Injector Offset ?'s vs LS1 edit

[John Skiba]

Guys, I am not here to say THIS is the correct or incorrect way to do it. There are MANY tuning methods out there on the NET. I agree with some and disagree with many. I am merely sharing my own personal experiences from over 2+ years ago.

That being said, I just recently revisited the offset table because NOW we have all sort of support tables and VERY cool tools to collect this data with. Thanks EFILive!

2+ years ago, using LS1Edit, a Techedge wideband, I wanted to tune the car for maximum performance while keeping things simple and together. This meant using a known (GM MAF Table - Z06 85mm screenless) since that's what I was using, using 32lb injectors with math correct IFR table (since this is a known by flow data).

I merely wanted the PE table to be predictable. Meaning, if I commanded 12.9 AF in the PE table, then my wideband will also show 12.9 AF. After all, isn't the commanded AFR supposed to match the actually AFR? :P Is trying to keep things simple to much to ask for?

At the time, I was looking at "Professional" tunes for help. What I found instead simply left me in . 2+ years later, some things haven't changed... good or bad.

Anyway, the offset table was derived from a known offset table for the injectors. It worked. It still works. All tuning was and still is predictable and easy. Never blew up the motor despite having 86+ thousand miles on it and still running strong 95mph/119mph w/ A4 through a baby cam 216/220. Remember, this was WAY before the VE and SD rage! Now, I'm going to VE tune and by the looks of it, my VE tune isn't going to be crazy changes with MASSIVE spikes and valleys, etc. Just a nice little fine tune. Hopefully.

So, I figured I'd have others try it and so far good results. The below screen shots are from a beta testers LTRIM's with a first crack at 30lb injectors with stock offset table and 30lb injectors with matching modified offset table. NO VE tuning done, etc. This is a cammed car, 224 I believe.

Looks like it worked all while retaining the proper IFR table and I'm sure AFR. But hey, it ALL only my opinion!

There are MANY people from all walks of life that read this board, feel free to drop me a note with any thoughts about this.

Happy tuning all!

[bink]

John - Thanks for he post and images .

I'm in total agreement as to the importance of correct offset tables. I don't have proof but I know how much my Wideband O2 (FJO) AFR vs Commanded AFR cleaned up after I used the correct offset table with the GTP injectors. I'm open loop (NoGo VE tune) - so I don't have the fuel trims.

Cheers,
joel

[oztracktuning]

I have found Chris Bs spreadsheet for SVO 30s on the the LS1 Edit Faq website

Its based on the Ford offsets

At the Voltages 6, 8, 10, 11, 12, 13 ,14, 15 ,16 and at O pressure

4.6475
2.1182
1.3965
1.1973
1.0313
0.9033
0.7861
0.7148
0.7148

How much can we trust these values?? Are they close to what you are seeing John ?

I have a spreadsheet of numbers i can try.
Eg at 13.0V it is

0.899079
0.99541
1.091739
1.12385
1.155959
1.18807
1.18807
1.18807
1.220179
1.220179
1.220179
1.25229
1.284398
1.284398
1.316509
1.316509
1.316509

[oztracktuning]

I notice that if moving between 12.5V to 13.5 at 50MAP the change is only from 1.218ms to 1.261ms in the spreadsheets values

rather than from 0.653 to 0.547ms as in 'my' stock ones.

Both values move in different directions??

I dont trust the way the data works out.


The original spreadsheet is at http://ls1edit.slowcar.net/injectoroffset.xls

[oztracktuning]

I just prepared these values between 11.5V and 14.5V to use.

0.926358 0.861813 0.802884 0.749232 0.700744 0.657730 0.621406
0.947780 0.881742 0.821451 0.766558 0.716949 0.672940 0.635776
0.969202 0.901672 0.840017 0.783884 0.733153 0.688150 0.650146
0.990624 0.921601 0.858584 0.801210 0.749358 0.703360 0.664516
1.012046 0.941531 0.877151 0.818536 0.765563 0.718570 0.678886
1.033468 0.961460 0.895717 0.835862 0.781767 0.733780 0.693256
1.054890 0.981390 0.914284 0.853188 0.797972 0.748990 0.707626
1.076312 1.001319 0.932851 0.870514 0.814177 0.764200 0.721996
1.097734 1.021249 0.951418 0.887840 0.830382 0.779410 0.736366
1.119156 1.041178 0.969984 0.905166 0.846586 0.794620 0.750736
1.140578 1.061107 0.988551 0.922492 0.862791 0.809830 0.765106
1.162000 1.081037 1.007118 0.939818 0.878996 0.825040 0.779476
1.183422 1.100966 1.025684 0.957144 0.895200 0.840250 0.793846
1.204844 1.120896 1.044251 0.974470 0.911405 0.855460 0.808216
1.226266 1.140825 1.062818 0.991796 0.927610 0.870670 0.822586
1.247688 1.160755 1.081384 1.009122 0.943814 0.885880 0.836956
1.269110 1.180684 1.099951 1.026448 0.960019 0.901090 0.851326

Can anyone indicate what the risk is in trying these values - the stock ones are below in the same range

0.714283 0.607900 0.516715 0.425530 0.364740 0.303950 0.273555
0.744678 0.638295 0.547110 0.471123 0.410333 0.364740 0.303950
0.775073 0.653493 0.577505 0.516715 0.455925 0.395135 0.349543
0.775073 0.668690 0.592703 0.531913 0.471123 0.425530 0.364740
0.805468 0.683888 0.607900 0.547110 0.501518 0.455925 0.395135
0.805468 0.683888 0.607900 0.562308 0.516715 0.455925 0.395135
0.820665 0.699085 0.623098 0.562308 0.516715 0.471123 0.395135
0.835863 0.714283 0.623098 0.562308 0.531913 0.471123 0.395135
0.851060 0.714283 0.638295 0.577505 0.531913 0.471123 0.395135
0.866258 0.729480 0.638295 0.577505 0.531913 0.486320 0.410333
0.866258 0.729480 0.653493 0.577505 0.547110 0.486320 0.410333
0.881456 0.744678 0.668690 0.592703 0.547110 0.501518 0.425530
0.896653 0.759875 0.683888 0.607900 0.562308 0.501518 0.425530
0.896653 0.775073 0.699085 0.607900 0.577505 0.501518 0.440728
0.911851 0.805468 0.699085 0.623098 0.577505 0.516715 0.455925
0.927048 0.820665 0.714283 0.623098 0.577505 0.516715 0.471123
0.942246 0.835863 0.714283 0.623098 0.577505 0.516715 0.471123

[joecar]

I can't say anything about risk either way...

I don't think it could hurt, since isn't the injector closing event the fixed timing point and these values just move up the opening event...?

The gradients are in the same directions so it would probably be okay.

I'm interested in how you obtained the new values...?

How do you measure the effect of the new values...?

Regards
Joe

[oztracktuning]

I got the Ford ones - that just rate zero. I took a punt on the 0 to 80 pressure spacing (top to bottom) - looking at the stock values and at the other suggested values in the ls1edit faq spreadsheet - then i just let them do a linear fill in between - vertically only between the zero pressure cell and the 80 cell for that voltage.

I am hoping to see what John Skiba has to say about them. These SVO 30s seem to give people issues at idle - mine are fine everywhere else - i am guessing and hoping that this table may be why.

[jfpilla]

I've had an SVO 30 Offset Table for some time. I used the calculator with some values that, I think, Allcammedup had posted on the Corvette Forum. I forgot I had it because I was concerned about doing something bad. This thread gave me the push to try it out. Man, I wish I had done it long ago. I'm now using the stock MAF table. Trims are more equal from cell to cell, rafacig is -3 to +2, iacltdac is -2 to +2, the best they have ever been. No BS when I say that the car is idling and running as smoothly as when I had it in SD.
I'm not suggesting anyone do it. I still have some residual fear and want to run it a few days and see how it holds up.

[joecar]

... isn't the injector closing event the fixed timing point and these values [the offset table] just move up the opening event...?

Would this be a correct statement...?

[jfpilla]

Would this be a correct statement...?

I think so ,although, I still don't really know what I'm doing. My thinking is to attempt to inject the same total amount of fuel as when my MAF values were higher, but do it over a longer period of time. The larger injectors apparently are slow at low RPM, so it seems to make sense that injecting fuel sooner could smooth things out. I suspect that we all know this but don't have an SVO 30 table that we are confident is right.
I should mention that Dynair matches perfectly with MAF up to 3000rpms. That's the highest I've reved so far. Cells 7, 10 and 11 seem to lock at 0 consistantly. I need to go to the track to test, as John said, the predictability of the PE table.