fine tuning--injector timing tables

Discussion in '1994 - 1995 Specific Tech' started by Blackened302, Oct 20, 2007.

  1. i'm at a stump in the road, gents. i'm working w/ two tunes right now, trying to iron out driveability w/ a little performance.

    these two tunes (which are based off a j4j1) are the same except for the injector timing table values (as pictured below).

    for clarification purposes, "tune 1" is the yellow lines across (some cells are not highlighted) and is wrapped in red rectangles, and "tune 2" is the rows that aren't highlighted, each w/ their respective load values @ the different rpms.

    here's what i'm trying to figure out:
    - w/ tune 1, there's more grunt in performance--trouble is, the idle is crap--surges and can't seem to find a place to settle.

    - w/ tune 2, the idle is solid! but there is a bad backfire (sounds like it's coming from the intake mani) when revving and poor throttle response.

    please help me clarify one thing first: the stock j4j1 values are "300" all across and down the table. now, the "300" is in degrees?? and decreasing/increasing the "300" does what exactly?

    only thing i can see *really* different between the two tunes is the upper-right corner of the table vales... those are significantly different in relation to the rest of the comparison. i guess that makes sense of the backfire/poor throttle response w/ tune2, but how does that make for a crappy idle w/ tune1?

    what should i try to find a healthy medium between the two w/out having to datalog (don't have access to the r/t right now, unfortunately, but for the datalogs these tunes are based off of, please refer to THIS thread, post #7) to get the steady idle from tune2 and the better throttle response from tune1? :shrug: it's kinda tricky in that this is the only difference between the two tunes (went through both files completely)... when i switch from one to another, the difference in idle/throttle response is almost instant.


    Attached Files:

  2. Hey man those small differences in the injector timing down low shouldn't be causing the symptoms that you are seeing -- something else is different.

    Here's a test though - copy the bottom four rows from the tune that idles well into the other tune and see how it goes.

    For an excellent explanation of what this table does, download EECAnalyzer (free) and read the help file in the "Cam Specs" tab. The values are in degrees of crankshaft rotation (720 total), higher numbers firing later in the intake cycle.

    Shoot me an email of the two tunes and I will run a "diff" on them.


    P.S. Here's a quick excerpt from the help file on the "Cam Specs" tab -- there is much more there than this:
  3. Well Paul

    You're now venturing in areas that separates the men from the boys :rlaugh:

    Drivability ... it can make you :bang: :crazy: :fuss: :chair: :scratch:

    Here is where datalogging is immeasurably important ;)

    Like you ... I'd say those radically different values in the upper right corner
    seem to be out of place :shrug:

    As for the idle :bang:
    The prob could be many things
    Only one simple thing

    A surging idle will a lot of the time be the mixture is too fat :)

    A shot in the dark would be ....
    Use the values that make most power but give bad idle
    Try upping the low slope 5% :shrug:
    Backing off the offsets a bit :shrug:

    I like Wes's idea of mixing up the values between the two tunes :nice:

    Good Luck Paul!!!

  4. thanks for the replies, Wes & Grady. good bit of info/insight there.

    here are the links to the two tunes:
    tune 1:
    tune 2:

    i went through both of them extensively to make sure that they were exactly the same except for the Injector Timing Table values, and i've found no other differences, just to be sure.

    both you gents, i agree with--the lower values are too similar to make that much of a difference in the idle, i'd say. other than that, the injector scalar values are the same.. offset, pulse width, etc.

    i'm thinking that maybe i just calculated the values incorrectly to begin with in EA...

    what should the following be set at (considering my cam specs are already loaded, which is the Comp FW NX282HR-14):

    i appreciate the help, guys.

    Attached Files:

  5. I too am starting to get into this but my EA does not look like that it has trailing edge. It is a MUCH older version. I remember reading and reading about the settings...Fox's seem to be "locked" IIRC while we can actually change ours but at that time there was not alot of testing that had been done with the cbaza (maybe thats why the newer version looks diff?).

    My hangup with really getting into the idle is its fairly solid and I only drive it once every few weeks at best and I have the batt. undone just incase its a long time as to not kill an optima. So my tune never really has much time to stray and get funkdy. Maybe next spring I will drive it for a few weeks and really get at it.
  6. Try these settings here.


    Attached Files:

  7. will do, Wes--thanks!
  8. I ran a quick compare on the tunes, like you say, the only difference I found was the injector timing.

    Are you running lean at idle? I see your injector settings are sort of a mix between j4J1 and something else, looks like between the low slope and the injector/battery offset function you'd be getting too little fuel -- just my 10,000ft view of the tune.


    EDIT: Set your Spark Tip In Retard back to 5 at least - 1 is a tad low. :)
  9. lol, yeah--i just noticed the tip-in-retard a while ago, too. thanks, Wes.

    about the injector scalar settings: i realize now they're not the stock j4j1 values (some). i think i arrived at those values based on some of the CalEdit write-ups/Guides. guess i'll put that back to the stock settings, though. thanks, meng!
  10. alright, about to try the following:

    1. tune w/ combined Injector Timing Table values from tune1 & tune2 (lower rows from 2, upper rows from 1)
    2. tune w/ completely new Injector Timing Table values using the EA settings Wes provided above

    - the "minimum-spark-for-tip-in-retard" scalar is now set to 20 (not quite sure what my overall Spark value is... dizzy is set at 17 [i know it should be at 10..] and the Spark tables and scalars are all set to stock j4j1 values)... which is better than "1", hehe.

    - stock j4j1 values for Injector related scalars

    let's see how this goes.
  11. results:

    #1 didn't work so well... bad backfire in exhaust, but the idle was there.
    #2 seemed to work better w/ both a smooth idle and nice throttle response, no backfire.

    i'm gonna have to drive it a bit more later today--gotta head off for now.

    thanks for the help, guys. if it's cool, i'd like to get back to this later today or sometime tomorrow for more input. have a good Saturday!
  12. With that much timing on the dizzy that may be a big chunk of your problem as well...

    Set that sucker back to 10 ASAP your mid load timing is prob. going nuts.
  13. Any chance you've tried setting your injector high/low slopes to the Cobra ones of 24.84/24.84?

    I see that your Injector Offset vs Battery Voltage function looks to be the same as the Cobra one which means either that function needs to change to match your injector settings or vice versa.

  14. well, what i did do was use the stock j4j1 injector-related scalars (off set, high/low slope, etc)... that ok?
  15. The high and low slopes were the only ones that looked like they were a tad off - 24/30 high/low if I remember correctly.

    Set them the same and see if it changes anything - could be something, could be nothing. :)


    EDIT: Clear the KAM's when you do it!
  16. ok, cool, thanks Wes.

    i did set the high/low slopes the same value (the stock j4j1... 24.xx, i believe) and cleared the KAM.

    i'm having some difficulties w/ my tps at the moment (lowest i can set it is at 1.4 volts... already elongated the holes and no luck), though, so i'm trying to take care of that first, then i'll get back to the tuning.

    i appreciate the help, though.
  17. I'd +1 this :nice:

    I've found if you do different slope values the low offset values like you find
    in the same slope j4j1 kind of tuning do not work all that well.

    Compare the offset values between the t4m0 & j4j1 ;)

    I've seen peeps arrive at a low slope being at 5 to 30% higher than the
    high and the more the difference between the slopes, the higher the
    offset values seem to turn out to be.

    Also ... if you do the stock j4j1 slope values ...
    I'd use the stock j4j1 breakpoint as well.

  18. yes, i'm now using the stock j4j1 breakpoint as well, thanks Grady.

  19. Punisher it's been awhile since I worked with the injector timing and I don't recall which one I used, but I used the settings that generated all the same numbers, i.e. 372, for all cells. I think it was "End" and "TDC". Since it generated all the same numbers I figured my settings was correct and I was on the right path since the original J4J1 tune had all 300s in the table in its tune.

    The great thing is you can run it as many times as you want to see which is the right one.

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