MME Motorsport GCU7 User manual

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Gear Control Unit
GCU7 Manual

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Contents
Contents........................................................................................................................................................ 2
I. GENERAL OPERATING GUIDE................................................................................................................ 3
II. CONNECTING TO THE GCU.................................................................................................................... 3
III. UPGRADING THE FIRMWARE................................................................................................................ 5
IV. GAUGES OVERVIEW .............................................................................................................................. 6
V. GENERAL/SENSORS............................................................................................................................... 7
VI. H-PADDLE SHIFTER ACTUATORS SETUP.............................................................................................. 11
VII. H-PADDLE SHIFTER ACTUATORS SETUP - ADVANCED ........................................................................ 13
VIII. UP........................................................................................................................................................ 14
IX. DOWN ................................................................................................................................................. 18
X. CLUTCH................................................................................................................................................ 21
XI. MISC/LOGGING ...................................................................................................................................25
XII. SEQUENTIAL GEARBOX –QUICKSTART...............................................................................................27
XIII. H PATTERN GEARBOX –QUICKSTART .................................................................................................29
XIV. FREQUENTLY ASKED QUESTIONS AND TROUBLESHOOTING.............................................................. 32

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I. GENERAL OPERATING GUIDE
-In order to shift from Neutral to 1st, you need to press clutch + N/R button + paddle up. Clutch
and N/R checking can be deactivated in the software, but we do not recommend it. There’s
always a chance that someone would accidently touch the paddle while the car is running,
causing the car to start driving without driver control.
-Similarly, when shifting from 1st to Neutral (or Neutral to Reverse), you need to press clutch +
N/R button + paddle down. Again, Clutch and N/R button can be deactivated in the software.
-In H pattern mode, pressing the clutch + N/R button for 3 seconds restores the gear to neutral
from any position (even if invalid)
-For H pattern, synchromesh mode (with clutch actuator), to shift from neutral to 1st, you need to
press brake and shift up. When you release the brake, car will start moving.
II. CONNECTING TO THE GCU
GCU7 uses CAN BUS to connect to the computer so special interface is needed.
GCU Interface uses FTDI drivers which are usually already installed by default. If you’re having detecting
USB device, go to FTDI site and download the VCP drivers for your OS.
If you have USB CAN 3 and GCU with LED diode (on the side), you don't need to do anything else. CAN
Interface port is high speed (CAN FD) and is already terminated so you just need to connect the
connector.
For GCU without the LED connector, follow the instructions below:
Each CAN BUS must be properly terminated (by 100-120 ohm resistor) on each side.
If you’re connecting to a car that already has a CAN BUS, nothing is really needed, because your CAN
BUS is already properly terminated. You just need to connect the CAN+ and CAN- to existing line and
that’s it.
If your car does not have CAN BUS or you’re only connecting the GCU7 on a test bench, you need to
insert a jumper in the GCU interface to successfully connect to the GCU.

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Remove the two screws:
Insert a jumper:
Please note: all GCU interfaces come with jumpers installed so if you’re connecting to the existing CAN
BUS, you need to remove the jumper.

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III. UPGRADING THE FIRMWARE
Please note that firmware and software are published together and they must match. If they do not
match, serious problems can occur so always make sure the version of the firmware and software is the
same!
Steps to upgrade the firmware:
-Download and run the new software
-Wait for the device to connect and read the settings from the device. Make sure you wait for all
the settings to load!
-Save the settings to a file, let’s call this file “before.dat”
-Open upgrade window, click open and select firmware .bin file (that matches the version of the
software)
-Click connect to device and turn the device off and on so device is found and is ready to
upgrade.
-Once it’s connected, click write new firmware and wait for it to finish.
-Turn the device off and on, wait for the settings to finish loading, then open the “before.dat” file
using the file->load settings and send new settings to the GCU. After the upgrade, all outputs are
disabled due to safety reasons, so you need to send the settings to the GCU to activate them
back.
-Turn the device off/on and enjoy the new firmware 

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IV. GAUGES OVERVIEW
RPM
RPM Gauge shows number of RPM.
GEAR POSITION SENSOR - GPS
Gear position sensor as the GCU sees it. Green field represents a gear and the range where gear is valid.
Gear ranges are only used if GCU is in “Sequential” mode. In H-Paddle Shifter mode, gear position is
calculated based on the position of the actuators & shifting direction. GPS value under the gauge is
degrees and raw value of the position sensor in the brackets.
If vehicle speed is enabled, you will find detected speed under the RPM along with the calculated rpm
based on the current gear.
THROTTLE POSITION SENSOR –TPS
0 - 100% of the throttle pedal pressed.
AIR PRESSURE
Air pressure in bar if air pressure transducer is used, otherwise only simulated number is shown
(minimum pressure from the compressor tab)
CURRENT GEAR
Gear which the gearbox is in. Total shifts is number of shifts since the last counter reset. Counter can be
reset by pressing the RST button next to the gear.
INPUTS & OUTPUTS
Status of each input and output. If active, it’s marked with white on red.
TESTS
By pressing one of the buttons it manually triggers the command. Please note that UP and DOWN
actuators are only available when Sequential Gearbox is used.

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V. GENERAL/SENSORS
Please note: if any parameter is changed, settings must be sent to the GCU (Settings –send to GCU or
Send Changed to GCU - F5) in order to take effect.
GEARBOX
There are currently two types of gearboxes supported. Sequential & H-Paddle Shifter (Synchro /
Dogbox).
Gearbox Type: Sequential
This is regular sequential gearbox with up/down movement. Only two valves (1 two way actuator) is
used in this configuration.
Gearbox type: Type: H / Synchro or H / Gearboxes
H-Paddle is MME Motorsport actuator assembly that controls 8 valves and shifts any H pattern. For
more H-Paddle Shifter options see H-Paddle Shifter actuators.
Number of forward gears is in the Number of gears dropdown.
Mid neutral
If gearbox with neutral between the 1 and R is used (like Sadev ST75), this option is used to allow the
GCU to shift only partially. See MISC/LOGGING for setting up the neutral.

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Gear ratios
Gear ratio for each gear. GCU will calculate the safe RPM for each gear, according to max engine RPM
under the Down tab. See Downshifting for more info.
FD is final drive ratio and is currently only used for if speed sensor is enabled. Can be ignored in most of
applications.
CAN BUS
Enable to use CAN BUS support. Power to the GCU must be cycled if CAN BUS is enabled (and was
previously disabled). If CAN BUS speed is unknown, 500 Kbps and 1000 Kbps are common values in
automotive industry.
THROTTLE POSITION SENSOR –TPS
There are two types of TPS readings available
Type: Potentiometer
This is standard 3 pin potentiometer found on almost every car. When this type is selected, GCU pin B1
must be connected to analog 0-5V sensor. This sensor must first be calibrated. See TPS CALIBRATION
below.
Type: CAN
Reads the TPS value from CAN BUS. No calibration is needed.
Type: Integrated DBW
This option is only supported in GCU versions that have 2 CAN BUS connectors and a LED indicator on
top. These GCU can control the DBW directly. See wiring.
CAN Device
If CAN is enabled select the ECU you have. If your ECU is not in the list, please contact us with car info
and ideally CAN BUS dataset so we include this in the software & firmware.
TPS calibration
TPS sensor must first be calibrated. TPS sensor is calibrated in a way that user presses and releases the
pedal and GCU stores the sensor value and calculates the % of pedal press.
To start, click the CALIBRATE button and follow the instructions. Press the throttle & click the button
again, then release it and click the button again. Don’t forget to send the data to the GCU.
TACHO SENSOR
There are two types of TACHO sensors supported.
Type: Pulse
This is standard 0-12V pulse generated by the ECU. See ECU pinout for your car.
When this type is selected, GCU pin M4 must be connected to the corresponding pin on your ECU.

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Type: CAN
Reads the RPM from CAN BUS.
CAN Device
If CAN is enabled select the ECU you have. If your ECU is not in the list, please contact us with car info
and ideally CAN BUS dataset so we include this in the software & firmware.
Pulses / Rev
This is where you select how many cylinders you car have. This also depends on the tacho output of your
ECU so try few options if RPM reading is off.
Not used if CAN is used.
Pulses / Rev –Custom
If you car has unsupported TACHO pattern or is strangely off, you can enter a factor here.
Not used if CAN is used.
GEAR POSITION SENSOR
Gear position sensor is only available in Sequential mode.
There are 3 types of Gear Position Sensor available.
Type: Potentiometer
This is standard 3 pin potentiometer found on almost every sequential gearbox. When this type is
selected, GCU pin A2 must be connected to analog 0-5V sensor. This sensor must first be calibrated. See
GEAR CALIBRATION below.
Type: CAN
Reads the gear position from CAN BUS. This sensor must first be calibrated. See GEAR CALIBRATION
below.
Type: RM22
This is SSI sensor found in one of the older designs. It is now absolete.
CAN Device
If gear position is connected to the ECU and your ECU supports sending the value to the CAN BUS, select
the ECU you have. If your ECU is not in the list, please contact us with car info and ideally CAN BUS
dataset so we include this in the software & firmware.

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Gear calibration
In sequential mode, gears must be calibrated. By clicking Calibrate it will walk you through all of the
gears and store the values for each gear in the boxes next to the gear. Numbers in boxes are values (0-
1024) where gear is detected. You should shift up & down few times to see if the range is correct and
adjust accordingly. Second box next to a gear is the window in which this gear is still valid. Alternative to
the calibration is to just shift to a desired gear and press “<” label next to the box.
AIR PRESSURE SENSOR
Enabled if pressure transducer is installed on the bottle and connected to the GCU Pin A1. If you haven’t
specifically ordered this, this sensor is not available.
NEUTRAL SENSOR/SWITCH
This switch is used to prevent downshifts from 1st to N accidently. For most applications, Type Switch is
used. If switch is on, when it should be off (mechanically), you can Invert it.
CLUTCH SENSOR/SWITCH
This switch is activated when clutch is pressed, either manually or automatically. For most applications,
Type Switch is used. If switch is on, when it should be off (mechanically), you can Invert it.
If switch is disabled, switch is always off so every function in the system that counts on it, will fail.
Duration in milliseconds specifies how long we wait for the sensor to stabilize.
Typical value: 5 ms
SPEED SENSOR
Enable this if you have wheel speed sensor install (Not needed in most of applications).
H-PADDLE SHIFTER ACTUATORS
Only used if GCU is in H-paddle Shifter mode.
Window shows the position of each actuator. Before first use (or if actuators seem off), actuators need
to be configured and calibrated. Click Setup configure the gearbox shifting pattern (which way is
reverse, 1st –6th gear and so on), actuator tolerance and other H-Paddle Shifter actuator related
parameters and then Calibrate and follow the instructions. You can calibrate the actuators using the
Test button too. For more info on setup, see H-PADDLE-SHIFTER ACTUATOR SETUP
Test window is only used to verify the valve connections and allows you to turn on/off individual
actuator valve.

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VI. H-PADDLE SHIFTER ACTUATORS SETUP
This screen can be opened by clicking the Setup button on GENERAL/SENSORS tab in H-Paddle Shifter
actuator region.
Before configuring the shift patterns, make sure your Number of gears parameter is correct
(GENERAL/SENSORS)
For each gear you need to set the position of each actuator.
Vertical actuator (See shift pattern image) usually has 3 positions. Position 1 is fully closed, Position 2 is
half-way open, Position 3 is fully opened.

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Horizontal actuator can have 2, 3 or 4 positions, depending on number of gears and shift pattern.
Position 1 is fully closed.
On power on options allow to set up what actions are taken when you power up the gcu. Vertical
actuator: go to position 2 if invalid will move the vertical actuator to position 2 if position on power up
is not in the middle (2), completely out (3) or completely in (1). This allows you to always start with a
neutral gear if car stops somewhere “in between”. Horizontal actuator: lock if valid means that we lock
horizontal actuator from moving on power on if it’s in correct position (either 1, 2, 3 or 4 –depending on
the number of positions). This allows you to have direct shift ready when you start the car. If this
actuator is not locked, when shifting, GCU will run 3 commands, first it will move to neutral, then it will
move horizontal actuator in desired gear position and lastly, it will move vertical actuator to “in gear”
position.
Cylinder tolerance allows to set how much +/- of each position is still valid. For most applications, 20-30
is ok. Depending on selector wear or free-travel of each gear this will have to be adjusted.
Typical value: 20-40 mm for the vertical and 30 for horizontal.
Vertical/Horizontal sensor tolerance sets how much time (in milliseconds) particular sensor needs to be
in position to treat it as “stable”.

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VII. H-PADDLE SHIFTER ACTUATORS SETUP - ADVANCED
Here you can program the valves for each shift. More info on setting up these parameters coming soon.

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VIII. UP
Please note: if any parameter is changed, settings must be sent to the GCU (Settings –send to GCU or
Send Changed to GCU - F5) in order to take effect.
Allow shift N to 1: If disabled, the only way to shift from neutral to 1st, is by hand. If in H-Paddle Shifter
mode to shift to 1st gear, beside this switch enabled, clutch button must also be pressed.
Typical value: Disabled in Sequential mode, Enabled in H-Paddle Shifter mode
Allow shift from R to N: if disabled, the only way to shift from reverse to neutral, is by hand.
Typical value: Disabled in Sequential mode, Enabled in H-Paddle Shifter mode
Before the shift:
Min between shifts: the time in milliseconds allowed between shifts.
Typical value: 150 ms
Delay after cut: how many milliseconds after we cut the power, we actually shift. Please note that this
parameter excludes the Actuator preload. If you want to use delay after cut, actuator preload must be
set to zero.
Typical value: 0 ms
Actuator preload: how many milliseconds before the cut, we start the shift. Air valves usually need
around 20ms to fully open, so we can preload the actuator before cutting. Use higher value if pipes to
the valves are longer. Please note that this parameter excludes delay after cut. If you want to use
actuator preload, delay after cut must be set to zero.
Typical value: 15 ms for dogbox.

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During shift:
Switch UP/DOWN ports (sequential only): if checked, up and down output ports are swapped.
Restore power after (deg): This option allows you to return the power before the gear is completely in.
If this option is used, it’s very important that the engine ECU takes care of the soft power return
(gradually applying the full power). This way UP shift can be much smoother.
Typical value: 0 degrees.
Close throttle instead of CUT: If checked, instead of cutting the coil supply or sending “cut” signal, GCU
will close the throttle (only available if MME TBC or GCU DBW is used).
Cut over CAN: If enabled, you GCU will send the cut signal to various supported devices. If your device is
not listed, let us know.
After shift:
Keep in gear after shift (ms): how many milliseconds after the gear is engaged, we’re still pushing in.
Typical value: 50 ms
Keep cut after shift: how many milliseconds after the gear is engaged, we’re still cutting the power.
Typical value: 0 ms
Lever return actuator: one some sequential gearboxes, when actuators are mounted, the return spring
is too soft to return the gear lever back into the position. What this does is it pushes the actuator back
for specified milliseconds. Only used in Sequential mode.
Typical value: 10 –15ms if return is slow in sequential mode.
Shift timeout: how many milliseconds we wait for shift to be finished. If gear is not engaged in this
period, all the actuators are unlocked and power is restored.
Typical value: 500ms in dogbox, 1500 in synchro
Auto retry (on failed shift): if shift is not successful, this option allows the GCU to shift again once again.
If shit is not successful the second time, shift will fail. Not recommended in sequential mode and should
be disabled.
Typical value: Disabled.

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Autoshift:
Autoshift Mode: Defines the mode used. See below.
Activate after (rpm): After which RPM, Autoshift becomes active. RPM must be over this value to start
and, when active, If the rpm drop below this rpm, Autoshift is stopped. Please note that this is NOT the
rpm where GCU will shift the gear. That is defined in Autoshift at. Only used with 2 stage Autoshift.
While TPS over (%): This is the minimum TPS that needs to be set in order for the Autoshift to work. If
TPS drops below this value, Autoshift stops.
Autoshift at (rpm): At which RPM GCU will shift up.
Activate after 2nd gear: If this option is enabled, shifting 1-2 is done manually by the driver and
Autoshift will only work in 2-3 and higher. Only used with 3 stage Autoshift.
Autoshift Mode: 3 Stage
In order to use this mode, ECU must support launch control. GCU (Pin G1) will send »Launch« request to
the ECU and ECU input must be configured that when this happens, ECU goes into the launch mode
(Limit the RPM)
Procedure to start:
- Holding Autoshift button for more than 2 seconds, activates the Launch control. GCU sends active low
(ground) signal to the ECU via G1. ECU Must be able to enter Launch state. LED will be blinking slowly.
- While still holding the Autoshift button, we accelerate to a point that we don't need the Launch mode
anymore to accelerate freely (car gets enough grip to be able to push 100% throttle)
- We release the button and GCU deactivates the Launch mode (Pin G1), turning the Launch mode inside
the ECU off. LED is blinking faster.
- GCU will autoshift to the next gear when RPM is higher or equal to Autoshift at (rpm). If Activate after
2nd gear is enabled, it will only shift when in 2nd or higher gear. Driver needs to shift to 2nd gear in this
case manually by the paddle.
- Autoshift will continue to shift for as long as TPS is higher than While TPS over (%) and Paddle
up/down is not pressed. If TPS drops under the While TPS over (%) or up/down is pressed by the driver,
Autoshift will stop. LED is turned off.

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Autoshift Mode: 2 Stage
Procedure to start:
- Driver must turn the autoshift mode on with the autoshift switch. It’s important that this switch is
toggle (fixed position) and not momentary type. LED will turn on.
- When RPM is over the Activate after N rpm & While TPS is over %, autoshift mode is activated. LED
will be flashing.
- When RPM reaches the specified Autoshift AT rpm, it will automatically shift up. LED will still be
flashing.
- If throttle is below While TPS over (%) or if paddle up/down switch is pressed, auto shift is
automatically disabled. LED will be off.
- To turn on the auto shift mode driver must switch the autoshift off and on again.
Autoshift Mode: Rally: up shift only
- Autoshift switch must be on. LED will be on.
- When RPM is over or equal than Autoshift at (rpm) & throttle is higher or equal than While TPS is
over % it will automatically shift up.
- If Autoshift switch is deactivated, autoshift is disabled.
External cut:
External cut enabled: If enabled it allows to cut the engine via external switch. For this option, GCU Pin
C2 must be connected.
Typical value: Enabled for sequential (if system has a mechanical load/cut switch), Disabled for H-Paddle
Shifter Mode.
Wait for new gear and turn off: If enabled, cut will be active for as long as the gear is not engaged, but
not more than Max duration. If this option is disabled, cut will be active for fixed time, Max duration.
Typical value: Enabled.
Use strain gauge (pin B3), treshold: if this option is enabled, voltage on B3 pin will tell the GCU to shift if
voltage is over the treshold. Please note that voltage here is represented with a 10 bit value, so 0 = 0V
and 1024=5V. You can see current voltage in digital form next to the treshold window.
Max duration: Specifies the maximum duration of engine cut. Also see External cut - Wait for new gear
and turn off
Typical value: 600 ms.

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IX. DOWN
Please note: if any parameter is changed, settings must be sent to the GCU (Settings –send to GCU or
Send Changed to GCU - F5) in order to take effect.
Allow shift 1 to N: If disabled, the only way to shift from 1st to Neutral is by hand. If in H-Paddle Shifter
mode to shift to Neutral gear, beside this switch enabled, clutch & neutral button must also be pressed.
Typical value: Disabled in sequential mode, Enabled in H-Paddle Shifter mode.
Allow shift N to R: If disabled, the only way to shift from Neutral to Reverse is by hand. If in H-Paddle
Shifter mode to shift to Reverse gear, beside this switch enabled, clutch & neutral button must also be
pressed.
Typical value: Disabled in sequential mode, Enabled in H-Paddle Shifter mode.
Max engine RPM: Specifies the maximum rpm engine is allowed to reach after a downshift. Exact
downshift rpm is calculated based on a gear and gear ratio (see GENERAL/SENSORS). Which is the
calculated rpm is shown for each gear in the boxes below.
Example: If Max RPM for your engine is 6300 rpm and your second gear ratio is 3.571, GCU calculates
the Downshift if under rpm for second gear is 3928. What this means is that in second gear, you will not
be allowed to shift over 3928 rpm. If you’d shift down in second to first over 3928 rpm, in you would
reach more than 6300 rpm in 1st gear which is more than Max Engine RPM is.
Blip over CAN: If enabled, GCU will send the blip signal to various supported devices. If your device is
not listed, let us know.

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Before the shift:
Disable shift if TPS > %: If throttle is applied (more than Disable shift if TPS >) we don’t want to allow
downshift.
Typical value: For a dogbox Disable shift if TPS > 20
Min between shifts: the time in milliseconds allowed between shifts.
Typical value: 150 ms
Queued downshift:
If Enabled, GCU will allow the gears to be queued if RPM is too high or If Throttle is over degrees. What
this does is it allows the driver to preselect the desired gear while pushing the throttle. When throttle is
released and “safe” rpm is reached, GCU will automatically downshift. The harder you brake, the faster
GCU will downshift.
Typical value: Throttle is over 90 %, RPM is too high disabled.
Throttle blip:
Blip enabled: Enables throttle blip actuator. Throttle blip must be connected to GCU Pin J3. See wiring
diagram.
If MME Throttle Body Controller or Integrated DBW is used you can specify just how much you want to
blip the throttle (Blip amount), otherwise this option is disabled and you need to set the travel
mechanically. If MME TBC is used, you can set custom % for each gear using the Custom % for each
gear.
Typical value: Enabled on a dogbox, Enabled on synchro with DBW.
Disable blip if RPM <: If RPM is under this value, blip is not used. On a dogbox, blipping in low rpm
actually does more harm than good, so we don’t want the blip in low rpms.
Typical value: 3000.
Cut and wait for target tps max duration: the time in milliseconds we cut the power the same time we
apply the blip. This allows us to fully open the throttle before giving it the power to blip.
Typical value: 0 ms
Stop blip when revs match: if enabled, blip is applied until rpm for target gear is reached (or Max blip
duration has elapsed). Currently only used with clutch unit. If clutch is not used, leave this disabled. If
Cut after tps off is enabled, GCU cuts the ignition as soon as these RPMs are reached (instead of just
lifting off the throttle)
Blip until barrel moves: Stops blip when relative movement of the gear position sensor is N degrees.
Typical value: 0.
Max blip duration: Specifies what the maximum throttle blip duration is (in milliseconds). Even if
specified degrees are not reached, GCU stops the throttle blip.
Typical value: 100 ms.

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Close blip in ms: how many milliseconds does it take to close the blip (ramp). Only used with MME TBC
module.
Typical value: 0 ms.
After throttle blip:
Delay before activating valve: how many milliseconds after the throttle blip is closed we activate the
downshift actuator.
Typical value: 20 ms.
During shift:
Cut during shift: if checked, GCU will cut the ignition during movement of the actuator.
Switch UP/DOWN ports (sequential only): if checked, up and down output ports are swapped.
After shift:
Keep in gear after shift (ms): how many milliseconds after the gear is engaged, we’re still pushing in.
Typical value: 50 ms
Lever return actuator: one some sequential gearboxes, when actuators are mounted, the return spring
is too soft to return the gear lever back into the position fast enough. What this does is it pushes the
actuator back for specified milliseconds. Only used in Sequential mode.
Typical value: 10-15 ms.
Cut after successful shift: the time in milliseconds we cut the power after the shift is complete.
Typical value: 30 ms
Downshift timeout: how many milliseconds we wait for shift to be finished. If gear is not engaged in this
period, all the actuators are unlocked and power is restored.
Typical value: 500ms in dogbox, 1500 in synchro
Auto retry (on failed shift): if shift is not successful, this option allows the GCU to shift once again. If
shit is not successful the second time, shift will fail.
Typical value: Disabled.