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Thread: quick chrome injector scale question

  1. #11
    Forum User Not Verified Feedback Score 2 (100%) RealMcCoy's Avatar
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    Quote Originally Posted by mc24 View Post
    They are the ones in the second link (3sx). I changed the injector scale back to 525. I even added 25 percent and then another 25 percent to the latency and idle trims still plus 12.5. All other tables left alone for now. Stock fuel pressure setup. I'm going to do some more research on scaling and latency setting I guess and mess around with them. If things don't start getting better the injectors are off for testing and cleaning.
    Let me try to clarify the relationship between high load and injector size so you can get what I'm talking about...

    If your car was working well with stock injectors set to the factory 361cc setting then you know the ECU has the right scale. Installing 550 injectors "should" require setting the size to 550. You should be able to tell exactly what your injectors are flowing by the required injector size in your software assuming no other issues in the car.

    Latency is irrelevant to that process. (let me explain why):
    The latency setting is a compensation for the amount of time it takes for the injector to physically open. As you'll see in the stock table at operating voltage, that's approx. .45ms on a stock injector.
    For discussion, let's assume that your car idles at a 2.0ms IPW, and on a high load pull reaches 20ms... If you make a -.2ms adjustment to your latency, you would subtract that number from your IPW to see the effect you made. In this example just made the idle IPW 1.8ms,(a relevent adjustment) and you made the high load IPW 19.98ms (a completely irrelevant change)

    "IF" you are confident there is no other issue in the car causing a lean condition. I think you've already established that those injectors are not flowing as expected...
    Last edited by RealMcCoy; 03-07-2020 at 01:50 PM.


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    Well car ran fine before but was on the original ecu. It's a Fed spec 1994. Im sure nothing wrong with the chrome ecu. I think at this point better to be safe than sorry and get them pulled and tested. I'll throw the stocks back in and try the new chrome ecu and factory ecu see if things are the same. I have some 1000cc Delphi brand new that I was going to install after getting used to chrome tuning and run e85 but don't really want to tackle that if I'm have problems just getting started already. I'll report back after they r cleaned and reinstalled. Thanks Soo much for the help.

  3. #13
    Forum User Not Verified Feedback Score 2 (100%) RealMcCoy's Avatar
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    Quote Originally Posted by mc24 View Post
    Well car ran fine before but was on the original ecu. It's a Fed spec 1994. Im sure nothing wrong with the chrome ecu. I think at this point better to be safe than sorry and get them pulled and tested. I'll throw the stocks back in and try the new chrome ecu and factory ecu see if things are the same. I have some 1000cc Delphi brand new that I was going to install after getting used to chrome tuning and run e85 but don't really want to tackle that if I'm have problems just getting started already. I'll report back after they r cleaned and reinstalled. Thanks Soo much for the help.
    Tossing the stock injectors back in while you're having the 550's checked would be a perfect confirmation that the rest of your setup is correct. If your current setup works correctly with the stock injectors, that's just another finger pointed at the 550s

    Have you checked the part numbers on the side of those injectors, and confirmed they are in fact what they are supposed to be..? It wouldn't be the first automotive part to be mislabled or misboxed....

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    So swapped injectors back to the stock ones and set chrome back to stock scaling and latency. Car runs fine but low fuel trim still adding fuel on the low trims. I'm sure there are some small vacuum leaks but fuel trims are not maxed out by any means. I'll do some more cruising around and let the settle in while the other injectors are getting tested. Swapped back the the stock ecu and having same results there. The 550 injectors have AFI 23-550 hand etched in them seems odd that's on there. Also has factory numbers 01d139b and 55lb/hr

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    Do you happen to have a Supra/Denso fuel pump with stock resistor still hooked up?

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    Well I'll have to check that out was waiting to install aftermarket fuel pump and hot wire kit til later. Of course someone before has messed with things too. They have the fuel relay bypassed with jumper wire already.

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    Then by process of elimination I think your injectors are wrong or clogged. i can't think of anything else.

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