Oil pressure relief, oil cooler, and accusump interaction Options

[Seabird]

Good morning everyone. I am in the process of upgrading my oil system. This is on my dedicated track 914. The upgrades include remote oil cooler, accusump, and CB Maxi oil pump.

In my research for installing the accusump it seems like there are two places that are recommended, in the cooler return line with a check valve and direct to the block. I did not want to use the sandwich plate adapter so I opted for the block option. Simpler with less seals to fail.

As I looked into the workings of the type IV oil system I found a potential problem with both these locations; the oil relief valve on the front of the engine. VW used this valve to bypass the cooler when the oil is thick. But this also means the cooler is bypassed when the oil pressure is high. Does the use of an oil accumulator negate the oil cooler system by maintaining oil pressure?

While on the straights the pump could potentially make 50-60 psi of oil pressure. (the 30mm pump that was in the engine produces those pressures much of a 20 min session) At those oil pressures the cooler will be bypassed based on what I know of the relief valve (bypassing cooler at 60psi, partially open at 35 psi, and sealed at 12psi). The accusump will also build up to that pressure. When I go to brakes and the revs drop the accusump will start pushing back and keep the pressure up till the differential is corrected. If I am back on to the next straight in that time then the pump starts building the pressure again.

Options:

1. Am I making a mountain out of a mole hill? Leave it alone.

2. Plug that relief valve so it stays closed and let the oil cooler thermostat bypass the oil when its cold. This is a pre 76 case so there is the secondary relief valve by cylinder 1. Might be able just to invert the piston so the bypass grove is below the bypass passages.

3. There is also the high pressure pistons sold by pelican parts and others. Does this just shift the bypass window to a higher pressure range?

I would love to hear people's thoughts on this.

Miguel

[Seabird]

Thanks for jumping in Randal! I was just (IMG:style_emoticons/default/poke.gif) at folks (IMG:style_emoticons/default/wink.gif)

I guess I could have been clearer with my original post. Where the accusump input is isn't the problem; its the oil relief valve that acts to bypass the cooling loop. Oil pressure above 35psi will essentially cut the flow to the cooler. Hot oil goes directly to your crank and gets hotter.

An accusump works as an oil pressure dampener. If the oil pressure stays above 35 psi the cooler never gets a chance to cool the oil. At some point viscosity gets critically thin and then it starts passing through the cooler. But this might be to late; the oil might already be burnt or below a healthy viscosity.

Its apparently a common problem when using a 30mm pump. I had no I idea at the time but my first trip to the track with my 914 resulted in this. After a 20 min session on track, driving through the pits my oil pressure warning light would come on at idle. I had to keep the revs up just to maintain 10-15 psi! A little stressful. When I checked my oil the dipstick looked completely dry!! It was so thin it would not cling to the dip stick. I freaked out and added 3qts to the motor. When I checked again after a few minutes the dipstick showed 3qts high! I had to drain off the excess oil which was black after just one session (it was new oil with zero miles before the session.)

I am just piecing the puzzle together now that I am researching the inner workings of the oiling system. (914 noob here (IMG:style_emoticons/default/biggrin.gif) )

And no my oil temp gauge was not functioning. An issue that is being resolved currently.

There is a thread on the Samba from a while back that covers the high pressure pump issue well. Its for VW 1600 motors but their oiling system and the type IV are very similar. Check it out here >>> Duel relief oiling system

I have since swapped out the 30mm pump for a 26mm pump. But I am worried that the accusump will cause the same issue.

Hopefully I was a little clearer this time.

Regards,

Miguel