Ok, let me open by saying I got up at 1:30am here while thinking about the injector duty cycle at 6000rpm. (when I say thinking I mean
dreaming. Yes this is sad but I've always been kinda this way)
Anyway I came up with 20ms. Then I got to remembering there was a thread that had a table in it with various injector lag times and wanted to find it. Well I did. This is it. OK so now read on......
Quote:
Originally Posted by XfireZ51
Scott,
Yes, its msec. And the variance is the point of posting this.
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Yes, variance is the point of the post. I agree. Now, how much variance is too much and therefore a
tuned chip is needed vs kinda wanted? (you know to be dead nuts on).
Quote:
Originally Posted by XfireZ51
An injector isn't just an injector. Swapping different brands, although same fuel flow rating, has consequences in the tune. This is especially true at idle and short pulsewidth situations where the opening time is a proportionately larger part of the total calc'd pulsewidth.
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I agree lower rpm and idle would feel the differences (make more difference). Now lets run some actual numbers.
Quote:
Originally Posted by XfireZ51
Now some on this board might say, "yeah but.." when you tune to 14.7:1 or to a 128 BLM, doesn't the ECM overcome this. Without the correct injector offset, you'll undershoot or overshoot the actual calc'd pulsewidth the ECM is looking for. In some cases, you may "run out of injector" or have too high a duty cycle.
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Now this is the area in which the dream centered. It's an accurate statement but..... what are some numbers? Given the worst case OT (also CT) in the table on the link given in your OP what can the ECM do to correct it? (how far down the BLM table must it go?)
Does it in fact run out of room? Also how would the component to component variance (inj to inj) of a singe vendor fare? That is, given a batch of inj that were not "matched", when does trouble begin? (largest variance to be tolerated in OT as effected by internal resistance?)
For sake of computation we could even use an OT larger than any listed e.g. 2ms.
To do all this we'd need some info. What is the max swing (in ms) the ECM can effect on pulse with from min BLM to max BLM? I have no idea. Maybe you do?
Quote:
Originally Posted by XfireZ51
By using the correct offset, you may find that you can lower the overall VE% and have a smoother VE map which means the motor operates more smoothly and predictably in varying conditions.
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Yes, we may indeed find.
FYI did you notice in the table they talk about OT and CT being important but the table makes no effort to show CT. Seem it only shows OT.
Surely they can not be suggesting they are the same.
So ok, I've written up all that was buzzing around in my head. Time for more ZZZs. I wonder if I'll return to this topic in my dream?
