turbo oil supply restrictor pressure drop over distance

[omgjames]

My friend has an issue regarding oil pressure/flow drop over a short distance I'd like to get other opinions on.

A GARRETT GT25 frame turbocharger requires only 35-40 psi of oil pressure supplied to bearing section to perform reliably (as per GARRETT). Anything above ~40 psi begins to force it's way past the seal and into the exhaust stream, thereby causing a smokey mess.

The oil pump he is using surpasses the 40 psi max by a lot, so a restrictor is necessary to decrease pressure/flow. Specifically, there is a oil supply routing that goes as follows:

Oil Pump-----Engine Block Junction------2ndary Junction---Turbocharger

GARRETT's technical department didn't have a solid explaination on the placement on the restrictor in the oil supply route. They only stated that the restrictor should be placed at the inlet of the turbocharger. I don't think he was an engineer, just customer service.

Can the restrictor be placed at the 2ndary junction, which is about 5" before the turbocharger inlet, without a critical pressure/flow drop (beyond what's necessary for turbocharger oil supply)?

 

[patprimmer]

The pressure drop will be the same no matter where in the final turbo oil supply line the restrictor is, however, the farther from the turbo, the greater the time to build up oil supply to the bearing on start up.

I would put it at the inlet to the turbo.

Regards

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[omgjames]

Hmmm...I didn't think of the start up issue. This is something to consider. I wonder how much of a concern the oil supply delivery delay will actually affect the bearing at start up. It's only a 5" difference. I will relay the message.

Thanks!