Mitsubishi Lancer Evolution X
ASC Off = does NOT cut power but still uses individual braking control (not sure if it's all the time or only sometimes)
Hold ASC OFF for 3 sec = no cutting power and no individual braking control
-The MR has 11 pounds more sound insulation than the GSR
-The Enkei cast alloy GSR wheels weigh 22 pounds, while the BBS forged MR wheels weigh just under 20.
AYC / ACD System Explained:
The AYC (active yaw control) and ACD (active center differential) system in the Evolution X is very complicated mechanically and there has been much interest in how to service the system.
There are three main parts of the system:
1) The Transfer Case. This houses the ACD clutch pak and the ACD activation ring piston circuit. It also houses the front differential and parts of the center differential (actual center diff is in Transaxle on both 5 speed and SST).
2) The Rear Differential. This houses the AYC clutch paks (there are two, one for the left wheel and one for the right wheel) and the AYC activation ring piston circuits (there are two as well). It also houses the rear differential.
3) The ACD / AYC Pump. This is in the rear passengers side fender / bumper. This pump produces hydraulic pressure to active the AYC and ACD circuits, which can be as high as 150 PSI. It also has an accumulator to store pressure (around 300 PSI). This pump is connected to the reservoir in the trunk.
AYC - dual line, dual clutch pack (right and left) circuit.
AWC-ECU performs a calculation based on the information from ECU, sensors, and switches. Then,
based on the calculation value, it appropriately operates the hydraulic units (for ACD, AYC, ASC, ABS) to
control in response to the driver's operations and
vehicle behaviors.
Item
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Control content
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ACD transfer
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The basic structure and operation are the same with EVOLUTION IX, but the
strength of each part has been enhanced to support the high-powered
engine.
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AYC differential
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The basic structure and operation are the same with EVOLUTION IX, but the
strength of each part has been enhanced to support the high-powered
engine.
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Hydraulic unit (For ACD/AYC)
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The basic structure and operation are the same with EVOLUTION IX, but the
shape has been changed to accommodate the change of on-vehicle layout.
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Hydraulic unit (for ASC/ABS)
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In addition to the brake control of ASC and ABS, it also performs the AYC
brake control.
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AWC-ECU
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Based on the information obtained via CAN communication and others, it
appropriately controls ACD, AYC, ASC, and ABS.
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Sensors
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Adding to the sensors (throttle position sensor, G sensor, steering sensor,
wheel speed sensor) that provided information to EVOLUTION IX, the
following sensors have been equipped: Engine torque sensor, engine speed
sensor, yaw rate sensor, and wheel cylinder brake fluid pressure sensor.
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Two lines go to the AYC but they are for two different clutches, and one line goes to the ACD. There are NO RETURN LINES.
With the cornering performance of when vehicle is
steered to trace a turning circle of certain radius
while the speed is gradually increased, the understeer is further suppressed compared to the
ACD/AYC control adopted with EVOLUTION IX,resulting in a further improvement to cornering per-
formance. For the quick steering lane change on a
slippery road surface, the stability and convergence
of vehicle behavior at the completion of lane change
have also been improved.
In addition to the conventional lateral torque movement control, a new brake control has been added to
AYC. It is activated near the driving limit range to
assist the yaw motion control.
Brake force is applied to the inside wheels while the
vehicle behavior is understeer during cornering, and
to the outside wheels when oversteer, achieving the
vehicle cornering performance that corresponds to
the driver's operation. Also, the spinning of front
wheels at vehicle start is suppressed by the brake
force, improving the traction performance.
This brake control can be deactivated with the ASC OFF switch.
This brake control can be deactivated with the ASC OFF switch.
EFFECTS OF BRAKE CONTROL:
The understeer behavior and oversteer behavior near the driving limit range are further suppressed.
INTEGRATED CONTROL OF ACD/AYC/ASC/ABS:
ASC has been added to ACD, AYC, and ABS that are equipped with LANCER EVOLUTION IX, and an integrated control is performed to enhance the driv- ing performance, cornering performance, and stabil- ity in any driving condition during acceleration, deceleration, and cornering.
ADDITION OF TC-SST CONTROL <VEHICLES WITH TC-SST>:
For vehicles with TC-SST, AWC-ECU communicates with TC-SST-ECU via CAN line to suppress unnecessary gear shifts during cornering which hamper the sport driving.
The understeer behavior and oversteer behavior near the driving limit range are further suppressed.
INTEGRATED CONTROL OF ACD/AYC/ASC/ABS:
ASC has been added to ACD, AYC, and ABS that are equipped with LANCER EVOLUTION IX, and an integrated control is performed to enhance the driv- ing performance, cornering performance, and stabil- ity in any driving condition during acceleration, deceleration, and cornering.
ADDITION OF TC-SST CONTROL <VEHICLES WITH TC-SST>:
For vehicles with TC-SST, AWC-ECU communicates with TC-SST-ECU via CAN line to suppress unnecessary gear shifts during cornering which hamper the sport driving.
The main electric pump : operates at 12v (relay circuit) constant, 2-3
amp draw. Operates only when the pressure sensor drops below 2 volts
(this means there is less than 150psi left in the accumulator).
Both gear oil (Diaqueen LSD or equivalent) and ATF fluid (Diaqueen SP3 or equivalent) is used in the system.
The pressure sensor : is supplied with 5v constant, also has it's own
ground. It OUTPUTS between .5v-2.7V. The low end of the range means no
pressure in the system the higher end reading (2.7v max) is MAX
pressure. When it reaches 2.7v and above, it SHUTS down the pump and
shuts down the AYC. They call this the "Fail-safe" function.
The AYC proportioning valve : operates between 0-4v. The low end of the
range (zero volts) means it's completely closed. The high end of the
range (4v) means the valve is completely open, therefore allowing ALL
pressure that is available to go to the clutch pack that has been
selected. It draws between 0-500milliamps when working.
The AYC RH and LH directional valves : operate at 12v constant, and are either ON (open) or OFF (closed).
Bleeding in these steps:
1) ACD (transfer case). Jack up the car, open the bleeder screw (there is just one). Make sure you have plenty of fluid in the reservoir. Attach a long clear vinyl tube (I think 1/4 or 3/8" is good, Home Depot has it) to the bleeder. Turn the ignition "ON" and then floor the gas pedal (obviously do not start the car). Do this 4 or 5 times or until you see a stream of fluid (without air) in the clear vinyl tube. Then close the bleeder and your done.
2) Bleed the AYC (this is the part I am working on with the plan to build a custom electronics box to do it). It's more complicated with the AYC because it's two circuits and there are actually two bleeders, side by side, where the lines attach to the diff. They are hiding behind the rear sub frame, so it's difficult to see them. One you hook up a clear vinyl hose to and the other you just open up. Fluid comes out of the one on the left and air bubbles on the right.
No reason you can't bleed the ACD and then wait to bleed the AYC, but you MUST do the ACD first. You CANNOT drain the ACD and then not do the bleed process described in step (1)!!! You would be running a completely dry ACD then, (1) !!!
1) ACD (transfer case). Jack up the car, open the bleeder screw (there is just one). Make sure you have plenty of fluid in the reservoir. Attach a long clear vinyl tube (I think 1/4 or 3/8" is good, Home Depot has it) to the bleeder. Turn the ignition "ON" and then floor the gas pedal (obviously do not start the car). Do this 4 or 5 times or until you see a stream of fluid (without air) in the clear vinyl tube. Then close the bleeder and your done.
2) Bleed the AYC (this is the part I am working on with the plan to build a custom electronics box to do it). It's more complicated with the AYC because it's two circuits and there are actually two bleeders, side by side, where the lines attach to the diff. They are hiding behind the rear sub frame, so it's difficult to see them. One you hook up a clear vinyl hose to and the other you just open up. Fluid comes out of the one on the left and air bubbles on the right.
No reason you can't bleed the ACD and then wait to bleed the AYC, but you MUST do the ACD first. You CANNOT drain the ACD and then not do the bleed process described in step (1)!!! You would be running a completely dry ACD then, (1) !!!
Some consensus info:
1) You NEVER need to change, drain, bleed, or otherwise service the fluid in the ACD/AYC pump circuit UNLESS lines where removed, the differentials where replaced, or the system experiences catastrophic failure. Just keep it in between the levels in the reservoir in the trunk. Bleeding the system requires the Mut3 factory tool and costs $$$ at the dealer, the procedure is a real PITA. Evoscan may support this in the future.
2) The fluid in the AYC / ACD pump circuit (fed by the reservoir in the trunk) is ISOLATED completely from the ATF fluid in the rear differential (clutch paks) and the gear oil in the transfer case (both in the clutch pak and the rest of the case). The fluids should NEVER mix.
3) A big thing that throws most people into confusion is that the ACD clutch pak sits in gear oil, and the AYC clutch paks sit in ATF fluid. Neither is pressurized. The fluids just sit there and lube the clutches, there is an air pocket at the top in ALL CLUTCH PAKS.
4) The ACD / AYC Pump (called the "Hydraulic Unit" in the service manual) uses high pressure to activate the ACD and AYC clutches.
5) If you notice the level of fluid fluctuate slightly in the rear reservoir for the ACD / AYC Pump circuits, it's normal. If it becomes completely filled and overflows or it runs completely out of fluid there is a problem, at this point the system will most likely throw codes and warnings.
6) Change your gear oil in the Tranny Case every 30k miles for normal use. Change it every 15k miles for severe conditions and track use.
7) Change your ATF fluid and gear oil in the Rear Differential every every 30k miles for normal use. Change it every 15k miles for severe conditions and track use.
8) Various problems plague the ACD / AYC pump (Hydraulic Unit) but most have to do with something called "Galvanic Corrosion". This occurs when two dissimilar metals with a fluid layer in between them form corrosion. There is no real solution to this problem in terms of preventative maintenance except changing the fluid in the Transfer Case and Rear Differential (gear oil and ATF) more often. DO NOT service/change/drain the fluid in the AYC / ACD pump in terms of preventative maintenance. Keep it at the correct level and make sure it's not brown and smelly (indicates BIG failure) and your good.
1) You NEVER need to change, drain, bleed, or otherwise service the fluid in the ACD/AYC pump circuit UNLESS lines where removed, the differentials where replaced, or the system experiences catastrophic failure. Just keep it in between the levels in the reservoir in the trunk. Bleeding the system requires the Mut3 factory tool and costs $$$ at the dealer, the procedure is a real PITA. Evoscan may support this in the future.
2) The fluid in the AYC / ACD pump circuit (fed by the reservoir in the trunk) is ISOLATED completely from the ATF fluid in the rear differential (clutch paks) and the gear oil in the transfer case (both in the clutch pak and the rest of the case). The fluids should NEVER mix.
3) A big thing that throws most people into confusion is that the ACD clutch pak sits in gear oil, and the AYC clutch paks sit in ATF fluid. Neither is pressurized. The fluids just sit there and lube the clutches, there is an air pocket at the top in ALL CLUTCH PAKS.
4) The ACD / AYC Pump (called the "Hydraulic Unit" in the service manual) uses high pressure to activate the ACD and AYC clutches.
5) If you notice the level of fluid fluctuate slightly in the rear reservoir for the ACD / AYC Pump circuits, it's normal. If it becomes completely filled and overflows or it runs completely out of fluid there is a problem, at this point the system will most likely throw codes and warnings.
6) Change your gear oil in the Tranny Case every 30k miles for normal use. Change it every 15k miles for severe conditions and track use.
7) Change your ATF fluid and gear oil in the Rear Differential every every 30k miles for normal use. Change it every 15k miles for severe conditions and track use.
8) Various problems plague the ACD / AYC pump (Hydraulic Unit) but most have to do with something called "Galvanic Corrosion". This occurs when two dissimilar metals with a fluid layer in between them form corrosion. There is no real solution to this problem in terms of preventative maintenance except changing the fluid in the Transfer Case and Rear Differential (gear oil and ATF) more often. DO NOT service/change/drain the fluid in the AYC / ACD pump in terms of preventative maintenance. Keep it at the correct level and make sure it's not brown and smelly (indicates BIG failure) and your good.
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