For completeness:
1.8T oil pressure guide (lots of great information):
https://www.audizine.com/forum/showt...leshooting-DIY
Regarding the 1.8T dual pressure valve system:
Why are there two Pressure Relief Valves? I've tried to find a concrete answer to this question, but to no avail. So I really wanted to know which valve has the lower opening pressure rating.
According to the Bentley Manual the bypass valve spec at 12 Bar (174 psi).
That's what I found on a couple of sites. Past my own explanations you would need to take it up with the engineers that designed the system. Short story is the pumps integrated valve opens at about 174 psi.
Pump Volume:
From the B6 site"
The AMB engine and most late model 1.8t engines use a Gerator style oil pump. Basically the pump has a 6 tooth gear which rotates eccentrically inside of a 7 tooth internal gear ring. (fig-11) For every 30ー of pump shaft rotation a cavity is formed between the two gears and the sidewalls of the pump housing. Because the components of the oil pump are precision machined and clearances between the teeth of the gears are typically less than .075mm a vacuum is created each time a cavity is formed. The volume of this cavity is approximately 2800 mm^3 or 0.0028 liters. As the gears continue to rotate the cavity collapses forcing oil to the pump outlet.
For every revolution of the pump the 7 cavities are formed and collapsed, so the pump displacement per revolution is 0.019 liters. Also note that the pump is driven by a chain sprocket from the crankshaft at 70% of the crankshaft speed. So for every revolution of the crankshaft the theoretical displacement capacity of the pump is therefore 0.014 liters.
The 2.0t pump has a six lobe ring and a five lobe "gear" or rotor that is 2.8 cc's per cavity (my measurement using a plaster cast and a burette). That is .0028 liters. Six cavities, so the pump displaces .0168 liters per revolution, slightly less than the 1.8t pump, however the 2.0T's pump is running at the same speed as the crank so you get the full volume per revolution. Basically the 1.8t pump running the 1.8t gears has .014 liters per rev of volume and the 2.0T has .0168 liters per rev.
That works out to 1.2 times the greater theoretical flow than 1.8T's pump at its stock drive ratio.
The 2.0T's pump has a higher volume per crankshaft revolution than the 1.8T's pump
There is a fix using factory parts:
Diesel pump gear with the 1.8T pump to increase the volume:
https://www.audizine.com/forum/showt...740&viewfull=1
06A115105B pump
038115121A gear from 2.0TDI oil pump
06A105209 crank gear
yes i have more pump turns/rpm, If use stock oil pump gear(1.8t) pressure is too low on idling speed (800 rpm)
That confirms that you can overdrive 1.8T pump to better match the volume of the 2.0T's pump. Short story is there is a better option if you want to go the pump retrofit route. Use the TDI pump drive to increase the volume and a 1.8T filter housing and adaptor to get the correct relief valve pressure. The other options are of course keeping the stock 2.0T pump and chopping the shaft or fitting an idler gear.
I had been meaning to measure the 2.0T's pump volume for a while, I have never seen any published data s this is probably new info. I hope this helps, at the very least it's good to know that the 2.0T used a higher volume pump the the 1.8T. I have the 2.0T pump on my 1.8T and it seems to work really well with better oil pressure at idle than stock. Part of that is its a fresh motor, the other part is the higher volume pump.
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