C7 inj duty cycle max 49% ?

[Higgs Boson]

This is exactly why I have been asking why we don't just start injecting at or just after EVC, which seems like the earliest logical time to put fuel in the cylinder. I don't see the point in pushing it to the latest point possible.

With respect to pressure, increasing pressure with an early injection would shorten the fire time even more, right? It seems only necessary in applications where even the longest window is still too short, or is it again a mixture issue?

I guess if the weather is decent (which it won't be) I will get the car out and set SOI to just after ECV for ALL cells (so put them all at like, 340) and see what happens.

[Wnts2Go10O]

sounds like the more time the fuel has to mix, the better (to a point i expect like most things).

[Wnts2Go10O]

is the fuel pressure electronically controlled on the C7 as well?

[Higgs Boson]

Something occurred to me just now about why a later injection might make sense.

The idle area and high RPM low load areas have later injection. These are some of the highest times of vacuum, which also means that they would be the highest times of crankcase suction and direct injection dirty valve syndrome.

Based on the pics I've seen of the DI injector angle it is pointed right at the intake valve and that would be a great time to spray an opened intake valve.


Thoughts?

[Wnts2Go10O]

Something occurred to me just now about why a later injection might make sense.

The idle area and high RPM low load areas have later injection. These are some of the highest times of vacuum, which also means that they would be the highest times of crankcase suction and direct injection dirty valve syndrome.

Based on the pics I've seen of the DI injector angle it is pointed right at the intake valve and that would be a great time to spray an opened intake valve.


Thoughts?

are they trying to hit the open valve with fuel spray or simply use incoming air to mix the air/fuel?

[Higgs Boson]

I don't know. It was really just a thought, I don't know if the angle is enough to hit the valve but it seems like a logical solution to the dirty valve problem.....except for the dirty intake runner problem.

It just seems like a strong correlation to late SOI with high vacuum conditions.

[Proxses]

I doubt it's able to hit the valve with fuel. Possibly the late injection is to deal with low cylinder pressure mixing. Maybe compression heat can aid in vaporization. So they delay, thus keeping fuel from puddling.
But you may hit on a point about strange flow under high vacuum conditions when the intake valves open.

Anyone notice the intake valves appear to be coated? Might be to reduce deposits.

[Wnts2Go10O]

I don't know. It was really just a thought, I don't know if the angle is enough to hit the valve but it seems like a logical solution to the dirty valve problem.....except for the dirty intake runner problem.

It just seems like a strong correlation to late SOI with high vacuum conditions.

could also have something to do with mass flow compression.