Injector timing

[ViennaHog]

Typical sequential EFI systems open the injector right before the intake valve opens to get optimum mixing of air and fuel. AFAIK this timing is not accessible via our trusted tuning systems or is the TTS IVO function among other things used to move the injector timing around? If not what is the effect of a mismatch between intake valve opening and injector opening? If you compare the specs of a typical HD stock cam even with a mild cam like the 57H the difference in IVO is significant. Any thoughts?

[ultraswede]

I used to tune the 5,3l Gen III GM v8 with HPtuners.

I experimented a bit with injection start timing, witch is accessible on HPtuners.
What I saw, was a significant worsening of fuel consumption when I moved the start of injection to spray on an open valve.

The thing to do is to spray on the hot closed valve, to give the fuel time to evaporate, and cooling the valve at the same time.
Then we will also avoid raw fuel hitting the cylinder wall, potentially washing away the oil film.

[joe_lyons]

I too have wondered about this.  And didn't get much of anything when I talked to Steve Cole.  And now I wonder about the Delphi ignition system knowing when max cyl pressure is and from that we could tune ignition a lot better I would think.

[strokerjlk]

I too have wondered about this.  And didn't get much of anything when I talked to Steve Cole.  And now I wonder about the Delphi ignition system knowing when max cyl pressure is and from that we could tune ignition a lot better I would think.

thats what started all this mt 8 BS.
you were not around here at that time. but everybody used to whine about it .
everyone wanted calibrations with diff cams. unable to produce actual maps from bikes with diff cam timing events,we got the mt 8 fluff.
it worked, it shut everone up. until now.

[joe_lyons]

From what I got from Steve Cole was that the cam selector doesn't mess with injector timing.  I would like to know when the injector fires though.

[rbabos]

From what I got from Steve Cole was that the cam selector doesn't mess with injector timing.  I would like to know when the injector fires though.

Just before the intake opens. Not sure there is any (normal) means to change this in the Delphi.
Ron

[joe_lyons]

Stock cam is around 3°-12 atdc but most aftermarket are 15-30 btdc.  Just saying that if it timed for 3° then its quite a bit off unless stock it fires at 30 or so?

[ultraswede]

Just before the intake opens.

How do you know that?

[rbabos]

Just before the intake opens.

How do you know that?

Standard proven method with the best results.
Ron

[ultraswede]

Standard proven method with the best results.

The norm is to inject on a closed inlet valve.

Has anyone actually measured when our system inject the fuel.
It can be easily done, if one has an oscilloscope.
Take one pule from a known ignition timing, and one pulse from the injector then compare the time in between compensated for the Rpm.

I don't have an oscilloscope

[rbabos]

Standard proven method with the best results.

The norm is to inject on a closed inlet valve.

Has anyone actually measured when our system inject the fuel.
It can be easily done, if one has an oscilloscope.
Take one pule from a known ignition timing, and one pulse from the injector then compare the time in between compensated for the Rpm.

I don't have an oscilloscope

Just before the intake opens means the valve is closed. Didn't think that needed to be explained.
Ron

[ultraswede]

[quoteJust before the intake opens means the valve is closed. Didn't think that needed to be explained.
Ron][/quote]

Sorry for not understanding the engineering expression "just"

[Rider57]

65ms  before the valve opens if I remember correctly.

[ultraswede]

[quote65ms  before the valve opens if I remember correctly.][/quote]


With due respect, I don't think 65ms is possible.

At 2000 rpm the crank moves 12 degrees every ms.
That would make 12x65 = 780 degrees.

[Rider57]

Thats what I come up with also, but thats what I measure with the oscope.
There is some variation that I think is caused by the chain drive and cam timing lapse vs. what is being told to the ecu via ckp.

[FLTRI]

Kinda addresses the importance of precise injector timing.
Bob

[Rider57]

 

Kinda addresses the importance of precise injector timing.
Bob

[1FSTRK]

It is always amazing how things that are out of reach for adjustment or not fully understood are judged to be unimportant.

[FLTRI]

It is always amazing how things that are out of reach for adjustment or not fully understood are judged to be unimportant.

...or judged to be important. 
Bob

[joe_lyons]

I sent this question to the president of dynojet so hopefully an answer within a couple of days or mabie tobefrank knows?

[hrdtail78]

It fires on a closed valve.  Changing cams?  The ECM still knows when that valve closes.  We can see what the ECM reads with MT8's and the "fluff" of cam data.  6-7 IVO valvues?  Why couldn't injector timing be treated like  ignition timing in a MAP based system?

[ViennaHog]

There are a few tuning devices out there for race car applications that based on the cam profile allow to set injector timing. To me it appears much more complicated than just firing at the closed valve. From a brief look it seems more like firing when the cam is on the 'right' spot of the lobe. System voltage is another consideration as it affects the 'lag' of the injector between the actual command to fire and the reaction of the injector.
So I doubt that a few data gleaned from the map sensor readings would allow the ECM to recalculate the correct timing after a cam change.

Again, I just read a few articles so WTFDIK

[hrdtail78]

Ok.

[FLTRI]

So I doubt that a few data gleaned from the map sensor readings would allow the ECM to recalculate the correct timing after a cam change.

So uh how do it know? It don't. That's why TTS has a cam estimator feature?
Bob

[joe_lyons]

Ole king Cole already said that cam tune has nothing to do with injector timing just map sample.