Dual relief oiling system. How it works.

[mark tucker]

yup

[Ohio Tom]

9 pages of comments.
Thought I'd throw mine out there.

As one who has College level hydraulics and work with Hydraulics almost every day, I have a few observations:

The oil cooler valve seeks to bypass the cooler to prevent excessive head pressure created by the cooler when oil is cold.
You can call it a "relief" valve, but it's not really relieving the oil, Rather it' is bypassing the cooler.

"some" oil is always flowing thru the cooler. Once warmed up, all of the oil flows thru the cooler as long as pressure is not excessive.

The pressure control valve (a true relief valve) is factory calibrated at 42psi.
It is closed until pressure pushes it open. Pressure only pushes it open just enough to maintain 42psi. It doesn't go from zero, to 100%. It's always floating like the lid on a pressure cooker.

The 5mm relief port into the case was fine for a stock motor running 4,500rpm.

In All of the Hi-Po builds I do, I open up the 5mm dump port on the pressure control (relief) valve. This prevents the skyrocket oil pressure when cold.

A number of companies make pressure relief oil pump covers. they are nice because they just dump the oil right back to the pump inlet so there is not a drain-back issue.
Makes running a 30mm pump a good proposition.

Most high-strung drag motors want 70-80psi oil pressure.
A modification to the stock relief valve, and a 30mm oil pump are the only way to get there.

Now, most drag motors don't get a warmup cycle, so the oil is cold and you are lined up to do a 7,500rpm burnout.

This is where you NEED and external relief so as to keep oil pressure constant hot or cold.

[PT Racing]

Excellent diagrams and explanation of the oil system. Do you have similar information for and engine that uses a CB Performance dry sump oil pump set up. In this set up a separate oil cooler is used. On my race engines the original oil coolers are removed and I believe the blanking plate blocks the oil path used for the stock cooler. As I am new to VW engines, I am trying to educate myself.

[Drewmon]

[ALB]

Don't mount a cooler to the back side of the shroud- you're preheating the cooling air! Think about it- it's counterproductive- you want the air as cool as possible as it enters the fan shroud so it can carry away the most heat (that's it's purpose). The hotter the air going in the shroud the less heat it takes out (and the hotter the engine gets). Get the proper factory cooler and put it on the engine- not only is it simpler (no hoses to mess with and leak) and more compact, with the pre-doghouse shroud the cooler is needed inside to keep air pressure (and temps) even from side to side. The cooler is needed to balance the side to side airflow in the earlier shroud- without it, temps will be substantially higher on 1 side. And if it has a doghouse shroud, same thing-
get the proper cooler and all the relevant sheetmetal installed. Remember that everything is engineered to work together. And the flat part goes in first with the cupped end against the spring.

Hope this helps. Al
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[grandpanystrom61]

wonderful thread, read it all, and still have the same question as I did not find the 1600 DP mexico AS41 engine produced in aug 1973.

I have the front control valve with the rear relief valve, pulley end.
Now the control valve has a short spring with a solid plunger, and with mild force I can screw the plug back in against the spring tension.

Now that relief plunger is got the grove in it, and has a much longer spring, and it takes a lot of force against the plug against the spring to get the threads started so I can screw it in until seated tight.

I found all this out as I was putting the temp. sensor in place of the plug at the relief valve, pulley end.

Sensor is to big for oil drain plug location, so I used the relief valve port ???? good idea or very bad one........

Would it be better located at the control valve location ?

I found out I have no oil cooler on the engine, a bypass plate was installed on the motor when fan shroud was changed, but some one just looped the a hose on the ports.

So have the smaller external oil cooler on order, will mount an the backside of the fan shroud area where those oil ports are.

What about these relief valves... mine are flat on one side and cupped on the other side......so does flat side go in first, cup side rides on the spring ?

Or does the flat side ride on the spring and the cup side faces upward when putting it into the case ?????



Help me........

[mbw65bug]

I don't think many ppl wanna read this old thread again, but I really wanna share my experience;

I decided to use 32mm pump.
My case is AS.
I enlarged the relief hole to control the pressure from 5 to 10mm.
I put 20-50 oil into the motor.
The temperature is 5℃, so 41℉.

When I started the motor, the pressure was around 3bar at 1500rpm, and even after kept idling for a half of a hour, it remained at same. VDO oil temperature gauge hadnt moved.
I revved it to 4000rpm immoderately after I started it, and the pressure was slightly less than 5bar throughout the reving, which exactly I had expected when I measured the rate of the spring of the oil pressure relief valve. So, it was great.

What was not great is I can't open the relief valve of the oil cooler. It's supposed to open more than 6bar. The pressure hardly go beyond 6 unless I recklessly rev it.

I think I enlarged the relief hole a bit too much. I hope someone can learn from my failure and figure out the ideal size for 32mm pump.

[ozzo]

I installed a vdo for oil pressure.
After 30 min driving
Idle 1 bar or 15 psi
3000 rpm 3 bar or 45 psi

Even increasing rpm pressure does not go higher than 3.5 bar warm engine.

Looks good or idle pressure is to high?
This is a european 1978 as 1600 case.... probably the pressure control bleed off is already increased because i m getting this reading with 15/40 mineral oil and 30mm pump.

[Juanito84]

[mark tucker]

THE IDLE PRESSURE HAS NOTHING TO DO WITH THE COOLER RELIEF ( when the engine is up to temp). but your 15-40 might. if your woried go to a 10-30. feal the cooler to see if it is hot, feal to see if warm or hot air is blowing from the cooler outletwhen the engine is warm/hot. mine takes aboyut 4 miles when it's cool out side and about 8 miles when cold out side. my car is heated by the oil cooler,so it's kinda easy to feal when it's warming up the air. when cold I block off the cooler for a few miles so it can get oil temp faster.(My ext cooler is always blocked off when cool out side)

[Juanito84]

Seeing how everyone's engine is going to be different, why not just get a cheap pressure gauge from a hardware store and a couple adapters and stick it in your oil pressure switch hole and find out what your pressure is doing?
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[ozzo]

Ok. Thanks for the replt. I think i have to add more info.
The engine is a 90.5*76 that goes in a bay with a Dk t3 gearbox. So i have long gearing an rpm will stay under 4500rpm always.
I did all hvx mod but did not open up the relief passage as written here.
I do have external 48 plate mesacooler and oil filter.
I have no idea if my idle pressure with a 30mm pump would go low enough to close the cooler by pass. Oil is 15-40w elf mineral. Anybody with similar set up and oil pressure gauge? The vdo oil pressure stuff is accurate enough to monitor this?

[mark tucker]

larger gallys slow down the oil....if the oil is going to fast it may miss the turn to the main or something else and end up in encino.....it can actuly starve a bearing for oil.enlarging most gallys isant practicle,but some can be done. the small block mopar suffered from this above 8000 rpm, the fix was to add an extra gally to feed to the other end also witch would then slow down the oil speed, it's flowing a lot of oil but due to 2 paths it has cut the speed in half so the oil can now feed all the bearings as they need to be fed. the acvw I dont think has this issue, the main is fed from close to the center branching out both ways.,but some cases do have small pasages to the cooler. I would think the cooler bypass spring on those cases would be quite importaint and need to be soft. And no you just cant take out the spring , the bore has a vent, and the piston will let oil spray out the vent.the vent is not the outlet,it is a vacume break type of vent.

[Juanito84]

[miniman82]

...except that the HVX mods entail getting more oil to the rockers, which DOES increase oil flow.
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[Dale M.]

Dont think enlarging passages has real effect on volume once they are filled.... What probably has most effect is size of bearing and lifter clearances that controls the volume of flow past bearings or by and through lifters... Getting larger volume of oil to the bearings and such does not always require bigger volume pump...

Its sort of like having a 6 inch (152mm) water pipe full of water, but if you have valve on end of pipe that will only flow 1/4 inch (6.3mm) diameter stream of water you only need to replenish amount that exits valve...

Enlarging passages only means oil gets there with less restriction of flow...

Dale
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[ozzo]

Very interesting thread.
Does anyboby have information about oil pressure after performing ALL HVX mods?
Opening all those oil passages looks like need the 30mm pump after.... or not?

[Juanito84]

[Juanito84]

[Boolean]

Just want to add that real surface area does not matter, only diameter of plunge.
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