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  • 4.5 bar at idle isn't important. Its the pressure on boost that's important. If you inlet vacume at idle is about -0.5 bar and you have 4.5 bar fuel pressure then your base pressure is 5bar. So at 2 bar boost you should have 5 bar base plus 2 bar boost = 7 bar fuel pressure. That's a lot.

    You can confirm your base pressure by leaving engine off but running the fuel pumps. As intake pressure is 0 bar then you can accurately read base pressure.

    Buts it's pressure on boost at max power that's important. You need to measure that. What's your fuel pump setup.

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    • Hmm, quite high idle fuel pressure..? You car makes vacuum under idle I suppose?

      Ooh, des had already explained...

      Audi UrS4 Avant 2.5 20vt - twincharged - Project
      Audi 80q B4 Sedan 2.2 20vt - Daily user
      BMW 320d Touring e91 M-Sport - Daily user
      BMW 740iA e38 - Project

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      • It does sound high base pressure. I'm wondering if the vacume hose that runs from the fuel pressure regulator to the intake manifold is missing or blocked or something. Or the regulator is stuck. This would give 4.5 bar fuel pressure at all times and so a 2 bar boost you only have 2.5 bar fuel pressure to force fuel in so the injectors are working hard?

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        • Originally posted by diesel des View Post
          It does sound high base pressure. I'm wondering if the vacume hose that runs from the fuel pressure regulator to the intake manifold is missing or blocked or something. Or the regulator is stuck. This would give 4.5 bar fuel pressure at all times and so a 2 bar boost you only have 2.5 bar fuel pressure to force fuel in so the injectors are working hard?

          Sent from my LG-H955 using Tapatalk
          No, on 2bar boost fuel pressure is 6,5bar or Bit more. I look at it

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          • Is this pressure measured in the fuel rail?

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            • Yes i adjust Bit more because the injectors on the small side. On idle i have ~0.2 vacuum

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              • Is this e85 or petrol. Seems odd that you need so much fuel. Are the injectors tested to prove flow rate?

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                • I have 600whp on 1300cc ev14@ 3.6bar base pressure (2.3bar boost) and 95% jutycycle on e85.
                  1360kg/600Whp Avant 0-200km/h 9sec

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                  • Originally posted by diesel des View Post
                    Is this e85 or petrol. Seems odd that you need so much fuel. Are the injectors tested to prove flow rate?

                    Sent from my LG-H955 using Tapatalk
                    On E85 with very fat adjustmant, lambda 0.79.
                    The same injectors which i had by my old Setup with 840hp.
                    So i have to control if the pressure is correct.

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                    • Originally posted by hammer View Post
                      Dont wont bigger injectors because the cold Start is a Horror.
                      Thinking about 10 injectors, but this means many work again....
                      It's just the Mapping! The cold start on E85 is not a problem until about +5°C. Even with the 2200cc injectors! You could start it without throttle if its done correct.
                      Audi Coupe Typ89 10V Turbo - VEMS - Billet K26 - Deka 630 - E85 - 3" Exhaust

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                      • Originally posted by Tille View Post
                        It's just the Mapping! The cold start on E85 is not a problem until about +5°C. Even with the 2200cc injectors! You could start it without throttle if its done correct.
                        By a normal car. Not with my cam Timing and injectors 8 cm more back then oem. Also the inner diameter is bigger, so its not enough flow with starting rmp

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                        • Today i testet 3 pressure sensors and all Shows they same. 4.2-4.5bar fuelpressure

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                          • Did they show this pressure while on full boost

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                            • Originally posted by diesel des View Post
                              Did they show this pressure while on full boost

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                              No, on idle

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                              • Ok so at full power and 2 bar boost you should be seeing almost 7 bar of fuel pressure on the fuel rail. That's the important part and will show up any issues with pumps and filters etc.

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