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2001 V11 Sport petcock options?

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Pressure is typically measured relative to something. The nipple being open to atmo means that the fuel pressure it maintains is relative to atmospheric pressure. A cool example of this is; I have a cool liquid filled tire pressure gauge. I mainly use it for the Jeep. When we travel for our Jeep trips we often end up at a much higher altitude. If you don't "burp" the gauge it will read noticeably wrong. As I recall it reads low when you are at a much higher elevation if you don't burp it to relieve the excess pressure inside the gauge. Most gauges are vented to the atmosphere, but a liquid filled gauge typically has a rubber plug that keeps the liquid in. If atmospheric pressure has dramatically changed, like if you go from 500 ft above sea level to 5 or 6 thousand feet above sea level or more, you need to pull the plug enough to let the pressure in the gauge equalize with the pressure outside the gauge.

The have been attempts to connect that nipple to the intake manifolds (to the vacuum port(s) there), but while that idea might sound good on paper it never seemed to work well in practice.

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In the very early days of the Ducati 851 used to connect the intake manifold to the reg but they quickly dropped the practice. It was obviously designed to regulate fuel pressure to manifold intake pressure and bikes that used the reg sense port had different chips. I suspect in the end it didn't have enough impact on the fuelling to persist with. 

When I upgraded my 888 race bike to the quad injectors I also went to the vented reg.

Ciao

 

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On 12/18/2019 at 1:30 PM, Lucky Phil said:

In the very early days of the Ducati 851 used to connect the intake manifold to the reg but they quickly dropped the practice. It was obviously designed to regulate fuel pressure to manifold intake pressure and bikes that used the reg sense port had different chips. I suspect in the end it didn't have enough impact on the fuelling to persist with. 

When I upgraded my 888 race bike to the quad injectors I also went to the vented reg.

Ciao

 

It shows it that way in this early document 1989, https://dpguzzi.com/efiman.pdf This is a great read if you want a  basic understanding of EFI

Connected to the manifold it would constantly be changing the injector pressure, I imagine it would put a lot more strain on the regulator and probably made it tricky to calculate the Mapdirect

As it runs now the injectors run under choked flow conditions, the manifold pressure has no direct effect on the injector flow rate, thats a function of the ECU  calculation.

The ECU includes an Absolute Pressure transducer that signals so it can compensate for Altitude by changing the open time. Of course it also included revs, temperature, throttle position, battery Voltage and a few other parameters in the injector time setting (just not by tweaking the supply pressure)

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