prj tuning

He who stops being better stops being good.

Archive for March, 2013

It is now possible to map the 2.2T Motronic to run off of the MAP sensor instead of the MAF.
The speed-density calculation is fully implemented in custom code in the ECU.

The upsides and downsides of running speed-density are:
+ No need for a MAF, so plumbing is simpler.
+ Atmospheric dump valves and an atmospherically vented N75 can be used further simplifying plumbing.
+ No problems with the MAF maxing out, as MAP sensors are readily available even for 6 bar boost.
+ Little effect of air leaks on cylinder charge calculation.

-  The MAP signal is somewhat slower than the MAF signal.
The air charge calculation relies on an engine efficiency map in the ECU, thus if engine efficiency (flow) changes, it means that the air charge calculation will be wrong and a remap will be required. For example changing the intake or exhaust manifold, camshafts, porting the head and so on.
Difficult to dial in the VE table properly on the road, as every possible pressure and RPM has to be visited, because linearization is RPM and MAP based.

Compared to mass-flow:
+ Directly measures airflow, so changes to engine efficiency do not affect charge air calculation.
+ Somewhat faster signal than a MAP sensor.
+ Very easy to map on the road, as a pull goes through the entire range and linearization is flow based.

All air flow must be re-circulated, no air can leak after it has gone through the MAF, as otherwise the charge calculation will be off, more difficult to plumb
If the MAF maxes out, charge air calculation does too. Meaning that after it does the ECU essentially runs Alpha/N, which is inaccurate.