What is 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.

Transient Throttle Page

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.

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.