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Thread: Larger injector scaling for smaller injectors

  1. 02-28-2021 #1
    StreetBikeSammy
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    Larger injector scaling for smaller injectors

    I recently had some issues with cylinder airmass g readings and was playing with injector data and timing. I pulled a injector today to read the model # and it turns out they are focomo 18lbs @ 3bar. Tsp sent me the wrong size, I ordered 42lbs @ 3bar and scaled them for it. So my car is running 18lb injectors with the 42lb scaling. What I dont understand is the car is not running lean at all, duty cycle is at 40%(Probably will change if scaled down) and runs pretty good. It made 411hp on a mustang dyno last year with these injectors. I also have a 340lph pump.

    My question is this, do injector companies reuse the injector body/ housing and just add different parts in them? How is the car running good with smaller then factory injectors? Are they just stuck open dumping fuel at WOT? Is my fuel pump working overtime at WOT?

    I bought them at texas speed last year they were supposed to be FIC 42lbhr @3bar, hopefully I can return them and get the right ones because these are not worth the money I paid for them.

    Car is a H/C 04 gto
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    Last edited by StreetBikeSammy; 02-28-2021 at 02:43 PM. Reason: Added log and current tune
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  2. 02-28-2021 #2
    kevin87turbot
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    Those are 48.5 lb/hr at 58 psi. If they were 18 lb/hr, they wouldn't support near the hp that you're making.

    It's pretty common for injector manufacturers to alter a low flow injector and make it a higher flow injector. They can either redrill or decap them to increase the flowrate.
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  3. 02-28-2021 #3
    StreetBikeSammy
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    Are you sure? They don't look like the ones I ordered in the picture and if you search the # on the injector (jr3e-9f593-ab) they come up as 18lbhr at 43psi also one of the numbers is scratched off on each injector
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  4. 02-28-2021 #4
    kevin87turbot
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    Quote Originally Posted by StreetBikeSammy View Post
    Are you sure? They don't look like the ones I ordered in the picture and if you search the # on the injector (jr3e-9f593-ab) they come up as 18lbhr at 43psi also one of the numbers is scratched off on each injector
    Yes I am. I used to work at a major aftermarket EFI/Injector supply company.
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  5. 02-28-2021 #5
    StreetBikeSammy
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    Right on I changed them to 48.5 @ 60kpa or so. Also changed my injector boundary back to 6.50. Don't know why that was 7.27. I don't usually see people mess with injector boundary
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