Acceptable oil pressure with turbo
 

Hi All,

I have about 8k miles on my new BP motor. Running around 19psi boost on a larger turbo, fully built bottom end, slightly ported head, oil cooler, stock (brand new) oil pump.

I use 15w50 synthetic oil (only run the car in the summer and most of the time it is hard) and I note just over 40psi of oil pressure at redline fully warmed up. At idle it sits around the 15-20psi mark. My motor is built with tolerances on the looser side to improve oil flow.

The pressure builds quickly but relief is set quite low for all my extra oil paths (cooler, turbo).

I noticed lots of Miatas that add turbos see lower oil pressure. Is the pressure I am seeing a concern? Should I tear into the motor to reshim the oil pump?

Thanks in advance!

Your oil preasure is what I would say was on the low but safe side. At least what I have seen in race motors. I would like to see what others have to say, but I would not change anything yet. As the engine naturally wears, oil preasure may get lower, and you may need to do something about it.

I would probably start to worry if it went under 15 at idle. 40psi on the throttle is ideal. What is it when cruising? I will check what mine is at idle, cruise, and redline and get back to you.

If it really starts to freak you out, go with 20w50.

stock gauge or aftermarket?

That's low unless your gauge is fuxored...which it probably is.

Gauge is an aftermarket single wire autometer (works very similarly to the stock linear gauge).

At cruise it's around 35-37psi warm. Hot, redline, just above 40 like I mentioned - around 43psi or so but the resolution on the gauge face is quite poor.

I also have no lifter noise (which is associated with poor pressure since the head is the last to receive oil)

is the sensor above horizontal?

above horizontal? not sure what you're asking. It is plugged in the back of the block where the stock sending unit is plugged.

inverted. It sounds like its not though.

I really think your oil preasure is ok.

On both engines I've had the warm idle oil pressure has been 10psi according to my AutoMeter gauge. My current motor was assembled with all new internals and a brand new oil pump, so I think it's fine.

What is your pressure at redline?

About 48 psi. Oh, and it idles at 12 psi, not 10 like I thought.

My mechanic is getting out 99 ready for the track next week and I had him install two gauges, one oil pressure and the other water temp. Temp is good staying between 180 and 185. The oil pressure sender is installed at the oil filter sandwich plate. It reads 75-80 cold, runs 60 hot and idles at 45.

Thanks for the replies so far. Any more views are welcome. The solid lifter cars run higher oil pressures usually because they don't have the flow path to the lifters.

sounds like another good reason to upgrade to solid lifters!

Now now Jon, let's not get ahead of ourselves :) Not sure if a 99 head is worth it for me at this point