That's my understanding of it. Further refinement of final AFR .Quote:
all that matters is in what happens when the voltage changes
FWIW.
Cheers,
joel
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That's my understanding of it. Further refinement of final AFR .Quote:
all that matters is in what happens when the voltage changes
FWIW.
Cheers,
joel
The attachment shows the ltft's for my normal driving. It seems that the offset curve depends on GM MANVAC and BATTERY VOLTS.
Been lurking for a while and have a few questions...
What does this table actually do/represent? It appears this table will adjust the IPW based on MAP and battery voltage. Are we sure that's what it's doing?
What physical properties of the injector/fueling system warrant molestation of this table? I would think coil resistance and valve design (pintle, disc, etc..) would warrant changes, but are those the only factors? Which factors have the most significant impact to this table?
Given an OLSD tune, can an error factor for Injector Off Set table be calculated?
Based on John's posts, if you have a known good MAF calibration, and your IFR table is correct, you now have 2 constants to tune the offset table with. However, in OLSD, with the IFR as your only constant, if you tune your VE table to a commanded 14.63 AFR, then change commanded AFR to say 13.0, it appears you VE table needs more tweaking, when the culprit may be the off-set table. Can the subsequent VE table error somehow be used to calculate a correction factor for the IOS table?
If an error factor cannot be calculated for the IOS table, how do you actually create a valid IOS table?
The fuel injector is basically a selinoid
Reluctance (NOT RESISTANCE) is a form of electrical resistance unique to coils. Electric current flows through the coil’s windings, it builds a magnetic field pulling the pintle off its seat and releasing the fuel. The time it takes for this to happen is directly influenced by the voltage applied to the circuit. And as that field grows, its lines of magnetic force pass through the same windings, causing a reversed-polarity voltage resisting the applied current. As the reluctance disappears about the time the coil reaches full saturation, the lines of magnetic force become stationary and theapplied current reaches its maximum. When the PCM cuts the injector coil circuit, the magnetic field collapses. But as it collapses those same magnetic lines of force pass through the coil windings in the other direction, thus extending the duration of the magnetic field and the opening of the nozzle.
The injector offset is I think there to allow you to tune for different sized coils and adjust for there reluctance. Different sized coils will act differently depending on the number of windings/turns and other factors. I've used the injector offset as a tool to help bigger injectors idle.:muahaha:
Dennis
Quote:
Originally Posted by TAQuickness
Originally Posted by TAQuickness
Been lurking for a while and have a few questions...
What does this table actually do/represent? It appears this table will adjust the IPW based on MAP and battery voltage. Are we sure that's what it's doing?
......Have to log GMMANVAC to link for tuning. The table is from 0 to 80.
......It must adjust IPW. When I lowered my MAF to stock I had to increase IO. It can also be seen in the logging afer making changes.
What physical properties of the injector/fueling system warrant molestation of this table? I would think coil resistance and valve design (pintle, disc, etc..) would warrant changes, but are those the only factors? Which factors have the most significant impact to this table?
......I don't feel like a molester. Whatever the mechanical differences of SVO's I don't know. We think they have a different curve. That's what I'm trying to see.
Based on John's posts, if you have a known good MAF calibration, and your IFR table is correct, you now have 2 constants to tune the offset table with. However, in OLSD, with the IFR as your only constant, if you tune your VE table to a commanded 14.63 AFR, then change commanded AFR to say 13.0, it appears you VE table needs more tweaking, when the culprit may be the off-set table. Can the subsequent VE table error somehow be used to calculate a correction factor for the IOS table?
........I'm trying it from the other end. Hopefully I can get reasonable trims across the board with the MAF and then run in SD and see the affect on PE and VE's, if any. There should be on PE if IPW is affected by IO. PE would seem to be the hard part because it requires so many WOT runs to get good info and the make changes. I was told by a tuner not to bother. Just get close and adjust PE accordingly. He said he has done thousands of tunes and has never seen perfect PE math. Might get lucky.
Given an OLSD tune, can an error factor for Injector Off Set table be calculated?
........Good luck.
Cool. :mrgreen:Quote:
Originally Posted by jfpilla
My idle (open loop, through the MAF) was more stable in terms of AFR and quality once I inserted the GM Offset table for the GTP/WCC/36lb injectors.
Have a Great weekend Joe!!
Cheers,
joel
is that 36 ls/hour@58 psi or 43.5
Joel,Quote:
Originally Posted by bink
Rub it in. Where can we get a table for SVO's?
Enjoy yours too.
Joe
Dirk,
I'm using 43.5. It seems to work as far as tables lining up. I know that there is 40.0 as a possibility. Given the end game it doesn't matter too much.
I may need bigger injectors late spring anyway. I may have to go with injectors that have tables available. LIKE JOEL's.
Joe
My comments are just my opinions, feel free to correct me if you think I'm wrong.
You shouldn't adjust the IPW with offsets.. You can affect IPW by not understanding the values you put in the offset table. Adjusting these values will increase or decrease the amount of time the PCM thinks it takes to reach fully open and fully closed for the injector.
Injector offset affects both the opening and closing of the injector.
I think someone posted that you can adjust IPW's by tweaking the offsets. You should read my previous post in this thread. My guess is that the injector manufacturers base their offset values from the performance characteristics of the coil portion of the injector.
Some more food for thought.
The 98 Corvette and the 98 Z28 uses the same 28.8lb injector but the injector offset tables are different for all entries. TheVette values are higher except from 4.5v – 6v where they are lower. At 13v/50kPa they are 0.167173ms longer.
Maybe this is due to a longer wiring harness and more resistance or maybe just IPW trim.
John
Neither, that's at the GTP pressure (48 psi?).Quote:
Originally Posted by Dirk Diggler
From the Bosch Motorsport Catalog, that Marcin found they are:
34.54 lb/hr @ 43.5 Psi ( 3 Bar)
39.89 lb/hr @ 58.02 Psi (4 Bar)
Cheers,
joel
so what numbers would you put into the spreadsheet 39.89 @ 58.02?Quote:
Originally Posted by bink
and what about 42lb injectors?
thanks!!!!
I have been watching this thread for a while hoping for the silver bullet that suddenly made all the injector tables make sense, especially the Voltage Offset table. Sadly it appears that it is still a bit of a black art.
It would be nice to be able to produce a map that essentially used a factor (similar to BEN) to map out the correct Offset table.
Anyone?
Cheers,
Without the performance characteristics of the injector coil you wouldn't be able to calculate the injector offsets. It's really not a black art, the unknown value is the reluctence of the injector coil at various voltages. Could be that some manufactures cheat the larger injectors by changing the offset value.
:banana:
Quote:
Originally Posted by WicketMike
39.89 lb/hr = 5.026 g/sec.
This is the flow rate at 0 kPa Vacuum (101.3 kPa atmospheric).
Here are the values I use:
Injector Flow Rate (Grams/Second)
Manifold Vacuum kPa Value
0 kPa - 5.031250 g/sec
5 - 5.093750
10 - 5.101563
15 -5.148438
20 - 5.179688
25 - 5.203125
30 - 5.218750
35 - 5.250000
40 - 5.304688
45 - 5.335938
50 - 5.359375
55 - 5.375000
60 - 5.406250
65 - 5.421875
70 - 5.468750
75 - 5.484375
80 - 5.539063
Cheers,
joel
And you also have tables B3702, B3703, B4001, B4003, B4004 and B4005 - which all seem to be injector specific.Quote:
Originally Posted by MN C5
I wonder if RC Engineering. or similar injector service co., can determine these values when they flow and blueprint??
:cheers:
joel
If there was a means of measuring and correlating the mechanical motion and the electrical waveform
for opening and closing of injectors, that would clear all this up...
Good question Joel, I wonder if they could. You'd think they certainly should have the answers.Quote:
Originally Posted by bink
:exactly:
Perhaps because the values being dealt with are so small (millisecounds) that changing some of the other values has little affect on how the injector performs.
Unless I missed something, I don't think you need a MAF to do this. Just to make sure my foot doesn't fit in my mouth, I'm gonna go try a few things before I elaborate too much.
A way around this may be to look at a peak and hold injector driver. I went with an acceleronics versafueler, which allows me to run stock offset tables (Perhaps with minor tweaking down the road) and get very high quality, low pulsewidth performance from the new 72# delphi (low z) injectors. As of my last drive this morning, I am sometimes seeing a steady 1.7-1.8 pulsewidth at decel and idle. From a fuel point of view, it is almost like my wife's stock Avalanche (you have look past the cam bumpin ;))
I ran the truck briefly (~15min) at idle with the old 60# motos and it was smoother than without the versafueler for sure... My idle AFR was 15.0 without the device, and 13.8 after installation (and no change to the tune file) -- thats pretty good pulsewidth that could be reclaimed.
The driver works with either high or low z injectors.
I have with my offset values met a bit of a problem.
I have been trimming and trimming my VE table and having trouble getting some cells to become lean enough. I have even tried reducing the low map offset values eg the ones at 80-55 manifold pressure ie 14-45map.
It helped a bit but some cells dont want to lean out.
The culprits are
1200rpm at 25map 0.922
1600rpm at 20map 0.87
1600rpm at 25map 0.90
1600rpm at 30map 0.92
2000rpm at 20map 0.89
2400rpm at 20map 0.94
3200rpm at 20map 0.88
All other cells are fine. Including
2800 at 15 map and
surprizingly 3200 at 15 (when 20 was bad??)
I am wondering if i need to tweak the minimum pulse width settings or something?? What can i do.
The car is set at the moment with DFCO turned off. Should i turn the DFCO and not worry about it or maybe even just go back to the stock offset figures. I had the AFRs good everywhere before???
Good if someone can help - i am technically stuck.
Ok, I installed my 60 lb mototron inj. IFR table from spreadsheet etc. When I hold the rpms constant at 2K, the car misses and I can see the AFR go from 14 to about 15 or 16 momentarily. I am thinking that the 60 lb inj require more time to open. So I start increasing the offset table in 10 % increments. At 30 to 35% increase, the miss is gone. However, I am running very rich at higher rpm (no load so far). So, for for my application, it seems the offset table needs to be tweeked. I will now reduce the lower manifold vacuum values to probably 15% then do some logging to dial it in further.
I have heard that some people only adjusted the IFR table for these injectors and they run fine. It is a little frustrating if this is true and why would it be diff. for my application? I question if I am compensating for a bad injector.
I have found out the problem is that SVO 30 injectors use older technology and cant open any shorter than what mine are now. So the problem is unsolvable with these injectors. I have gone back to the original offsets at the moment....
You need to adjust the IFR table and the VE table to get the mixtures right , adjusting the injector pulsewidth voltage table is not the right place to be looking, its a offset for varying voltage and needs some special equipment to get it rightQuote:
Originally Posted by hpcubed
what kind of equipment?Quote:
Originally Posted by Delco
A full injector test bench with variable voltage , pcm simulator etcQuote:
Originally Posted by TAQuickness
I have a few comments on this topic and may be completely wrong, but may not...
The way I understand the injector offset, its an adder to the total pulsewidth used to make up for the time it takes the injector to fully open and close. So once the PCM calculates the needed fuel and determines the injector time, it looks up the offset and adds that value to get the final pulsewidth. This value is unique to each injector and should be supplied by the manufacturer, not calculated or scaled.
The offset becomes very important in idle / low rpm tuning. At idle when pulsewidths are small, the offset is a much larger percentage of the total than at high rpms. If the offset is .5 milliseconds at 14volts and the pulsewidth is only 2.5 milliseconds, the offset is 20% of the total. Compared to only 3% of a 15ms pulsewidth at higher rpms.
Now some will say you can just adjust VE to bring idle fueling back in line, which is true. ... but only for that specific voltage. Once there is a voltage difference (under loads, cruise, idle, etc...) and the PCM uses a different offset, the fueling is off a little again. Get the correct offsets input first, then tune VE and fueling should be very similar under those different conditions.
To take it beyond the normal thinking - You could add a fixed amount of fuel to every pulsewidth by increasing the offset table. In effect, that would make a greater percentage change to idle fueling.
From my personal experience just last week -
I installed a set of Bosch green top injectors, a set of TEA heads and a new cam. I took my PCM completely back to default values in timing, MAF, VE, idle airflow, etc... I plugged in the new IFR, new offset values, and set idle at 700 rpms. Idling for 10 minutes, one bank showed +1.95 the other was a solid 0. Cruising trim values were between -2 and -4.
For the offset, I found a few posts on the internet referencing the offset values from Ford PCMs that basically matched the post by ChrisB with the values. There seemed to be some confusion as the same offset values were posted for the red top and green top injectors, both claiming to be from the lightning truck. Finally, I hit paydirt and found offset numbers for the green tops that had just been independently tested. The numbers were slightly smaller than those I had previously found, but more than double the original values my PCM had to begin with.
please send me the green top's offset numbers to marcinpohl at gmail dot com
thanks
True to a degree but hopefully you have a fully functing alternator regualted properly so the voltage the injector normally sees is nice and constant the table is to account for changes in this offset.Quote:
Originally Posted by BigTex
Yes GM did a very good job on this part of the calculation and changing the injectors is going to affect it slightly BUT unless yopu have the right test equipment you are going to make the problems worse rather than better.
A much clearer explaination:thankyou2: I share your understanding of the purpose of injector offset and how the PCM applies the values to the injector signal.
:banana:
lol I thought just explaining how a magnetic coil worked would help:nixweiss:
That's fine, your explanation is good :cheers:;Quote:
Originally Posted by MN C5
injector does not react instantly;
the coil has inductance, so it's has finite electrical response (which also depends on applied voltage);
the pintle has mass, spring pressure, FPR/MAP pressure difference across it, so it has finite mechanical response to the electrical response.
This table tries to account for this; but how much do we alter this table when changing injectors...? :nixweiss:
And as Delco said, your alternator/regulator is working within limits [hopefully], so at most you'll ever see is a thin stripe thru this table.
I did actually create a MAP of this table just out of interest and noticed (in my case) that the only columns that were hit were 13.5 and 14 volts.
IFR table is known for the given inj. For this test, I am using the maf so no VE correction. I know what the BEN factors are from using the stock inj which gives the error in either my maf or the stock inj. offset table.Quote:
Originally Posted by Delco
When I put the 60 lb inj in and brought the motor up to 2K it would miss (go lean momentarily). When I richened the mixture in my open loop table I did not see the corresponding decrease in AFR meaning the inj. are not opening soon enough to compensate for the slower 60 lb inj.
The inj. offset table is not only an offset for varying voltages, it is also an offset table for a specific injector. So if you are not using the stock inj. then I think that this table may need adjusting.
These 60 lb inj are rated with an opening time of 1.14 ms @14V. Anyone know what the stock inj. turn on time is or the SVOs? This may give a correspondence to the inj offset table.
Thats the thing, you should get the offset information from a reliable source - either the manufacturer or from a trusted source with the proper testing equipment.Quote:
Originally Posted by Delco
I figured you would be interested in the info. Doing my research, I stumbled on many of your posts from several different forums regarding this topic. I'd like to say thank you for digging up as much info about these as you have. Made my work much easier.Quote:
Originally Posted by redhardsupra
Here you go:
6v - 2.55
7v - 2.55
8v - 1.95
9v - 1.48
10v - 1.14
11v - 0.92
12v - 0.75
13v - 0.64
14v - 0.56
15v - 0.49
16v - 0.13
These numbers came from AEM electronics forum. Apparently they will test any customers injectors that aren't in their database. They then add this info to their EMS products install wizard. Read info here:
http://forum.aempower.com/bbs/viewtopic.php?t=11333
For comparison, at 14volts and 0 vacuum, a C5 has a value of .2887 and the green tops have a value twice the size at .56. The previous "known" value for these SVO injectors was thought to be .78x.
Richard
Edit...Never mind...
http://www.bjacked.net/LuvToHunt/for...Dead_Horse.jpg
jfpilla - Any more results?
This is from a while ago but it worked for me:
LABELS Battery Volts {link: GM.VOLTS}
Manifold Vacuum kPa {link: GM.MANVAC} 11.5 12.0 12.5 13.0 13.5 14.0 14.5
0 1.109418 1.033431 0.957443 0.896653 0.835863 0.790270 0.744678
5 1.185406 1.033431 0.987838 0.972641 0.927048 0.942246 0.805468
10 1.185406 1.033431 1.003036 0.972641 0.942246 0.942246 0.835863
15 1.170208 1.033431 1.003036 1.003036 0.942246 0.972641 0.835863
20 1.139813 1.048628 1.003036 1.003036 0.972641 0.972641 0.881456
25 1.200603 1.048628 1.033431 1.003036 0.972641 0.972641 0.881456
30 1.200603 1.079023 1.033431 1.018233 0.972641 1.003036 0.881456
35 1.230998 1.079023 1.048628 1.018233 0.972641 1.003036 0.881456
40 1.155011 1.094221 1.048628 1.018233 1.003036 1.003036 0.881456
45 1.230998 1.094221 1.048628 1.018233 0.972641 1.003036 0.881456
50 1.230998 1.094221 1.048628 1.018233 0.972641 0.896653 0.881456
55 1.230998 1.079023 1.048628 1.018233 0.972641 0.972641 0.835863
60 1.155011 1.079023 1.033431 1.003036 0.972641 0.972641 0.835863
65 1.230998 1.079023 1.033431 1.018233 0.972641 0.972641 0.835863
70 1.246196 1.094221 1.048628 1.018233 0.972641 0.972641 0.835863
75 1.246196 1.094221 1.048628 1.018233 0.972641 0.972641 0.835863
80 1.185406 1.094221 1.048628 1.018233 0.972641 0.972641 0.835863
LABELS Injector Flow Rate (Lbs/Hour)
Manifold Vacuum inHg {link: SAE.MANVAC} Value
0.0 36.954888
1.5 37.202908
3.0 37.450927
4.4 37.636942
5.9 37.884961
7.4 38.194985
8.9 38.318995
10.3 38.629019
11.8 38.753029
13.3 39.063053
14.8 39.187063
16.2 39.497087
17.7 39.621097
19.2 39.931121
20.7 40.055131
22.1 40.365155
23.6 40.489164
LABELS MAF Sensor Calibration (Lbs/Minute)
Hz {link: GM.MAFFREQ} Value
1500 0.188081
1625 0.232518
1750 0.277988
1875 0.327592
2000 0.378230
2125 0.430934
2250 0.489838
2375 0.552877
2500 0.623149
2625 0.702722
2750 0.789528
2875 0.883569
3000 0.982777
3125 1.088185
3250 1.200827
3375 1.318636
3500 1.442646
3625 1.578023
3750 1.725802
3875 1.888048
4000 2.062695
4125 2.245609
4250 2.442991
4375 2.651741
4500 2.872891
4625 3.105409
4750 3.352395
4875 3.608682
5000 3.881503
5125 4.163625
5250 4.463315
5375 4.776440
5500 5.108166
5625 5.462627
5750 5.842923
5875 6.243888
6000 6.666554
6125 7.112989
6250 7.579059
6375 8.069931
6500 8.582504
6625 9.114712
6750 9.671723
6875 10.247334
7000 10.842581
7125 11.459529
7250 12.097145
7375 12.755430
7500 13.438517
7625 14.140205
7750 14.862562
7875 15.609720
8000 16.379613
8125 17.175342
8250 17.995873
8375 18.846373
8500 19.724775
8625 20.632113
8750 21.569419
8875 22.537728
9000 23.534973
9125 24.564253
9250 25.625569
9375 26.718922
9500 27.847410
9625 29.007934
9750 30.204627
9875 31.434390
10000 32.702389
10125 34.003458
10250 35.338629
10375 36.715136
10500 38.128847
10625 39.583894
10750 41.078210
10875 42.620064
11000 44.201188
11125 45.832949
11250 47.508113
11375 49.235981
11500 51.013454
11625 52.845697
11750 54.732711
11875 56.674496
12000 58.678286
Worked for me in the past, but that was a while ago... will let you know if still valid this spring. 32lb Accel injectors. I haven't had much of a chance to play with it over a year+ so these are only for information purposes.
HPQuote:
Originally Posted by hpcubed
Mine are 30lb SVO's and I'm finding the table slopes opposite of the stock table. Your big Injectors are probably more extreme.
You make, I think, a good point about needing adjusting for different injectors. If we install injectors that require a different offset table and we don't adjust the IOS then aren't we in affect keeping an incorrect offset table or am I off base?
Joe?
i think you're completely on the money. if it's not perfect, it's wrong :)
so what i'm thinking to eliminate the posibilities of screwing up is to install a fuel regulator that will keep it perfectly flat. this way the whole table looks like the static value, which is one of the few pieces of data we actaully get with the injectors.
is this a proper 'runaround/possible problem eliminator' for something like this?