# Stock fuel pressure regulator vacuum???????



## Dcnxer0 (Aug 25, 2017)

Im bootsing my m54 and was wondering, where/what do i do about the vacuum line to the stock 3.5 bar fuel pressure regulator (fpr). 
First question: Will the vacuum port on the turbo be sufficient enough to control that?
Second question: Will I need to run a after market vacuum block?


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## M3 Muscle (Aug 18, 2018)

I'm not exactly sure what platform your car is, but in my E36 M3, I connected the stock FPR to the intake manifold plenum ports. You have to connect it there, because the fuel pressure regulators job is to ensure the fuel injectors always have the same differential pressure on them. I had to get a distribution block because I also had to connect a line from the blow off valve, wastegate, and boost gauge.


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## Dcnxer0 (Aug 25, 2017)

Thank you for the reply. Its a e36 w\m54 turbo and im using the e39 fuel filter and regulator (donor car). Im trying to figure out the vacuume line placement that will work best with a turbocharged system. Can't attach it to the intake cuz of boost psi will pop it off or blow the diaphragm out in the fpr. So i was woundering will the vacuum port on the turbo work. OR.....will the fpr work the same with the positive psi.


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## M3 Muscle (Aug 18, 2018)

*You have to connect it to the intake so the FPR sees boost*. The E36 stock regulator works as a boost referenced FPR and continues to increase your fuel pressure as boost increase. I assume the E39 FPR is the same. If it isn't you need to buy an E36 regulator, or buy and aftermarket FPR. Either way, fuel pressure must continue to climb as boost does because the boost inside the intake pressurized the bottom of the injector. This creates less differential pressure on the injector and will reduce your fuel volume being injected....something you don't want. Also, your fuel being injected will not be atomized as well due to the lower pressure. The intake is the best spot as that is the same pressure your injectors always see.


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## M3 Muscle (Aug 18, 2018)

*You have to connect it to the intake so the FPR sees boost*. The E36 stock regulator works as a boost referenced FPR and continues to increase your fuel pressure as boost increase. I assume the E39 FPR is the same. If it isn't you need to buy an E36 regulator, or buy and aftermarket FPR. Either way, fuel pressure must continue to climb as boost does because the boost inside the intake pressurized the bottom of the injector. This creates less differential pressure on the injector and will reduce your fuel volume being injected....something you don't want. Also, your fuel being injected will not be atomized as well due to the lower pressure. The intake is the best spot as that is the same pressure your injectors always see.


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## Dcnxer0 (Aug 25, 2017)

Ok so ill leave it were its at just put a better hose clamp on it then.


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## Dcnxer0 (Aug 25, 2017)

Ok so ill leave it were its at just put a better hose clamp on it then.


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