Way to increase oil pressure from oil pump modification?

Tippy · 11-08-2016, 05:12 PM

Have a 3.2 (3.4) that I rebuilt about 5 years ago. The crank and bearings spec'd nicely to the manual dimensions. I replaced all bearings new with Glyco.

The oil pressure will get below 1 bar at idle on 100°+ days using VR1 20W-50 or Rotella T6 10W-40.

Question is, can I lap parts in the pump to get more oil pressure?

Didn't touch it when I tore it down, just pickled.

Am I overlooking anything that'd allow lower pressure?

chris_seven · 11-08-2016, 05:55 PM

What do you mean by pickled? Sounds frightening.

Also what is the pressure at higher revs.

If the clearances are all OK then the flow of the pump must be responsible

It may be worth looking at the clearances and end float of the cams.

Check that the pressure reducing valve is fully seated as a small amount of dirt may prevent it from fully seating.

The pump has 3 places where it can cause problems .

The first is the axial clearance which will allow significant 'spill' if this is excessive.

The second is the radial clearances between the rotors and the housing and any scoring or wae could be an issue.

The third is spill though the mesh in the gears. This is not very common unless there is wear in the bearings/bushes which allows the gears to separate and this can also affect the clearance to the housing and this may show signs of wear,

If the axial clearance is too high you could adjust the housing and you could fill any scores or radial grooves with a good epoxy/metal compound such as Belzona 1111.

If the gears are worn there is not much to do other than replace them.

If you dismantle the pump I would mark the gears to re-assemble them with the original engagement.

Tippy · 11-08-2016, 06:01 PM

Pickle or pickling is referring to submerging components/parts in preservation oil and wrapping up to protect from moisture.

I was worried that if I try to decrease the tolerances too much, it might have too much pressure?

Not sure what the specs are.

chris_seven · 06:23 PM

In the UK pickling normally refers to an acid dip

The pump doesn't really produce pressure it is the flow against the restriction to flow that provides the pressure.

If the pump is producing optimum flow any excess pressure will be dealt with by the pressure reducing valve so if flow is being lost due to excessive clearances in the pump then correcting these problems will just restore the flow.

If you tighten the axial clearance too much you will damage the body before the pump will produce too much flow.

As far as I know there aren't any published flow specifications for a 911 pump and testing flow is a complex process which is why inspection of axial clearance and the radial surface of the housings is a good idea.

Tippy · 11-08-2016, 06:28 PM

Thanks Chris, your input is always top notch.

Guess I'll leave it alone. Too risky, and probably not an issue other than in my head

Rawknees'Turbo · 06:37 PM

Cory, what RPM is your idle when it reads below 1bar oil pressure during 100+ degrees operation?

For example, my idle is set at about 1000-1100RPM - it idles nicely there (super low compression engine, as you know) and that helps to compensate for the -/+ 200 RPM drop when the a/c is on (most of the time, buttofcourse!), and when it is 100 out, my engine oil temp is in the 220-230 range (sometimes a little higher depending on if I'm stuck in a traffic jamb - lower when highway cruising) and idle pressure will be a little below 1bar (around .8bar). The operator's manual for my 1987 says this is normal.

This is with Motul 300v4T 15w50 oil.

Tippy · 11-08-2016, 06:38 PM

I'm about 900. Your readings are about the same as mine when that hot.

I don't have a manual to refer to, so maybe I'm chasing a ghost?...

dap930 · dap930's Garage

Is the Carrera pump the same size as the 930 pump? I thought the 930 pump was larger to provide the extra flow for the turbo. I installed a 3.3 930 pump in my 3.0 case which require some mods to make it fit.

jrbennett · 11-09-2016, 09:14 PM

You can add the updated cam line oil restrictors to help boost the pressure.

1978 Porsche 911 SC Coupe - Camshafts & Timing Chains - Page 2

Tippy · 11-09-2016, 09:37 PM

Quote:

Originally Posted by dap930

Is the Carrera pump the same size as the 930 pump? I thought the 930 pump was larger to provide the extra flow for the turbo. I installed a 3.3 930 pump in my 3.0 case which require some mods to make it fit.

Dunno?

Tippy · 11-09-2016, 09:38 PM

Quote:

Originally Posted by jrbennett

You can add the updated cam line oil restrictors to help boost the pressure.

1978 Porsche 911 SC Coupe - Camshafts & Timing Chains - Page 2

Thanks!

Tippy · 11-09-2016, 09:39 PM

You know, I overlooked the fact my engine originally left the factory NA and is now turbo.

Rawknees'Turbo · 10:19 PM

Hey Cory, check out this linked thread, and search "930 oil pump" if you want to look at others, for some explanations about the differences between the pump types. Mainly I see noted differences in flow volume, but not pressures, since that is not determined by the pump as much as the size of the oil passages throughout the engine, etc.

SC oil pump improvements

Rawknees'Turbo · 11-09-2016, 10:18 PM

Quote:

Originally Posted by Tippy

Thanks!

One thing to consider about the oil line restricters is that they actually reduce oil volume to the cams, and at least one top builder here (Steve W., I think) advises against them for that reason (not a good trade-off in order to get higher pressure at idle).

Tippy · 11-10-2016, 04:35 AM

Thanks Ronnie for the heads up!

chris_seven · 11-10-2016, 04:39 AM

930 'Turbo' Pumps have a greater flow capability on the pressure side of the pump to deal with higher volume piston squirters needing increased flow. This is achieved by increasing the gear length on the pressure side of the pump.

This, however, means that the scavenge section reduces in size and this is likely to increase the amount of oil vapour in the crankcase which in turn will increase the parasitic loss due to windage at high engine speeds.

On a normally aspirated engine this doesn't seem a good idea as it will also tend to increase oil temperature.

If you have enough volume flowing to make the PRV operate and moderate engine speeds any extra flow capability from the pump achieves nothing as it will just arrive at the same equilibrium condition by dumping more oil into the return.

Tippy · 11-10-2016, 04:45 AM

So since I'm now turbo, do you recommend the 930 pump?

chris_seven · 11-10-2016, 07:29 AM

If you have changed the piston squirters to the Turbo parts then the pressure section of a 4 bar SC pump may be a bit small.

If you haven't changed the squirters then the oil flow will still be OK but your piston crowns may be too hot.

Turbo's engines are outside my experience range but I would be concerned.

Tippy · 11-10-2016, 07:33 AM

It's a 3.2 and I never modified any oiling

Steve@Rennsport · 11-10-2016, 07:41 AM

Quote:

Originally Posted by chris_seven

930 'Turbo' Pumps have a greater flow capability on the pressure side of the pump to deal with higher volume piston squirters needing increased flow. This is achieved by increasing the gear length on the pressure side of the pump.

This, however, means that the scavenge section reduces in size and this is likely to increase the amount of oil vapour in the crankcase which in turn will increase the parasitic loss due to windage at high engine speeds.

Actually Chris, the scavenge side and the pressure side of the 930 pump are BOTH bigger than the early pumps as well as the SC/Carrera ones. 964/993 ones are the same size, but made from magnesium.

Before the GT3R pump, these 930 ones were the go-to item for all race engines since 1976.