Oil pump does not deliver enough oil ! - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 28 (permalink) Old 07-30-2019, 04:35 PM Thread Starter
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Oil pump does not deliver enough oil !

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Originally Posted by Rancidpegwoman View Post
My reasoning is the barely adequate oil pump does not deliver enough oil to the crankcases below 3000 rpm to allow the crankshaft to splash feed the exhaust cam or cylinder walls.

Regards
Peg.

Interesting observation, how do we know this?
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post #2 of 28 (permalink) Old 07-31-2019, 05:38 AM
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Originally Posted by Freakmaster View Post
Quote:

Originally Posted by Rancidpegwoman View Post

My reasoning is the barely adequate oil pump does not deliver enough oil to the crankcases below 3000 rpm to allow the crankshaft to splash feed the exhaust cam or cylinder walls.



Regards

Peg.



Interesting observation, how do we know this?
Didnt you know she has clear plastic cases and cylinders? Probably judging from camshaft wear, i think she does more miles than a lot of tired old farts in here why the pump is inadequate in that particular bike and one of the best pumps of that era in the rest of the bikes is still unclear.

Last edited by Twintorsk; 07-31-2019 at 12:24 PM.
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post #3 of 28 (permalink) Old 07-31-2019, 06:00 AM
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Quote:
Originally Posted by Freakmaster View Post
Quote:
Originally Posted by Rancidpegwoman View Post
My reasoning is the barely adequate oil pump does not deliver enough oil to the crankcases below 3000 rpm to allow the crankshaft to splash feed the exhaust cam or cylinder walls.

Regards
/>
Based on what data? Your expert opinion?
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post #4 of 28 (permalink) Old 07-31-2019, 06:34 AM
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Do a simple slightly crude test..with the engine fully warmed up, remove oil fil cap and observe the return flow at 2500 rpm and let's say 3500 rpm...If you see a noticable difference it might be true..

As mentioned, my 750 has an oil pressure gauge, fully warmed up the pressure is pretty much the same at 2500 and 3500, 65 psi...I suggested since the leakage past the rod bearings primary determines oil pressue, can we assume the volume of oil is about the same in my example?...Disclaimer, you bike may be different and if you have no oil pressure gauge you have no clue...
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post #5 of 28 (permalink) Old 07-31-2019, 12:41 PM
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Quote:
Originally Posted by Truckedup View Post
Do a simple slightly crude test..with the engine fully warmed up, remove oil fil cap and observe the return flow at 2500 rpm and let's say 3500 rpm...If you see a noticable difference it might be true..



As mentioned, my 750 has an oil pressure gauge, fully warmed up the pressure is pretty much the same at 2500 and 3500, 65 psi...I suggested since the leakage past the rod bearings primary determines oil pressue, can we assume the volume of oil is about the same in my example?...Disclaimer, you bike may be different and if you have no oil pressure gauge you have no clue...
System pressure is set by the PRV, return flow is a completely different system. They dont really say anything about each other, other than that if oil stops coming out the return - then the pressure pump stopped supplying the crank a while back. Cams should be drip fed by oil returning from the rockers as well. I really think more oil in the crankcase of a dry sump engine isnt just a good thing, theres good reason the return pump is bigger. Aftermarket would have supplied a pump assembly with a 10% smaller return piston if there was a perceived need. The morgo rotary also has a bigger return side. If you want more oil delivered straight to the cams, people are drilling funny oilways all over these poor engines with little or no results. I think you would only get a smokey, oil drinking engine barely fit for road use.
Only oiling modification i have done is restricting the tank vent, thus sending more oil to the rockers, and cams. Seem to work fine.
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post #6 of 28 (permalink) Old 07-31-2019, 01:06 PM
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Quote:
Originally Posted by Twintorsk View Post
System pressure is set by the PRV, return flow is a completely different system. They dont really say anything about each other, other than that if oil stops coming out the return - then the pressure pump stopped supplying the crank a while back. Cams should be drip fed by oil returning from the rockers as well. I really think more oil in the crankcase of a dry sump engine isnt just a good thing, theres good reason the return pump is bigger. Aftermarket would have supplied a pump assembly with a 10% smaller return piston if there was a perceived need. The morgo rotary also has a bigger return side. If you want more oil delivered straight to the cams, people are drilling funny oilways all over these poor engines with little or no results. I think you would only get a smokey, oil drinking engine barely fit for road use.
Only oiling modification i have done is restricting the tank vent, thus sending more oil to the rockers, and cams. Seem to work fine.
At 2500-3500 rpm when fully warmed up the engine oil pressure, 60-65 psi is below the OPV operating range, at least on my engine..I can see this on the gauge when the engine is partially warmed up and the pressure goes to 70 psi and suddenly stops as the OPV opens...
The pressure side and return side are mutual not exclusive...More oil flow on the supply equals more oil flow on the return...
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post #7 of 28 (permalink) Old 07-31-2019, 01:49 PM
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There was a Triumph service bulletin in which they would cut a portion of the scavenge pipe to allow more oil to retain in the crankcase

I believe it was around 1965

I am not saying do this, but just an observation

Are you measuring the oil in your sump after a ride? - is this how you are coming up with your conclusion?
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post #8 of 28 (permalink) Old 07-31-2019, 02:38 PM
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Quote:
Originally Posted by Truckedup View Post
At 2500-3500 rpm when fully warmed up the engine oil pressure, 60-65 psi is below the OPV operating range, at least on my engine..I can see this on the gauge when the engine is partially warmed up and the pressure goes to 70 psi and suddenly stops as the OPV opens...

The pressure side and return side are mutual not exclusive...More oil flow on the supply equals more oil flow on the return...
Its still always gonna be pumping some air and not building any pressure on the return side no matter what you do to the pressure side though. It dumps a lot more oil in the crankcase when the valve opens, and i doubt they need all that oil slung around at low rpms. If the crankcase was operating with a lot more oil in it at low rpms people would search for a cure for that, im sure. Noone like a smoky sluggish engine.
I still say its better to lube the cams from above with a healthy rocker supply.
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post #9 of 28 (permalink) Old 07-31-2019, 04:25 PM
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Oil is present in 2 forms in the crankcase:

A - the fine mist/splash in the rapidly spinning, turbulent atmosphere of the case.

B - the small pool of liquid oil that gathers at the lowest point of the case for the return pump pickup.

In a fully warmed up engine with a sound oil pump and delivery oil seal -

(A) derives almost entirely from the oil that exits the rapidly spinning bigends and performs all of the essential lubrication of the main bearings, camshafts, cylinders and small ends. This is controlled by the clearance in those bearings, the oil pressure and the viscosity of the oil (this is an integral part of the engine and oil system design). The only variable (in any particular engine) here is the oil pressure, which will usually vary from tickover (say 20 psi) to something like 60 psi (which should be achieved by say 3500 rpm). Once that maximum pressure has been achieved (regulated by the OPRV) the maximum flow through the bigend clearance is also achieved and maintained at higher rpm (with the caveat that the centrifugal oil pressure will produce increased flow as rpm increases).

The OPRV pressure limit isn't to safeguard the bigends from being broken by oil pressure (the perhaps 250 extra pounds of stress on the bolts is trivial in comparison with what they have to cope with at TDC), it is there to limit the density of oil mist in the case, so as not to overwhelm the oil rings.

(B) derives from what is injected into the case by A, which coalesces on the case surface and drains to the lowest point. Also some arrives from the rocker feed down the pushrod tubes/cam followers, and at higher rpm from the OPRV bypass. This pool of oil is undesirable, serves no lubrication function, and the larger return pump does its best to minimize it. If it is able to get to a level close to the flywheel, that is where wet-sumping issues start to occur, as the oil can then be drawn up by the flywheel and add a massive extra amount of oil splash within the case, which will overwhelm the oil rings, producing a smokey exhaust and probably increased oil loss from the crankcase breather (pre-70 models).

It could be said that as the pump doesn't get the system up to its design pressure until maybe 3500 rpm, that the pump is "barely adequate" below that rpm. But the lubrication requirements at lower rpm are much less than at high rpm (I wouldn't be surprised if there isn't at least a square law in there, Kommando would have the details I'm sure). As long as the bigends are being supplied with oil (as evidenced by some oil pressure) we know that an end-fed crank still has plenty of flow at the bigend journals by the centrifugal delivery.
The forcing of oil through the bigend clearance isn't reliant upon the oil pressure alone, but also the centrifugal force on the oil. It would be an interesting experiment to see how the flow changes in a fully heated engine, at the same feed pressure, when static and when spinning. I would suspect that flow will increase with rpm, when the OPRV is still closed.

I think that 99% of the cam lobe/follower lubrication is done by the splash from the bigends, because what drips down from the top end is so minimal. Even if you trebled the flow through the rockers, it would still be trivial in comparison with the crank feed.

Apart from the issues that sometimes arose prior to nitrided cams (69 or thereabouts) I think the concerns were more about limiting the amount of oil splashing around in the case, to make a motor that didn't burn too much oil or eject much through the breather. I don't think it lacked enough oil for the long term survival of the major bearing surfaces at any stage in its history.
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post #10 of 28 (permalink) Old 07-31-2019, 09:19 PM
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Hi All,
I did not think that such a casual throwaway remark would create so much interest, I should have known that showing any hint of contempt for Edward Turners much loved lubricator was asking for trouble. Now I know how Epimetheus felt.😊

The first reason that I like to keep above 3,000 rpm on a Meriden engine is partly due to the design and partly due to the pump.
If we look at a couple of popular contemporary engines by other manufacturers I believe they have an advantage over the Triumph:

The BSA twin engine has one camshaft, the lobes are quite close together, but the camshaft is situated at the rear of the engine benefiting from oil being directly flung up from the flywheel, the cams also dip into an oil trough that is fed from the oil pump.

The Norton engine is also single camshaft, but is placed at the front of the engine, so does not benefit much from direct oil splash from the flywheel as most will be flung off at the rear of the engine, but it has its cam lobes quite wide apart bringing them more in line with the big end bearings, so oil escaping from the big end helps lubricate the cams.

The Meriden Triumph is twin cam with the lobes right in the centre so are not in line with the big ends and are almost completely masked by the flywheel . The inlet cam benefits from oil flung up from the flywheel, but the exhaust cam lobes only get a residual amount of oil as most is thrown off at the rear of the engine.

I would want as much oil as possible being thrown about in the crankcases due to the position of the exhaust cam, but the barely adequate (please note I did not say inadequate) oil pump does not deliver very much oil at low rpm. Flywheel splash is not going to be that great.

The answer might have been to pressure feed the cam followers, and Triumph did this. However, because the oil pump has so little reserve capacity it was necessary to fit a restrictor jet, or use timed pulses for the tappet feed to reduce the flow of oil to the cams, so that the big end bearings are not at risk from oil starvation. The pressurised cam followers are rendered pretty much useless.

Most of us have been inside the engine and have seen the cams pretty much always have score marks on them, I know the small tappets create a lot of pressure at the cam lobes, but I believe lack of lubrication plays a major part in this.These are after all nitrided camshafts and

I try to choose a gear to keep the engine at over 3,000 rpm as much as possible, knowing the oil is not at reduced pressure reassures me that there will be enough flow to splash feed the cam lobes (a least a little bit).




Given the Triumphs propensity for detonation it might have been advantageous to direct oil jets to the underside of the pistons, so they are cooled, just like they do on the Norton Commando with drillings in the con rods; again the oil pump has so little reserve capacity that the brief venture into this in 66 was soon reverted back.


It also might have been nice to pressure feed the rocker gear, rather than rely on the 0.3psi generated by the oil return system.

Apart from all roller bearing engines, dropping to 20psi at tickover seems ridiculous to me, the lack of reserve capacity is worrying. That said Meriden Triumph twins are not renowned for wearing out big ends, thankfully.

I often see on this forum, the opinion that the oil in frame tank with itís reduced capacity adequately cools the oil, in fact over cools it as the oil does not get very hot. I am not convinced it is the tank over cooling the oil, but instead it is the lack of oil flow that does not draw enough heat from the engine at lower rpm.
If I am just running about town or riding in the countryside the engine gets pretty hot, but the oil remains relatively cool.
If on the other hand I hit the motorway for any length of time at an RPM that means there is a reasonable oil flow, for example 4500 rpm, not a crazy speed by any stretch of the imagination, if I look in the oil tank the oil is very hot with the consistency of water.
These two contrasting scenarios might be an argument to take the Trident T160 approach, high oil flow with thermostat controlled oil cooler. The Triples seem happy with sustained motorway speeds, where as the Meriden twins just do not seem happy at all.

Enough conjecture from me.

Regards
Peg.
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