I’d really appreciate detailed information on injector tuning (Direct Injection)

There’s a lot of things I don’t understand yet about Direct Injection, but seeing that my car is direct injections and I’ve been tuning it and I’m currently trying to push E85 with an upgraded pump, my lack of knowledge in this area has really shown through.

i don’t understand how to know when I’m out of injector, when I should start injection, when I should end injection, how to determine the maximum pulse width, when or why to inject different types of fuels, etc. I’ve looked for this information for awhile, but it’s been a struggle.

im not sure if im out of injector, if i can advance SOI, ETC. my logging options is pretty garbage too, I only have access to AFR, Pulse Width, and Trims.

theres also the idea of upgrading the pump, I’ve noticed that I’ve had issues with high fuel pressure runaway with the new pump, been trying to figure it out but assuming it’s an issue with how the ecu calculates the fuel per stroke

i use Sim2K which is similar to SimOS18

The Injection window with a DI engine is much shorter that that of a port injected engine. The typical window for injection on a DI engine is between the closure of the Exhaust valve and the ignition coil firing, with some ECU's having a gap between EOI and Ignition to allow for further homogenisation of the mixture in the combustion chamber. Some DI systems will fire the ignition when the injection is occurring (stratified operation) as this allows for a rich mixture to be present around the spark plug to allow for easier ignition, whereas the remainder of the chamber is lean (stratified).

Changing the HPDP can cause problems if the volume delivered per stroke value isn't changed. The ECU will be calculating the amount of fuel that needs to be delivered by the pump into the fuel rail to maintain the Aim Pressure and the replace the amount of fuel that has been removed from the rail by the injection pulse/s. If the volume delivered per stroke is greater than that that the ECU is using, each time it opens the delivery solenoid to supply fuel into the rail, more fuel will be delivered than has been calculated, leading to an increase in the rail pressure.

If the ECU/Engine was originally tuned for use with non ethanol blended fuels, and doesn't have a flex fuel capacity, the injectors may not have enough headroom to be able to deliver the extra 30% of fuel required, even with a higher volume pump, the standard bleed valve on most of the cam driven DI pumps opens around 22mPa, so if you are requesting more pressure than that, it will not deliver the pressure requested.