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  1. #1
    Electronic Ignition!
    Join Date
    Oct 2020
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    17

    Question I need help learning to tune

    I have been trying to read anything I can find on tunerpro and do this on my own but I cant my brain is hurting...

    My car is 1994 Camaro z28 automatic trans, I put flattop Hyperutectic pistons .030 over in, The cam is a bullet 288/196-10HR 236 intake @.555, 244 exh. @.555 , LT4 springs, chromoly pushrods, some adjustable guide plates, and injectors, and LT headers, light port match on the intake side, used roller rockers that might be 1.6 RRs. So it doesn’t idle anymore unless i give it a little gas. It does start and run tho. I did manage to download the bin and start working on it. For the easy stuff like AC delete, air injection delete, 3row radiator. It has a CAI, Ill have to make a separation piece for so it is really cold air. I have a 52 mm BBK I haven’t put on yet because I’ve been afraid that would stop it from running then I wouldn’t be able to get a comparison Data log. I’m new to tuning so I could be wrong there. If there’s something else you need to know about the car/build, that’s all I can think of for now. I haven’t pulled my computer to check the computer number yet. I just need to know how to tune this thing now. Any help or guidance and or direction would be greatly appreciated.

    I have read this

    http://www.gearhead-efi.com/Fuel-Inj...amaro+auto+adx

    I have been googling and reading quite a few related articles. But I like a plan of attack, like (I’m speculating here)
    first - fuel tables
    Next - spark tables

    What I should change and the order I should do it in?

    Found this read it too.
    http://www.gearhead-efi.com/Fuel-Inj...mpala-Caprice&
    Tried this out of there

    "Idle speed based timing corrections

    EE has a mechanism that makes fine timing adjustments in an attempt to stabilize idle rm errors, due to the fact that timing can make minor engine speed adjustments more quickly than the idle control valve.

    On a car with a lighter rotating mass (such as an aluminum flywheel), or with quite a bit of natural idle surge from a cam, the stock corrections may be too extreme.

    Typically anywhere from 50-150RPM of surge is normal for a larger cam or a light rotating mass, and trying to fight it can end up causing larger speed fluctuations and instability.

    Try lowering them substantially to try to let the car idle more naturally. This is also recommended if the base timing (above) was increased dramatically, as the stock settings may enter dangerous timing territory during a large RPM error.

    For example, if a tune at 32 degrees @ 700 RPM idle drops to 500rpm, with the stock settings it would have 37 degrees of final timing, possibly with even more from the coolant temp adder table!

    The following settings work well with an aluminum flywheel and a mild cam."

    It still didn't Idle.
    I tried a tune off the F-body site linked there. I think if I could have checked the lt4 medium cam box and medium cam improved Idle it would have been a good starting point, but they are greyed out. Anyway If any one is willing to explain to me in simple terms or send me a similar bin where I can compare the two and figure it out on my own that would be great.

    I have already flashed the bin on the car with the idle timing changes, If I can't get open loop idle to work, after I figure out how. I'll enlarge the Idle passage, but I want to exhaust bin changes first. This is what i'd like to do out of that article.

    "Idle BLM splits, and the idle passages

    If you have tried all of the tricks in the headers and cam sections, as well as the individual fuel trims mentioned earlier in this section, and you find your BLMs are still split, you might have to give up and run open loop idle.

    But first, one major cause of BLM splits at low RPM is insufficent feed through the idle ports in the intake manifold. Due to the length of the plenum, idle air is supposed to be drawn through a series of ports on the bottom of the manifold instead of through the plates to ensure even low RPM feed.

    Ensure your IAC counts are fairly high (35+), by closing the throttle plates. If further adjustment isn't possible, enlarging the bypass hole in the throttle body may be necessary. Some aftermarket throttle bodies don't even have an idle hole, contributing to the problem.

    Open Loop Idle

    For substantially larger cams, dealing with corrupt o2 readings which tend to force a very lean idle may be impossible or undesireable. Not to mention, big cams really like to idle rich, and closed loop simply will not do it.

    The LT1 doesn't have open loop idle settings, however you can cheat using the PE tables.

    Ensure PE activation around your idle speed happens at 0% TPS, and then use your low RPM PE table to affect idle fuel mixture. Remember there are two PE tables, rpm and temperature, make sure they both correspond to your desired settings.

    idling in pe mode

    Somewhere between 8-10% added fuel seems to be an appropriate starting point for most cams, but that depends how accurate your VE or MAF table is in the first place.

    Tuning for Headers

    Reference Voltage

    When installing headers on an LT1, due to increased distance of the o2 sensor a change in exhaust pressure near the o2 sensor, as well as a slight increase in resistance due to o2 extensions, and an operating temperature difference, increasing the o2 swing voltage about 50-75mv is reccommended as partial compensation for what usually becomes a slight lean condition.

    Experimentation and reading spark plugs may also assist in getting a true 14.7:1 AFR once longtube headers are installed.

    o2 swing altered for headers

    Integrator Delay

    Changing the distance of the oxygen sensor in relation to the exhaust valve will change the time that exhaust gasses (and obviously the fuel corrections being measured by the oxygen sensor) will take to become measurable.

    As the stock calibration expects the change to be measurable fairly quickly, the integrator becomes particularly unstable and innacurate if the delay is not increased. The effect is more dramatic at lower airflows.

    Making the integrator delay too large may result in a delay in fuel corrections, but increases stability dramatically. For longtube headers, doubling or even tripling the integrator delay is reccommended.

    int delay altered for longtubes

    Tuning for Cam Swaps

    Also see "Stabilizing Idle"

    Pulling Timing

    The stock timing table has a substantial amount of low rpm timing in driving range. Cams which are less efficient in this range require a substantial reduction in timing to avoid cam surge.

    It is reccommended that timing be completely reconstructed so it increases gradually to the new torque peak of the cam. This is one situation where just increasing timing until you encounter knock would be a BAD idea.

    This should be done at least to a certain extent before any other tuning is attempted, as cam surge can cause map fluctuations, affecting fueling, and also cause MAF inaccuracies.

    The map below was necessary to eliminate cam surge in a fairly small cam, larger cams may require more dramatic adjustments."

    Thanks in advance, I"m posting here because I didn't get responses in the Introductions thread. If this is the wrong area, I'll post where ever is appropriate.

    Also I have no histograms or accurate BLMs, I haven't gotten it out to drive it on the road yet, it is still on jack stands. I think I can do a log of any data I can that way. It would just keep dying out on the road though, and I'm not fortunate enough to have a Dyno.
    Last edited by Blue z28; 10-11-2020 at 07:01 AM.

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