Pump Power Reduction

[bigTomHanks]

I put together a stand alone oil system to feed a turbocharger and am having problems with the pump drawing too many amps(10A).

The system goes like this:

Turbo Outlet ->(3/8" Line)-> 1 Gallon Vented Oil Tank ->(3/8" Line)-> Pump Inlet ->(5/8" Line)-> Pump Outlet to Tee Fitting ->(5/8" Line)-> Turbocharger / Pump Outlet to Tee Fitting ->(3/8" Line)-> 1 Gallon Vented Oil Tank (to regulate pressure)

The pump is a brass/bronze gear style pump with a 12V DC motor driving it.

Would changing the line size help reduce the amp draw on the motor while maintaining a minimum of 20psi?

How much would thinner oil impact the power usage? I'm using some 10W40 I had laying around to run the test.

Will the required power become lower once the turbocharger starts spinning due to the oil having an easier path to flow?

 

[racookpe1978]

I'd change the 3/8 discharge lines to 5/8 before doing anything else.

True, they are going to the (vented) oil tank, but they are the most restrictive part of the flowpath.

Amps are high, but are you getting enough oil to the turbo bearings to keep them cool?

 

[bigTomHanks]

I'll try changing the discharge line to the larger size. I had concerns that by increasing the discharge line size it would kill my feed line pressure to the turbo but I may be missing something there.

How I have it set up the turbo bearings are getting 20 psi with plenty of volume, I think this is adequate for the journal style bearings. The problem that I have is that the pump motor is rated to run around 5 amp and it's running over 10 amps causing it to shut off due to heat after a certain amount of time. This would be unacceptable with the turbo installed on my truck and would result in ruining the turbo.

The way I found that the motor was running over 10 amps is that I put a 10A fuse in the line and it blew once the line approached 20psi.

I may just have to plumb an oil line from the engine and then use the electric pump to scavenge the oil back to the crankcase (very little build up of pressure in line) but I was hoping to do a stand alone setup to isolate the engine and turbo oil.

 

[chicopee]

Before making any change, have you reviewed the pump manufacturer's specifications?

 

[Tmoose]

Seems there is likely a pressure relieving bypass in the system somewhere since it is a gear type pump. If it is spinning "too fast" and simply bypassing much of the oil is pumping, slowing the pump (lower voltage) might better match the required flow and lower the amps.

If I was really concerned about the pressure at the turbo I'd put a gage there.

Look what size line was adequate for a Corvair turbo fed at ~ 45 psi. I believe there was an orifice in the fitting at the Turbo to boot. Yhe line might have been a wimpy 3/16" as I vaguely recall.

http://upload.wikimedia.org/wikipedia/commons/e/e1/Corvair_turbo_engine.jpg

 

[bigTomHanks]

I haven't been able to find a good spec for this pump. It's a china made ebay item that didn't come with documentation. I think it's primarily intended to pump fluid without creating much line pressure. I thought it might work because others on the internet have a similar setup but their pumps may be different internally even though they look similar.

I was thinking that someone might say that my supply line to the turbo is too larger and that using a smaller line would reduce the amount of work required by the pump but this does not appear to be the case. I'll just have to plumb an oil line from the engine and use the pump I have to scavenge the oil back to the engine.

 

[JJPellin]

A positive displacement pump will draw power depending on the downstream pressure, speed of the driver and viscosity of the fluid. You are either running the pump with a more viscous fluid than it was designed for, running it at a faster rpm than it was designed for or running it against a higher pressure than it was designed for. If you need 20 psi for your applications then you can't change that. I would start with a thinner oil (especially if it will normally be pumping a thinner oil). Slowing the pump down is a very good option, but I don't know the best way to accomplish that.

Johnny Pellin

 

[Tmoose]

Any model and manufacturer on the pump? It often surprises me what OEM documentation is available online.

 

[LittleInch]

JJPellin has it about nailed. Your pump is essentially a fixed flow pump which at a fixed speed from your motor wants to pump a certain flowrate. The power it takes from the motor is affected by it's discharge pressure and density of what it is pumping. Your motor wants to maintain a fixed speed and simply draws more power (current) to maintain that speed regardless of what it says on the rating plate

Therefore in essence your pump is simply pumping at too high a pressure for the motor you have got on it.

Your options are:
Reduce the pressure by your pressure control (tee fitting to tank), probably to about 10 psi. If you don't change anything else this will result in less flow through your turbo as more flow will just go via the pressure controller back into the tank.
Buy a bigger motor
Increase tubing size to reduce friction losses (only works if helps reduce pressure output from the pump but maintain flow through your turbo)
Reduce viscosity of fluid (which will reduce your friction losses, but unless you change the pressure setting that alone won't help much.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[chicopee]

Well, it's tricky when you buy Chinese made stuff of that caliber. Brooms and mops from China would be OK but more sophisticated items, I would buy USA made, pay a little bit more and do away with the headaches.