Optimizing oil pressure on rebuild?

[cgarr]

I have had to fix oil pump pickup tubes before, seen them come loose, they are just bonded into the pump.


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[bpu699]

Will check...

But the pressure side of the pump I think is fed straight from the oil tank?

Will also check the main pressure relief, the one with the short spring...

[bickyd]

Carrera tensioner questions
just a thought. may help.

[smokintr6]

Originally Posted by otto_kretschmer

looking for a problem that is not there is kinda like fishing for tuna in a swimming pool

This...

Do the rebuild. check all the clearances and inspect parts. don't lose any sleep

[chris_seven]

You could check the spring with your 23 cent stretch gauge and see if it has a linear rate

[bpu699]

Originally Posted by chris_seven

You could check the spring with your 23 cent stretch gauge and see if it has a linear rate

MacGyver would be proud .

['76 911S 3.0]

Here is my EOP curve, filtered out for temps>150F



I have a 3.0L case, 964 oil pump, and cam feed restrictors installed.

I idle right around 1.3 to 1.5 BAR at 1000 rpm...Rotella T6 10w-40 oil

[Trackrash]

Here is mine. Raises quickly to 60psi then slowly after that.

[bpu699]

Originally Posted by Trackrash

Here is mine. Raises quickly to 60psi then slowly after that.

That's EXACTLY what mine does. By 3500 rpm you are just under 4 bar (call it 50 PSI), and then goes up a smitten more from 3500 rpm to 6000 rpm (60-65 psi). My pressure is pretty much like yours (my gauge is different) and peaks at 60-65 psi-ish. Lower when hot on the track (you did it at 180-190 degress... suspect its lower at 220-230). If I blip the throttle like you did, it goes past 60psi a bit.

I would love to see 5 bar... none of my cars had near that.

It was pointed out that shimming the oil pressure relief valve should raise the oil pressure. It doesn't. I believe Wayne's book mentioned that the relief valve opens at 75 psi or 5 bar. If you are making less than 5 bar, then the relief valve never comes into play.

I know you are also rebuilding your motor. And, I agree with posts that its probably "not something to worry about." But if others are getting >>>5 bar, then that's got to be better that 4 bar... right?

Waiting for parts to come back from various machine shops, will recheck tolerances, and will disassemble the oil pipe. If everything looks good, then it is what it is. Car was happy with the 4 bar...

[bpu699]

Originally Posted by '76 911S 3.0

Here is my EOP curve, filtered out for temps>150F



I have a 3.0L case, 964 oil pump, and cam feed restrictors installed.

I idle right around 1.3 to 1.5 BAR at 1000 rpm...Rotella T6 10w-40 oil

How are you getting such a (near) liner progression? You are hitting almost 6 bar (90 psi!!!)... And that's on 10-40? That's awesome.

My suspicion is that on the 930's the piston squirters open at around 45 psi, and thats what "levels off" the oil pressure and makes it much more nonlinear...

Are folks seeing 5 bar warm/hot on their 930's???

[Trackrash]

I'm going to pull the relief spring and take some measurements, and shim it with a washer. I'm also going to use a gauge on my motor to confirm the readings on my dash. Might be a couple of days, but I will report my findings.

[Catorce]

Nope, the piston squirters do not open at 45 psi. They open at much lower pressures. I can't talk about it right now but we have new piston squirter product upcoming.

Let's just say I have spent the last 2 months extensively flow testing stock squirters and in my testing they can be opened by as little as 10 pounds of air. Opening rates with liquids vary, but think 20-25 psi of water opens them.

[chris_seven]

We currently have the longer version fitted into an engine and haven't yet reached a conclusion.

We have been testing the height of the spray with an air over oil pressure intensifier.

[Catorce]

Chris, do your contain a check valve?

[bpu699]

Originally Posted by Catorce

Nope, the piston squirters do not open at 45 psi. They open at much lower pressures. I can't talk about it right now but we have new piston squirter product upcoming.

Let's just say I have spent the last 2 months extensively flow testing stock squirters and in my testing they can be opened by as little as 10 pounds of air. Opening rates with liquids vary, but think 20-25 psi of water opens them.

So if it's not piston squirters, why does the pressure level off at 3500 rpm? Again, had 3 911 all did the same. I know I'm not delusional, as trakrats car does the same...

I understand bearings bleed off pressure. But I would think it would be a fairly linear curve...

Why the plateau? The relief spring isn't opening at 50 psi so that ain't it.

[bpu699]

Originally Posted by Trackrash

I'm going to pull the relief spring and take some measurements, and shim it with a washer. I'm also going to use a gauge on my motor to confirm the readings on my dash. Might be a couple of days, but I will report my findings.

Pelican used to sell an add on pressure gauge that feeds off the pressure port. Gauge is tiny, but useful...

[chris_seven]

Originally Posted by Catorce

Chris, do your contain a check valve?

Yes, but I am not sure that this is too important on race engines.

At the moment we have used a commercially available miniature check valve but we will try to make our own part.

[Trailbraker]

Interesting this is with the cam oil line restrictors. I have them, but have not installed them yet. Valve adjustment coming, so considering doing it then, but the engine will not be removed, so uncertain how feasible this is.

To the point: where is your oil pressure sensor located? Is it at the back, like my 84 911 Carrera, or, is it at the front, near the oil thermostat? The 993 is supposed to read higher oil pressures on the instrument panel gage, and some early and racing 911's had the pressure sensor at the front too. I think this is the biggest reason for reading higher pressures. Pressure reading are dependent on where the pressure reading is taken. Oil only flows from higher pressure to lower pressure.

[bpu699]

Originally Posted by Trailbraker

Interesting this is with the cam oil line restrictors. I have them, but have not installed them yet. Valve adjustment coming, so considering doing it then, but the engine will not be removed, so uncertain how feasible this is.

To the point: where is your oil pressure sensor located? Is it at the back, like my 84 911 Carrera, or, is it at the front, near the oil thermostat? The 993 is supposed to read higher oil pressures on the instrument panel gage, and some early and racing 911's had the pressure sensor at the front too. I think this is the biggest reason for reading higher pressures. Pressure reading are dependent on where the pressure reading is taken. Oil only flows from higher pressure to lower pressure.

Adding oil restrictors takes 10 minutes and some busted knuckles... motor stays in.

[Trackrash]

OK, background. Fresh 3,0 SC motor, '78, with a new pressure spring update. Also oil line restrictors, opened to 2,5mm and pressure fed tensioners and BP 20-50 oil. I have a new sending unit installed at the front of the motor.

Previously I documented the fact that the oil pressure rose quickly to 60 psi at 3K rpm, hesitated at 60psi until around 4K rpm, then rose slowly above that. Oil temp at 185 F.

I confirmed my oil pressure readings with a mechanical gauge installed.

Here is what I found when I removed the pressure relieve spring.
You will notice that the spring is 86.5 mm long. Spec is 88mm. EDIT: I found this to be in error. It should be 86mm.


I chose to add two washers under the spring on re-install. That gives me a total spring length of 89mm.

Result. Mixed. Now the oil pressure raises quickly to 60psi at 3k rpm, then more slowly after that. It does not hesitate at 60psi as it used to, and it raises continually after that to about 10psi higher than it used too. It shows about 75psi at 6K rpm. I am good with that.

I am wondering if I should shim the safety spring?