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What is normal TR3 hot idle oil pressure after a good run on a hot day? I realize that it would vary due to engine condition. My gauge sits between the 50 and the 60 at hot idle(not that I'm complaining)which seems very good.The engine probably has less than 10K on a rebuild. I'm wondering if the gauge is accurate since it seems to me others have mentioned 30 -40 psi at hot idle?
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TR2/3/3A TR3 Hot Idle 50/60?
- Thread starter karls59tr
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TR3driver
Great Pumpkin - R.I.P
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If it bugs you, hook up another gauge temporarily and compare.
But that pressure sounds fine to me, it doesn't have to drop at idle. Last time I did an engine "right", it would hold 70 psi at 1200 rpm (and didn't like to idle much lower than that).
My current engine drops to about 20-25, but I'm sure it is well-worn in many places. I stuffed some rod bearings in it last year, the old ones were worn into the copper layer.
But that pressure sounds fine to me, it doesn't have to drop at idle. Last time I did an engine "right", it would hold 70 psi at 1200 rpm (and didn't like to idle much lower than that).
My current engine drops to about 20-25, but I'm sure it is well-worn in many places. I stuffed some rod bearings in it last year, the old ones were worn into the copper layer.
Darrell_Walker
Jedi Knight
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At the risk of starting another oil debate, there is a school of thought that you only need 10 psi per 1000 rpm. Oil flow is important, perhaps more than pressure, but of course pressure is easier to measure.
What weight oil are you using? What pressure to you see at higher RPMs? If you really have 50-60 PSI at hot idle, there could be something obstructing your oil passages. Or maybe you should be using a lighter weight oil.
What weight oil are you using? What pressure to you see at higher RPMs? If you really have 50-60 PSI at hot idle, there could be something obstructing your oil passages. Or maybe you should be using a lighter weight oil.
TR3driver
Great Pumpkin - R.I.P
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That is a generally accepted rule of thumb, but not necessarily always applicable. For example, the stock oil pressure relief valve in a Stag is set for 40 psi, but factory redline is something like 5500 rpm.Darrell_Walker said:
But in any case "only need" doesn't necessarily imply that more is bad. You wouldn't want to spin a bearing just because the oil got a little overheated (and thinned out), for example, so having <span style="font-weight: bold">some </span>margin over and above what is needed is a Good Thing IMO.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Oil flow is important, perhaps more than pressure,
[/QUOTE]
I would go so far as to say that flow is the ONLY thing that is important. The higher pressure at higher rpm is only to get more flow to carry away the extra heat generated (and possibly to overcome centrifugal effects).
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
but of course pressure is easier to measure.
[/QUOTE]
Exactly!
Darrell_Walker
Jedi Knight
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TR3driver said:
Yes, margin is good. But if you can get adequate pressure with a lower weight oil, you should be getting more flow, right? If you run 20W-50 and have 70 PSI at redline, and say 40 PSI at idle, but with 5W-20 you still have 60 PSI at redline, and say 20 PSI at idle (assume idle is 1K RPM, redline is 5K RPM), which would be the better choice?
The other factor to consider is startup. If it is true that most wear happens at startup, then having a lot of pressure, but low flow when cold (because the oil is still thick) may not be a good thing.
TR3driver
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I can't prove it one way or the other, but my choice would certainly be for the heavier oil, in a TR motor.Darrell_Walker said:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The other factor to consider is startup. If it is true that most wear happens at startup, then having a lot of pressure, but low flow when cold (because the oil is still thick) may not be a good thing. [/QUOTE]
Actually, I think that is a myth perpetrated by unscrupulous companies trying to sell snake oil. Even the FTC said it wasn't true.
But when the bearings are cold, they don't really need much flow, just a layer of oil. And heavier oil tends to stick to surfaces better, leaving more in the galleries and bearings. Many years ago, I happened to drop the pan on a TR3 motor with straight 40 weight oil in it and then leave it sitting that way for most of a year. When I finally got around to removing the rod caps, there was literally enough oil still in the crank to drip! 10W30 won't do that.
The super-thin oils have become popular mostly because they waste less energy (giving a slight improvement in fuel mileage) IMO. Not a bad idea, when the engine has been tested with them, but even my Buick calls for 5W30.
Doh! I should have thought of the high idle as Moseo pointed out. I have a mild street cam so I have the idle at 12-1400rpm as it idles smoother there.If I dropped it down to 750 I would probably get the usual 35-40 hot idle. I am running castrol GTX 20/ 50. as Randall mentioned I could swap in my TR4A oil pressure gauge to check the reading. CK.
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How can that little banjo type fitting at the engine, and that basic fitting at the gauge accomplish any kind of seal that could accurately measure pressure?
And, is all this being accomplished based on pressure of the oil being pushed through the galley in the block at the base of the filter?
I've never understood how oil pressure could accurately be measured in that fashion.
And, is all this being accomplished based on pressure of the oil being pushed through the galley in the block at the base of the filter?
I've never understood how oil pressure could accurately be measured in that fashion.
TR3driver
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I'm missing your point here. Since there is no flow through the gauge, the size of the passage to it makes no difference to the reading. And high accuracy is not a requirement, +/- 10% or even 20% isn't really a problem (which is why modern cars generally only have an idiot light that goes out at 10 psi or so).KVH said:
BTW, the gauge doesn't read pressure in the oil gallery, but actually before the oil filter. On very early cars, that was the same as the gallery (since they used a bypass filter); but they didn't relocate the fitting when the filter was changed to a full-flow design in 56. So the pressure in the gallery is less than the gauge pressure, by the drop across the filter.