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Old 09-19-2009, 12:29 PM   #1
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Default Oil pressure loss when installing oil cooler

I tried to install a Supra oil cooler a few months ago, using a remote oil cooler kit and a oil thremostat. I kept the runs as short as possible even usinh 1/2 hard stainless lines to reduce the restrictions as much as possible. Still I had huge pressure drops. The dash oil press gauge showed <10 psi at idle where it would usually read over 20 for hot idle. Even at 5500 rpm oil press would only go up to 35 psi. And that is running the same 10W30 I have always ran.
I have always shot for at least 10 psi/1000 rpm and this just seemed to low for me. It seems like there is just to high a pressure drop over the cooler, thermostat and remote filter (even though its a PH8filter).

I took it right off the car but now that I am planning on doing a turbo in the near future I was wondering about oil coolers again. What kind of pressure drops do you guys that have oil coolers see?

If I use a sandwitch plate instead of the remote filer will I see less of a pressure drop? I guess my question is really, does a sandwitch plate redirect all the flow or just part of the flow to the oil cooler. I was also wondering about getting a electrical oil pump to drive the oil cooling loop off of a seperate oil loop taking suction from the oil pan or even turbo return hose. This might sound strange but its just an idea. I can't seem to find a resonably priced oil pump that will handle the higher temps seen on track.
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Old 09-19-2009, 12:33 PM   #2
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Me thinks 1/2" lines are HUGE.
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Old 09-19-2009, 01:37 PM   #3
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I have all the parts to switch all the lines to 3/8" amd was thinking about doing it that way. But that would result in even a larger pressure drop wouldnt it?
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Old 09-19-2009, 02:34 PM   #4
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I'm unsure if this transfers over, but doesn't smaller hoses = less flow greater PSI. Larger hose = greater flow, less psi. This does not take into account the restriction of the cooler itself.

Cue the smart/experianced guys.
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Old 09-19-2009, 02:39 PM   #5
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When dealing with oil cooler plumbing, smaller lines cause a greater pressure drop than larger lines. Another thing to keep in mind is the hose ends. If you're using banjo fittings or machined elbows, then you'll have pressure loss here as well.

relte, pictures of the hardware you used would be helpful.
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Old 09-19-2009, 03:22 PM   #6
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+1 to what Joe said... bigger is better on oil lines.
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Old 09-19-2009, 04:37 PM   #7
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Thanks Joe, I've allways understood that bigger is better with oil lines. What Im trying to figure out is the relationship between psi and flow. Aparently the drop in psi due to smaller lines, is becuase the sender is after the restrictions.

Back to the thread.
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Old 09-19-2009, 05:08 PM   #8
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Quote:
Originally Posted by dstn2bdoa View Post
Thanks Joe, I've allways understood that bigger is better with oil lines. What Im trying to figure out is the relationship between psi and flow. Aparently the drop in psi due to smaller lines,
When you flow a volume of fluid through a restriction, you get a pressure drop. If you flow the fluid through multiple restrictions in series, then you get several pressure drops, which are additive in nature. It works exactly like electricity flowing through series resistors. And as with electricity, you will measure a different pressure in the system depending upon where you take the measurement- ie: which restrictions are before the measurement, and which are after it.

The biggest restriction in the system is the bearings. After them, you have zero pressure, and before them, you have some pressure. We want to measure the oil pressure just before the bearings.

In the stock system, there is only one other major restriction- the oil filter. The pressure sensor is placed after this, so it reads the pressure at the bearings, or at least as close to that pressure as is practical.

If you add another restriction after the oil filter but before the pressure sensor (a cooler and lines) then of course the pressure loss across that restriction will show as a drop in pressure at the sensor. The key point is to make this path as non-restrictive as possible, by using large diameter lines, hose-ends that are gradually swept rather than a sharp turn, and a cooler that is of the parallel-plate design.


Quote:
is becuase the sender is after the restrictions.
This is why you are able to see it, yes. If the sender were before the restrictions, then you would see a higher pressure, but this would not accurate reflect what was going on in the parts of the engine where it counts.
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Old 09-19-2009, 05:47 PM   #9
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I am using 1/2 swagelok SS fittings. Most of them are straight tube fittings that have very little restrictions, they maintain the same ID as the 0.049 wall 1/2 tubing. I have one brass tee I put inline to run a oil temp sensor in. The rest is just the remote oil filter mounted right in the passenger wheel well with the cooler and oil thermostat placed as close as possible to it and still have proper airflow. I did a very similar setup on my brothers Factory Five cobra, but that V-8 probably produces a lot more oil flow than our little 4-bangers.
I guess one question I still have is weather a sandwitch plate directs all flow through the plate or just bypasses some of the oil flow through the oil cooler. If the whole volume does not have to flow through the oil cooler system it should reduce the pressure drop. Sure you won't be rejecting as much heat but I am sure it will make a difference.
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