Applying Load to the Engine

Applying Load to the Engine

To avoid engine damage, an engine should always be tuned rich then slowly leaned out until the desired AFR is reached.
Always ensure that an engine is in good condition before performing any tuning.
Watch coolant temperatures closely during any tuning session as engines are operating under high load.
If any signs of detonation is detected, then reduce load (close the throttle) immediately.
If mixtures become very lean under load, then reduce load immediately and correct the fuel tables before apply load again.

Once the engine has been tuned properly for no load conditions it is possible to begin loading the engine. The best method of applying load to the engine is using a dynamometer. Whether the vehicle is on a chassis dyno, or the engine on an engine dyno, the principles of programming the Haltech ECU are the same.

Take the engine RPM up to an RPM range in the table. For this example, we will use 1000 RPM. Apply partial load and adjust the cells at the given load in the 1000 RPM range. The load is held at -30kPa in the example below.

Return the engine to idle. The idle load at 1000 RPM should already be tuned to the correct mixture. If not, then go back to Tuning with No Load before proceeding. We can now linearise between the two tuned points. Select between the newly tuned point (-30kPa) and the already tuned idle point (-60kPa), and linearise the cells in between.

This provides an approximation for all the cells in between. These cells need to be checked, but tuning each cell individually is not practical if dyno time is limited, and would also add unnecessary wear and tear on the engine being tuned.

Continue, adding more load, up to the full load column. Each time you tune a point, linearise the points in between the tuned cells. Ramp the engine through these points and increase any areas where the engine runs leaner than the desired AFR.

Increasing Load

As a general rule, injection time should increase with increasing load.

  • When tuning with Injection Time, you will see this effect directly reflected in the table.

  • When tuning with VE Tuning, you may see this reflected as a slight increase in VE as load increases, but the increasing manifold pressure will increase calculated injection time (assuming VE is not rapidly falling away).

When you have tuned a cell, check that the cells to the right with higher load, have a value at least as high as the newly tuned cell. This will help ensure that when you venture into the new parts of the table, that the mixtures start out rich.

Increasing RPM

A similar rule can be applied to RPM - as the engine becomes more efficient, it will want more fuel with increasing RPM. This trend will not be sustained over the whole RPM range, but if you use this rule, it will help ensure that the un-tuned parts of the map are too rich, rather than too lean (running too rich is much safer than running too lean). Take extra care in forced induction applications where the increase in fuel might increase at a rate that is much sharper than a linear rate. In those cases, keep the load points closer together, so that you do not linearise over a wide span of loads. This method should produce a fairly good approximation to the required curve. Repeat this for the the remaining engine speed ranges, e.g. 1500 range, 2000, 2500 etc. The engine should be fairly drivable at this point.

Note: Despite the fact that the Haltech ECU is a true real-time programmable device, it is good practice to not hold the engine at high load at high RPM for longer than necessary to check the mixtures. When you approach full load at the midrange and high engine speeds, its good practice to apply the load and watch the mixture. Then un-load the engine while making adjustments in the software, then re-apply load to check the mixture with the new changes. This will keep engine stress and heat to a minimum.

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