When does an injector "turn-on"

[MNR-0]

When does an injector turn on? What tells is to? The reluctor wheel? Cam pickup sensor?

Ideally an injector should fire when the valve is opening. Is there any way to control the turn-on point in reference to degrees camshaft rotation or calculated valve opening?

Adjusting the injector offset is purely a compensation for injector current saturation plus other mechannics. It is not a timebase past or before top dead centre.

[Chris@HPTuners]

the PCM has an end of injection target in crank degrees (not in the editor for LS1's but is there for LS2's). it calculates the start of injection angle from the desired injector pulsewidth and works back from the EOT.

Chris...

[redhardsupra]

so does that mean it's got a preset angle for which it thinks there's an optimal injection timing? wouldnt messing with valve event timings change this constant to an variable? can we view/edit that final value for which it's aiming?

[MNR-0]

Thanks Chris.

This EOT, what is it? I realise it must be hard-coded.

When you put in a much larger camshaft, you increase the duration of the valve open. It would be nice to tune injectors to take advantage of this as opposed to timing off a stock camshaft profile, puddling off the valve.

If I know what that EOT is, with respect to crank degrees, then I can re-phase the reluctor wheel for optimum injector timing. Ignition timing will just follow anyway.

[Chris@HPTuners]

there are tables in the PCM for the EOIT, just not in the editor for now.

[MNR-0]

OK. This would be great as an advanced feature in the future.

Ignition and injector timing together. What more could you want.

I think EFILive has injector timing...

[MNR-0]

Ive opened up my stock tune using the demo version of EFILive and can see the Injection Timing and Injection Timing Trim. It seems to be in ms with boundaries of 0-8ms.

Here are the tables:

-This table will offset the actual opening of the injector referenced to the reference pulses and engine coolant temperature.
{B3702}
40 2.550781
-28 2.550781
-16 2.550781
-4 2.550781
8 2.550781
20 2.550781
32 3.550781
44 4.550781
56 4.550781
68 5.550781
80 5.550781
92 5.550781
104 5.550781
116 5.550781
128 5.550781
140 5.550781

This table modifies the timing of the additional pulses that maybe required after the {B3702} Injection Timing offset limits are reached. These values should not exceed those in {B3702} Injection Timing.
{B3703}
40 5.550781
-28 5.550781
-16 5.550781
-4 5.550781
8 5.550781
20 5.550781
32 5.550781
44 5.550781
56 5.550781
68 5.550781
80 5.550781
92 5.550781
104 5.550781
116 5.550781
128 5.550781
140 5.550781

I *assume* these are delays or adders to injector turn-off times. Can't see where we can change the EOIT hardpoint though. Won't accept negative values.

Am I incorrect in thinking the EOIT is preset at BDC?

[Chris@HPTuners]

i think someone needs to revisit their units

there is also an extra value (the injection boundary) that defines the offset from TDC where the EOIT is measured from, i just added these things to the definitions for all LS1's. Should be compiled into the latest beta over the next day or so.

The mouseover help should explain it enough to understand, if not email me.

Chris...

[WS6FirebirdTA00]

interesting...

[MNR-0]

i think someone needs to revisit their units

there is also an extra value (the injection boundary) that defines the offset from TDC where the EOIT is measured from, i just added these things to the definitions for all LS1's. Should be compiled into the latest beta over the next day or so.

The mouseover help should explain it enough to understand, if not email me.

Chris...

Awesome Chris! Waiting for Beta now...

For those that want to know why I bothered with all this, read here ==> http://fordfuelinjection.com/files/T...tor_Timing.pdf
Its for a Frog, but the same principle applies.

I too couldn't understand the units as "ms" to control EOIT - WTF!!!????

The LS2 does have nice crank angles to work with. Those units in EFI Live should read crank degrees. Now THAT makes snese. I also realise this will mostly affect idle and off-idle response, but anything to help tuners to control air, fuel and spark everywhere is a welcome addition.

[WS6FirebirdTA00]

yeah that would be great

[Chris@HPTuners]

well actually the LS1 is not degrees either, its measured in crank refernce pulses. all you need to know is bigger numbers mean longer.

[MODDOO]

Anyone playing with this yet?

[VYSSWagon]

so does that mean it's got a preset angle for which it thinks there's an optimal injection timing? wouldnt messing with valve event timings change this constant to an variable? can we view/edit that final value for which it's aiming?

Consider that as Injector Duty Cycle approaches 100%, the pulse width approaches the point where the valve doesn't close - optimal injection timing becomes irrelevant.

Larger injectors have the benefit of being able to fire while the intake valve is open at high RPM WOT (into moving air), but it wouldn't be capable of doing a short enough pulse with for low RPM part throttle and forget idle.
Small injectors are open so long that inject fuel at a closed inlet valve. Neither can be good for efficiency.

Wouldn't primary and secondary injectors be great...

[redhardsupra]

ok cool. so how do we determine the happy middle? what condition do we want to achieve? spraying only when the valve is open?

[MODDOO]

Or only when it's closed?

I remember another thread where this ws discussed.
The heat from the valve vaporizes the fuel better...

[redhardsupra]

doubt it, vaporization happens best when not puddled (sitting on top of a valve)

[VYSSWagon]

ok cool. so how do we determine the happy middle? what condition do we want to achieve? spraying only when the valve is open?

Inlet valve duration (seconds) = Inlet Valve Duration (degrees) / (3 x RPM)

Example:
Say 6000 RPM and 240 degree duration:

240/(3 x 6000) = 13.3 ms

And say I can run at 0.9g/cyl of air at an AFR of 12.5

Fuel per cylinder = 0.9 / 12.5 = 0.072g

Required IFR = Fuel per cylinder / Inlet valve duration
= 0.072 / 0.0133 (secs) = 5.4 g/s (Probably at 0-2kPa vacuum - near atmospheric pressure)

That is one big MF injector!! Stocker 28lbers are about 3.7g/s, so it would be about a 42lb. You go forced induction it gets worse...

Idle RPM would be driven by minimum pulse width, say 1200RPM to give you about 0.18g/cyl of air (pulse width of about 2ms)...

It doesn't work for every day use, but for a race/drag situation I suppose it would be ok.

[MNR-0]

Interesting data that. Still, 42lbs aint gonna be near enough. Even though you have 240* duration, you want the fuel to spray on average around the peak cylinder vacuum point (mix of max. cylinder speed and cam lift) which is usually around 70* BBDC, so now you have 140* crank angle.

Do that math on that and you need around 2 times the size of the 42lbs. Now that's at 6000. You need to account for max RPM, thus if its 7000RPM redline, its even bigger.

[redhardsupra]

guys, do you have any charts/diagrams for this? i think visually, and with this whole 'two rounds on a circle' approach i get lost. i've seen some cool crank degrees vs injector flow graphs before. could someone make a chart like that, showing where and how long we wanna spray?