Bypass Valve on Stock Oil Filter Console, Looking for relief pressure of bypass valve to help with design of remote oil filter and cooler Options

[Mr Beckstar]

Hi all.

I have a 4 cylinder 2 litre and am adding a remote oil filter and oil cooler circuit via a spin on adaptor attached to the stock oil filter console mount. But I noticed the oil filter bypass valve in the stock oil filter mount (circled in photo below) and now I’m concerned that, at high rpm, I’ll be bypassing the remote cooler/filter circuit. Does anyone know the bypass valve relief pressure setting? Knowing that would at least allow me to judge whether it’s an issue.

[Superhawk996]

Where in the world did you come up with 3 psi?

I appreciate the idea that you’re going to try to measure the pressure drop across the filter but I’d seriously suggest you look into the accuracy of the gauges you’re using to do the measurements. If you’re using conventional dash mounted pressure gauges, the measurement will be lost in the noise and inaccuracy of the gauges. As a mechanical engineer, I will tell you that if I were trying to do what you’re proposing, it would be done on the bench and the test would be done on the filter console only without bringing an bunch of other variables into the test.

If you’re that worried about bypassing the external cooler, you should be using a full flow cooler and should not be using a spin on adapter.

[Mr Beckstar]

Where in the world did you come up with 3 psi?

Montreal914 and Chris Foley said it’s “a couple of PSI” so I’ve taken 3PSI as a bypass valve setting. I can’t find any better information.

I appreciate the idea that you’re going to try to measure the pressure drop across the filter but I’d seriously suggest you look into the accuracy of the gauges you’re using to do the measurements. If you’re using conventional dash mounted pressure gauges, the measurement will be lost in the noise and inaccuracy of the gauges. As a mechanical engineer, I will tell you that if I were trying to do what you’re proposing, it would be done on the bench and the test would be done on the filter console only without bringing an bunch of other variables into the test.

Sorry, I mustn’t have been clear. I want to measure the extra backpressure created by the entire remote filter/cooler loop attached to the standard filter console. That includes the hose, the hose fittings, the remote filter mount, the oil cooler and the remote filter. I’m also a mechanical engineer and done a fair bit of test work/condition monitoring in my life; I’m comfortable I can get the necessary accuracy to achieve a practical result. I mean, if it turns out it’s less than 5 PSI and hard to see the drop on the instruments, then it’s probably just a case of making sure the modified stock bypass valve is set to about 10 PSI and it will be all good. And yes the accuracy of these gauges is not awesome, but I can reverse the connection points and take the average to make sure the conclusions aren’t too far skewed.

If you’re that worried about bypassing the external cooler, you should be using a full flow cooler and should not be using a spin on adapter.

Yes, that makes sense to me now. However, it was already installed by others. It cost me a fortune through a highly experienced VW shop that’s been trading for 50 years. I just spent a small fortune fixing all the poor workmanship, poor material selection and poor routing of all the hoses. I didn’t know about the filter bypass and nor was anything mentioned to me about the limitations of the system when I paid for the job to be done. It’s only when I worked on it myself that I noticed the filter bypass valve. I’m quite disappointed about the whole thing.

Anyway, moving forward, I'm happy to spend a bit of time and effort making it work better. I don’t really want to spend another small fortune redoing the whole thing again unless I have to.

[Superhawk996]

I’m also a mechanical engineer and done a fair bit of test work/condition monitoring in my life

Sweet - so let’s review the check valve. It works via differential pressure that is a function of the area of the check ball exposed on the filter supply side (which is smaller) and the area of the check ball that is behind the filter (which is larger).

The spring that is there is very low rate and basically exists only to keep the check ball in contact with the orifice during initial start up before oil travels through the filter media reaching the back side of the check ball.

So how exactly are you going to modify the check valve to adjust the pressure at which it operates since that is a function of the exposed ball areas on each side of the orifice?

Basically your options are plug it completely or design your own check valve by altering the ratio of exposed check ball areas.

Food for thought.

[Mr Beckstar]

I’m also a mechanical engineer and done a fair bit of test work/condition monitoring in my life

Sweet - so let’s review the check valve. It works via differential pressure that is a function of the area of the check ball exposed on the filter supply side (which is smaller) and the area of the check ball that is behind the filter (which is larger).

The spring that is there is very low rate and basically exists only to keep the check ball in contact with the orifice during initial start up before oil travels through the filter media reaching the back side of the check ball.

So how exactly are you going to modify the check valve to adjust the pressure at which it operates since that is a function of the exposed ball areas on each side of the orifice?

Basically your options are plug it completely or design your own check valve by altering the ratio of exposed check ball areas.

Food for thought.

To modify the check valve relief pressure, change the spring rate. Ie a heavier spring to increase the relief pressure.

When the valve is closed, the effective area of the valve is the area of the hole on which the ball seats. The edges of the ball that are larger than the hole have the same pressure on both sides, which cancels each other out. So it’s just the hole diameter that’s used in the [pressure=force/area] formula.

The spring will dictate the [force], the [area] is calculated as mentioned anbove, and that allows calculation of relief [pressure]. I know there are other factors when the valve opens eg pressure drop on opposite sides of the ball when oil flows through the valve, but I don’t think that sort of accuracy is needed here. I’m more concerned about opening pressure.