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Thread: new to ECU tuning, LT1 383 with 24x and LS1 ECU

  1. #1
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    new to ECU tuning, LT1 383 with 24x and LS1 ECU

    Hello everyone

    I've just assembled my LT1 gen2 383 with trickflow 21deg heads and 231/239 .594/.606 110 LSA cam and upgraded opti to torqhead to be able to use HPtuners. Interface has arrived few days ago and I started with stock LT1. I have knowledge about engines but in the past I was mainly carburetor guy so for me this transition is not easy however just trying to read forum as much as possible to get things right.

    Fist problem was no start or really rough idle as engine wanted to pour a lot of fuel into cylinders, then I have changed injectors parameters and then I used idle tuning basics presented somewhere on forum (VE table reduction up to 1200rpm) add some spark at idle etc. The engine can start now and run but it is not able to maintain desired 950rpm because it is surging a lot - I believe something is really not OK with commanded AFR is jumping from 9 to 11.2 and maybe with IAC counts are they are steady on 310 mainly (set screw on TB?)

    Can anyone look briefly into log and guide me in what direction shall I go? Thanks

    1MAR24 cyl volume ifr 30 VE modified.hpt02MAR24 idle draft too rich.hpl1MAR24 cyl volume ifr 30 VE modified.hpt02MAR24 idle draft too rich.hpl

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    Need to add what injectors are being used.

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    The AFR change is from OL warmup. You're not getting a reading from the front O2's. Are they wired up correctly?

    Also, more info on the fuel system. Pressure setpoint, vacuum-referenced reg or not (tune IFR is referenced, Offset non-referenced), and injector part number as mentioned above.

    Highly recommend a wideband for this build; however, a lot of work can still be done without for now.
    Last edited by SiriusC1024; 03-02-2024 at 10:04 AM.

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    Quote Originally Posted by gtstorey View Post
    Need to add what injectors are being used.
    Quote Originally Posted by SiriusC1024 View Post
    The AFR change is from OL warmup. You're not getting a reading from the front O2's. Are they wired up correctly?

    Also, more info on the fuel system. Pressure setpoint, vacuum-referenced reg or not (tune IFR is referenced, Offset non-referenced), and injector part number as mentioned above.

    Highly recommend a wideband for this build; however, a lot of work can still be done without for now.

    Hi guys

    Yep, you have raised important question. I did not tell this at the beginning because I was testing few things within fuel supply.

    So I have crappy accel yellow 30lb and referenced supply. Theoretically LT1 pressure is about 43.5 psi however I've hooked up today a mechanical gauge to test and WITH vacuum line connected it was jumping at that rough idle from 46 to 48psi. I will measure again with vacuum unplugged but I believe FPR might be shot (aeromotive but I have bought it used)
    Additionally I believe also I have leaking injectors - once fuel pump is priming then I have 43-44 PSI but when it's switched off then drastically pressure's dropping to almost 0 (drastically means 60-80seconds)

    This night I'm gonna pull them out and see, anyway I will replace them immediately and get new ones with proper data...

    O2 sensors hmmm let me take a look - this is fbody 1995 and wiring is stock, just torqhead and it is using same wiring...thanks for catching this!

    i have WB MTX-L plus waiting to be connected only (new exhaust) plan is even to have 2nd one in pass side header to read both banks)
    Last edited by v8roush; 03-02-2024 at 02:05 PM.

  5. #5
    Tuning Addict blindsquirrel's Avatar
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    Aeromotive regulators do not hold pressure at key-off, these aftermarket companies try to sell you on the story that this somehow 'enhances performance'.
    https://forum.hptuners.com/showthrea...y-off-pressure

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    Quote Originally Posted by blindsquirrel View Post
    Aeromotive regulators do not hold pressure at key-off, these aftermarket companies try to sell you on the story that this somehow 'enhances performance'.
    https://forum.hptuners.com/showthrea...y-off-pressure
    thanks mate, that explaines that sudden drop. I think I will replace injectors and FPR for normal stock one from AC Delco.

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    That reg should be adjustable. Set it for 58psi with the vacuum line unplugged so that GM injector data can be used. As far as injectors definitely get properly sized GM injectors. Don't make the mistake of getting 80lb/hr or something like that for N/A. I've seen it often enough that I have to mention it.

    If you're getting an AC Delco reg make sure it's the correct 58psi pressure.

    Blindsquirrel and many others vouch for these, but you'll need to adapt them.
    https://www.ebay.com/itm/274424906026

    Data available at:
    https://forum.hptuners.com/showthrea...l=1#post766924

    Adapter requirements:
    https://forum.hptuners.com/showthrea...l=1#post745108


    Spark profile won't look anything like an LS btw. That's part of the problem. First, figure out the narrowband issue and get a wideband at some point. Without some sort of O2 exhaust monitor you won't be able to do anything.
    Last edited by SiriusC1024; 03-02-2024 at 02:37 PM.

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    Quote Originally Posted by SiriusC1024 View Post
    That reg should be adjustable. Set it for 58psi with the vacuum line unplugged so the injector data will be more accurate. As far as injectors definitely get properly sized GM injectors. Don't make the mistake of getting 80lb/hr or something like that for N/A. I've seen it often enough that I have to mention it.

    If you're getting an AC Delco reg make sure it's the correct 58psi pressure.

    Blindsquirrel and many others vouch for these, but you'll need to adapt them.
    https://www.ebay.com/itm/274424906026

    Data available at:
    https://forum.hptuners.com/showthrea...l=1#post766924

    Adapter requirements:
    https://forum.hptuners.com/showthrea...l=1#post745108


    Spark profile won't look anything like an LS btw. That's part of the problem. First, figure out the narrowband issue and get a wideband at some point. Without some sort of O2 exhaust monitor you won't be able to do anything.
    Thanks. What about these?

    GTP 36lb (39.87lb@4bar) injector in Gen 3 format - Bosch 0280155868

    I saw these in your post in topic you've linked. It seems they are available easily in Poland and I could get them quite fast

    My reg is adjustable, I will try setting it for 58 psi, but what then? Shall I run with vac unplugged all the time to keep pressure stable?
    Last edited by v8roush; 03-02-2024 at 02:42 PM.

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    Sure thing. They'll work great.

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    Quote Originally Posted by SiriusC1024 View Post
    Sure thing. They'll work great.
    I was wrong = they are not available anymore. I just found green giants 42lbs here..still ok or better to look for 36?

  11. #11
    Tuning Addict blindsquirrel's Avatar
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    Ancient, slow. Modern injectors are much better behaved.

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    (also, see link in signature)

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    Quote Originally Posted by blindsquirrel View Post
    (also, see link in signature)
    that's the real knowledge share! ;-)

    OK, ICT billet has adapters from LS1 to truck injectors

    I believe LS1 injectors same as LT1 injectors physically which means that with adapters I can put them in old LT1 intake. Just to find USCAR connectors.
    Last edited by v8roush; 03-02-2024 at 03:43 PM.

  15. #15
    Tuning Addict blindsquirrel's Avatar
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    https://www.ebay.com/itm/132370243894

    Much better than the typical Amazon plug-in adapters.

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    thanks. you've been great help today.

    So I have ordered already adapters and EV6 pigtails. I need to order only injectors ac delco 217-3412 it seems. Rockauto is my typical first choice to get parts - they have these but are they proven supplier for injectors too?

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    OK, o2 wiring is fixed already, WB installation is on going...

    I have next question as I was reading multiple articles yesterday and it seems that using SD instead of MAF and relies only on VE tables in OL mode might be a better way for me to tune my car now....are you guys runnin on SD or MAF?

  19. #19
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    That will run much better in SD. 100%

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    This would be a lot better in SD.

    With that cam in a LT1 it's likely going to suffer the "split BLM" problem. This is when one bank goes full rich while the other goes full lean at an idle. Its a product of that short runner the LT1 intake has. You might find yourself needing to be in open loop also on this one.


    You will likely need a throttle body adjustment. But don't worry too much about that while the engine is so rich. If you set it up for a rich engine it will be much to high later on.
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