Quote:
Originally Posted by Damian
What FPR are you using?
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The computer controls fuel pressure in the high pressure pump. The LNF motor in the cobalt ss is direct injection. There is a "lift pump" in the tank, just like a diesel, and it is regulated to like 60 psi I think. But the low pressure pump is not the problem until like 500whp.
The fuel pressure is set to a certain demand, the high pressure injector pump tries to keep up but the fuel pressure in the rail drops because the injectors are open for so long. The stock injection window opens much later in the intake cycle. It is now beginning to spray at like 320* before top dead center and sprays until it is starting the compression stroke. Since my airflow across the MAF is quite high the HP pump can't keep up with demand since the injectors are open for so long. That is why I am seeing such a drop in fuel pressure in the rail.