Can a supercharger or turbocharger oil feed line be too big?
I am wondering this because I went to check valve lash after my first drive around the neighborhood. When I removed the valve covers, I was surprised that there wasn't much oil lying in the valvetrain area. At first I was thinking it was because the pushrods are the "restricted" type, but I had to make sure.
with the valve covers removed, I started the car. After 2 minutes idling, I had no oil coming through the pushrods. I became worried about the Vortech at this point, so i removed the line, spray nozzle, and belt from the s/c. I then started the car and had almost a qt of oil come out the nozzle in less than a minute!
I decided to plug the supercharger oil feed line, and see what happen's.
With the s/c oil line plugged, I now have almost 5psi more oil press at idle, (45#without oil feeding s/c) and I have oil coming out all pushrods.
WTF! It doesn't make sense to me... does anyone have any ideas? I am running a -6an line to feed the supercharger, and a -10an for a return. I am running this from the origonal oil pressure sender port on the block. I am running a Stephs pan and pump combo with 10w30 motor oil. this is on my 355ci SBC with a Y/S-trim.
Thanks in advance, DonB.

 

Well I don't know about the supercharger setups but a turbocharger doesn't need much oil pressure or flow. I'm using a #3 line with an oriface to slow the oil down and a #10 return line on my lt1 turbo system.

 

Thanks turboSpeed,
I am running a -10 return, I'll try Vortech again today, and see what they say about the feed line size. I am beginning to think it is due to the fact that I have restricted pushrods, and a feed line I have can handle some volume... enough so that the oil is taking "the path of least resistance". I hope to figure this out by this weekend, I want to do some shakedown passes!

 

Not a problem man! LMK if vortech can't help for some reason. It's easy to build a restricted line.

 

There are oil feed restriction orifices within super/turbochargers. These regulate oil flow through the unit and are small compared to the oil feed line size. They are sized based on expected oil pressure and requirements of gears/bearings.

Since oil is flowing through the super/turbocharger, the guage will register lower oil pressure until the engine rpm is increased to the point where the internal oil pump bypass opens, which will hold the oil pressure constant at around 50 - 60 psi. That is why oil pressure doesn't increase linearly with rpm. So, at low engine speeds, feeding oil to a super/turbocharger will net lower oil pressure.

That being said, if the oil pressure at idle is acceptable (>20 psi), you're OK because that is the pressure going to your bearings/valvetrain. Making a "restriction" oil line will reduce oil flow to the compressor unit to a possibly unacceptable level.

If you are uncomfortable with your idle guage oil pressure, you could switch to a high-volume pump. This will supply added oil volume at low speeds which would then give you more pressure.

Mike