Config:Fuel

Fuel menu

Fuel

This menu is used for any fuel-related configuration and tuning.

This menu enables the configuration of:

• Physical hardware - output pins
• VE tables
• Fuel trims (short and long)
• Lambda control (AFR correction)
• IAT/CLT/Other corrections
• Table switch
• And others...

You can find the individual options below.

VE Table

This is the main VE table used for fuel calculations.

Override VE table load axis

Override the Y axis (load) value used for the VE table.

This is for advanced users only. If you aren't sure you need this, you probably don't need this.

Fuel strategy

See Fuel strategy.

Injector setup

This menu enables the configuration of the physical injector layout and output configuration

Injection configuration

Injection

Injection Enabled

Fuel Injection is enabled

Disable Fuel Pump

Disable fuel pump

Disable injector prime pulse

Do not prime injectors

Mode

This configures the injection model:

• Simultaneous - All injectors are opened at the same time, with the fuel load being divided over the whole 720 degree cycle (a 4 cylinder engine will squirt 4 times over 720 degrees).
• Sequential - All injectors are opened at their commanded angle and the cycle is tracked over 720 degrees. Requires Cam Sensor or phase guessing to function properly.
• Batch - Injectors are opened at their commanded angle along with their wasted pair. The same principle as wasted spark.
• Single Point - The same as simultaneous but with a single channel, with fuel calculations to suit.

Injectors are always wired to their respective cylinders and epicEFI handles the firing order and injector opening. Batch wiring is only needed when the ECU does not have enough outputs to wire single injectors to a single channel.

Alpha-N uses IAT density correction

When set to true, it enables intake air temperature-based corrections for Alpha-N tuning strategies.

Override VE table load axis

Override the Y axis (load) value used for the VE table.

This is for advanced users only. If you aren't sure you need this, you probably don't need this.

Override AFR table load axis

Override the Y axis (load) value used for the AFR table.

This is for advanced users only. If you aren't sure you need this, you probably don't need this.

Injection phase control mode

Defines when fuel is injected relative to the intake valve opening. Options include End of Injection or other timing references.

Injector Settings

Injector flow

This is your injector flow at the fuel pressure used in the vehicle.

See units setting below.

Injector flow units

Select whether to configure injector flow in volumetric flow (default, cc/min) or mass flow (g/s).

Fuel rail pressure sensor

Select which fuel pressure sensor measures the pressure of the fuel at your injectors.

Injector flow compensation mode

This is the injector flow compensation mode.

• Manifold Referenced Pressure Regulator - The car is equipped with a manifold-pressure referenced pressure regulator.
• Returnless fuel system - The car is equipped with a returnless fuel system (regulator in tank or dead-head system).
• Sensed fuel pressure - The car is equipped with a fuel pressure sensor.

Injector reference pressure

This is the pressure at which your injector flow is known.

For example if your injectors flow 400cc/min at 3.5 bar, enter 350 here.

This is gauge pressure reference to atmospheric.

Use small pulsewidth correction lookup curve

Use the small pulsewidth correction table to correct small injector pulse width behaviour.

This feature should only be needed if running very big injectors (>1500cc) and you have idle fueling problems, or you want to limit the minimum pulsewidth. Do not use otherwise.

Fuel characteristics

Gasoline (E0) Stoichiometric ratio

Stoichiometric ratio for your primary fuel. When Flex Fuel is enabled, this value is used when the Flex Fuel sensor indicates E0.

E0 = 14.7

E10 = 14.1

E85 = 9.9

E100 = 9.0

Ethanol (E100) Stoichiometric ratio

Stoichiometric ratio for your secondary fuel. This value is used when the Flex Fuel sensor indicates E100, typically 9.0

Current Ethanol Content

Some pump gas has ethanol in it. Please adjust this to match what you fill up with.

Use this as default ethanol content for fueling when no flex sensor present.

This will scale Air/Fuel ratios and fueling accordingly.

Global Fuel Correction (1=100%)

This is the global fuel correction applied to the final pulse width.

Please note that this is a rudimentary correction and should be used only for troubleshooting and diagnostics.

Fuel flow rate smoothed alpha (display only)

This controls the logged "fuel flow rate" and how much smoothing is applied to that logged value. This has no actual impact on fuelling and the fuelling model.

Use absolute fuel pressure for dead time calculation

This changes the deadtime calculation to use absolute pressure. Otherwise, differential pressure is used.

Injection hardware

Injector Outputs

Injection Output x

This is the physical output pin for the injector output for cylinder x.

Injector Enable/Disable

Injector x disable

This menu is used to disable individual injector outputs for troubleshooting.

Cylinder Banks - Closed Loop Feedback

Cylinder x

Select which fuel correction bank this cylinder belongs to. Group cylinders that share the same O2 sensor 1.

Injector Deadtimes (BatV vs fuel pressure)

This table defines the Injector Dead Time. The dead time is the time in milliseconds that it takes for the injector to open and start spraying fuel. It is pressure and voltage dependant.

This table configures the relation of pressure/voltage and deadtime in ms.

Injector Timing Advance

This is injection angle in relation to TDC ignition stroke. Values are ATDC. i.e. If ignition timing is 14 advance, this value has to be -14 to match that event. -400 in this table would put injection well into the intake stroke. 50 here is 50 degrees after TDC compression stroke

Override the Y axis (load) value used for the injector advance table.

Override the Y axis (load) value used for the injector advance table.

Please note that this is a rudimentary correction and should be used only for troubleshooting and diagnostics.

Primary Injector Small Pulsewidth Table

This is the injector small pulsewidth correction. This table is used to re-map a small pulsewidth to a bigger one or vice-versa.

This is used to improve idle behaviour and other transient situations.

This feature should only be needed if running very big injectors (>1500cc) and you have idle fueling problems, or you want to limit the minimum pulsewidth. Do not use otherwise.

Primary Injector Small Pulsewth vs BatV multiplier

This is the small pulsewidth correction in relation to battery voltage. Small pulse width behavour can change with battery voltage, and this can be used to correct that behaviour.

This feature should only be needed if running very big injectors (>1500cc) and you have idle fueling problems, or you want to limit the minimum pulsewidth. Do not use otherwise.

Injector deadtime assisted tuning

epicEFI firmware includes an Injector Deadtime Tuning Tool that works by alternating between sequential injection and batch injection on a schedule.

This method works because switching between these two modes changes the number of injection events per engine cycle. In batch mode, the injector fires twice per cycle, while in sequential mode it fires once per cycle.

In both cases, the total amount of fuel delivered per cycle remains the same. The difference is that in batch mode the fuel is split into two injection events, whereas in sequential mode it is delivered in a single event. Since injector deadtime is added to every injection event, the total added deadtime per cycle differs between the two modes.

If the deadtime values are not accurate, switching between batch and sequential injection will result in a measurable change in AFR at the exhaust.

The epicEFI Injector Deadtime Tuning Assist automatically switches between sequential and batch modes on a set schedule, allowing you to log the AFR difference. You can then adjust the deadtime table until no AFR change is observed between the two modes, indicating that the injected fuel quantity is consistent in both cases.

It’s advisable to disable short-term fuel trims and to run this test with the engine fully warmed up.

At first, the engine may struggle to stay running when the mode switch occurs. This is expected if your deadtime values are off, since those inaccuracies are usually already “hidden” in the VE table.

If the engine goes too lean and won’t stay running, you can use the Global Fuel Correction to richen the mixture enough to keep it alive.

The Global Fuel Correction does not affect injector deadtime. It simply scales the overall fuel delivery, allowing you to keep the engine running while you dial in the correct deadtime values.

Enable deadtime tuning cycle

This is the master switch for the tool.

Use sequential

Enable sequential fuel mode into the scheduled switching.

Use batch

Enable batch fuel mode into the scheduled switching.

Use simultaneous

Enable simultaneous fuel mode into the scheduled switching.

Cycles

Switch fuel strategy every this many cycles of the engine.

Min RPM

Minimum RPM for the tool to run.

Injector Advance Assisted Tuning

epicEFI firmware includes the Injector Advance Tuning Tool. This enables the optimization of the injector close angle (also called end-of-injection) by offsetting it on a schedule. This enables you to test out the injection end angle by listening how the engine runs.

Let's say the injector needs to close at 90 degrees crankshaft angle and the tool is enabled and configured for -10 and +10 degrees. The injection end-of-injection will be changed by each step each number of cycles from 80 to 100 degrees.

Enable

Enable Injector Advance Tuning Assist

Degrees per step

How many degrees to increment each scheduled event.

Cycles per step

How many crankshaft cycles occur per step.

Min RPM

Enable above this RPM

Max RPM

Disable above this RPM

Start Retard (deg)

Start injector advance offset

End Retard (deg)

End injector advance offset

Fuel trim cyl x

This is the fuel trim per-cylinder.

Staged injection

This is the configuration for Staged Injection. Used for staging of injectors (primary-secondary) and the associated corrections.

Staged Injector Settings

Staged Injection Enable

This is the master switch for staged injection.

Secondary injector flow

The flow rate of the secondary injectors.

See Injector flow

Secondary injector flow compensation mode

The flow compensation mode.

See Injector flow compensation mode

Secondary injector reference pressure

The secondary injectors reference pressure.

See Injector reference pressure

Use small pulsewidth correction lookup curve

See Use small pulsewidth correction lookup curve

Staged Injector Deadtimes

This is the deadtime of the secondary injectors.

See Injector Deadtimes (BatV vs fuel pressure)

Staged Injector outputs

Injection Stage 2 Output x

These are the physical output pins for the secondary injection stage.

Staged Injector % table

Dtaged injector % table is how much of the staged injector to be used at RPM vs load. 0% means here all primary, and 100% all secondary fuel injectors.

Staged Injector Small Pulsewidth Table

This is the small pulsewidth correction for the secondary injection stage.

See Primary Injector Small Pulsewidth Table

Target AFR

This is the target lambda/air fuel ratio that is used for corrections, LTFT, STFT and fuel calculations.

Target AFR warmup enrichment (CLT)

This is the AFR ratio target correction in regards to warmup enrichment.

1.0 means no correction.

1.2 means 20% richer fuel target

0.8 means 20% leaner fuel target

Manual warmup enrichment (CLT)

This is the manual warmup enrichment in regards to coolant temperature. This is a global multiplier.

1.0 means no correction.

1.2 means 20% richer mixture

0.8 means 20% leaner mixture

Intake air temp correction (IAT)

This is the intake air temp correction curve. This is a global multiplier.

1.0 means no correction.

1.2 means 20% richer mixture

0.8 means 20% leaner mixture

Deceleration fuel cutoff (DFCO)

Enable Coasting Fuel Cutoff

This setting disables fuel injection while the engine is in overrun, this is useful as a fuel saving measure and to prevent back firing.

Disable fuel cut on clutch

Inhibits DFCO from activating when the clutch is pressed. This helps prevent transient knock during shifts.

No cut below CLT

Fuel cutoff is disabled when the engine is cold.

RPM cut fuel above

This sets the RPM above which fuel cut is active.

RPM restore fuel below

This sets the RPM below which fuel cut is deactivated, this prevents jerking or issues transitioning to idle

Vehicle speed cut above

Above this speed, allow DFCO. Use this to prevent jerkiness from fuel enable/disable in low gears.

Vehicle speed restore below

Below this speed, disable DFCO. Use this to prevent jerkiness from fuel enable/disable in low gears.

Cut fuel below TPS

Throttle position below which fuel cut is active. With an electronic throttle enabled, this checks against pedal position.

Cut fuel below MAP mode

• Fixed - MAP threshold cut fuel when conditions are met
• Table - Use a curve to vary the MAP threshold based on engine RPM

Cut fuel below MAP

MAP value above which fuel injection is re-enabled.

Fuel cut delay

Delay before cutting fuel. Set to 0 to cut immediately with no delay. May cause rumbles and pops out of your exhaust...

Inhibit closed loop fuel after cut

Pause closed loop fueling after deceleration fuel cut occurs. Set this to a little longer than however long is required for normal fueling behavior to resume after fuel cut.

Use DFCO exit enrichment

When exiting DCFO and all the fuel film from the intake runners has evaporated, there is a lean condition on the first few combustion events when resuming normal injection. This attempts to fix that by injecting extra fuel on DCFO exit.

DFCO exit enrichment max RPM

This is the maximum RPM for DCFO exit enrichment.

Ignition retard during cut

Retard timing by this amount during DFCO. Smooths the transition back from fuel cut. After fuel is restored, ramp timing back in over the period specified.

After cut timing ramp-in time

Smooths the transition back from fuel cut. After fuel is restored, ramp timing back in over the period specified.

DFCO MAP to RPM threshold

DFCO will activate when operating below this curve. Used to allow a higher threshold at low RPM where less vaccuum is generated.

Long Term Fuel Trim

This configures the Long Term Fuel Trim. This is used to trim fuel over long periods of time, such as injector aging or similar factors.

To enable long term fuel trims, short term fuel trims should be configured and active.

Long term fuel trims

Long term fuel trim

Gathering Data

Enables lambda sensor long term fuel corrections data gathering into LTFT trim tables

To enable long term fuel trims, short term fuel trims should be configured and active.

Time const

Commonly referred as Integral gain.

Time constant for correction while in this cell: this sets responsiveness of the closed loop correction. A value of 30.0 means it will try to make most of the correction within 30 seconds, and a value of 300.0 will try to correct within 5 minutes.

Lower values makes the correction more sensitive, higher values slow the correction down.

Max add

Maximum % that the long term fuel trim can add

Max remove

Maximum % that the long term fuel trim can remove

Learning deadband

When close to correct AFR, pause correction. This can improve stability by not changing the adjustment if the error is extremely small, but is not required.

Apply Correction

Apply LTFT trims into fuel calculation on top of VE table.

We do not adjust VE table automatically, please click 'Apply to VE' if you want to adjust your VE tables and reset trims.

Enable Autosave LTFT

Automatically save Long Term Fuel trim to backup

Enable Writes While Engine runs (experimental) every 10 minutes

This enables configuration writes every 10 minutes while the engine runs.

This feature is experimental and could result in tune loss on the ECU. Use with caution.

Refresh TS with live write every 10 minutes

Refreshes TunerStudio with the live write.

This feature is experimental and could result in tune loss on the ECU. Use with caution.

Flash Write delay after engine off - seconds

Delay flash write after engine stop for this long.

Long Term Fuel Trim Bank 1 - BACKUP

This is the bank 1 long term fuel trim backup. On ECU boot, this is copied into the active table.

Long Term Fuel Trim Bank 2 - BACKUP

This is the bank 1 long term fuel trim backup. On ECU boot, this is copied into the active table.

Short Term Fuel Trim

This is used to configure STFT. This trim is applied fast and used to correct the fuel in very short periods of time.

Short term fuel trim Setup

Short term fuel trim

Short term fuel trim

Enables lambda sensor closed loop feedback for fuelling.

CAN BOX AFR Trim range ADD MAX (+) (lambda)

maximum afr trim

CAN BOX AFR Trim range REMOVE MAX(-)(lambda)

minimum afr trim

Logged Tuned VE correction multiplier

Multiplier for corrections applied to tuned VE that's logged

Startup delay

Delay after starting the engine before beginning closed loop correction.

After DFCO delay

Pause closed loop fueling after deceleration fuel cut occurs. Set this to a little longer than however long is required for normal fueling behavior to resume after fuel cut.

After DFCO pause or disable STFT

This eliminates the interference between DFCO and SFTF.

• True - Pauses the short term fuel trim
• False - Disable STFT after DFCO is active

Minimum CLT for correction

Below this temperature, correction is disabled.

Use AFR (Gasoline scale) or Lambda for limits

Use Lambda or AFR for limits

Minimum AFR for correction (Gasoline scale)

Below this AFR, correction is paused

This is corrected for current flex fuel percentage.

Maximum AFR for correction (Gasoline scale)

Above this AFR, correction is paused

This is corrected for current flex fuel percentage.

Minimum Lambda for correction

Below this Lambda, correction is paused

This is corrected for current flex fuel percentage.

Maximum Lambda for correction

Above this Lambda, correction is paused

This is corrected for current flex fuel percentage

Adjustment deadband_rich - MAX RICH %

When close to correct AFR from rich side, pause correction. This can improve stability by not changing the adjustment if the error is extremely small, but is not required.

Adjustment deadband_lean - MAX LEAN %

When close to correct AFR from lean side , pause correction. This can improve stability by not changing the adjustment if the error is extremely small, but is not required.

Ignore error magnitude (error is always 0.1% - simple mode)

If enabled, adjust at a constant rate instead of a rate proportional to the current lambda error. This mode may be easier to tune, and more tolerant of sensor noise.

Short term fuel trim Time Constant (I)

This is the integral component of the short term fuel trim.

Short term fuel trim Add Authority (+)

Define how much fuel the short-term trim system is allowed to add at a given RPM vs. load (MAP/AFR) point.

For example, if you want the system to only add fuel in boost and never remove it, you can set the Remove Map to 0 above 100 kPa and above, say, 2000 RPM.

Short term fuel trim Remove Authority (-)

Define how much fuel the short-term trim system is allowed to add at a given RPM vs. load (MAP/AFR) point.

If you want the fuel trim to reset immediately on lift-off (when vacuum drops very low and the engine rides the bottom row of the map), you can set the authority to 0 in that area.

VE Table Switch

VE Table Switch x Settings

VE Table Switch x Pin

Full table switch or blend pin.

To find the actual value for your hardware, see Hardware.

VE Table Switch x Pin Mode

This is the pin mode for the switch input pin.

See ECU input mode selection.

VE Table Switch x Parameter

This defines the table switch parameter.

VE Table Switch x Blend Mode

Blend mode adds or multiplies the switch table with base, default is switch.

VE Table Switch x Y axis override

This overrides the Y axis of the table switch table.

VE Table Switch x

This is the table which is used after switching/blending.

Target AFR Table Switch

Target AFR Table Switch 1 Settings

Target AFR Table Switch 1 Pin

Full table switch or blend pin

To find the actual value for your hardware, see Hardware.

Target AFR Table Switch 1 Pin Mode

See ECU input mode selection.

Target AFR Table Switch 1 Parameter

This defines the table switch parameter.

Target AFR Table Switch 1 Blend Mode

Blend mode adds or multiplies the switch table with base, default is switch.

Target AFR Table Switch 1 Y axis override

This overrides the Y axis of the table switch table.

Target AFR Table Switch 1

This is the table which is used after switching/blending.

Fuel Corrections

Barometric pressure correction

This is the barometric pressure correction in regards with a baro sensor.

Charge temperature estimation

This is the charge air estimation used to approximate the cylinder air/fuel charge temperature based on CLT and IAT.

Mode

• RPM+TPS - Use RPM and TPS for air charge estimation
• Air Mass Interpolation - Use the air mass interpolation method for charge air estimation
• Table - Use the table for charge temperature estimation

Increase rate limit

Maximum allowed rate of increase allowed for the estimated charge temperature

Decrease rate limit

Maximum allowed rate of decrease allowed for the estimated charge temperature

RPM+TPS mode

Low RPM/Low TPS

The low RPM/low TPS coefficient for estimation.

Low RPM/High TPS

The low RPM/high TPS coefficient for estimation.

High RPM/Low TPS

The high RPM/low TPS coefficient for estimation.

High RPM/High TPS

The high RPM/high TPS coefficient for estimation.

Airflow interpolation mode

Low flow coefficient

Heat transfer coefficient at zero flow.

• 0 means the air charge is fully heated to the same temperature as the coolant temperature
• 1 means the air charge gains no heat, and enters the cylinder at the temperature measured by IAT.

High flow coefficient

Heat transfer coefficient at high flow, as defined by "max air flow". 0 means the air charge is fully heated to the same temperature as CLT. 1 means the air charge gains no heat, and enters the cylinder at the temperature measured by IAT.

Max air flow

High flow point for heat transfer estimation. Set this to perhaps 50-75% of your maximum airflow at wide open throttle.

User Switchable Lambda Target Multipliers

This affects the AFR target output, this is a multiplier, and the value stacks with the multipliers.

0.9 = MORE fuel (lower lambda)

1.1 = LESS fuel (higher lambda)

Target Lambda Multiplier x pin

This is the physical input pin for the lambda multiplier.

To find the actual value for your hardware, see Hardware.

Target Lambda Multiplier x pin mode

See ECU input mode selection.

Target Lambda Multiplier x value

This is the multiplier value for the lambda target.

TPS Acceleration Enrichment/Wall Wetting AE

This is the acceleration enrichment (AE) setting. They can be

• Delta-TPS based - The TPS delta (TPS speed) is used for acceleration enrichment (simpler)
• Wall Wetting - Complex wall-wetting algorithm based on fuel evaporation time

Acceleration enrichment Base settings(AE)

Acceleration Enrichment Methods

Enable TPS Acceleration Enrichment

TPS acceleration enrichment enabled

Enable wall wetting Acceleration Enrichment

Wall wetting accelerating enrichment enabled

Use MAP estimate during transient

During the TPS AE period, use the MAP estimate table value instead of true MAP (if greater than real MAP). This basically briefly runs in alpha-n during a transient, then returns to normal speed-density mode.

Wall Wetting

Wall fueling model type

Specifies the wall-wetting mode.

• Basic - Constants are used to vary tau/beta
• Advanced - Tables are used to vary tau/beta

evaporation time constant / tau

Length of time the deposited wall fuel takes to dissipate after the start of acceleration.

added to wall coef / beta

• 0 = No fuel settling on port walls
• 1 = All the fuel settling on port walls

Setting this to 0 disables the wall wetting enrichment.

TPS AE: Settings

Enable TPS Acceleration Enrichment

TPS acceleration enrichment enabled

TPS AE fast or slow callback

This is how fast the AE callback is invoked (how fast the AE is calculated)

• True - 200Hz
• False - 20Hz

Delta TPS Average Smoothing Factor

A higher alpha (closer to 1) means the EMA reacts more quickly to changes in the data.

1 means no filtering, 0.98 would be some filtering.

Use calculated threshold from averaged delta TPS

Use calcualted threshold from averaged delta TPS

Average static threshold curve and dynamic threshold

when using dynamic threshold from averaged and multiplied deltatps, average with static threshold curve

Sample Length

How long to look back for TPS-based acceleration enrichment. Increasing this time will trigger enrichment for longer when a throttle position change occurs.

Instant Fuel Pulse

Send a simultaneous shot to all injectors upon TPS AE

Instant Fuel Pulse Multiplier (global)

Extra shot multiplier

Instant Fuel Pulse Inhibit Cycles

Inhibit Extra Shot for this many cycles

TPS AE Burn Skip count

Hitting  "Burn" sometimes causes a spike in sensors, TPS AE burn skip count ignores AE triggers for the duration of that.

TPS Accel resets EGO to 0%

TPS AE resets current EGO to 0%

Inhibit closed loop fuel after accel

Pause closed loop fueling after acceleration fuel occurs. Set this to a little longer than however long is required for normal fueling behavior to resume after fuel accel.

TPS AE: Fuel multiplier by engine cycle

This is a TPS acceleration enrichment multiplier based on engine cycle

TPS AE: Delta TPS Average Multiplier for Dynamic Threshold

Delta TPS average multiplier curve

TPS AE: TPS change threshold by RPM

Above this curve, the engine is considered to be in acceleration enrichment.

TPS AE: TPS vs CLT AE SCALE

This is the acceleration enrichment scale based on CLT

Predictive Map Blend Duration

This is the duration for the MAP estimation.

TPS AE: RPM correction

This is the RPM correction for TPS acceleration enrichment.

TPS AE: CLT correction

This is the CLT correction for TPS acceleration enrichment.

MAP estimate table

This table represents MAP at a given TPS vs RPM, which we use if our MAP sensor has failed, or if we are using MAP Prediciton. This table should be a direct representation of MAP, you can tune it manually by disconnecting MAP sensor, and filling out the table with values that match an external gauge that shows MAP. Additionally, you can also use MLV to get the map values and/or generate the table for you.

TPS AE instant pulse multiplier vs RPM

This is the RPM multiplier for the instant fuel pulse.

TPS AE instant pulse multiplier vs TPS

This is the TPS multiplier for the instant fuel pulse.

TPS AE instant pulse multiplier vs MAP

This is the MAP multiplier for the instant fuel pulse.

TPS AE instant pulse multiplier vs CLT

This is the CLT multiplier for the instant fuel pulse.

Evap from wall time

This is the base evaporation time of the fuel based on coolant temperature (Tau)

Stick to wall fraction

This is the base impact fraction basaed on coolant temperature (Beta)

Evap from wall table

This is the Tau table in regards to MAP.

Stick to wall table

This is the Beta table in regards to MAP.

Throttle Model Flow

Uses "flow through an orifice" set of Bernouli's equations to attempt to calculate air mass.

This is experimental/for educational purposes only.

Throttle effective % area (TPS ->% throttle boy area)

This is the transfer function between TPS percentage and the throttle body area percentage.

Throttle Model Flow Discharge Coefficient

This is the discharge coefficient.