Thanks for the info. Your curve differs a fair amount from Chris B.'s at the low end.

I had tweaked the MAF settings at the low end to reduce my Ltrims down to negative 5% - 8%. I'll bet fixing the offset would cure some of the richness at closed loop start-up too.

 

Actually, that's why I started to modify the offset curve (the final straw at least). I was setting SES lights in the morning because of B1 and B2 rich.

 

Any new info?

 

Is the injector offset truly used to position the
fuel shot? Or just to calculate out the "effective
pulse width" error from finite opening/closing time?

 

You guys have been totally ignoring my posts on the LTFT issue haven't you. If you have a lid it does that. The MAF does not read the same with the lid. An interesting point from another one of my posts, the Holdens have the MAF installed at a 90 degree angle from ours. They specifically did it so that the readings were not skewed. Unfortunately, the way they designed our intake on top of the radiator prevents us from doing this, so I can't test it without major changes. The last thing that may be hurting us is reversion in the intake tract. I am not sure how serious that is in cammed cars, and I don't know how much that could be affecting it. One guy put his stock lid on and his trims went back to zero. It's so frustrating that I am about to start running without my MAF. I wanted to use the Dynamic Air Flow PID to log the difference between the speed density airflow and MAF airflow, but unfortunately the Dynamic Air Flow only appears to be a speed density calculation when the MAF is disconnected.

 

I read them. In fact I once suggested (half in jest)
that there might be a "magic MAF angle" that made
a descreened MAF most proper-reading. But in the
end if it's a MAF problem the MAF table can true it
up.

So if you have the MAF attached, does the Dynamic
Air Flow ever differ from the MAF airflow? Like, logging
them both and looking for deviation between them,
might highlight the regions where the speed density
is taking over in full or in part?

 

I tried that. As soon as you plug the MAF in they match. It sucks. The MAF must take over or something.

 

I have been tuning for the last few days without it and life is easier i can tell you that

 

The injector Flow rate is the Actual flow rate of the injector. The injector Offset is used to compensate for the Injector opening time. It is really a fixed pulse width that is added to every pulse to account for the injector opening time.

 

The way I make it out the table is an "effective"
open-time offset, based on system voltage (which
makes sense because voltage is time-to-current
in a solenoid and current is what moves it over the
spring and pressure head). The voltage axis is volts,
not mV.

I haven't seen anyone discuss the PCM implementation
of injector pulse width calcs but I believe it embeds
this offset as an adder after calculating the shot pulse
width from the main fuel air multiplier, dynamic airflow
and RPM. Or just dynamic cylinder air. The offset, added
to a calculated fuel shot, is meant to make the pulsed
mode delivery match "straight flow" based arithmetic.

I think (and hope to prove) that inj offset can be
calculated from a two-pulse-width injector flow test.
Like using 2mS/10mS and 8mS/10mS pulses, the X
intercept of a straight line fit (flow vs pulse width)
will be the offset.

Just the small matter of building a sub-%-accurate
injector pulse driver/counter and fuel sysem, and
away we go.

 

Jimmy - looks to me (intuitively, since I really don't understand your basic assumptions) like you're correct. Here is the table comparison values for a stock 2001 LS6 and a GM ASA Tune with the Bosch GTP inectors. Seems like the values in the useful range are a multiple of 0.015198. Make sense??





LABELS Battery Volts {link: GM.VOLTS}
Manifold Vacuum kPa {link: GM.MANVAC} 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0
0 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.045593 0.045593 0.015198 0.015198 0.015198 0.030395 0.030395 -0.015198 0.015198 0.015198 0.015198
5 -5.136758 -5.136758 0.075988 0.151975 0.106383 0.075988 0.060790 0.045593 0.045593 0.030395 0.030395 0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.015198
10 -5.121560 -5.121560 0.075988 0.167173 0.121580 0.075988 0.060790 0.045593 0.030395 0.015198 0.015198 0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.015198 0.015198
15 -5.136758 -5.136758 0.075988 0.151975 0.121580 0.075988 0.060790 0.045593 0.030395 0.030395 0.015198 0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.015198
20 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.045593 0.045593 0.015198 0.030395 0.015198 0.030395 0.030395 -0.015198 -0.015198 -0.015198 -0.015198 -0.015198
25 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.060790 0.045593 0.015198 0.015198 0.015198 0.015198 -0.015198 -0.015198 -0.015198
30 -5.121560 -5.121560 0.075988 0.151975 0.121580 0.075988 0.060790 0.060790 0.030395 0.030395 0.015198 0.015198 -0.015198 -0.015198 -0.015198 -0.015198 -0.015198 0.015198
35 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.045593 0.045593 0.015198 0.015198 0.015198 0.015198 -0.015198 -0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198
40 -5.121560 -5.121560 0.075988 0.151975 0.121580 0.075988 0.060790 0.060790 0.045593 0.015198 0.015198 0.015198 0.030395 0.030395 0.015198 -0.030395 -0.030395 -0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.015198
45 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.060790 0.045593 0.030395 0.015198 0.015198 0.015198 -0.015198 -0.030395 -0.030395 -0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.015198 0.015198 0.015198
50 -5.121560 -5.121560 0.075988 0.167173 0.106383 0.075988 0.060790 0.045593 0.030395 0.030395 0.015198 0.015198 0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.015198 0.030395 0.015198 0.015198
55 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.060790 0.030395 0.030395 0.015198 0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198 0.015198 0.030395 0.030395 0.015198 0.015198
60 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.060790 0.060790 0.045593 0.030395 0.015198 0.015198 0.030395 0.045593 0.015198 -0.015198 -0.015198 0.015198 0.015198 0.030395 0.030395 0.030395 0.015198 0.015198
65 -5.121560 -5.121560 0.075988 0.151975 0.106383 0.075988 0.075988 0.045593 0.030395 0.030395 0.030395 0.015198 -0.015198 -0.015198 -0.015198 0.015198 0.015198 0.030395 0.030395 0.030395 0.015198 0.015198
70 -5.121560 -5.121560 0.075988 0.151975 0.121580 0.075988 0.060790 0.060790 0.045593 0.015198 0.015198 0.015198 0.015198 -0.015198 -0.015198 0.015198 0.015198 0.030395 0.030395 0.030395 0.015198 0.015198
75 -5.136758 -5.136758 0.075988 0.151975 0.106383 0.075988 0.060790 0.045593 0.045593 0.030395 0.015198 0.015198 0.015198 -0.015198 0.015198 0.015198 0.030395 0.030395 0.030395 0.015198 0.015198
80 -5.121560 -5.121560 0.075988 0.167173 0.106383 0.060790 0.060790 0.060790 0.030395 0.015198 0.030395 0.015198 0.030395 0.045593 0.015198 -0.015198 -0.015198 0.015198 0.015198 0.030395 0.030395 0.030395 0.015198 0.015198


************************************************** ************************************************** ******************************************

HAPPY THANKSGIVING TO ALL!!!

 

Anyone else still trying to figure out this damn offset issue?

I'm running SVO 30's and just did a quick 'test' at WOT. I believe I read somewhere (can't remember where now) that the SVO's have an offset of ~0.8mS at 12V (I really need to find where I read that). Based on the stock table, that's approximately a 25% longer offset than the stock 28lbers. So, I increased the table by 23~26% (due to PCM rounding to the nearest multiple of 0.015198) and went for a quick drive. The AFR leaned out a bit at WOT. It could just be a calibration error in the butt dyno, but I thought the car felt like it pulled a little harder. Then I started thinking...feels a little stronger....wants more fuel....maybe I'm on to something here.

So, back to my original question....anyone have any idea what to do with the offset table?

 

There is no single answer that suits all, unfortunately. Offset is determined by a combination of factors:

quality injector coils
state of electrical system
quality of injector drivers in PCM
fuel pressure to overcome
vacuum/boost to add/overcome
accessory current and voltage draw

And that's just before you get to the electro-mechanical bits that determine *ideal* dead time. And to accurately meter all the fuel, you need to factor in not only the time the injector takes to open, but the lag on closing.

The you have to find out whether the manufacturer flow rates their injectors using a gas or a solvent. Solvents typically drop 3lbs/hr over gas, and most manufacturers rate their injectors in gas to overstate their *higher* flowing injectors, for marketing reasons.

The most accurate way is to scope the injectors and measure them real-time.

I have read though, that 1.3ms on-time is average for saturated injectors and 0.6ms for low-Z.

 

Wow. OLD POST.

This post was made back when LS1 Edit showed the Short-pulse adder as the injector offset. Not the current tables that are available now.

At WOT everything is batch anyways, so the offset of the injector doesn't matter that much. Just change your WOT commanded A/F to compensate.

I use the same SVO 30# table that I developed back then (2002?) for my RC 75# injectors and it works fine.

 

Can you post the tables you have modified for your SVO 30s?

 

just use the values from the stock ford tunes, they got voltage offset tables. empirically i arrived at this relationship:
offset=k/(voltage^3) where k is some constant that i dont know what it means, probably based on impedance and physical characteristics of an injector

 

#1 I've never seen a stock Ford tune and don't know how to get my eyes on a copy of one.

#2 Do they use the same 'drivers' mentioned above. If not, won't that affect the performance of the injector in our cars?

 

SCT software has ford tunes, and now that HPT got into Ford stuff, you can view it that way too.

i dunno anything about the 'drivers'

 

Do either of those vendors offer a demo copy of thier software (like EFILive does) so that I could load a tune into it and see what the tables are set at?

 

nope.

hack the planet!