[parish8]

how do you know when you are out of injector? old school was hit 100% and your done. what about now with di?

i am looking at the soi(start of injection) tables on hptuners and it seems to make sense. the highest numbers on that table are 340deg before tdc. that would be 20deg of crank rotation into the intake stroke. the stock numbers at peek load and rpm are more in the 330deg area.

i always run my stuff at a safe 15deg btdc when boosted and have had good luck, not sure if di is the same but lets say it is. to add a margin of safely lets say we want the injection to stop at 20deg btdc.

if we were to spray from 340deg btdc to 20deg btdc that would give us a window of 320deg. at 6000rpm that would be (320/720)*20ms= 8.89ms or 44% duty cycle.

take that up to 6500rpm still 44% duty cycle but only 18.5ms to work with = 8.14ms.

am i on the right track? is this how it will likely work in the real world as i turn it up? what happens if you are still spraying fuel after ignition?

i just looked at the z06 numbers. it has a peek of 356deg btdc for soi. that would add a little more time but doesn't the lt4 motors have a smaller cam? the exhaust valve may close a little sooner on that motor allowing an earlier soi?

more numbers. the z06 injectors are rated at 140lb/hr on the hptuners file. there is a multiplier of 1.44 at 20MPa of fuel pressure and 1.03 for 80% alcohol. total of 207lb/hr injector. 207*8*.44dc = 728lb/hr total fuel flow.

(728lb/hr)/.90bsfc(boosted e85) = 808hp on e85.

thoughts?

[EFI Tuning]

You are correct in your thought process.

The ECM will force EOI to be 5 degrees before the spark advance. The maximum window is going to be from the time the exhaust valve closes to the 5 degrees before the spark advance. That's not to say that window is ideal.

time (ms) = degrees / (6 * RPM)

time = 320 / (6 * 6500) = 8.2 ms window

Tim