Major Update - 10/22/2025

New Acceleration Enrichment Logic

Acceleration Enrichment has been overhauled to now contain a slow and fast component. The slow component handles the additional fuel needed when load changes and the fast component takes care of additional fuel required due to large almost instantaneous pressure changes in the intake manifold.

• Slow Component - The slow component functions through modifications to the existing BMW AE Logic. The associated tables are defined in the XDF under Fuel → Fuel Acceleration Enrichment as shown below. For most tuning purposes only the Positive and Negative Component should be the only tables modified (if deemed necessary).

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• Fast Component - The fast component handles the additional fuel required to maintain the fuel wall film when the pressure inside the intake manifold changes suddenly (such as a neutral rev blip). This system has now transitioned away from pressure based to throttle position setpoint. This change was necessary due to the manifold absolute pressure sensors inherent lag causing stumbling during fast throttle blips. The associated tables are defined in the XDF under MHD+ Suite → NXM Port Injection → Fuel Acceleration Enrichment.

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• Acceleration Enrichment Threshold to Disable STFT - During large acceleration enrichment events it is necessary to temporarily disable the short term fuel trim or closed-loop fueling logic. This is required as acceleration enrichment is not tuned by actual measured air to fuel ratios but by feel/response of the engine. This can lead to a sudden change in measured AFR when compared to the AFR target and can cause an oscillation in fueling as the short term fuel trim tries to correct a short-term event. Due to this it’s important to have accurate fuel scalar maps so fueling is still accurate during the short period of time when operation switches to open-loop.

Improved initial cold engine startup and warm restart

Cold start and warm restart have been improved in multiple ways.

• Batch Pre-Injection - This feature allows for pre-wetting of the intake port and cylinder before ignition is released by the DME. For the first fuel injection event (after engine synchronization has completed) the injector pulse width is activated on all 6 cylinders at the same time. Due to physical design choices made by BMW and Continental with the MSD8X DME’s this feature requires any signal controllers purchased before 09/01/2025 to be updated. Signal controllers must be sent back to us for updating or you can do an exchange process where we send you a new controller and you send back your old one to minimize downtime. Note that this is only a requirement for batch pre-injection. Email support@nexsysmotorsport.com to get your existing signal controller updated.

• After Start Enrichment and Warm Restart - After start enrichment tables and warm restart tables have been better calibrated to avoid initial startup stumbles experienced by some users. For the very first startup of the day the engine requires substantially more fuel to stabilize. Likewise once the engine has been running for any period of time the amount of fuel needed is reduced greatly. The warm restart table improvements help reduce the after start enrichment after the engine has been running.

Dynamic Start of Injection Angle

This feature is always active in the background and does not need to be enabled. In the event that the start of injection angle in the tunable tables is not sufficient to fit the entire injection pulse we will dynamically move the start of injection angle further back up to 720*. This feature allows for tunability of the SOI while also providing a safety mechanism to ensure the entire pulse is able to be timed correctly and safely.

Fuel Scalar Expansion

The existing fuel scalar tables have been limited to 2.0 until now. This update brings an expansion for the fuel scalar up to 4.0. Do to how MHD scales boost (to achieve over 22 psi) it was possible to max out the fuel scalar at high boost. This limitation has now been resolved!

Base Map Generator/Updater Tool

In an effort to reduce tuner load and tune revisions we’re proud to announce a new utility that allows tuners to upload an existing tune or original.bin. The tool will then apply all required changes for port injection, our recommended base map values and injector calibration data. The result is a tune that can be sent to the customer immediately for testing. The base map generator/updater tool can be accessed by clicking here.

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