems are for traction control but with a much better result with less obtrusive bad habits. Not exactly the sort of thing that the aftermarket often messes with but still an interesting thought.
As for how it would respond to mods, it only makes sense that this system may be more sensitive to change in that they take more factors into account than just wheel speed. With that said I would also think that like most OEM systems there would be a decent margin for error.
As for performance applications, it seems that the same system could be used in the same way ABS systems are for traction control but with a much better result with less obtrusive bad habits. Not exactly the sort of thing that the aftermarket often messes with but still an interesting thought.
Jan 23, 2007, 08:50 AM
#4
I think the EVO EBD system takes into account wheel speed, steering angle, yaw, braking force, and maybe a couple other variables.
I would say the difference in available braking traction between the 4 wheels will be higher with bigger, stickier tires. For example:
Dunno if it works like that - just a thought?
EVOlutionary
I would say the difference in available braking traction between the 4 wheels will be higher with bigger, stickier tires. For example:
Stock Tires/suspension
Lets say you have 40 "Traction Units" available. When driving in a straight line you may have 11TU available for each of the front tires and 9TU available for each rear tire. When you hit the brakes and take a sharp right turn, the right rear tire loses alot of weight and traction (sometimes comes off the ground), and the front left tires gains alot of weight and traction, so now the distribution might be LF-17 RF-11 LR-11 RR-1.
Big Fat Sticky Tires/good suspension
Now lets say you have 80TU's available. In the same braking and turning scenario as above the distribution might be LF-35 RF-22 LR-22 RR-1
So you have a higher ratio of available traction between the LF and RR wheels, and if you could adjust the EBD to apply more power to the LF - you could get more braking force to the ground before the RR wheel locks up.Lets say you have 40 "Traction Units" available. When driving in a straight line you may have 11TU available for each of the front tires and 9TU available for each rear tire. When you hit the brakes and take a sharp right turn, the right rear tire loses alot of weight and traction (sometimes comes off the ground), and the front left tires gains alot of weight and traction, so now the distribution might be LF-17 RF-11 LR-11 RR-1.
Big Fat Sticky Tires/good suspension
Now lets say you have 80TU's available. In the same braking and turning scenario as above the distribution might be LF-35 RF-22 LR-22 RR-1
Dunno if it works like that - just a thought?
EVOlutionary
Jan 23, 2007, 09:22 AM
#5
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In order to tune EBD, I think we first need to know:
- What is it's intent: Is the algorithm written to induce a yaw moment during turn in (more braking force to the inside wheels) or to limit lockup of unwieghted wheels and stablize the car while braking (more braking force to the outside wheels)...or is it some cobination of the above, more braking force to the inside wheels during turn in, then tranfer braking force to the outside wheels as lateral forces climb.
- What mechanism does it use to distribute brake forces to each wheel independently.
Jan 30, 2007, 12:25 AM
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From what I can gather, the EBD & ABS ECU is integrated into the hydraulic controller located on the firewall on the passenger side of the engine compartment.
Brake pressure can be varied left to right and front to back by use of solenoid valves.
What follows is a more specific explanation, anybody know how to tap into the ABS ECU?
Brake pressure can be varied left to right and front to back by use of solenoid valves.
What follows is a more specific explanation, anybody know how to tap into the ABS ECU?
SPORTS ABS
• 4-wheel independent control optimizes the brake
force to each wheel to achieve a balance of
improved braking force and braking stability.
• A steering angular velocity sensor was added to
monitor the steering angle status. Braking force is
altered in response to the steering status to
improve the quality of steering when braking in
corners.
• The steering angular velocity sensor, lateral G-sensor
and longitudinal G-sensor accurately
monitor driving conditions and optimize ABS control
to match the specific driving conditions.
force to each wheel to achieve a balance of
improved braking force and braking stability.
• A steering angular velocity sensor was added to
monitor the steering angle status. Braking force is
altered in response to the steering status to
improve the quality of steering when braking in
corners.
• The steering angular velocity sensor, lateral G-sensor
and longitudinal G-sensor accurately
monitor driving conditions and optimize ABS control
to match the specific driving conditions.
EBD (Electronic Brake-force Distribution
system)
system)
• Rear brake power is electronically controlled to
optimize performance in accordance with road
and load conditions and to ensure optimal distribution
of braking force between the front and rear
brakes.
• Rear brake fluid pressure control employs a
brake modulator hydraulic unit solenoid valve that
made it possible to eliminate the pressure control
valves (proportioning valves).
• Effective use of rear wheel brake force reduces
temperature build-up in the front brakes under
hard braking conditions.
• Independent control of the left and right rear
brakes when braking during cornering achieves a
balance of improved vehicle stability and braking
force.
optimize performance in accordance with road
and load conditions and to ensure optimal distribution
of braking force between the front and rear
brakes.
• Rear brake fluid pressure control employs a
brake modulator hydraulic unit solenoid valve that
made it possible to eliminate the pressure control
valves (proportioning valves).
• Effective use of rear wheel brake force reduces
temperature build-up in the front brakes under
hard braking conditions.
• Independent control of the left and right rear
brakes when braking during cornering achieves a
balance of improved vehicle stability and braking
force.
Jul 9, 2008, 08:37 PM
#7
So, bringing this back from the dead, if one were to modify the parameters of the EBD system so that it locked up the outside rear tire MORE, it could help induce trail-braking OVERSTEER to help the car rotate into a corner. . . no?
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Jul 10, 2008, 09:35 AM
#9
Adding front inside brake force on the other hand will immediately add a destabilizing yaw moment proportional to the amount of braking force added. Similar effect to having toe out on the front.
although in general I would be against using the brakes to promote rotation in a racing class where the suspension is adjustable. If the suspension were setup around good steady state balance, underbraking the car becomes substantially more unstable. meaning turn in shouldn't be a problem under braking. if it is there are other issues at hand. Probably toe compliance.
In my experience the EBD system adds a significant amount of stability under braking. I have no idea how it actually does it, but if i were to guess I would say the system is using the various sensors to measure the oversteer/understeer of the car and if it sees oversteer over some threshold it increases braking force to the outside front (or decreases braking force to the inside front) to keep the car from spinning. The confidence gained from knowing that you can't spin the car under braking really allows the drivers to attack corner entry. It also allows the car to be setup closer to a neutral balance because you don't have to compromise the steady state setup to keep the car from spinning under brakes (or have the driver ***** foot the braking zone).
So even if i had the ability to change the ebd programming, I wouldn't.
Something else I just thought of. The non sport version of EBD used on pretty much everyother car with abs only means that the company saves money on putting proportioning valves on the rear brakes and the just let the rear wheels over brake until they lockup and the let the abs handle the biasing from there. The evo also does this, so the rear brakes should already be doing as much braking as they can. Not much head room to increase the rear bias unless you just want the rears to just stay locked.
Last edited by griceiv; Jul 10, 2008 at 09:53 AM.
Jul 11, 2008, 09:53 AM
#10
Not trying to start an argument here just want to state my thoughts on the situation:
Generally more rear brake bias going into a turn will create oversteer, not necessarily snap oversteer unless you're actually locking the rear wheels which ABS should prevent. Creating a controlled amount of oversteer during turn-in using brake distribution is common practice on racecars. The reason most cars come standard with generous amounts of front bias to prevent the general public from spinning around if someone decides to use the brakes while in a corner.
As far as left-right proportioning goes if more brake force is sent to the inside wheels during a turn this would aid in rotation of the car again unless lock-up occurs, which would be common since weight is shifted to the outside of the car. Since we're talking about front-heavy Evo's here braking hard going into a turn the inside rear wheel will have very little weight on it if it isn't already hangin in the air therefor sending brake bias to that corner would do no good.
I'm sure the stock EBD computer does a good job of keeping everything in check but I would think it could be beneficial to have it tweaked for a more racing oriented distribution. Perhaps the amount of force and/or speed at which the system reacts to certain situations could be made better.
P.S. EVOlutionary thanks for linking to this over on the other thread.
Generally more rear brake bias going into a turn will create oversteer, not necessarily snap oversteer unless you're actually locking the rear wheels which ABS should prevent. Creating a controlled amount of oversteer during turn-in using brake distribution is common practice on racecars. The reason most cars come standard with generous amounts of front bias to prevent the general public from spinning around if someone decides to use the brakes while in a corner.
As far as left-right proportioning goes if more brake force is sent to the inside wheels during a turn this would aid in rotation of the car again unless lock-up occurs, which would be common since weight is shifted to the outside of the car. Since we're talking about front-heavy Evo's here braking hard going into a turn the inside rear wheel will have very little weight on it if it isn't already hangin in the air therefor sending brake bias to that corner would do no good.
I'm sure the stock EBD computer does a good job of keeping everything in check but I would think it could be beneficial to have it tweaked for a more racing oriented distribution. Perhaps the amount of force and/or speed at which the system reacts to certain situations could be made better.
P.S. EVOlutionary thanks for linking to this over on the other thread.
Jul 14, 2008, 12:08 PM
#12
Not trying to start an argument here just want to state my thoughts on the situation:
Generally more rear brake bias going into a turn will create oversteer, not necessarily snap oversteer unless you're actually locking the rear wheels which ABS should prevent. Creating a controlled amount of oversteer during turn-in using brake distribution is common practice on racecars. The reason most cars come standard with generous amounts of front bias to prevent the general public from spinning around if someone decides to use the brakes while in a corner.
Generally more rear brake bias going into a turn will create oversteer, not necessarily snap oversteer unless you're actually locking the rear wheels which ABS should prevent. Creating a controlled amount of oversteer during turn-in using brake distribution is common practice on racecars. The reason most cars come standard with generous amounts of front bias to prevent the general public from spinning around if someone decides to use the brakes while in a corner.
As far as left-right proportioning goes if more brake force is sent to the inside wheels during a turn this would aid in rotation of the car again unless lock-up occurs, which would be common since weight is shifted to the outside of the car. Since we're talking about front-heavy Evo's here braking hard going into a turn the inside rear wheel will have very little weight on it if it isn't already hangin in the air therefor sending brake bias to that corner would do no good.
Jul 15, 2008, 10:44 AM
#14
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our ABS/EBD system is one part of the active yaw control systems found on JDM models. the system monitors not only the angle of steering input, but how fast you turn the wheel.
Try it... on a slippery surface, hit the brakes hard enough to activate the ABS and cut the wheel hard...
