oil pressure, VVT head with non-VVT (thin) oil pump
 

Anyone noticed a drop in oil pressure?

With 82*C oil (180*F), I only get
16-17 psi at idle,
28 psi at 3000 RPM, and
38 psi at 6000 RPM.

With stone cold morning oil (50 *F) it's 65 psi at idle and tops out at 75 psi, so I know my oil relief valve is working.

Maybe it needs to be shimmed.

There is a reason they increased the size, the oil pumps are designed at exactly what they need to be to create the proper flow in the engine. 38 PSI sounds very low to me, I'd be worried about your bearings. There is a reason why I recommend 70-90 PSI for my customers! All that extra flow affords a lot of protection.

Neo shimming won't help because 38 psi is below the bypass opening pressure.

Would thicker oil for higher pressure help? This won't improve flow though.

No, the thicker oil won't do anything for you. What you need is flow!

Flow is what actually keeps the surfaces apart. You can drop a fork into a 5000psi body of water and it'll sink at the same rate as one at atmosphere. The high speed movement of the fluid pushes the metal parts apart doing the bulk of the work.

Ideal would be dynamic viscosity being low, and pressure is high! 0w-20 @ 90 PSI!

Argh PSI is dictated by other things as well including various restrictions etc. I thought what you wanted with the oiling system was massive flow, not pressure.

BTW FWIW Y8S and I, with VVT heads never see more than 45psi or so at 5000RPM. VVT will fuck with the oil pressure too.

Fae,

Which oil pump do you have?

BTW Travis,

If 100% true, why not use 5w-20 oil and get more flow despite less pressure? (for those with lots of pressure)...

Oh I definitely have more than 50psi at or above 5000rpm, albeit this is a stock VVT engine, not a built one.

mz-bp4w-14-100A

I have no clue what year that pump is from. It is an old miataroadster billet OPG assembly. It would be nice if I could find out :{


How much more? 50psi @ 5000RPM is about where mine tops out at.

60 to 65.

Does that not rob horsepower to have oil pressure at a high PSI?

OK NM

The MZ-bp4w-14-100A is the oil pump that was standard through '99. A "non VVT oil pump".

Why is all the PSI necessary? If there's a film of oil, there's a film of oil right? Doesn't matter what the PSI through the system is does it?

All else being equal more oil pressure means there's more flow too.

Now if you're in the middle of the acceptable ranges, is thinner oil for more flow better, or thicker oil for more pressure?

Arrrgghhh!!! I'm not getting significantly higher oil pressure with 5w50 oil

How do I change the oil pump without pulling the motor?

Anyone want to buy billet OPGs blueprinted in its housing, for a non VVT application?

Can be done but you will need to raise the car up enough to work under and then prepare to break your back several times. I would rather pull the engine out.

Pulling the motor is the easiest way to swap oil pumps. So what gears are you using? I am using a 94 OP with the BE billet gears on my 94 block with the VVT head and oil pressure has been fine so far. I will look tonight to see what my oil pressure is at idle, but I do not think it is anywhere near as low as yours?

Jason, before pulling the motor do an oil analysis. That's what I'm doing at the next oil change.

Warmed up I sit right above 30psi and cruising at 45mph in 5th I am a little below 60psi. When VVT kicks in oil pressure does drop a little. I am still using the stock oil pressure sender from my 94 with the stock gauge.

I have access to a lift.
What's the easiest way to pull the oil pump?

It's high RPM oil pressure that's important, as long as idle has > 10 psi.
I barely get over 30 psi hot at 4000 RPM. 5w50.
My main bearing clearance are ~0.0028 - 0.0032"

I have a 91+ real OPG which I verified with another gauge.

shuiend,
How much does your OP drop when VVT "kicks in"? What do you mean by "kicks in"? AFAIK

faeflora,
I did an oil anaylisis at 3000 miles and it looked "normal" for an engine that's <5000 miles since a rebuild. I hadn't been revving the engine all that hard.

Honestly a lift will not be to helpful. You need to lift the engine up a little bit with a cherry picker. Then unbolt it from the subframe. Next it taking off the oil pan. Then oil pump. The hard part is putting the pan back on correctly.

If you have help there is no reason why you could not pull the motor and replace oil pump in a weekend.

My oil pressure seems to drop about 5psi when VVT kicks in. Still well above 50psi+.

What are you bearing clearances?

Are you saying your pressure drops 5 psi when you run anything less than full retard?

I honestly do not remember what my bearing clearances were. I know they were within stock spec.

Oil pressure seemed to drop about 5psi when the came were not at full retard. My vvt has not been tuned yet at all and I was going off settings I got from y8s, so that may change. I know when I had VVT disabled my oil pressure would not drop any.

Maybe this helps. ~70psi during WOT pulls. It's the red graph. You can actually see the pressure going down as the oil temperature goes up.

Attachment 188861

What software are you using to log oil pressure? Maybe I need to figure out how to get MS to log it.

I don't understand why you are pulling the motor then. I had a long talk with clevite or king-- I forget. I was telling them that I was considering pulling my motor because I had somewhat low oil pressure, stock bearings, and was heavily boosted. They emphatically suggested a) looking at the oil filter/oil for particles and b) doing an oil analysis. They said that if there are no particles and the analysis comes back ok, don't worry about it.

Honestly, I do worry about it but their recommendation makes sense to me. Do you think otherwise? I am open to persuasion on this matter.

Ahh makes sense, thanks.
Perhaps I should do a track day then send the oil for ----.

First I was like.... :hustler: but then I :laugh: