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Thread: injector sizing

  1. #1

    Default injector sizing

    I know that with a mapecu3 it is suggested that you go no larger than 2x the size of stock injectors because of the resolution. Does this apply both regular gas and e85? Or can we get larger than 2x injectors for use with e85?

  2. #2

    Default

    Good question. Yes, that guideline is for regular gas. You need more fuel when running e85 so you can go bigger again. Just be aware of the limitation if you want to run regular gas and e85.
    MAP-ECU Support

  3. #3

    Default

    Quote Originally Posted by MAP-ECU Man View Post
    Good question. Yes, that guideline is for regular gas. You need more fuel when running e85 so you can go bigger again. Just be aware of the limitation if you want to run regular gas and e85.

    So, my 2jzgte had 550cc injectors when it was stock. I currently run 1000cc of regular gas. If running on e85, I could go to say 1650cc or 2150cc?

  4. #4

    Default

    I didn’t believe even e85 will cause you to use double the fuel volume so I think 2150cc is too big. You might want to consider using the flex fuel option because it seems not all e85 is created equally and the ethanol content is variable. Doesn’t e85 use about 27% more fuel than gas, therefore 27% bigger injectors?
    MAP-ECU Support

  5. #5

    Default

    so flex fuel plus 1650 injectors would be appropriate?

  6. #6

    Default

    1650cc injectors still feel more than double plus the the additional required for E85?
    MAP-ECU Support

  7. #7

    Default

    My understanding of that "no more than double" rule is because if you get large injectors, you may get rough idle since most injectors dont work too well with less than 20% PWM. If you really want larger injectors for whatever reason, I think you will be fine if you can tune your idle RPM up a little bit.

    My stock injectors are 320cc, and I switched to 720cc, and I set my optimal RPM from 650 to 750 and everything worked awesome.

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