Spark & It's Effect On Low End Torque

Discussion in '1994 - 1995 Specific Tech' started by final5-0, Oct 15, 2007.

  1. Some of you may know I like to collect dyno curves from combos :D

    I've been wondering for some time now .........

    Will spark optimization visibly boost a low end torque dyno curve :scratch:

    Those of you who self tune know all too well :nice:

    Increasing the amount of spark
    Getting it in sooner

    Well ... it makes a difference that can certainly be felt :Word:

    Then ... you consider how much difference the tip in retard can make ;)

    So.... What do all you guys think :shrug:
    I got my opinion :D
    I wanna hear what ya'll got to say :hail2:

  2. You're asking if spark timing has a significant effect on how much power a motor makes down low?

    Well of course it does! Otherwise we wouldn't bother with things like vacuum advances, electronic advances, spark tables, etc.

    Something I think that's just as important but often overlooked is spark intensity and duration. I think that many folks overlook spark duration without even thinking about it.

    What I mean is: Folks run out and get MSD ignition boxes and the like... an ignition that provides a quick and hot spark (great for the upper RPM range and boost) but forget that the OEM ignition system was/is perfect for the low and mid range. Longer spark duration, spark through a much longer portion of the rotation = more complete burn.

    Sure, many aftermarket boxes provide a second spark per rotation to reduce the effect that a quick, high intensity spark has vs. a much longer fatter one but it's still not as efficient and your old OEM ignition for these circumstances.
  3. I've noticed that professional tunes for our cars tend to increase the spark at lower RPMs quite a bit.

    The EFI books I have read mention loading an engine on the dyno and finding max torque by slowly increase spark at each rpm/load point.

  4. Well I admit that surprises me. I would have thought that once ignition has started adding additional spark or extending the duration of the spark is an unnecessary redundancy. So exactly why is there a "more complete burn". Isn't the fuel, once ignited, ignited? I can see were timing is important so as to ensure that there is sufficient time for the burn to complete before being exhausted. I'm just puzzled and amazed.

    The reason behind the longer spark is to make sure there is a complete and thorough burn of the air fuel mixture. With high dome pistons, tight valve shrouding and other issues, you can get portions of your mixture that do not get a decent ignition. By holding the spark up to 20° of crankshaft duration you virtually eliminate these problems (if your engine is in proper tune). The additional duration because of the above issues ensures a more stable flame front resulting in a more complete burn.
  5. I agree - until the 94 (AODE) I ran all the low-end timing I could. I'd deal with top end issues accordingly. I could get kinda close with recurving the dizzy and playing with the jetting. WIth a torquey bottom end, it makes it even easier (though I had good luck doing this with 4 bangers and the like as well).
    I'd shoot for having all the timing in by around 2700 RPM (plus or minus a little depending upon when the secondaries were coming on, etc).

    I still feel about the same way with the stick cars but not so much with my particular automatic (and having numerically higher gears not handle as much timing as the lower ones). I've never had the ol' 94 ping at WOT hardly but I've dealt with a grip of low RPM, 3rd and OD ping. As Wes can tell you, I have pulled a TON of sub 2000 RPM timing out of the 94 and it made a noticable SOTP difference (the car is slower but it's what I needed!).

    Mr Wes is the expert on the AODE's and timing! He knows all the tips and tricks. I try to follow along but get lost with all the variables (interrelations of timing, converter, etc etc).

    Confining my thoughts to sticks, I agree in full however. It just seems so much easier with a mechanical dizzy and a carb. :banana:

    Ok brainiacs, as you were. :nice:
  6. While I did not specify a stick or auto trans application I do admit to having
    the most experience with stick cars.

    Like JT ... back in the 60's & 70's we were playing around with mechanical
    adjustments with the dizzy to get the spark in quicker.

    With quicker and sooner rate of advance along with more total spark
    you could really wake up a little 260, 289, or 302 back in the day :)

    Of course these days the method to do it has changed
    The principle of how or why it works is the same ;)

    So ... I guess you agree with me that the spark being optimized is
    something that is gonna show up on a typical dyno chart :D

    I have seen many curves of oem combos that had such soft low ends
    I got to thinking along these lines :scratch:

    Most of them do not have any pcm tuning what so ever :nono:
    They don't benefit from spark table optimization
    You can only go so far with twisting the dizzy before ping can occur


  7. The way it's been explained to me (I have to burn cycle video to show) is that there are multiple instances during a combustion cycle that are ideal for mixture ignition. Equally, there are instances that are NOT ideal.

    Multi-spark ignition systems deal with this by sending multiple sparks (of course) at different portions of the compression stroke in an effort to hit one of those ideal ignition instances (thus you end up with two burning ignition fronts in a cycle so long as each spark ignites some portion of the mixture). With your typical OEM ignition, the spark is on and stays hot through a much broader portion of that stroke (igniting a potentially infinite number of additional points within the combustible mixture during a time when the mixture 'should' be ignited).

    That's where the more complete burn comes from. The mixture is constantly swirling in the cylinder. Burning that mixture from as many fronts as possible within the cylinder is where you would get your best burn.

    I do see what you're saying though, about the varying degrees of burn efficiency with this type of head or cylinder vs that one. This doesn't take away from that. It's only an additional factor.

    Ideally, I'd think that you'd want both. A long fat initial spark to light off the mixture followed by a short high intensity one to light things off as a back-up (thinking boosted apps etc.), or at worst, an additional spark to start one more burning front.
  8. if anyone has a graph of how much they are putting in low end id love to see it.

    AODE's def need some low end grunt booster, i used to just add spark to the top 2 rows, going to slowly bring up the bottom end of the graph
  9. I'll post up a good starting point later on today.


    What turner are you using?
  10. Here, look at my tune, combo in "More Info" in sig.

    I can put up somewhat aggressive N/A spark/fuel tune using all four spark tables and adders etc if anyone is interested.

  11. cool i was just looking at my base files, i use SCT, and my current file was low 2-3 deg spark from idle to 70-80% of the graph compared to stock computer timing... so im running 10 deg base with stock U4P0 timing curve. Feels much better down low already.
  12. im running SCT couldn't open your bin file

    if i had a place to upload pics id just print screen it.
  13. thanks looking at it now
  14. well i have it opened and loaded but there is nothing about spark, just maf settingings

    found the view window all but 3 things are greyed out, spark #2 being one of them
  15. Couple things you have to do - from the buttons below on BinaryEditor, Load your definition file (CBAZA) and then Load the binary file (my tune).

    From there hit the "Tables" tab to see the spark settings - they'll all start with "Spark -" if your using "CBAZA Rev 21" or later as your definition. If it doesn't come with that holler back and I'll email you mine.

    I'm also on AIM if you want to chat about it in realtime.

  16. got it open found the table, looks like your running alot of timing :)

    even though i have a blower im looking at the under 2500rpm spark and yours is up to +10 deg higher, when mine is low and only 0-2 pounds of boost. im wondering if i can sneek some more timing there to get this thing off the line.
  17. You can get away with stock timing when you are at low boost. That timing works out great for me on the street in the 100deg heat we have here... I'm running 13lb.


    P.S. What I would do is sneak up on my numbers. Take it a couple degrees at a time and listen for detonation. Gains from added spark is HUGE on boosted cars. Don't be afraid of adding it in but do it slowly and test.

    My WOT spark is still a bit soft compared to some guys so there is further improvement there.
  18. Sorta going back on topic, this weekend at the dragstrip I went from 18 total across the board to a 21-19deg total from launch to 4k in first and picked up about .04 on the 60ft and .2 off the ET.

    You can see the log here...

    Spark on boosted cars is huge :)

  19. Dagger I think you have it a bit wrong...most multiple spark boxes produce 6 sparks below 3000rpm where as the stock system produces only 1. Also, these boxes intercept the stock signal and send 6 of their own to the coil. These 6 sparks occur over a period of time greater than that of the stock single spark. Indeed around 3000 rpm those 6 sparks are so close together that its pretty much 1 really long spark. However as I mentioned before since the boxes are intercepting stock signals and sending out their own any lag in this process will slightly retard spark timing (if you dont adjust your timing after install of course).

    Hmmmm.....I wonder if you check (but not adjust) you timing before and after a msd box install will there be any noticable change/retard in timing? I also wonder if lag between input and output is different in analog boxes vs. digital boxes such as MSD 6AL vs. Crane Hi-6?

    Sorry if I'm derailing your thread Grady:p