oil pressure

[itchyfeet]

preload is 17mm on a 60mm long spring ( by measurement of components 77mm internally 94mm stack height)
plus 9mm is 26
total remainder of spring 34mm before it vents
using a 35mm grubscrew as a depth guage 11kg on scales or 24.2 lb

0.31 sq inch is 78 psi or 5.4 bar

now that changes things for me because if it's not bypassing under normal running then the spring tension won't affect temperature

[silverbullet]

My money was on rather less tbh. VW called it a "thermostatic" relief valve, my gut reaction would be that once the valve has left its seat it will blow off.

(That will make T.I.O.O.C. for sure)

[silverbullet]

There is a type 4 tech bulletin doc on line that shows the same PRV arrangement.

[itchyfeet]

My money was on rather less tbh. VW called it a "thermostatic" relief valve, my gut reaction would be that once the valve has left its seat it will blow off.

(That will make T.I.O.O.C. for sure)

Well gut feeling is not what's needed, far too much rumour and theory in all this for my liking, evidence is what we want.

Any body seen more than 5.5 bar on their oil pressure guage cold even when revved? No thats probably why.
ok hot hoil will be a bit runnier but by the time it's hot you have no where near as much pressure

With 17mm spring compression preload I got 6kg or 13.2lb or 42psi or 2.9 bar

so a hot engine needs to be working at high revs to vent

[silverbullet]

Quite agree. Measure not rumour.

At higher revs you really want a bit more pressure... so the system limits max pressure no matter what.

Put a thick washer or two under the spring and see what results?

[itchyfeet]

Quite agree. Measure not rumour.

Put a thick washer or two under the spring and see what results?

might try that but I struggle to get 3 bar hot anyway

[silverbullet]

Ok. We need a fresh one to prove. Very busy at the moment... I should bring my engine building home. Or sleep at work.

[itchyfeet]

Sorry to hijack the thread wizwilson but hopefully of interest to you all the same.

I'm thinking turn the shoulder/lip off the screw in plug then you can adjust preload while running and measure where it's making a difference hot and cold, no guesswork on washer thickness ( may drip a bit but probably not much)

once you have a feel for if it you could then cut a solid rod (for testing only) and then you are in direct control of the piston so you can say have it slight open cold ( so you don't over pressure), then close it. Set a pressure by revs then slowly open it, that will give you a better feel for the pressure vs piston position.

[wizwilson]

Hi Itchyfeet, no it has been good reading, the other thing to consider is as the oil gets hot it gets thinner so any irregularity's in the piston and its seat could be a point of pressure loss, so guess its worth taking out and cleaning well, and see if you can see the seat surface, may try the washer trick, they do sell an adjustable relief valve.

http://www.mamotorworks.com/VW/product/ ... tor-380800" onclick="window.open(this.href);return false;

[itchyfeet]

Thats for Aircooled not sure if it's suitable for wbx or fits
Something written up here about that...
http://vwparts.Aircooled.net/mobile/Pro ... tCode=3049" onclick="window.open(this.href);return false;
I purchsed a new piston and they are not precision made on the seating surface, a bit rough and ready it's true.

If you turn your mains tap on so it's dripping you don't loose any measurable pressure, you need quite a bit of flow to loose alot of pressure.

[silverbullet]

Found the type 4 oil pressure blurb....I put a link to it in Syncro Simon's DJ oil cooler thread

https://club8090.co.uk/forum/viewtopic.p ... 0#p8040348" onclick="window.open(this.href);return false;

Original source. See page 7 http://www.volkspage.net/technik/ssp/ssp/SSP_24.PDF" onclick="window.open(this.href);return false;

[itchyfeet]

Thats an Aircooled document and the way I read that is the relief valve hot, when pressure is lower forces the oil via the olkuhler (oil cooler?) when cold it can take either route.

would very much like to see a wbx version of that document because I suspect the valve is just to release excess pressure to the sump only and has nothing to do with the oil temperature

didn't realise oil filter was before valve, learn something new every day

is it me or is that gearbox the wrong way around on page 21

[silverbullet]

I took it that the OP releif valve is exactly the same on a type 4 or wbx?
As for illustration errors: just look closely at the bodyshell/chassis cutaway drawing...
Ia that what we could have had before the accountants got to it?

[itchyfeet]

Well if you have a case split you can have a look, the two short engines I have in the shed are not split so not easy to see whats going on inside.

[silverbullet]

http://www.volkspage.net/technik/ssp/index1_eng.php" onclick="window.open(this.href);return false;
SSP 47, page 13