Transient Throttle
Transient Throttle is a fuel correction function used to compensate for an opening or closing throttle body. As the throttle is opened and air enters the inlet manifold there is a period of time where the manifold pressure has not reached its final amount for the new throttle opening. During this transition, the airflow is also not stable and we see a lean condition until airflow and pressure has stabilised. The same occurs with a closing throttle, with a rich condition occurring during the transition from an open throttle to a closed throttle. Other influences can be a change in manifold pressure after the injector has been fired for that cylinder. For these instances, the Transient Throttle function allows for precise control of enrichment amount and duration during opening throttle conditions and disenrichment amount and duration for closing throttle conditions.
The enrichment can be delivered to the intake via the increase of normal sequential injection pulses which is known as Synchronous Enrichment, or via additional injector pulses inserted between the sequential events which is known as Asynchronous Enrichment.
The ignition timing can also be corrected for advance/retard as well as for duration when the transient throttle is active.
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Transient Throttle Tab
General
Load Type
Selects the sensor type to be used for Transient Throttle Detection. (Default = Throttle Position)
Throttle Position
Selected when a Throttle Position Sensor (TPS) is being used to detect transient conditions. This is the preferred method for most applications.
Manifold Pressure
Selected when either no TPS is present or MAP is preferred for the detection sensor.
Enable Disenrich
Enables the ability to add disenrichment with a closing throttle. This will work the opposite of enrichement, by leaning the fueling when the throttle is moving from an open to a more closed position. (Default = Disabled)
Enable Overall Corr
Enables the Overall Correction table, which allows for quick overall adjustment of the Enrich Amount.
Enrichment
Load Rate Dead Band
The minimum amount of positive throttle rate of movement (TPS or MAP Derivative) that is required to trip an Enrichment transient event. If this is set too low, it will cause false activation with unwanted enrichment events. If this is set too high, it will cause initial lean spikes due to delayed detection, together with no detection for small throttle movements. Typically set to 25 to 50%/sec for Throttle.
Load acceleration Dead Band
Once a transient throttle enrichment event is triggered, the acceleration of the load source must exceed this value to maintain enrichment. This acts as a Decay system. For longer enrichment periods use a low value, for shorter enrichment periods use a larger value.
Detect Duration
The minimum time required for a transient throttle enrichment event to be triggered. A longer duration will reduce false trips at the cost of a more delayed reaction.
Ign Corr Decay Time
The Ignition Correction Decay Time is the amount of time over which the Transient Throttle Ignition Correction decays back to zero.
Enable Async
Enables the ability to add enrichment via additional injector pulses. Enabling this function will add the Enrich Amount (Async) table in the Transient Throttle section. (Default = Disabled)
Max Async Injector Pulses
Sets the Maximum number of Async Injector Pulses. This tends to need high numbers the further the injectors are located from the valve.
Async Holdoff Time
Amount of time that has to pass after an Async enrichment event before another Async enrichment is allowed. This is to prevent a build up of multiple events occurring if Transient occurs before the last event has completed. Typically 0 to 400ms.
Disenrichment
Load Rate Dead Band
The minimum amount of negative throttle rate of movement (TPS or MAP Derivative) that is required to trip a Disenrichment transient event. If this is set too low, it will cause false activation with unwanted disenrichment events. If this is set too high, it will cause delayed detection, together with no detection for small throttle movements. Typically set to -25 to -50%/sec for Throttle.
Load Deceleration Dead Band
Once a transient throttle disenrichment event is triggered, the deceleration of the load source must exceed this value to maintain disenrichment. This acts as a Decay system. For longer disenrichment periods use a low value, for shorter disenrichment periods use a larger value.
Detect Detection
The minimum time required for a transient throttle disenrichment event to be triggered. A longer duration will reduce false trips at the cost of a more delayed reaction
Related Tables
Enrich
Enrich Rate
The Enrich Rate table is used to proportion how much of the Enrich Amount tables are applied. This calculation is based on the rate of sensor movement while opening the throttle (X-axis), and sensor position at the start of the movement (Y-axis). This table is often confused as being the Amount table. Up to 3D mapping is available.
Enrich Amount (Sync)
This table sets how much additional fuel is added during a transient event via normal sequential pulses, and multiplies with the Enrich Rate table to give a final amount. Typically mapped over RPM.
Synchronous refers to additional fuel being added to the normal sequential fuel output, and this is the more efficient way to deliver the additional enrichment required for transient conditions.
Typical values are 25 to 50 at low rpm, 100 to 200 for high rpm.
Although not true VE, the numbers are a VE approximation where larger numbers will give more fuel enrichment, and lower numbers will give less fuel enrichment. Up to 3D mapping is available.
Enrich Amount (Async)
This table sets how much additional fuel is delivered during a transient event via asynchronous mean, and multiplies with the Enrich Rate table to give a final amount. Typically mapped over RPM.
Asynchronous refers to additional fuel pulses being added between the normal sequential pulses. This is typically set up after the Sync table tuning has been completed.
Although not true VE, the numbers are a VE approximation where larger numbers will give more fuel enrichment, and lower numbers will give less fuel enrichment. Typically used when injectors are located far from the inlet valves, or in small amounts for engines with large ports or poor airflow at part throttle. Also commonly used for Rotary engine applications. Up to 3D mapping is available.
Ign Corr
The Amount of ignition timing correction to be applied during transient throttle conditions. Both advance (positive numbers) and retard (negative numbers) can be used with this table. This correction will decay over the time set for the Ign Corr Decay Time. Up to 3D mapping is available.
Disenrich
Disenrich Rate
The rate at which fuel disenrichment is applied in response to a lift-off transient throttle event. This table is used to proportion the amount of disenrichment based on the rate of closing throttle movement and the throttle position you were at when the movement began. Up to 3D mapping is available.
Disenrich Amount
This table sets how much fuel is removed during a disenrichment transient event (lift-off), and multiplies with the Disenrich Rate table to give a final amount. Typically mapped over RPM. Typical values are 25 to 50 at low rpm, 100 to 200 for high rpm. Although not true VE, the numbers are a VE approximation where larger numbers will give more fuel disenrichment, and lower numbers will give less fuel disenrichment. Up to 3D mapping is available.
Overall Trim
A final overall percentage change to the Transient Throttle Amount tables. This can be a handy table to make quick changes to see the effect of adding more or less enrichment. Up to 1D adjustment is available.
Coolant Temp Corr
A correction to the Amount tables based on Coolant Temperature. Colder engine temperatures sometimes require additional enrichment. Up to 2D adjustment is available.
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