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Production cost is my guess as it simplifies the oil galleries. It works fine as long as the drilling are accurate not to go too close to the cam bearings where it blocks flow to the mains. Evident in ecotec V6, hence the common failures in them.

The holes in the bearings themselves is what meters the flow in those setups but it isn't mod friendly unlike mains first setup.

Charlescrown wrote:I like around 50-60 psi oil pressure. 30 is getting a bit risky. If only you could see inside the engine when it's reving it's nuts off. Considering it was failing it still went really hard.

yeah everyone i talk to is telling me to aim for 10psi/1000rpm ... probably about half that now

My nephew's 4Runner with vr v6 engine idles at 60psi and peaks around 80psi at about 2500 to redline.

Big difference to the 10-30 psi the old VWs I played with when I was younger lol.

Boy I remember those old VW's. They had a dowel to locate the bearing and they often grabbed on the crank, tried to rotatae and seized the engine.
I think the problem with high oil pressure on a lot of the Jap cars is the oil pumps can't take it and crack the rotor but the Holden has a solid designed pump. I'd be aiming for 60 at high rpm's.

Yeah, the VW engines are shit as well as the cars lol.

Not really a weak pump problem but an inline engine problem. It's not uncommon for long crank engines to shatter oil pumps due to torsional vibration at high rpm and the fact that it seems all Jap engines use the 2 flat type pump drives, not ideal for chatter. Remedy is to use a good heavy race balancer.
Most people just get billet pumps which is a band aid but best is to upgrade both.

GM pumps don't seem to suffer this as they are short cranks being V engines so they are a lot more stiffer and GM changed to the 6 spline drive around 95 going forward.

key to remember psi is a measure of restriction. improve the flow and your moving more oil for less psi. psi cant be used as an absolute measure of how much oil you have where you need it.

Yea that's correct but increasing the possible volume will increase the pressure.

Yeah you wouldn't know unless you could measure oil flow rate and pressure and have a baseline of what's good for a particular engine to compare too. I feel like this is car manufacture R&D territory stuff.

Evidently it's complex when you see a block and notice certain mains/cam etc have different drilling sizes that were chosen for a reason that doesn't make sense to the average engine builder.

I sometimes question what manufacturers do and why they did it. How many new cars are having engine failure because of piston design. Bit of copy the other ones. to reduce their R&D costs.

Gear pump is positive displacement, so should be pretty easy to figure out the approximate flow rate at any given speed. If the pressure is low either not enough oil going into the pump, or the downstream restriction is too low.
As far as downstream restriction goes you could have a faulty relief valve cracking too early or otherwise the oil is going somewhere it "shouldn't" be such as a leak or turbo oil feed on a factory NA engine etc..
Changing the oil viscosity obviously changes the expected pressure for any given flow rate.