Tuning Base Tables

Tuning Base Tables

Tuning Method 

Injection Time 

The fuel table contain the base injection time for the given load and RPM at which the engine is operating. The base fuel map has the greatest influence on the air/fuel (A/F) mixtures. 
With injection time tuning, you will be adjusting injection times to calibrate against the efficiency of the engine as well as tuning for a desired Air Fuel Ratio (AFR). 

Volumetric Efficiency 

Note: Before performing any tuning using VE Tuning method, make sure that you have configured the following settings and tables before proceeding: 

  • Engine Volume setting 

  • Inj Flow Rate table 

  • Inj Dead Time table 

    Failure to configure these items will result in a VE table that has compromised accuracy. The more error that you have in any of the above settings or tables, the more the VE table will have to tune around these errors. This will result in accumulated error in your VE table. 

    If all tables and settings are 100% accurate, then it is theoretically possible to change any one parameter independently of another. E.g. If all tables are 100% accurate, it is theoretically possible to adjust Target AFR, with the resultant AFR tracking the changes perfectly. Similarly, if injector sizing is changed and the corresponding Injector Flow Rate table is changed to match the new injector sizing perfectly, then theoretically, the ECU should recalculate the injection time resulting the same mixtures as before the injector change. 

    In practice, there is always some small error, so mixtures should always be checked whenever changes are made. However, if errors are minimised, then the amount of re-tuning is also minimised 

The fuel table contains the Volumetric Efficiency (VE) of the engine. This is a percentage of available air that makes it into the combustion chamber for each combustion event. The term available air refers to the amount of air molecules that are available in the intake manifold after manifold pressure is taken into account.

The VE value used here is not a percentage of the the air available at atmospheric pressure. If this were the case, then the VE numbers would rise with rising manifold pressure. The VE values used here have already taken into account the manifold pressure, so the VE here purely represents the efficiency of the engine's ability to fill and trap the available air from the manifold into the cylinder for combustion.

The Target AFR table must be filled out with appropriate values when using VE Tuning method.

When tuning using VE Tuning method, always tune the VE in the Base Fuel table to achieve the AFR defined by the Target AFR table. If a different AFR is desired under a certain condition, then adjust the Target AFR table. 

VE Tuning is also referred to as Speed-Density tuning. 

Base Table Tuning

To tune your base fuel tables: 

  • If you are using VE tuning method, fill out your Target AFR tables with appropriate target AFR values. Typically, at idle and light loads, an engine will run close to stoichiometric mixtures (Lambda 1.0 or 14.7:1 AFR for petrol/gasoline). Under higher loads, it is usually necessary to run richer mixtures for engine safety and for maximum torque. 

  • Setup your A/F ratio measuring equipment to measure the A/F for the engine that is to be tuned. Check which base fuel map is used and select the appropriate map in the Elite Software Programmer (ESP) software to tune. Ensure that all correction maps such as coolant temp and air temp corrections are turned off or set to zero correction at this stage. 

  • Confirm base timing is correct with timing light (for more information see Calibrating Ignition Timing ). Ensure that the ignition timing is set conservatively to ensure that detonation doesn't occur if a momentary lean condition is experienced. 

  • Warm the engine up to operating temperature. 

  • Check your Injection Angle and adjust for smoothest idle. Typical angles are around 420° BTDC. 

  • Adjust the idle control or throttle stops to enable the engine to idle at the desired engine speed.

  • Tuning for Idle - While watching the A/F meter, adjust your Base Fuel Table so that as your measured idle mixtures are as close to your idle target mixture (usually 14.7 AFR) whilst ensuring that you can maintain a steady idle without any misfiring. 

  • While leaving the engine un-loaded, rev the engine in neutral through the rev range over which the engine will be operated. Adjust your Base Fuel table to set all the mixtures close to your Target AFR in the non-loaded part of the load range. This is typically 14.7:1. 

  • With the aid of a dynamometer or an alternative method of applying load, step through the load range for each given RPM range. 

  • If you are using VE Tuning, adjust your Base Fuel table until the measured AFR matches the values in your Target AFR table. 

  • If you are using Injection Time tuning, then you increase or decrease injection time until the desired AFR is reached.

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