Astra H Van with Z20LEH VXR Engine
This Astravan with Z20LEH engine, steel rods and GTX2867 garrett build was brought in for mapping and full rolling road set up.
The map it was brought to us with (which was not our software) was checked first and shown to be running 320bhp, with some fuelling and ignition timing issues.
We switched to a 3 bar map sensor (from a standard 2.5 bar one) and recalibrated the map so the ecu could correctly read boost pressure as the 2.5bar map sensor will go out of range on capable of reading up to 22psi of boost, hence the change to a 3 bar sensor. Correctly recalibrated the ecu can then read up to 29.4psi boost presure.
Also changed were the 875cc injectors to a much more suitable 630cc injector for the required power, again with suitable ecu recalibration. 875cc injectors for the required power prove way too big, and cannot be controlled accurately enough for part throttle fuelling (essential on a fast road car) due to the spray pattern plus fuel consumption will be higher, again another consideration for a car with road manners. When checked and datalogged first this car was running at 0.88 lambda on cruise, so clearly the map needed some work at this point. This is too rich and can cause bore wash and potentially internal engine damage. Big injectors are fine for stand alone management and for race cars which do not run at part throttle or cruise, but were just incorrectly specced for this particular applcation.
With a couple of bits still to do and after mapping and set up the result for now is 390bhp and much better, more controlled fuelling at part throttle and cruise. Fuel consumption will improve as well as 630cc injectors control part throttle fuelling more accurately.
Why the change of injectors? For better road manners; in simple turns the bigger injector (875cc) does not atomise the fuel as efficiently at slow duty cycle/engine speeds. So a 630cc injector can provide more than enough fuel for the power but still return better fuel economy due to its ability to better atomise the fuel.