Hi everyone. I'm starting to fiddle with target injector timing and wanted some input. How much does the timing need to change VS RPM/Load??

My ecu is a 3.2 so in the info page I used the formula to calculate target injector timing and I get 630. We went and used the engine dyno program to get my motor displayed and turned it over and the intake valve closes at about 630 degrees.

Now, originally I used 630 and used it in ALL the tables. Idle to redline. Dynoed well (477 rwhp mustang dyno) and drove well but idle and low speed driveability wasn't the sharpest.

The other day thinking my ecu might have been a version 3.02 and not 3.2 (3.02 uses a different calculation incl using base offest timing etc), I changed the target injector timing to 360. the wideband showed on the left side (rich correction) and the idle and throttle response was sharp as heck. i was surprised. The midrange and top end didnt feel so great.

Now the other day fiddling with the builders on the engine simulator software I see that my intake valve OPENS at 330 degrees. It closes at 630 degrees. Right now I have it set at idle at 300 degrees, then 170, then 40 and 630 for above 5500 rpm.

How much does the timing need to be changed vs rpm etc ? My LT4 is a solid roller that routinely sees 7800-8000 rpm. We came up with the numbers above thinking that spraying the injector right when the intake valve closes is best for high rpm because the motor is spinning so fast the fuel doesn't get much time to hit the valve. for idle we have the setting of 320 degrees. In that case we figured firing the injector 20 degrees before the valve opens is sufficient at idle because the air speed is very slow. In the middle rpms I just got the #s that were equally apart from when the valve closes at 630 degrees and when it opens at 330 degrees.


SOrry for all this I am still learning. I hope someone can correct me or add some info to help me understand this better. I Spoke to DFI and they just said dyno the car and increase/decrease by 90 degrees and see what it likes. But what about low rpm and idle..? part throttle?
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I just started thinking about the engine revolutions in degrees. AT what position is 0 ??

 

I just realized that something doesnt add up. My intake duration is 236 degrees. If my intake valve closes at 630 degrees. that would mean it needs to be opening at 630-236 would it not? That gives 394 degrees. hmm im confused

 

I went outlast night and just set everything to 590 using the 51 degrees intake valve closing angle off the cm card as the gen 7 says to do. She pull insane in the cold air last night !! Maybe i was just overthinking the firing times and that the ecu just needs to know when it closes so it can adjust on its own??

 

It's been my experience that you have to play with the target injector timing on the dyno to get it just right. You might not see much of a power increase, but you should see the fuel requirements drop a bit when you hit the sweet spot. Less fuel sticks to the area around the valves, so the engine gets fueled a little more efficiently, and therefore you need to inject somewhat less fuel to achieve the same result.

At lower engine speeds, I don't think that there is enough air velocity for the target injector timing to make that big of a difference. You'll do better tuning the transient fuel tables to make the driveability better down low.

If you're trying to tune on the street, use the help documentation as a guideline down low, and watch your Air:Fuel numbers as you get into it to see how your fueling changes as you tweak the injector timing for higher engine speeds.

 

Thanks for the reply. So with less fueling requirements I should be looking for a lower VE # ?

 

Your true VE isn't changing, but the numbers in your table may drop slightly because the engine is getting more of the fuel that you are injecting. By timing the injection event properly, more fuel gets to the cylinder and less fuel sticks to the surfaces around the intake valves.