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Fri Jan 04, 2013 12:07 am

Freshly rebuilt 2200cc motor with 1500 miles
Blueprinted 30mm pump and oil cooler
Shimmed spring
5-50w Castro Syntec oil
Mann oil filter
Temp needle halfway way on LED, I have 15psi at idle and 55psi at redline.
I do not have 29psi at 2000 RPM per Bentley, only 24psi. If I push the motor hotter, I have 10psi at idle. Push it very hard up a mountain road to 6000 feet, I have about 5 psi at idle and 40-45psi at redline. Oil temp was about 210-215. I am going to add a fan to the oil cooler with a temp switch.

Is this low oil pressure problem at idle? Thanks.

Fri Jan 04, 2013 8:20 am

I have a freshly built 2200 with about 600 miles on it. My oil pump is stock and no oil cooler. I have an oil temp gauge. At operating temerature (210 degrees F) oil pressure at 1000 rpm should be 10psi, 2000 rpm 20psi, 3000 rpm 30psi. Oil pressure numbers lower than this scale stated are too low.

Fri Jan 04, 2013 8:34 am

only very expensive gauges report accurately at low pressures
the vast majority of pressure gauges are +/- a few psi
the scales just offer reference to a normal and extreme operating conditions
your #s sound fine but I would not run 5w oils in a WBX motor no matter how renewed. I don't believe it's mfg to the same tolerences as a modern designed engine.. 10w at the least IMHO anyways
I am sure others may/will have differing opinions on motor oils. so take it as free advice found on the internet

Fri Jan 04, 2013 8:48 am

Old rule of thumb..10psi per 1000 rpm till the relief valve opens. Oil temp at 180*F

The high speed oil pressure switch is .9bar (13psi) an absolute minimum oil pressure above 2000 rpm.

24psi per 1000rpm is fine. Modern engine oils like 5-50w Castro Syntec oil flow better than the oils used in the Bentley. Try a Dino 15w40 HDEO and see if the pressures are higher.

Your oil pressure gauge could be slightly out of calibration too.

Fri Jan 04, 2013 9:42 am

that rule of thumb 10 psi per 1000 rpm I have always learned is a minimim limit (wear limit) this original poster says he has a new motor.

He needs a temp gage, as trying to determine if he has an oil pressure problem cant be done unless he knows if he has a temperature problem or not. If his motor is running too hot, that would explain low oil pressure.

I would NOT run a 5 winter grade multi vis unless I am driving in Artic conditions, even if it is a 5w-50 that is likely too thin to use, and does not meet the Bentrly (ie Official) specifications.

I run a dino oil, 20w-50 year around, coastal california, with occasional trips to the mountains and snow. Besure the oil you choose has a high ZDDP (Zinc) level, as our old style pushrod engines need the extra zinc, which has been removed from most new oils.

so change your oil, making sure it is high in Zinc, obtain an oil temp gage, either borrow one you can put in the dip stick hole, and take a reading, or mount on on the dash with a sendor on the engine for constant monitoring.

also, do not read too much into the oil pressure gage until it is calibrated. gages can red wrong, and remeber a gage is designed for the greatest accuracy mid range, the high and low ranges of a gage may suffer in accuracy even if the mid range is calibrated fine.

On first look, your pressures are low for a new motor, But, you have the wrong oil in my opinion, have an uncalibrated pressure gage, and have no idea what the oil temperature is. so the pressure reading may not mean anything is wrong with your motor, it cant tell you until you do some more work.

Fri Jan 04, 2013 10:25 am

http://www.bobistheoilguy.com/motor-oil-101/

Oil pressure is resistance to flow and as a PSI number alone, is not a single marker for engine health. A new engine will have its own unique operating oil pressure dependent on the internal clearances and calibration of the measuring instruments.
A high oil pressure number is not always "better". If that were the case we would run 60w or 20w60..and intuitively we know that is not desirable or ideal.
More confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. In fact this is the problem. It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup.

Nothing really wrong with a 5w40 or 5w50..yes your OP at operating pressures may be lower..but really..is your engine wearing itself out or grinding metal on metal? No. The engine oil is flowing better with less resistance, Yes.

24psi at 2000 rpm is not a failing engine, assuming the oil is at about 200*f and is consistent.

Our WBX engines use a primitive oiling system, designed long ago in the days of straight weight oils and seasonal oil changes for viscosity. New engine oil technology and synthetics have changed the way we look at the specifications.

If you really want to bump your oil pressure up..run a 20w50 or 20w60 or straight weight 40/50.

The oil pressure will be higher.

Fri Jan 04, 2013 10:58 am

Some engine will actually have less oil pressure on the gauge when running thicker oils as they go into relief sooner and then have more oil pressure loss in the galleys. Never checked to see if this happened on WBXer engines or not as I have never tried running anything super thick in one.

I have run a variety of 5w**, 10w**, and 15w** oils over the years and they have all worked fine.

Fri Jan 04, 2013 5:40 pm

My stock 2.1 has a worn out motor with low pressure. With fresh 20W50 it's sufficient enought to drive but I wouldn't take a long trip with it for sure.. I recently put in LiquiMoly 10W60 and noticed a huge improvement in my pressure. I am constantly monitoring the pressure with a dash-mounted gauge. So if any of you have a worn out motor you're trying to limp along, the 10W60 might help ya for awhile..

Fri Jan 04, 2013 7:06 pm

The best way to figure out what viscosity of oil you need is to drive the car in the conditions you will use. Then use the oil viscosity that gives you 10 PSI per 1,000 RPM under those circumstances. For some reason very few people are able to get this simple principal correct. I cannot explain further.

These same rules apply to engines of any age, loose or tight. Just because your engine is old does not mean it needs a thicker oil. It will need a thicker oil only if it is overly worn, whether new or old. Yet the same principals of 10 PSI per 1,000 RPM still apply. In all cases you need to try different grade oils and see what happens. Then choose the correct viscosity.

Read:
http://www.bobistheoilguy.com/motor-oil-101/

Some people have tried this and occasionally get a somewhat low oil pressure while at idle. This is fine.( Porsche 911s would have the oil warning lamp come on at idle/hot..the owners manual explained this is normal. Porsche finally put restrictors in the cam oil lines to up the idle oil pressure because it worried customers) There is no stress on parts at idle, the smallest oil flow will do the trick. It is at higher RPM where more BHP is produced. This is where we need the flow. Ferrari uses 75 PSI at 6,000 RPM (12.5psi per 1000rpm) with a V12 508hp Maranello (probably with 5W-40 Agip) as the place to test oil viscosity needs. If your oil gives this value under your driving conditions then your lubrication system has been maximized. Period. Our WBX engines are not that stressed.

Fri Jan 04, 2013 7:25 pm

If I were in your situation I would PM 10c with that question and listen well.

Fri Jan 04, 2013 8:44 pm

zuffenhausen1 wrote: My stock 2.1 has a worn out motor with low pressure. With fresh 20W50 it's sufficient enought to drive but I wouldn't take a long trip with it for sure.. I recently put in LiquiMoly 10W60 and noticed a huge improvement in my pressure. I am constantly monitoring the pressure with a dash-mounted gauge. So if any of you have a worn out motor you're trying to limp along, the 10W60 might help ya for awhile..

You may well be covering up the only symptom your engine will give you of impending rod bolt failure. An engine shouldn't need thicker oil as it ages, because the bearings shouldn't be wearing. With a 10w40 oil you should have sufficient oil pressure at idle to keep the oil pressure light off after a hard run. If you warning light is coming on at hot idle with 10w40 then you probably should park you rig until you can have the rod bolts replaced.

Sat Jan 05, 2013 12:29 am

Actually the oil pressure you should be looking at is approx 1 bar (not 10psi) per 1000 rpm on your VW. So the target "hot" should be 14.5psi/1000rpm. The dynamic oil pressure warning system is designed to warn you when you fall below 2 bar at 2000rpm...but you already know that per your Bentley comments :-) 10psi at 800 rpm, hot, is about right.

At 210-215F oil temps, and 5w-50, those pressures sound about right, perhaps a tad low, particularly given your warm coolant/low load temps and pressures. 10C will probably tell you the same thing...your issue is likely not oil pressure..it's oil cooling. The 5w-50 Castrol has tested just fine in my setup..albeit an i4 conversion...but with about 50% more HP than a stock 2.1.

Where is the oil cooler located? Is the stock coolant warmer/cooler still in place? With oil temps closer to 200C, you should be back at the 1 bar/1000 rpm when hot. I just went through the exercise myself: http://www.thesamba.com/vw/forum/viewtopic.php?t=531173 When cold, my setup is pushing about 8 bar into the accusump unit when rev'd up a bit. 10w40, and 0w40 don't provide pressures (in my testing and application) under heavy load/hot in the 1bar/1000rpm range..generally lower. You should see little difference between 5w50 and 20w50 hot based on both my own testing..and the oil spec :-)

Cheers,
Dennis.

Sat Jan 05, 2013 10:06 am

I don't think Garryv84 has an oil pressure problem with 2000 RPM and 24psi, hot engine. (12psi per 1000rpm)

The WBX 2.1 high speed oil pressure switch is .9bar (13psi) an absolute minimum oil pressure above (or at) 2000 rpm. (6.5psi per 1000 rpm) at the operating conditions you run the WBX engine at..

The lower speed oil pressure switch is .3bar (4.4psi) an absolute minimum oil pressure at idle.

10psi per 1000 rpm is comfortably above those absolute minimum numbers. Ferrari uses 12.5 psi per 1000 rpm as an ideal number for new engines making 500hp. Garryv84 has those numbers.

14.5psi (one bar) per 1000 rpm hot would indicate that your oil pressure is above an ideal number..not a real problem, except for your engine wear numbers at cold start-up, where 90% of engine wear happens.

Sat Jan 05, 2013 10:56 am

I would be afraid of having an oil filter failure if I were to see anything close to 8 bar. I would also be concerned with blowing oil galley plugs. It is possible to have too much of a good thing. All you need is enough oil pressure to get sufficient oil to the bearings. After that the bearings will build their own pressure which far exceeds 8 bar.

Tue Jan 08, 2013 8:04 pm

WT, Mahle filter burst pressure is in the 37 bar range, so 8 not even close. The "cold" oil pressure of 8 bar (120psi) is not measured at the gauge, but rather at my accusump which takes its charge pressure via a sandwich plate under the filter and holds that pressure via an electronic fill valve. The 5.5 bar rating of the oil pressure relief valve I'd guess is spec'd at operating temperature...so if you installed a pressure sender pre-filter my guess is that you would see ~8 bar cold with 5w50. My oil pressure gauge up front reads a max of 5 Bar which is easily maxed at 0C cold start at 3000 rpm. You can't see the bypass valve in operation because it's relief pressure of 75-80 psi is also at a typical VDO oil pressure gauge max of 80psi.

Given 8 years of problem free operation, (rebuilt Audi 2.0, digifant head, new pistons, bearings and personally assembled, blah blah) I suspect the pressures and temps on this i4 are typical.

Taking into account Garry has a 2.1 WBX, I'm still thinking oil pressure is fine...just needs more cooling.[/b]

Wed Jan 09, 2013 7:38 am

The MANN W719/12 oil filter goes into by-pass with at 1bar (14psi) pressure differential..pretty low and probaly the same as the MAHLE filter.

When the filter is in by-pass..the engine oil is not being filtered 100%

https://www.mann-hummel.com/mf_prodkata_usa/index....kToPage=12

So if the engine oil pressures are high..and the pressure differential is 1bar..like when you start the engine and hit 5bar+ supply side..and the service side of the oil filter is less (by 1bar)..the filter is in by-pass and not filtering the engine oil completely.

My point is that high oil pressures are not always a good thing and we should be concerned with engine wear at start-up and cold running. That's when our WBX engines are experiencing engine wear.

Wed Jan 09, 2013 9:26 am

AtlasShrugged wrote: The MANN W719/12 oil filter goes into by-pass with at 1bar (14psi) pressure differential..pretty low and probaly the same as the MAHLE filter.

When the filter is in by-pass..the engine oil is not being filtered 100%

https://www.mann-hummel.com/mf_prodkata_usa/index....kToPage=12

So if the engine oil pressures are high..and the pressure differential is 1bar..like when you start the engine and hit 5bar+ supply side..and the service side of the oil filter is less (by 1bar)..the filter is in by-pass and not filtering the engine oil completely.

My point is that high oil pressures are not always a good thing and we should be concerned with engine wear at start-up and cold running. That's when our WBX engines are experiencing engine wear.

it is not high pressure that triggers the bypass, it is pressure drop across the filter that triggers bypass. so long as the filter is flowing, the bypas will not trigger, regardless of the inlet pressure.

A nice high oil pressure will not cause the filter to bypass, a clogged filter will cause bypass. too thick an oil can cause bypass, but high pressure itself will not cause bypass so long as the filter is not clogged.

Wed Jan 09, 2013 9:39 am

I think we are saying the same thing.."and the pressure differential is 1bar"

Wed Jan 09, 2013 11:23 am

AtlasShrugged wrote: I think we are saying the same thing.."and the pressure differential is 1bar"

high oil pressure will not cause the filter to bypass any more than low pressure. a nice 50-70 psi oil pressure (what i get on a cold morning before she is warmed up) will not cause bypass of the filter. If the filter is clogged, or the wieght of the oil is too high for the tempoerature, then bypass can happen. with multivis oil, the danger of bypassing on cold start up is less than in the old days of single wieght oil. a clogged filter will bypass even at low pressure, so long as the drop across the filter is enough to trigger the bypass.

Wed Jan 09, 2013 12:41 pm

Filter bypass may occur if the filter is clogged or the oil is thickened by cold weather. The overpressure relief valve is frequently incorporated into the oil filter. See: http://en.wikipedia.org/wiki/Oil_filter

Look at it this way..take your favorite 20w50 dino engine oil..put it in the refrigerator overnight (about 40*F)

The next day..go pour it into a jar. See how it moves very slowly? Now imaging that same oil, cold, being forced though a very fine oil filter element.

It will take a while to equalize the pressures in the oil filter to less than 1bar..your by-pass is open.

Add in the fact that cold thick 20w50 oil is not reaching vital lubricating surfaces in your engine very fast either.

That's why 90% of engine wear is at start-up.