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Thread: Z28 LT1 $EE Tuning issues

  1. #1
    Fuel Injected! Terminal_Crazy's Avatar
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    Z28 LT1 $EE Tuning issues

    The Motor is a rebuilt 1995 Camaro Z28 LT1 383 M6 with the following parts
    Scat Forged Crank
    Scat ICR 6000 rods with ARP 2000-14 bolts
    Keith Blackj ICON 718 2618 Forged +0.030 Piston 1.130 Comp Height
    TOTAL SEAL Gapless Top Ring Set
    Cometic Head Gaskets 0.045 thick
    AFR #1101 210cc LT4 Competition Assy
    #8019 PAC Racing Spring 1.270 OD Hyd Valve Spring 155lb .650 Lift
    Lloyd Elliott Hi lift emission cam 223/231 .610 .594
    Comp Cams Ultra Pro Magnum XD Roller Rockers
    GM LS7 Lifters
    GM Performance LT1/LT4 Timing Chain Set
    Edelbrock LT4 Manifold - 7109 Air Gap LT4
    MSD LT1 Optispark Pro Billet Distributor
    JEGS Red Hot 8.0mm Plug Leads
    ATI Balancer
    42lb @ 3 Bar Modified Bosch Blue Demon 3 Fuel Injectors
    LT4 Knock Module
    SLP Air Foil
    Moroso CAI
    MAC Midlength Headers
    Pre Cat Electric Cut Out
    3" Stainless exhaust
    !AIR - !EGR - !Cags
    Throttle Body Bypass
    Proform 141-130 Polished Center Bolt Die-Cast Valve Covers
    Innovate LC-2 Wideband

    Fidanza Aluminum Flywheel
    KUPP Stage 4 Clutch Kit
    T56 Short throw Billet Shifter
    Lowered with Strano Springs & Koni 4/4 Shocks
    Hawk Pads - Stainless Hoses

    Tuning Software:
    Datamaster
    TunerPro
    EEHack
    Scan9495

    The motor runs pretty well but i've been suffering with split BLM's and a persistant knock issue appearing around idle/off idle and low cruise.
    All the usual BLM split causes have been checked & double checked without any issue being found & corrected really making much difference.
    O2's replaced & swapped. Throttle blades adjusted, bypass checked & drilled. Manifold idle bleeds drilled out. EGR block offs replaced/resealed. Injectors replaced & swapped twice.
    I usually hang out on LS1LT1 and have been here for a couple of months now.

    I've just added the wideband and logged the latest .bin from a cold start.
    The Idle was really stable & smooth (best it's been) until it hit closed loop around 60C then became much rougher & unstable like I'm used to.
    The idle was stable around target by 25 RPM & went to 50-100 RPM around target which is normal.
    The AFR was running from 12 upto 13.5 when it went closed loop.
    Closed Loop AFR went to around 16-17 not anywhere near 14.7 as I expected.

    BLM's & ST's are stable
    O2 swing voltage I've read is 450mV for stoich but stock PCM has them set around 424 currently set around 428.
    Stoich AFR is set to 14.7

    I've altered all the usual Int delays and the readings are fairly stable, just not matching the Wideband.

    Any suggestions on how to correct this without going Open loop idle ?

    Has anybody got Injector voltage/offsets for the Bosch 3 Injectors ?


    Thanks
    Mitch
    Last edited by RobertISaar; 12-17-2015 at 02:50 PM.

  2. #2
    Fuel Injected! steveo's Avatar
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    widebands can lie. read a plug?

    you may be expecting too much afr stability at low rpms with a build like that. at low airflows, all sorts of crazy stuff can happen, and measurements from exhaust gasses may not reveal true afr. having wb afr jump from lean to rich in closed loop is normal and becomes more intense with more overlap.

    lets see a log

    care to try eehack out? I can probably code an analyzer to filter something useful out of all that garbage data...

  3. #3
    Fuel Injected! steveo's Avatar
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    as far as the low rpm knock, is it real? use eehack to remove timing. pull like 10 degrees or something crazy. if timing doesn't make it better then it's false and just tune out the knock sensor within the range it occurs.

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    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by steveo View Post
    as far as the low rpm knock, is it real? use eehack to remove timing. pull like 10 degrees or something crazy. if timing doesn't make it better then it's false and just tune out the knock sensor within the range it occurs.
    Cheers Steveo I'll try that tomorrow night.

    I've hacked the bin all over, pulled timing etc
    I've added in Injector offsets back to stock settings instead of zero in Solomon's tune.

    Cold idle didn't seem anywhere near as smooth/nice as last night
    Closed Loop AFR was showing around 14 though

    If i turn the heater control on to A/C I still get A/C request & IAC still jumps up 10-20 points even though table is zeroed out & AC pressure/fan settings are all zeroed out now.

    Datamaster .uni file attached

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    Are you able to get the throttle blades closed? That's what helps with split BLM.

    Did you turn-off the CCP?

    I would expect the knock sensor to be useless or at least show false knock some of the time unless you have a LT4 knock module.

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    Fuel Injected! Terminal_Crazy's Avatar
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    Appologies for the linefeeds. I guess I'll have to use the PC on this site.Yes, done all that.Throttle body was removed & cleaned. Blades set to minimum without sticking.IAC Valve checked and cleaned.Idle hole enlarged.New gaskets.All idle circuits in manifold drilled out, matched and cleaned.CCP is still active as it allows access to cells 16-18.The hose had pulled off when i checked last night... still made no difference.Solenoid is not passing either.New Knock sensor torqued to spec.LT4 Knock module fitted with Mac Mid length headers.The lightened flywheel & clutch are noisy.It's a lot quieter with the clutch in but I still get knock & retard.ThanksMitch
    Last edited by Terminal_Crazy; 12-17-2015 at 03:30 PM.

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    You posted "Throttle blades adjusted, bypass checked & drilled" so are the butterflies drilled?

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    You mentioned in your first post that the open loop idle was pretty smooth, then the idle quality deteriorated when it went to closed loop. What RPMs was the engine running at when this happened? If it was running smoothly before the transition, then I think it's reasonable to assume that the motor (heads/cam/injectors/etc) is physically capable of running smooth but you've got a problem in the tune in closed loop.

    You said you tried adjusting the O2 sensor time delay in TunerPro to account for the headers.
    Have you tried reducing the O2 sensor integration gain (i.e. feedback sensitivity) at low rpm?

    Another trick is to turn the key on and leave it on for several minutes before starting the car. This allows the O2 sensor heaters to heat the sensors up before you start the car. Then see what happens when you actually start the car. You could have cold O2 sensors not giving you good feedback at idle.

    I've been out of tuning for months but this is where I'd start looking. I'd go back to the tune that idled well in open loop and go from there.

    For what it's worth, I would never use a set of injectors with unknown constants without first optimizing as much of the tune as I could with a fully characterized known set of injectors (like the stock ones). Get the car running as good as you can, then swap in the new injectors and change ONLY the injector parameters until it matches the drivability of the stock injectors.
    Last edited by sherlock9c1; 12-17-2015 at 10:19 PM.

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    BTW, I was tuning one car that had a lot of knock at 2000rpm across many throttle positions. I started pulling timing there but got nowhere. A few weeks later the owner was under the car and noticed that part of the transmission was up against the body. He adjusted everything for clearance and the knock went away. :) Not all knock is real.

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    Quote Originally Posted by lionelhutz View Post
    You posted "Throttle blades adjusted, bypass checked & drilled" so are the butterflies drilled?
    No The blades are NOT Drilled just the idle air passage to the manifold toget iac counts up.

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    Quote Originally Posted by steveo View Post
    drilling the idle hole out lowers counts.
    Correct. So it does.

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    Sure, but the actual IAC counts don't matter, just that the idle air is going through the IAC and idle passages instead of the throttle blades. So, you're doing everything right to try and balance the BLM values.

    Does the idle get better if you run/drive it and get the exhaust temperatures up?

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    Quote Originally Posted by lionelhutz View Post
    Sure, but the actual IAC counts don't matter, just that the idle air is going through the IAC and idle passages instead of the throttle blades. So, you're doing everything right to try and balance the BLM values.Does the idle get better if you run/drive it and get the exhaust temperatures up?
    I've pretty much gone through everything I can find & checked several times.No. The nice idle changed by about 50 RPM. Even hot it's changing by 75-100 RPM. I'll have a play with some of the feedback delay timings and try reducing them & see if that improves anything.I now know it can idle nicer than it does.I'm currently digging the drive up so might not be able to get out for a week or two.Thanks for the feedback.Mitch

  15. #15
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    first try overriding closed loop and resetting blms when it gets hot and acts up (use eehack). that will confirm 100% that its a problem with closed loop config. if it doesn't completely solve the problem by going open loop, look elsewhere for the problem

    if you need closed loop to make your car run properly, you blew your tune. It should run almost exactly the same in or out of cl.

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