High Flow Oil Filter

[Doug Hillary]

Hi,
ZeeOSix - Lubrication systems and their operation are never a one size fits all - variations are immense. Fluid dynamics are primarily a constant in principle and practice

Several years ago after a debate on the subject a Californian tuning shop used an engine dyno to track oil temp and pressure in relation to the 9bar system bypass. The engine was a Porsche V8 and the lubricant was M1 15W-50 which has great flow characteristics

It was found that it took around five minutes from ambient OT to dislodge the relief valve at around the engine's design OP parameter of 4krpm (5bar). The oil temp was then at around 95C IIRC. The bypass returns oil directly to the sump ex the pump. You can imagine in this case that very little (volume) lubricant would be flowing through the media. The FF filter had a media bypass setting of 2.2bar

 

[Steve S]

What was RPM was the cold engine run at for the test?

 

[ZeeOSix]

Originally Posted By: Doug Hillary
Hi,
ZeeOSix - Lubrication systems and their operation are never a one size fits all - variations are immense. Fluid dynamics are primarily a constant in principle and practice.


I totally agree, and if you read this thread from the very beginning you’ll see that the various dynamics is talked about many times. I mention many different scenarios when and how the factors come in to play. There are about 6 major factors that can influence the dynamics of the oiling system, and if one or more factors are changed it will influence the system to some degree.

Originally Posted By: Doug Hillary

Several years ago after a debate on the subject a Californian tuning shop used an engine dyno to track oil temp and pressure in relation to the 9bar system bypass. The engine was a Porsche V8 and the lubricant was M1 15W-50 which has great flow characteristics

It was found that it took around five minutes from ambient OT to dislodge the relief valve at around the engine's design OP parameter of 4krpm (5bar). The oil temp was then at around 95C IIRC. The bypass returns oil directly to the sump ex the pump. You can imagine in this case that very little (volume) lubricant would be flowing through the media. The FF filter had a media bypass setting of 2.2bar


Oil pump’s relief/bypass setting = 9 bar = 130.5 psi
Oil pump output pressure @ 4K RPM = 5 bar = 72.5 psi
Filter’s bypass setting = 2.2 bar = 31.9 psi

So if I’m following you’re description above, the oil filter was going into bypass (PSID @ 31.9 psi) when the engine was at 4,000 RPM and the pump was putting out 72.5 psi at 4K RPM (which was obviously not in pump relief of 130.5 psi). Oil at 95 C is pretty viscous, so I’d venture to say the GPM flow was probably pretty high at those conditions, especially if the oil filter was seeing a PSID of 31.9 psi … and/or that oil filter was very restrictive, maybe even half collapsed or clogged. Sounds like an application for a real, high flow racing oil filter.

Actually, it would be hard to say how much oil flow was going through the filter media at bypass, because at a PSID of 31.0 psi the filter bypass was closed (since it doesn't open until PSID = 31.9), and therefore 100% of the flow would still be going through the filter until the bypass actually started to crack open.

Do you have any idea what kind of GPM that engine’s (high volume ??) oil pump put out at 4K RPM?

 

[ZeeOSix]

Originally Posted By: Steve S
What was RPM was the cold engine run at for the test?


From his post:

Originally Posted By: Doug Hillary
Hi,
The following averaged data emerged;

Engine speed: at idle Lubricant: 15W-40 mineral HDEO
By-pass operating range: 15-22psi

 

[Doug Hillary]

Hi,
Steve S - I have tried to access the actual data and at this moment I can't. I believe it was constant for the test - that would mean 4k rpm at ambient and I thnk the engine load was 60%

The test was done to confirm that a popular synthetic 15W-50 lubricant was viscous enough at ambient to remain on bypass for some considerable time. In service Field Testing via IR and OP gauge from various sources had indicated that true stabilised oil temp of around 90-95C took up to 30 minutes to achieve. There was much data on this point - much of which I still have

For the record these "approximates" are relevant;

At 20C
M1 15W-50 = 327cSt
Del 1 5W-40 = 231cSt
M1 0W-40 = 166cSt

At 95C
M1 15W-50 = 21cSt
Del 1 5W-40 = 17cSt
M1 0W-40 = 15.9cSt

 

[Doug Hillary]

Hi,
ZeeOSix - I agree with much of what you have said. I suspect however that a considerable amount of lubricant would be flowing via the media bypass

In this lubrication system the bypass of course is placed before the FF (returns to suction side of pump) so the bypass will function until the media and media bypass are functional (progressively) in flow terms. We know that this is somewhat dependent on viscosity

 

[ZeeOSix]

Originally Posted By: Doug Hillary
Hi,
ZeeOSix - I agree with much of what you have said. I suspect however that a considerable amount of lubricant would be flowing via the media bypass

In this lubrication system the bypass of course is placed before the FF (returns to suction side of pump) so the bypass will function until the media and media bypass are functional (progressively) in flow terms. We know that this is somewhat dependent on viscosity


Just so I understand your terminology ... it sounds like:

What you've described in red above is the oil pump's bypass valve, also known as the "pressure relief" valve. It limits the oil pump to put out a set maximum supply pressure.

What you've described in green above is the oil filter's bypass valve, which will not open until the pressure difference (PSID) across the filter's media is equal to or above the filter's bypass valve setting.

The oil pump's bypass (pressure relief) valve only functions when the oil pump is trying to force more flow (GPM) down the oiling circuit than its fixed flow resistance will allow.

If the total flow resistance summation of the filter + the engine is not enough to cause the pump's output pressure to rise above the pump's relief setting, then the oil pump will never hit its bypass/relief point and never divert any oil back to the sump. Of course, thick viscous oil will make any oil pump easily hit its pressure relief/bypass setting, as it takes way more pressure to force X GPM of cold oil down the path than X GPM of hot oil.

The oil filters bypass valve operates independently of the pump's relief valve - all the filter "sees" is the oil flow volume (GPM) and viscosity. The actual PSID across the filter can of course go higher than the filter's bypass valve setting in certain conditions and cause the filter to go into bypass mode.

One or a combination of the following factors can cause a filter to do into media bypass. The main factors are:

a) filter too restrictive for the application (ie, high volume oil pump on engine or very high RPM or high viscosity usage),
b) pump output flow rate too high for max RPM range,
c) pump's output pressure too high, which causes a high pump flow rate,
d) oil viscosity too high,
e) filter flow blockage due to debris over-loading.

Factors b) and c) are tied to each other due to the fluid/pressure/flow relationship.

 

[Doug Hillary]

Hi,
ZeeOSix - You got it - but add d) with b) and c)

 

[ZeeOSix]

Doug - you said that filter had a 2.2 bar (31.9 psi) bypass setting. Was that a special racing filter, or just a normal "off the street" type of filter? Did you ever see any Flow vs. PSID test data of that filter from the manufacture?

In order to get that (assumed clean) filter to go in to bypass mode, it would take a very large flow volume of pretty thick oil. Of course, any engine that is putting out 130 psi of oil pressure at pump pressure relief point is going to be forcing more oil down the filter & engine than if the pump was running at say 80 psi in relief mode like most normal "street cars". Obviously (as I'm sure you know), in a racing application it's very important to use the right oil filter ... most filters for every day street use may not make the cut on the track.

 

[Doug Hillary]

Hi,
ZeeOSix - Standard FF filter from MAN, Knecht etc.

One must also realise that many motorists start their cold car and instantly drive it like it's hot. This is but one of the engine designers dilemmas!

Aligned with that is the application. Some Service "experts" for instance may say that they think the OEM recommended 0W-30 (example) lubricant is "too thin - we only use 20W-50" - and so it goes!

 

[Gary Allan]

Doug - correct me if I'm wrong.

The high bypass value of the Euro filter you're describing is simply because the high pressure and at the volume of the pump and the visc that the OEM prescribes.

Makes it so that the oil pump is in relief at start up ..and a good bit into the warm up stage.

If the filter had the common .5 bar bypass valve..the engine would/could be in relief for its entire life if the driver never drove more than ..say 15 minutes.

(shame on you, Doug. I thought you more noble than this)

 

[ZeeOSix]

Originally Posted By: Doug Hillary
Hi,
ZeeOSix - Standard FF filter from MAN, Knecht etc.

One must also realise that many motorists start their cold car and instantly drive it like it's hot. This is but one of the engine designers dilemmas!


Yes, revving the engine when the oil is still cold and thick will aggravate the filter PSID situation to some degree. But also keep in mind that when the oil is cold and thicker, that the flow volume (GPM) going down the path defined by the filter + engine will also be less due to the pump going into pressure relief mode (assuming the pump's relief valve works to keep the max pressure right at it's relief setting).

The flow resistance of the filter + engine circuit will only flow what the supply pressure and viscosity combo will allow. So at pump relief, the filter & engine will flow the max GPM allowed based on whatever the viscosity is at that point in time. I'm sure you know that, but many trying to discuss this stuff don't realize how the flow volume is controlled by the pump's relief valve - and how it will change as the oil viscosity changes.

Of course, in your example with the race car, that particular car had an oil pump that would put out 130 PSI maximum at pump relief, so that in itself would cause a relatively higher flow rate even with cold oil to occur at pump relief as compared to the same oil viscosity being forced at 80 PSI pump relief pressure typically found in a "street car".

 

[Doug Hillary]

Hi,
ZeeOSix - The engine was from a street car. Many Euro engines have lubrication systems with pressures as described

This particular engine family has a series of OP relief valves at various locations

 

[Doug Hillary]

Hi,
Gary - Noble me? - but you are correct

In the case of Donaldson's averaged test data - using the cellulose FF filter meant that the media relief valve at idle was open until the oil temperature reached about 70C. This is using a typical 15W-40 HDEO

Of course in a typical engine using these filters the sump size is around 40 litres and it take a very long time to reach 70C - even with a water to oil intercooler

 

[ZeeOSix]

Originally Posted By: Doug Hillary

In the case of Donaldson's averaged test data - using the cellulose FF filter meant that the media relief valve at idle was open until the oil temperature reached about 70C. This is using a typical 15W-40 HDEO


In order for that oil filter with a 2.2 bar (31.9 PSI) bypass valve setting to be in bypass at idle with cold oil, it would still mean that oil pump put out a ton of oil volume at idle speed.

Was the oil pressure at idle at 130 PSI with cold oil, or was it something less? What was the filter's PSID at idle with cold oil?

 

[Doug Hillary]

Hi,
ZeeOSix - You are confusing two situations. One was Donaldson's researched data and the other a Porsche engine on an engine dyno using M1 15W-50

 

[ZeeOSix]

Originally Posted By: Doug Hillary
Hi,
ZeeOSix - You are confusing two situations. One was Donaldson's researched data and the other a Porsche engine on an engine dyno using M1 15W-50


OK ... I was talking about the Porsche with the oil pump that puts out 130 PSI before relieving flow back to the sump. Do you have data at idle and at other RPM above idle with the oil viscosity near constant?

I'm trying to get a feel for the "flow resistance ratio" between the filter and the engine on that car.

 

[ZeeOSix]

To Gary ... I keep forgetting to comment on this. What were the conditions going on when this photo was taken? If this was the pressure before and after the filter, then I'm seeing a 4 PSID across the filter at this moment.

Originally Posted By: Gary Allan

People with engine side gauges can pretty much see when the filter is at elevated PSID. It will be where the needle climbs ..and then slows way down ..then finally settles out. You're witnessing the transition from high(er) PSID to (maybe) none. To "know" you would need one above ......like I used ...

 

[ZeeOSix]

To Doug - the graph below is a PureOne filter for a GM LS6 that puts out about 12 GPM at redline. This data was with a new filter and 5w-30 Mobil 1 at 200 deg F (yes, a much thinner oil than what the Porsche was running). As you can see, the PSID is around 5 PSID at 12 GPM. Of course, if the oil was more viscous (colder), then it would take less flow to get the same PSID, or the same flow would give a higher PSID.

Do you have any idea what the PSID of the filter (with a 31.9 PSI bypass) was on the Porsche when the oil was fully hot and the engine RPM near redline?

 

[Doug Hillary]

Hi,
ZeeOSix - I have no more readily available date on the Porsche engine. This engine was never run at redline in this sequence. With this engine family it was clear that very viscous lubricants produced very high OP above 4krpm. During its development Porsche went from recommending a 20W-50 viscosity mineral lubricant only above 15C (15W-50 below 15C) to FF with a synthetic 5W-40 and then later recommending 0W-40

These engines have a thermostatically controlled oil/water intercooler (fully open at 98C) and typically have an operating oil temperature around 93-95C