My fuel pressure at 0psi is about 43psi and at full boost...which is about 20psi...fuel pressure comes in at 65psi. At idle my pressure is at about 32psi. Hope this helps.
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FP setting
The factory likely gives a reading that's set with NO vac line attached. The pressure going UP when the line is disconnected is normal. when not under boost the vacuum in the engine is attempting to suck the fuel from th einjectors and thus the pressure at the regulator is dropped to compensate.
The reasoning this is all done is to make the creation of the ECU fuel maps easier. when they create those maps they'd liek o be able to asume a nice steady fuel suppply. Tuning for a constantly varying fuel supply would be a nightmare! So, they created a system that compensates for variations - boost attempting to push fuel back up the line is one example of a variation. To compensate for that they created a regulator that would increase fuel pressure for every 1PSI of boost pressure and do just the opposite for vacuum conditions. Following me? For instance - if you turbo a carb vehicle and don't compensate for this condition the carb will actually be receiving NO fuel when your boost level passes the base fuel pressure setting - it blows the fuel back down the line! Making sense? when pressure rises under boost you're no actually getting MORE fuel unless the pressure is rising faster than the boost is.
As for the correct base setting, I dunno'.
I'm not (yet) a Supra owner but I DO know how EFI fuel pressure is supposed to be set and WHY it's set that way. This is true for all EFI vehicles although the new returnless systems are probably REALLY funky (shiver).
The factory likely gives a reading that's set with NO vac line attached. The pressure going UP when the line is disconnected is normal. when not under boost the vacuum in the engine is attempting to suck the fuel from th einjectors and thus the pressure at the regulator is dropped to compensate.
The reasoning this is all done is to make the creation of the ECU fuel maps easier. when they create those maps they'd liek o be able to asume a nice steady fuel suppply. Tuning for a constantly varying fuel supply would be a nightmare! So, they created a system that compensates for variations - boost attempting to push fuel back up the line is one example of a variation. To compensate for that they created a regulator that would increase fuel pressure for every 1PSI of boost pressure and do just the opposite for vacuum conditions. Following me? For instance - if you turbo a carb vehicle and don't compensate for this condition the carb will actually be receiving NO fuel when your boost level passes the base fuel pressure setting - it blows the fuel back down the line! Making sense? when pressure rises under boost you're no actually getting MORE fuel unless the pressure is rising faster than the boost is.
As for the correct base setting, I dunno'.
I'm not (yet) a Supra owner but I DO know how EFI fuel pressure is supposed to be set and WHY it's set that way. This is true for all EFI vehicles although the new returnless systems are probably REALLY funky (shiver).1 - 15 of 15 Posts
