1JZ Single turbo, 440cc injectors, Stock ECU, why isn't the car running rich?

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Thread: 1JZ Single turbo, 440cc injectors, Stock ECU, why isn't the car running rich?

  1. #1
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    1JZ Single turbo, 440cc injectors, Stock ECU, why isn't the car running rich?

    So I'm running a 1jz non vvti in my mk3, has a fmic, 3" exhaust all the way back, pretty much it. This is my daily and I would like to make it a little faster. My plans were to keep stock ecu, injectors(380cc) , get something in the size of a GT35 or similar, maybe get a AFC to adjust full throttle in case I run to rich.

    The main thing I don't want is to run rich or lean while regular driving, and on stock injectors I should be fine. Under full throttle worst case I could adjust it with the AFC and take out some fuel if its running to rich.

    Here's the second option: I recently met someone who is running a 1jz non vvti, 6266 which is similar size to what I want but he's running @21 psi, stock ecu, with the 440 cc injectors from a 2jz, he has an afc but has not done any fuel adjustments. His AFR aren't rich nor lean regular driving, they are perfect and stay at 14.5-14.8, just like mine on the stock twins, only thing is he tells me is when under full throttle, he goes rich, down to the 10's which is understandable, if anything I would do the same except just take out some fuel with the AFC.

    MY QUESTION IS:
    Why isn't his car running rich when just regular driving, the ECU still thinks its on the stock 380cc injectors, so when he upgraded shouldn't it be dumping more fuel overall, even when regular driving?

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    Super Moderator Wreckless's Avatar
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    The factory O2 sensor is adjusting the A/F to stoich with the fuel trim adjustment built into the stock ECU. Fuel trims do not affect WOT and high load areas of the map which is largely why SAFC style piggybacks worked OK back in the day. So yes, right after the install or right after you disconnect the battery the ECU will dump fuel because everything's tuned for stock injectors but it's got 440's so it'll be rich by that much more. As it gets closed-loop feedback from the factory O2 sensor, it will gradually nudge the fuel trims in the light load/low RPM areas of the map accordingly back to stoich-ish. It's not a great way to do things but it kinda works.

    On a smaller injector upgrade like going to 2JZ 440's you can choose to leave it alone as that guy has, but I'm surprised he's running 21 psi on a turbo setup like that with just the 440's and it's not going lean. Did he do a bigger fuel pump and increase the base pressure at all?
    Jeff
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  4. #3
    Unlimited Time Attack A70 Twin2Turbo's Avatar
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    A 6266 at 21psi with 440cc The duty on those injectors must be maxxed out.
    -Nick

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  6. #4
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    Quote Originally Posted by Wreckless View Post
    The factory O2 sensor is adjusting the A/F to stoich with the fuel trim adjustment built into the stock ECU. Fuel trims do not affect WOT and high load areas of the map which is largely why SAFC style piggybacks worked OK back in the day. So yes, right after the install or right after you disconnect the battery the ECU will dump fuel because everything's tuned for stock injectors but it's got 440's so it'll be rich by that much more. As it gets closed-loop feedback from the factory O2 sensor, it will gradually nudge the fuel trims in the light load/low RPM areas of the map accordingly back to stoich-ish. It's not a great way to do things but it kinda works.

    On a smaller injector upgrade like going to 2JZ 440's you can choose to leave it alone as that guy has, but I'm surprised he's running 21 psi on a turbo setup like that with just the 440's and it's not going lean. Did he do a bigger fuel pump and increase the base pressure at all?
    Not sure man all he told me was that, he actually runs rich under load, in the 10's. I might just stick with the stock injectors, if I would like to upgrade and get a little faster, I guess I'll just upgrade to the 440cc injectors.

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