Toyota use EGR method to reduce NOx. Retarding engine also reduces NOx so maybe Toyota also retard engine. In UK at least I don’t think they test for NOx so removing any NOx reduction methods is probably OK.
Removing EGR and advancing engine timing are therefore the likely methods to improve “miles per gallon”.
Problem is how to advance timing on 2L-TE. I have read forums on this subject but….
As I understand it the injector pump has:-
1. Spill Valve (precisely meters bulk flow of diesel through pump)
2. Timer Control Valve (sets exact instant fuel sent to injector, any of the four injectors)
3. Mechanical alignment mark (suspect this is only a rough alignment for the distribution of fuel to correct injector – like distributor cap on old petrol engine).
ECU has timing input from the crankshaft sensor, these usually give a strong pulse for TDC and intermediate pulses every 15 degrees or whatever.
Crankshaft sensor is stuck in one place so cannot be adjusted. Forums mention that ECU calibrates timing after being reset but how can it do this?
All I think ECU does is use the crankshaft sensor, engine speed, other sensors etc. to determine the actual advance angle to use for controlling the Timer Control Valve from its preset tables/maps.
Mechanically moving the pump alignment mark should have no effect other than if the movement is large will stuff things up.
There does not seem to be any way to alter the timing (advance it a few degrees) of 2L-TE engine in any way from what the ECU decides.