royston1xxx

Should i be hitting 93% duty cycle at .90 bar boost with 850/1200cc injectors at 7600rpm,a/f was 11-1 with a gt35/40 turbo,power fc,mild port,dp,mp,blitz intake and nur catback,front mount intercooler,apexi bnr33 fuel pump and apexi 1-1 regulator.Seems too high to me,any advice would be great,Roy.

IGY

What is your static fuel pressure? Do you have a fp guage inside the car? Does the pressure go up with the boost?

rx7tt95

Yes, it's too high. Are you positive of the injector sizes? Sure the primaries are 850's? As Igy said, check your fuel pressure. Thing is, if the PFC or whatever computer you are using is showing those high duty cycles and your a/f is a known quantity (you're measuring with a wideband), then fuel pressure won't affect your duty cycles. It'll just blow your motor :-). The computer does not take fuel pressure into account when determining injector on-time. It's a purely mechanical function (fuel pressure) and not electronic like the injector on time is. You know, it makes sense that the two SHOULD be used together....would make a nice safety feature, no?

rx7tt95

Also check to make sure your actual boost pressure is .90kg. Maybe there's a calibration error somewhere with the stock MAP sensor or the settings on your computer to interpret the MAP's output voltage.

royston1xxx

My static fuel pressure is 40psi at 0 boost,and it does rise when boost is applied,also i have re-bored 1200cc injectors with the size and serial no.on the side(rc engineering) in the secondary location and have my old 850 secondary injectors in the primary slot with the midified rail,a/f was from a techedge wb02 wideband sensor.I changed the power fc to pri-64.7%-850cc +0.4ms and the secondary to 1200cc +0.4ms.What else could be causing this as i can't understand why the duty is so high,thanks for the help.

royston1xxx

The boost reading was from the avcr and also the boost gauge connected to the nipple on the upper intake manifold.

IGY

40 psi static, it is possible that everything is correct. That would mean that your car scoots along really nice, probably in the 400-425rwhp range. 45psi static would give fuel for about 450 and 50 psi would be good for 475. Looks like it is time for the 1680cc injs to me.

IGY

As a side note inj flow ratings are usually taken at 43.5psi of fuel pressure. This means at lower pressure they act like smaller injs.

Badog

Where are you? What was the temperature? Temperature correction factors are in play, I am sure.



Just as a side note: 93% inj duty on 4100cc of inj would equal about 460RWHP at 12 psi. That does not fit the behavior of a mild port engine with a GT3540.



Regards

1Revvin7

No doubt something is wrong.