Post by: Johnny4428 on July 15, 2023, 06:30:50 PM
Post by: Nurse Julie on July 15, 2023, 07:59:45 PM
Post by: Bryanj on July 15, 2023, 08:14:26 PM
As said i think 60 is about where the relief valve opens
Post by: Trigger on July 15, 2023, 08:21:04 PM
The only way to get a accurate reading is removing the oil pressure switch and screwing in a pressure tester at the pump. Bryan is correct, the oil pressure switch is set at 7.1 psi ;)
Post by: Trigger on July 15, 2023, 08:31:53 PM
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Post by: Johnny4428 on July 15, 2023, 11:56:30 PM
I’m quite sure all is well as far as oil pump goes, but I’m having doubts now about aftermarket oil pressure switch. (too tight to by an OEM one at the time)😆 Don’t know how accurate the gauge is Julie. I will see if I can test against some other known pressures. That explains why the gauge went up to 60psi and didn’t go above although I only tested up to 2500rpm. More testing to come.
Post by: Trigger on July 16, 2023, 08:27:22 AM
Maybe it is the aftermarket switch is at fault. Don't know if you read this, but i was getting different pressures with a aftermarket brake switch >>> https://www.sohc.co.uk/index.php/topic,29459.msg283073.html#msg283073
Post by: Johnny4428 on July 16, 2023, 01:25:29 PM
Post by: Johnny4428 on July 18, 2023, 11:35:42 AM
Post by: Trigger on July 18, 2023, 07:18:59 PM
Post by: McCabe-Thiele (Ted) on July 18, 2023, 07:40:39 PM
Post by: Matt_Harrington on July 19, 2023, 08:47:19 AM
My late father used to tell me never fit an oil pressure gauge if it isn't fitted as standard son as you will be disappointed with the readings.I was told the same - you only start to fret about the engine....
Post by: Johnny4428 on July 19, 2023, 10:50:38 AM
Post by: K2-K6 on July 19, 2023, 11:29:23 AM
Like blood pressure, it tells you a fair bit, but with the need to interpret what the system in that engine is making use of. Essentially it tells you the pump is working and there is resistance in the distribution system to give pressure by restriction against pumped volume.
On the 750 (unsure of location on others) the oil pressure switch is absolutely perfectly placed in crank supply gallery and after the oil filter. That tells you all that's needed really without extra monitoring.
A scenario though, if the small restrictors to head supply are blocked, you'll have perfect (possibly even higher ) pressure but with no supply to cam ! Starts to show the limitations of pure pressure report. The camshaft etc is effectively open bath so you can't monitor pressure there anyway.
Many views seem to assume that the pressure recorded is that which keeps the crank bearing and big ends from wearing. Particularly for big ends it would be nowhere near enough to perform in that way. The bearings operate by being flooded with oil, the film strength and shear properties of which then prevent the shells touching the metal. That oil film has to be changed, hopefully for each revolution, by the quantity that's supplied.
If you up the pressure of the system by going to a thicker oil viscosity, then the replenishment rate of those bearings reduces but pressure remains the same. In extreme cases the pressure in system (leak down performance set against pump supply) will blow open the pump pressure relief valve and now stall the supply pace to the crank. Most of the oil now returns to sump while relief valve is open.
You can now see that a maximum pressure (60 psi) that looks healthy, is getting the system close to a problem, similar to blood pressure in fact.
The pressure relief valve on all system is there to prevent pump and pump drive failure (you don't get one on a heart supplied system, well apart from elasticity in arteries etc) ultimately to make sure its reliable in service life, ideally the system needs to be run away from this risk.
Thats done by matching oil viscosity with the typical temperature its used at in service with engine warm.
Too thick a viscosity (with perfectly healthy sysem leak down performance) will raise risk, if oil supply volume stalls then oil film can break down locally through too much heat at crank bearings from not being replaced fast enough. The "classic" film failure on plain bearings is to get pickup of shell material onto journal as the oil doesn't keep them apart. Too much of that and a shell spins with obvious effects.
Very few discussions on engine involve the rate of oil replenishment, but just focus on pressure, the two go hand in hand with people worrying sometimes about the wrong one, or having confidence that the higher the pressure the better.
These engine are generally very good with the design they have, and very low problem occur. But it shows that oil pressure is not the full picture.
Post by: McCabe-Thiele (Ted) on July 19, 2023, 11:52:29 AM
You make a good point about replenishment rates - I'm thinking also that to save weight using narrower journals might be the reason that pressures might have increased on more modern engines.
Post by: Trigger on July 19, 2023, 12:18:31 PM
When i was a lot younger, people would say that British engineering was the best in the world, in later years when i trained at Honda i found it was a load of shite and Japanese engineering was far more superior ;)
Post by: K2-K6 on July 19, 2023, 12:53:02 PM
It's certainly in the Japanese technical psychology to just keep pursuing those improvement in development, manufacturing and product resulting from those process.
Whats not even now aknowledged, and in the light of thinner oils being used in current engines to general disbelief....comments like "how can it possibly last long running on that thin an oil ? pfft, you'll not catch me using that stuff, I'll run it on 20w50 " when in reality these Honda engines, even in the sixties are specified and toleranced to run on straight 20 viscosity at ambient temperature up to 60 F and 30 viscosity above that. They were that far ahead in manufacturing tolerance right from the early engine.
Post by: Bryanj on July 19, 2023, 01:08:18 PM
They work strictly to design parameters instead of the british saying "that dont look right, make it thicker!"
Post by: SteveD CB500K0 on July 19, 2023, 04:37:31 PM
Was there a spec for the oak?
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Post by: McCabe-Thiele (Ted) on July 19, 2023, 05:30:04 PM
Post by: K2-K6 on July 19, 2023, 06:58:21 PM
Was that 1853 Bryan?
Was there a spec for the oak?
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Only the best, oak from the New Forest King Henry ;D
Post by: K2-K6 on July 19, 2023, 07:04:28 PM
You'd need to run at higher pressure to reach the accepted volume required for bearing replenishment demands in a compressed design scheme.
Reduce the bore size of distribution must have increaesd pressure just to remain same delivery volume. There's not much choice apart from running less viscosity to do the same. Both those are used to achieve that balance on newer stuff.
Post by: Bryanj on July 19, 2023, 07:45:50 PM