Alpha N with MAP compensation, or just straight RPM / MAP?

Hi All,

Happy new year!

I have a question about the best mapping method for my project.

My ECU allows either:

Alpha N (throttle position / RPM) based primary table with a separate MAP compensation table

Or

Regular MAP / RPM based primary table.

My question is, which would be better?

I have a single electronic throttle body, the engine is a turbocharged Honda K24.

I'm thinking alpha N with MAP compensation will allow further options with regard to off boost timing etc.

Any advice much appreciated!

Cheers,

Adam

Conventionally you would set up this engine using MAP, not alpha-N. Alpha-N is more suited to engines where the MAP signal is not a good representation of airflow/engine load such as you will see with individual throttle bodies.

While you could set the engine up using alpha-N with a MAP compensation, you're really adding more complexity to your tuning than necessary, with minimal gain. As far as ignition timing goes, even if you're using alpha-N on a turbocharged engine you would retain MAp as the load axis for this table anyway.

You may see some small advantage from using alpha-N and MAP comp on a turbocharged car in that you can achieve more consistent part throttle mixtures when on boost. If you're using a normal MAP based load axis then the ECU assumes that for example 150 kPa boost at 5000 rpm will result in x mass of air regardless of the throttle position. In some instances you may be able to achieve 150 kPa at 100% throttle or 60% throttle and the mass airflow will be different in each scenario.