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Turbo oil supply line adjustable pressure regulation project

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Turbo oil supply line adjustable pressure regulation project.


Function:  Adjustable limit on the maximum oil pressure to the turbo.
Total Cost:  Around $30
Install Time: 3 hours

CAUTION!  Copper is not used on engines for a reason, if not secured property it has a tendency to fatigue and break quite rapidly. I suggest using a steel line if you are going to plumb this project in hard line, NOT copper as shown below.  Copper was used in this project as a quick and dirty method of getting the job done so I could test it.

The Story:
Recently, I started to notice excessive oil spit in my exhaust from my turbo charger.  This is a cheap turbo to begin with so I after 13,500 miles of hard use this was no surprise.  At first I was just going to replace the turbo charger until I stumbled upon a rebuild kit which happened to mention that most turbo chargers function fine on 15 – 20 pounds of oil pressure.  After reading several other write ups that mentioned similar numbers I began to wonder if regulating my oil pressure would cure my problem or at least reduce it.  Unregulated, my turbo was seeing about 55psi of oil pressure at 3000 rpm which is an excessive amount compared to the 15 – 20psi numbers that people were throwing around. After looking at various fittings and oil orifices I was left empty handed.  I wanted a way to regulate the pressure that had some type of adjust-ability to it, not just a certain sized orifice.  That’s when a friend of mine gave me the idea of using a valve to regulate pressure.  I had thought of this before but quickly dismissed it, usually one thinks of rubber plungers when thinking of valves, heat, oil and rubber just wouldn’t mix.  I started to think about using a brass needle valve that didn’t contain any rubber.  After a trip to Lowe’s and the local Ace hardware I seemed to have all the parts I would need to make this work.

The parts:
1 - 6” 1/8” NPT pipe
1 - 1/8” NPT T (female, female, female)
1 - 1/8” to ¼” compression fitting NPT 90 degree valve
1 - short length of ¼” copper tubing (or steel with the correct fittings)
1 - compression to 1/8” NTP fitting
1 - 1/8” NTP to ¼” flare fitting
1 - Gauge

The build:
My turbo was originally plumbed by using a ¼” flare fitting from the oil supply line, into an elbow which went to a 1/8” coupler and then to a short piece of 1/8” NPT pipe and into the top of the turbo.  The original plan was to replace the coupler with a T, that would give me a place for a pressure gauge, and then in place of the elbow I would use a 90 degree valve to which the oil supply line would attach.  I was presented with some problems though when making this work because I could not find a valve that was 1/8” NPT on one side and ¼” flare on the other.  The closest I could find was 1/8” to ¼” compression.  This however ended up working out great though because I was able to use a copper hard line up near the header and turbo, keeping the heat well away from the rubber hydraulic oil supply line.  Eventually I may even plumb the entire system in hard line and do away with the hydraulic line completely. After you collect all your parts the rest is simply putting them all together.  Make sure you use oil resistant tape (yellow) and not standard tape (white) to seal your pipe connections.  Also remember not to tighten them too tightly.  These are brass fittings and will split if tightened too much. Usually 1 turn past hand tight is fine.  Before installing the valve I removed the T handle from it to make it a little harder to get the adjustment out of whack once everything is set. Once everything was installed it was time to see if it worked.  I cranked the valve open a few turns and started the car.  On a cold start the oil pressure gauge in the car quickly shot up to 75psi, the gauge at the turbo which has a 0 – 60psi swing was reading about 55psi. I slowly turned the valve until the gauge was reading about 20psi.  Remember you will get a higher reading when the oil is cold so you want to do you final adjustments once everything warms up.  Once warm I adjusted the valve so the turbo was seeing around 17psi of oil pressure when the engine was at around 60psi.  At idle when the engine oil pressure drops to around 15psi, the turbo sees about 5psi of oil pressure.  I haven’t figured out the ratio of drop but it seems to be within an acceptable limit.

Less strain on turbo oil seals.  Total engine oil pressure increased by about 5 – 7psi at normal operating temp. Less blow by into exhaust and intake charge piping.  Oil is cooler when reaching the turbo. Ability to slow or stop oil to the turbo should something happen (IE: blown turbo seal).

Less oil to turbo for cooling.  Longer cool down period at idle. More places for leaks.

Do not know how well the valve, line or gauge will hold up under long term use.

All preliminary tests yield better then expected results.  

EDIT: 11/04/06  Follow up findings.
After a couple hundred miles of testing I have found no flaws thus far in this design.  Oil pressure to the turbo is rock steady with no creep in either direction so far.  I have found one major unforeseen quality in this setup which is heat dissipation factor.  I originally had some concerns with heat and how they would affect the gauge and valve.  Tonight I decided to check on how things were holding up.  Surprisingly after just driving 50+ miles and with the car still idling the gauge body was cool to the touch, and I was able to hold my hand on the copper line and fittings indefinitely.  The fact that the oil is now moving much slower and that the copper tubing dissipates heat so well, I could literally feel the difference in temp between the start and end of the short 1' line.

Future plans are now to plumb the entire oil supply line using hard line.  Perhaps even to add some kind of an 'in line' heat sink such as a section of ribbed tubing.

My only concern now rests on the valve.  This valve is designed for use with water, not oil.  There is a small rubber washer that goes around the shaft of the valve before it exits.  I do not know how oil resistant this rubber is.  If it begins to leak, replacing it with a gas proof valve will cure the problem and probably would not be a bad idea on any future installments.