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Sat Mar 14, 2015 9:15 pm

A friend of mine has a problem with his engine's oil pressure at idle.
It is mostly stock. No noises and has few miles on rebuild done by a race shop.
Anyway way, in thinking of solutions it occurred to me that a much higher flow oil pump would solve the problem.
It is costly but not nearly as bad as a rebuild to perhaps use a dry sump pump and drill holes in the separator plate on each side to make a 45mm or so pump. No longer dry sump pump but just a much higher flow one.
Yes, I know a perfectionist would insist it be rebuilt but that is not is not practical just now.
Back in the early 70's we increased the pump volume modifying an automatic stick shift pump. I still have one in the garage on my old engine. I don't remember the details now but those parts are quite expensive now and no better than the aftermarket pumps available now anyway.

Sat Mar 14, 2015 9:36 pm

It can be done but consider it a band aid until the motor is properly rebuilt. There is no need to go 45mm, that's crazy huge. If you need a pump that big, rebuild the engine instead. I went from a 26 to a 30 and that was enough to do the trick (until I rebuilt the engine). Oil pumps are not expensive.

Sat Mar 14, 2015 9:45 pm

Before you get another oil pump try a different weight of oil. What oil are you using now?

Sat Mar 14, 2015 9:57 pm

Low oil pressure is not a problem, it is a sign of a problem.
A larger oil pump won't fix it, but make him feel better, like advil?
Easier solution would be medicating the driver. LOL

Sun Mar 15, 2015 2:34 am

Advil is pretty thick, might upset some people if he uses that.

I'm wondering how much of a problem he has - the stock oil pressure light can come on at hot idle if the idle is a bit low, the switch a bit old and the oil a bit light. Engines can run for ages like that, but even better to correct the oil weight, low idle or tired switch. 45mm is definitely overkill, but if he has a stock pump he could go to 26mm, or from 26 to 30 with a light oil maybe (I know I'm stepping into dangerous territory here.)

Sun Mar 15, 2015 2:42 am

yeah, in stock form with...lets say 10-30 oil the light can be on at hot idle, that's probably ok, but is that the case here?

The problem might be the oil pump itself if it has excessive clearance, or it might already have a larger size one. Worth checking!
Safest to...assume nothing.

Sun Mar 15, 2015 7:13 am

I've seen a few people that insist their engine should idle at 600 RPM's.

Your problem may be as simple as raising the idle speed a few hundred RPM's. On all my engine with dual valve springs I set the idle at 1000 RPM's.

Sun Mar 15, 2015 10:36 am

Ok, lets redirect this conversation a bit. I know the guy will not spend the money to solve the problem.
I idle around 1200 due to the cams in my 2387cc engines.
However, brain storming about an non-intrusive solution to his problem got me thinking. Being an engineer I seem to brainstorm a lot. There are situations where a very high flow pump would be useful. Naturally if you wish to maintain a high oil pressure at hot idle after dropping off the interstate highway is one.
But others could be if you wanted to add oil jet piston cooling, or if you want to use an external pressure relief valve so that you can spray the unused oil into the head covers for some additional cooling of the heads.
Has anyone made such a modification to one of these pumps?

Sun Mar 15, 2015 10:45 am

If you run a doghouse oil cooler the high oil pressure will cause some oil to bypass the cooler causing higher oil temps.

Sun Mar 15, 2015 1:00 pm

I know for a fact that the 26mm pump will produce 260lbs of oil pressure with the tawain made chrome plungers and springs, i put in stock ones, oil pressure came back to normal.

Sun Mar 15, 2015 1:00 pm

I know for a fact that the 26mm pump will produce 260lbs of oil pressure with the tawain made chrome plungers and springs, i put in stock ones, oil pressure came back to normal.

Sun Mar 15, 2015 3:11 pm

Let's address a couple of things.
1. Increasing oil flow rate decreases oil flowing thru by-pass cooler.
The oil flow thru the by-pass cooler is related to the pressure differential across it and the viscosity of the oil. If anything the differential pressure will increase not decrease with increased flow rate. Also, as the oil thins due to temperature more there is more flow thru the by-pass cooler. The system is designed to do that so when the oil is very cold it is allowed to warm up.

2. Yes, you may get high pressure from a pump, but at what flow rate?
If you were able to get over 200psi at hot idle then the oil pressure would never drop to less than 50 or 60 psi. You can't have your cake and eat it too.
Has anyone an answer to my question? Has anyone used one of these pumps to make a high flow oil pump?

Sun Mar 15, 2015 4:59 pm

Bugpack makes a 32mm super oil pump P/N 3036. Try it out and let us know how it works out.

Sun Mar 15, 2015 8:14 pm

Empi makes a 36mm pump that will produce 85psi at a 750rpm idle. Why would you go through all the trouble of modifying a 2 stage pump to do what you can do with a $40 readily available oil pump.

Personally I think you are just adding a bandaid to a problem. What is his idle rpm and what weight oil is he running. Those are 2 critical points that need to be addressed. depending on what these 2 values are would indicate if he has an internal engine problem or not. If his idle is 650 with 20W50 oil he has a major problem. If it's 650 with 5W30 he might just have change oils or turn up the idle.

brad

Mon Mar 16, 2015 2:37 am

The OP admitted it's a bandaid, but if he would go to that expense rather than trying a $40.00 pump I wonder if he's an accountant rather than an engineer?

Mon Mar 16, 2015 7:03 am

Actually, he is a college professor, I am an engineer.

Mon Mar 16, 2015 8:19 am

VWturbine wrote: Actually, he is a college professor, I am an engineer.

That being said, please explain again why you are interested in half assing it.

Back in the day the auto stick pumps were used to make a full flow pump. I do not know how it was done, I've asked some old timers and got nowhere... Seems as it was lost to time! :roll:

Mon Mar 16, 2015 11:51 am

I use a OEM VW 30mm filter pump made in Mexico by Bocar, with a stock 1600 engine.

OEM stock VW springs and plungers.

Using 0W-20 synthetic in the motor.

Mon Mar 16, 2015 4:58 pm

#1
There is a valve that allows oil to bypass the cooler when pressure is over about 40psi.
Not pressure differential, OIL PRESSURE. That's how it works!

#2 Yes there were some guys that did it in the 70's, but I haven't heard about anybody using an autostick pump this century.

Large pumps waste HP and place additional stress on the cam gear, so I don't use them unless the engine has additional things that flow oil, such as a turbo or hydraulic lifters or piston coolers or god forbid all of the above.

Mon Mar 16, 2015 9:22 pm

That is not what I said. I said that the flow rate of the oil thru the cooler is related to the differential pressure across it and the viscosity of the oil.

The bypass valve is an absolute pressure valve. When the viscosity of the oil is high, the bypass valve opens up at lower RPM and it reduces the differential pressure across the filter. If you have no differential pressure in a system, i.e., pressure on equal on either side, there would be no flow.

Instead of using a temperature sensing bypass valve, VW used the oil's viscosity as a means of sensing the oil's temperature. It works pretty well unless you use near constant viscosity synthetic oil.
Many of us don't concern ourselves with that and use full flow external oil coolers without fans, or with fans and maybe with thermostatic switches. Or even a temperature sensing bypass valve if are running in real temperature extremes.