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EFI Fuel Pressure + Injector Sizing

Old 05-31-09, 12:15 PM
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EFI Fuel Pressure + Injector Sizing

Turbo car. 1:1 Rising rate fuel pressure regulator. 880cc primaries + 1050cc secondaries. Should baseline fuel pressure be 45psi? I'm going from memory. I also suspect folks will tell me I need larger secondary injectors? (60-1 HiFi P-Trim .01 AR)

The injector sizing came from [email protected] of Melbourne years ago...
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Old 05-31-09, 01:03 PM
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1:1 is straight rate, not rising rate. Which did you mean?
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Old 05-31-09, 01:08 PM
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1:1 is rising rate when it's based on manifold pressure. You set baseline and for every pound of boost fuel pressure goes up a pound.
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Old 05-31-09, 04:37 PM
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To get the flow the injectors are rated for you need the pressure they are tested at. Mazda rates their injectors at a lower pressure than most IIRC, but you aren't using stock injectors so it doesn't matter what Mazda does.

You obviously have a stand alone so 42-45 is where most systems are run at, start there. The system pressure is one of the changes you can make when tuning so change it if you need to later on on the dyno.
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Old 05-31-09, 04:43 PM
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I was wrong. Primaries at 800cc. They're from a 12AT motor.

Yes, standalone, Microtech MT-8.

Thanks!
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Old 02-21-10, 01:54 PM
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Well, I'll know more here soon. Ended up with an AEM EMS at the tuners request and while the car starts and idles they say at least one of the injectors is acting up so they're off to RC Engineering for a good cleaning and test session.

I see some folks Y-ing the feed line to fuel the primary and secondary rails in parallel rather than in series like they were stock. At what power level or injector size does this seem necessary?
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Old 03-02-10, 01:41 PM
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Okay, what were sold to me as 800cc+1050cc RC Engineering calls 690cc+960cc. We're going to run them on the dyno and watch the duty cycles but it feels like these injectors are going to fall short of the 400rwhp goals we had to the turbo'd motor.

If it was for bad luck with this RX7 build, I'd have no luck at all...
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