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Thread: End of Injection Timing Open Discussion

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  1. #1
    Fuel Injected! spfautsch's Avatar
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    Apr 2015

    End of Injection Timing Open Discussion

    In response to kur4o's recent work on eehack to enable more or less real time tuning of this parameter and some of the subsequent discussions I'm starting this thread. I'm pressed for time so I'll have to post links to some of what I feel are very relevant posts which I mentioned in the eehack discussion thread here.

    vilefly: apologies if this has already happened and I haven't seen it, but if you could find the opportunity to test and confirm the EOIT slider with another scope capture it would confirm kur4o's conversion formula so we would know exactly which way changes to the EOIT value moves the injection timing.

    I would attempt to do something with this myself but there's a gaping hole in my engine bay and my reciprocating assembly is sitting on a shelf in southern California at the moment waiting for me to specify the final bore size.

    This topic is not and should not be limited to the $ee mask.

  2. #2
    Fuel Injected!
    Join Date
    Mar 2013
    Some quotes on the topic


    Been reading up on the EOIT settings

    Can you clarify the TDC position... I'm guessing 0 timing is TDC at compression ?

    This is the Stock 1995 Z28 table.

    DegC Deg Hex TDC+
    spk btdc
    0 0 0 TDC
    -40 2 20 180 180 bottom of power stroke ?
    -28 2 20 180 180
    -16 2 20 180 180
    - 4 2 20 180 180
    8 4 40 360 0 TDC exhaust
    20 4 40 360 0
    32 4 40 360 0
    44 4 40 360 0
    56 5 50 450 90 90Ý down on intake stroke ?
    68 5 50 450 90
    80 6 60 540 180 BDC (Bottom of intake stroke?
    92 6 60 540 180
    104 6 60 540 180
    116 6 60 540 180
    128 6 60 540 180
    140 6 60 540 180
    152 6 60 540 180

    Each 90Ý is covered by 16 points so 5.625Ý == 1Hex value
    My cam is about 56 degrees overlap guestimating 34+ degrees bigger than stock
    6 x 5.625 = 33.75
    7 x 5.625 = 39.375
    so try adding 6 ... should have it at 573.75

    So fired it up let it idle for a while to warm up
    then played with EEhack eoit settings
    The table opens with a value of 270 which i guess is a 3 (30H) on the table.

    Moving the slider affected the fueling until CL settled down again so it is working.

    Initially I moved the slider a few points at a time without major improvement
    dropping the slider down to 96 seemed to give the smoothest fueling
    So I stepped 90 degrees at a time and reset BLM's each time until it settled...

    BLM's were
    96 110 120 & 113 121
    186 121 123
    276 105 128
    366 108 128
    456 108 128
    546 108 128
    636 108 128
    714 113 131 & 108 134

    With Control off (back to 66H)
    Resetting BLM's several times settled on
    118 121
    120 121
    123 124

    engine temp down to about 86C but smoking & spitting water - crap throttle, response boggy and hesitant.

    I've not driven the car yet, it's too cold wet and dark.
    I'll see if i get 5 mins tomorrow.

    Anyone else played with these settings yet?


    @ kur4o:

    Hi, Can you clarify some EOIT numbers please.

    EOIT is degrees ( Reference periods and fractions of 90 degrees) ATDC on compression.

    Stock LT1 has 6 in the table so would be at 540 degrees which would be at bottom of the intake stroke.
    IF B&Y cars are 270 degrees that would be 7 in the table?

    You say the table's highest figure is 6F which is 7 reference periods.

    On EEHack the Overide table will adjust from 96 degrees to 714 degrees.
    Does this mean the table starts at 90 degrees or your slider values are off ? 7x90 = 630 max ?

    Does this table have an offset similar to the HPTuners thread where it's referenced from -784 ( 2 revs, 720 and -64 degree offset) ?

    I've just realized that it could be the XDF I'm using to view it that's incorrect but all versions I have seem to have the same parameters.


    This graphic should explain it all.

    The red line is the injector firing.
    You can see the open event vary based on the commanded pulse lenght but the close event will be at the exact value specified at the table.
    If you want to fine tune, you should factor the time the fuel needs to evaporate also.

    The built in limit of 6f is a software limiation, the PCM might freak out if you go over it.

    You can chart your cam specs in the chart and see where is the overlap and make a tuning startegy from there.

    I charted the gm846 cam here.

    Green -yellow is the overlap at 0.05 lift. 4 degrees in total
    Blue -red is the total overlap.

    I am still looking for complete specs of stock gm b-body cam.
    It will be very good source how gm tuned it. As you can see the compression in the cylinder already.

    Sorry, I'm having difficulty matching the values.

    I was really after clarity on the numbers as they dont match with EEHack's control panel.
    The control slider adjusts from 714 to 96. Should it not start from ZERO?

    It states degrees ATDC of the cylinder fire event so I presume it counts in hex in 16ths of 90 degrees starting at zero?
    1995 LT1 Z28 has 6 or (Hex60) in the table when hot. That would be 540 degrees, ( 360+_180_ or 6*90).

    What does the B & Y body have in the table to get 270 ? I see it would need to be a 7 (6F MAX) ( 360+270 or 7*90 = 630)

    What is the degree value of each value in the bin?
    and can you confirm it starts at ZERO?


    720 - [value] * 5.625

    value = table value converted in decimal.

    That is the formula to convert the table value to degrees.
    You start at $01[ pcm will not like zero] and go to $6f max value.

    At ideal conditions $00 should be 720 degrees and $80 sholud be zero degrees.
    0-720 = $80-$00.

    At some point the counter should reset and start again at $80.
    That`s could be the reason to not go beyond 6f. The PCM might freak out.

    Aha, (720-) thatís the bit I wasnít seeing.

    Excellent, thankyou. Iíll have another play now I can see the numbers.


    I've been watching the discussion casually and recognized the value of tuning the EOIT parameter(s) a while back, but simply lacked the time to research. Since I'm sitting at home tonight anxiously awaiting a call from a machinist with news on my block getting bored and decked, and preparing mentally to replace the timing belt for the 4th time on my 460k mile diesel daily driver tomorrow morning (16 hours of relative boredom culminating in my hands smelling like diesel soot for 3 days), I thought I'd finally try to catch up.

    To summarize in one sentence, this is a fascinating topic and deserves it's own discussion thread. I have plenty of other projects to tend to at the moment, but if no-one else wants to I will try to find time to "fork" this to it's own.

    The scope capture vilefly grabbed for kur4o is very compelling. The last time I looked at it with any interest I was knee-deep in the diy-ltcc concept phase and only concerned myself with the optispark signals. But today I looked at it with the EOIT topic fresh in my mind and it strikes me as absolutely crucial information to anyone running a nasty (large overlap) cam and larger injectors. In the capture specimen the entire injection pulse is happening during the middle of the exhaust stroke right before the intake valve opens. I presume the strategy GM was employing here was to boil the entire fuel charge on the back of the intake valve before the air charge is drawn in. But for a cam with plenty of overlap I suspect (as has been attested to by numerous other scattered posts on the subject) that delaying EOIT so it happens after peak intake valve lift would do wonders to reduce the amount of raw fuel getting sucked into high performance scavenging exhaust systems and the O2 signal corruption that results.

    Testimonials by Rocko350 here, and by kevinodb1 here lead me to believe this may be the answer to eliminating cam surge and achieving stable closed loop idle. Thoughts?

    I played with the EoIT last week with not so unlikely results.
    My BLM's are slightly offset at idle. 120 & 122 when I started
    As i logged every 4 points across the table the "split' increased.99 143 was the biggest difference (split of 44 at 388 degrees 0x3B)
    ***Note: At about 56C-60C my RHS injector leans out (flatlines) The stock table has 0x40 at this temp ??

    The LHS went down lowest to 94 139

    Rolling back around the table the split came down the other way to a best of 118 117 @ 163 Degrees (0x63 in the table)

    It drove OK (OKish compared to usual) and fueling seemed to have richened up around the lower parts of the VE Table

    Anyone else seen anything remotely similar ?

    I have a full writeup if anyone wants it posting with Inj PW & fast & slow idle.

    Last edited by kur4o; 12-20-2018 at 04:10 PM.

  3. #3
    Fuel Injected!
    Join Date
    Nov 2014
    Hi There

    Cosworth DFV and BDG and Triumph 2500 PI's and TR6 have sequential timed mechanical fuel injection.

    I have done a bit of research on the timing previously in order to get a TR6 running with a very radical cam.

    I also have a 2500PI motor I am installing in a MK3 Sptifire and have adjusted the injection timing point on that.

    I have the data on the timing of all these engines somewhere, I will dig it out.

    As well as my 92 Corvette I also have a 94(With EEHACK) and 96 so am interested in this thread and the good work people are doing.

    New Zealand

  4. #4
    Fuel Injected! Stroked 388's Avatar
    Join Date
    Jan 2017
    Interested I this information also. Im new to the tuning world. How is the injector timing information labeled in tunerpro ?. I can't find it been doing alot of reading on this subject. Thanks in advance Gary
    Last edited by Stroked 388; 12-21-2018 at 11:15 AM.

  5. #5
    Fuel Injected! Terminal_Crazy's Avatar
    Join Date
    Oct 2015
    Lancashire England

    @ Kur4o:
    In the image you had of the EoIT scan (and others I have seen on the net) have the timing in degrees ATDC increasing to the right as would be correct for a timing diagram with time increasing going to the right.
    The calulation of 720-(VALUE * 5.625) is actually measured in degrees _before_ TDC.
    I drew a chart with the figures the usual way which had me confused somewhat.
    If concensus agrees this is correct, I'll redraw the chart with table values and swap the numbers to agree with Kur4o's additions to EEHack when I get a sec.

    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  6. #6
    Fuel Injected! spfautsch's Avatar
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    Apr 2015
    Thanks to everyone posting relevant info. There's lots of good stuff about the topic here but it's scattered in numerous threads.

    I keep re-reading this post by Rocko350 and thinking I'm not excited to rework my VE table. But it sounds like fine tuning the injection timing holds a lot of promise. In testing the diy-ltcc setup I spent a lot of time idling the car in the garage, and the gas fumes were unbearable. I'm hoping I can clean this up with eoit tuning.

    Got my "dirty diesel" daily driver all back together and running but have to wait for an activation key for the tuning software so I can set IP base timing. Made me appreciate a completely open tool like eehack that much more. I hadn't needed to use the software since the last timing belt change back in 2014, and somehow the volume id or something else in the virtual was changed that broke their activation / protection mechanism (vag-com / vcds).

  7. #7
    Fuel Injected! Stroked 388's Avatar
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    Jan 2017
    For the newbie taging along we're would you adjust eoit in tunerpro (how is it identified under what name) thanks Gary

  8. #8
    Fuel Injected! Terminal_Crazy's Avatar
    Join Date
    Oct 2015
    Lancashire England

    I've redrawn the EoIT Chart & placed the Chart, Printout, Basic Program & a Datalog writeup on my website.

    Feedback Welcome.

    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  9. #9
    Fuel Injected! spfautsch's Avatar
    Join Date
    Apr 2015
    Quote Originally Posted by Stroked 388 View Post
    For the newbie taging along we're would you adjust eoit in tunerpro (how is it identified under what name) thanks Gary
    The table you're looking for is at 12DF2 - End of Injection Target Location VS Cool Temp

    I just started doing some reading and comparison with my bin, and I'm confused. My Y body tune has 0x60 in all cells above 44c coolant temp, but kur4o's post here with vilefly's scope capture clearly shows the injector pulse turning off at 270 ATDC, and he states that's what the bin is set to. I've seen the following formula mentioned:

    EOIT = (720 - (<cell value> * 5.625))
    What am I missing? I've glanced at Terminal_Crazy's test info and EOIT chart, but I'm not finding any way to make 0x60 come out to 270 ATDC / 450 BTDC.

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