Oil's affect on motorcycle gear shift feel?

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Originally Posted By: digitalSniperX1
Besides viscosity, what is it about oil that creates smooth shifting and dampens notchiness? In fact, two different and high quality oils with the same viscosity can feel very different. Any input would be appreciated. Thanks.


Ive enjoyed following this thread, been WAY to busy at work and havent been in here much. Anyway, like most, find the oil subject fascinating at times. Yet, when you read these posts, its why I suggest to people who ask, its best to listen to your owners manual, because chances are, believe it or not, the people who design your engine know a heck of a lot more about what oil to use in it and whos engines and transmissions have been tested over and over again, then anyone in these forums who may suggest otherwise.

But to answer your question...
as a general rule I think most people find more heavy viscosity improves shifting as most people notice shifting gets notchy over time in shared sumps when hot due to shear.

I honestly believe viscosity is the biggest factor.

When you state, two highly regarded oils of the same viscosity can feel different, again I would say, out of the two of the same viscosity, I would still bet the one with the higher viscosity will feel/shift better.
Here is why, two oils of the same viscosity, really may not be the same viscosity, they maybe rated at the same viscosity but in reality one 50 weight oil can have a viscosity that is 25% MORE THEN ANOTHER AND STILL BE A 50 WEIGHT OIL. So the more heavy 50 will shift better when hot.

Im not saying this is the only reason, I am saying it is reasonable reason for an answer to most of your question.
Here is the range for rated viscosities, 20,30,40,50 etc but just because it falls in the rated range, it is not the true "weight" for lack of better words.

The chart shows the viscosity of a 50 rated oil (or any really) can vary by as much as 25%, I am willing to bet, the more heavy 50s shift nicer then the lighter. Again, NOT THE ONLY REASON but a big factor.


imgf000004_0001.png
 
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Above, you can bet the 50 weight oil that is near 21.9 is going to feel a [censored] of a lot better in your transmission then the 50 weight oil that is close to 16.
 
Originally Posted By: Shannow

Things like piston squirters rely on pressure to operate, more pressure, more oil flow through squirters.


Not in the context in which you/we are discussing this. The context in which your statement is true is if the oil pump is sped up, increasing flow and therefore back-pressure.

The context of this discussion is different. This context is comparing the flow of water through a certain size nozzle vs the flow of molasses through that same nozzle. The pressure behind the molasses _has_ to be higher just to bring the flow up to equal with the water.
 
Originally Posted By: bulwnkl
Originally Posted By: Shannow

Things like piston squirters rely on pressure to operate, more pressure, more oil flow through squirters.


Not in the context in which you/we are discussing this. The context in which your statement is true is if the oil pump is sped up, increasing flow and therefore back-pressure.

The context of this discussion is different. This context is comparing the flow of water through a certain size nozzle vs the flow of molasses through that same nozzle. The pressure behind the molasses _has_ to be higher just to bring the flow up to equal with the water.


We're not talking about molasses nor water in here, we are talking about oil at operating temperature (or we wouldn't be talking about cooling), which has neither the viscosity of water NOR Mollasses (why you would bring molasses in escapes me...for mental visual effect ??? it doesn't add to the discussion).

At the viscosities of warmed up engine oil, the squirter flow is certainly dependent on oil pressure. The flow is depended on orifice size, density, and pressure...lower pressure lower flow.

Of course if you ARE lubricating your bike with mollasses, YMMV.
 
That would suggest that even if the pump was operating in relief, higher oil pressure at operating temperature would equate to higher flow to all parts except plain bearings which can't be force-fed.

The reason oil pressure rises with rpm is because there is less time for bearing leakage for every rotation of the engine.

This discussion is a throw back to "a spring and a pressure gauge".

This same topic bothers me when it ends up in the Diesel threads.

The lower oil pressure that a 10W30 engine oil exhibits than that of a 15W40 in the same engine,
provides less piston and overall engine cooling through reduced oil flow at operating temperature.

Then someone will try and prove that 10W30, a grade not recommended by the engine manufacture is OK to use because UOAs tell us so.

The 15W40 provides a redundant level of protection over 10W30 engine oil. That should be accepted as a good reason to use it as prescribed.

Setting up experiments to show that 10W30 is all that is required seems like the wrong way to go about it, especially when the engine manufacture has done the viscosity testing and engine tear-downs for you?

Tell me, how can that logic be so wrong with so few?
 
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I totally understand the temp rise due to viscous friction, as in the ideal journal bearing supported by an oil film, there is no solid to solid contact. But what I don't quite understand are the other sources of heat to include simple conduction from a rod to turbulence in the oil film (and I'm sure there are other sources). Also this leakage from the system seems to be a design feature to required to allow restricted flow otherwise fresh/cooler oil won't be available. Having said that what little knowledge I have on this bearing topic, I wouldn't assume the leakage was some parasitic effect resulting from > 0 tolerances.
 
Originally Posted By: used_0il
That would suggest that even if the pump was operating in relief, higher oil pressure at operating temperature would equate to higher flow to all parts except plain bearings which can't be force-fed.

The reason oil pressure rises with rpm is because there is less time for bearing leakage for every rotation of the engine.

This discussion is a throw back to "a spring and a pressure gauge".


Got it, that's the problem that I have with the "pressure gauge is lubrication" crowd...

The bearings draw oil from a pressurised gallery, to suit their own needs...more pressure won't make the bearing take more within reason.

The oil squirters are a parallel activity, which have a flow rate that is a function of oil pressure...guy looking at a pressure guage doesn't know what the mix of flows inside an engine is, so what the result actually means, particularly translating that across other people's engines.

My comment re squirters being pressure driven, and unaffected by viscosity, here's a few pics.
_DSC3573.jpg

282738_Nissan_11560-05U10_FG01-01.jpg
IMG_9922_8c67e288-a73e-4f32-b270-afa651394dc5.jpg

04092011160-1.jpg


Common theme is that the diameter of the feed pipe is always considerably larger than the orifice through which it squirts, which is very short and narrow.

This reduces the effects of viscosity on the distance from the gallery to the orifice.

Once at the orifice, the flow rater is dominated by pressure/density...longer the narrow part, the more viscosity changes things, but they keep that part short, as you can control flow with an orifice, while a capillary is a lot more uncertain.

More pressure across an orifice - more flow.

And as Larry points out, we are only talking "3 gravity flow units" in 10-15, not mollasses to water.

Other interesting thing with squirters, is that while the galleries are filling, via the action of that positive displcement pump, they are flowing air (thinner than molasses OR water), reducing the opportunity for even that gallery filling flow to be operating the relief valve.
 
I hope you didn't dummy that down for my sake, after all I did read Wrap_Thesis_Felton_1994 more than once.
 
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Originally Posted By: digitalSniperX1
BLS just to be clear I don't race the zx14r. It is my street bike. Sees all kinds of traffic including idling in long congested traffic stops here in Florida. I used 15w50 for that reason. I've swutched to 10w40 and noticed about 2 mpg improvement in highway fuel economy and a slight increase in power, as you'd indicated the positives of using lower weight oil.


Not racing??? boy is my face red... post a photo of your prized zx14r so Shannow can see
what we are talking about... he's a cager that doesn't ride or own a motorcycle...
 
Originally Posted By: LoneRanger
The mechanical engineers (what 540 Rat claims to be) that designed the engine in my Ducati put a frame sticker on it that for oil requirement says "15W50".

Those silly Italians must not know anything about lubrication.


My silly Italian brothers do know about lubrication but you have to go beyond the stickers
and read page 232 of the official manual to understand all your oil choices...

 
Originally Posted By: Shannow


And as Larry points out, we are only talking "3 gravity flow units" in 10-15, not mollasses to water.


Preach it Sha... but would it kill you to dig up some Motorcycle piston oil jets instead of
those heavy and ponderous car squirters??? after all this is a motorcycle forum...

RC45 Oil System
RC45OilSystem.jpg
 
What the fluids are is irrelevant. Water and molasses help illustrate the effect. When talking of a given system, higher viscosity fluids flow more slowly through a given nozzle/orifice. Thus, the higher oil (back-)pressure generated by higher viscosity fluids is required just to 'catch up,' in terms of flow rate through a nozzle, with the lower viscosity fluids.

Your assertion is only true or useful here if you had been talking of two same-viscosity fluids operating at different pressures.
 
Originally Posted By: bulwnkl
What the fluids are is irrelevant. Water and molasses help illustrate the effect. When talking of a given system, higher viscosity fluids flow more slowly through a given nozzle/orifice. Thus, the higher oil (back-)pressure generated by higher viscosity fluids is required just to 'catch up,' in terms of flow rate through a nozzle, with the lower viscosity fluids.

Your assertion is only true or useful here if you had been talking of two same-viscosity fluids operating at different pressures.


Do you understand fluid flow kinetics ?

Obviously not, as you need the water/mollasses dtrawman to make a point...an irrelevent point, as we are talking fluids of nearly similar viscosity in a warmed up state (or we wouldn't be talking about cooling)

Can you demonstrate any single engine oil which has a viscosity of molasses at operating temperature (or one that's close to water even) ?

Strawman...not relevant.
 
First you said that higher viscosity fluids (which are what cause the higher pressures in this context) increase flow through orifices/nozzles. Now you're trying to marginalize the viscosity difference. You just marginalized your own assertion. Well done.
smile.gif


Whatever the relative viscosities of the two fluids, the higher viscosity fluid requires higher pressure in order to flow the same volume through an orifice, even if you're now marginalizing your own incorrect application of the initial principle.
 
Take Larry's measured figures at 6,000RPM, and assume Mr Honda's squirters are 1.0mm dia.

Oils are considered at 100C, as that's what the KV is on the data sheet.
30W - 60 psi - M1 AFE
40W - 84 psi - M 4T 10W40
50W - 90 psi. - M 4T 15W50

Flow Rate through each squirter in litres per minute (using Benoulli's equation)
30W at 60 psi - 4.6 l/min
40W at 84 psi - 5.4 l/min
50W at 90 psi - 5.6 l/min

All at pump relief (99psi)...5.9l/s

Now the piston cooling is clearly dependent on piston cooling squirter flow, so by choosing an oil simply because you don't want flow through the pump relief means nearly a 20% reduction in piston squirter flow in the mid range....simple physics.

But you'll bring up molasses and water again...

That's where Reynolds' Number Correction comes in, and again, I'll point you back to my discussion on the operation of squirters, having a larger diameter section before the nozzle, so that the orifice, pressure, and density are controlling the squirter flow, not the viscous effects of the fluid.

For the three oils and pressure, Re
30W - Re is 940
40W - Re is 760
50W - Re is 640

fto4.png


D2/D1 is the ratio of the hole to the feed pipe.

Clearly, the smaller the number (bigger feed for smaller orifice), the flatter the curve is in the range of Re's that we are talking for a piston squirter.

In the range of 0.5 (hole half feed pipe diameter), to 0.1 (hole 1/10 of pipe diameter) there's SFA difference (and you can see that the thinner viscosity is actually choked a little more (flows less) than the thicker oils around the 600 mark)...not enough to write home about


Again, if you are lubing your engine with Mollasses, and your mate is running water in his, YMMV, but engine oils at operating temperature aren't molasses versus water, whatever strawman you are trying to create.
 
Originally Posted By: bulwnkl
First you said that higher viscosity fluids (which are what cause the higher pressures in this context) increase flow through orifices/nozzles. Now you're trying to marginalize the viscosity difference. You just marginalized your own assertion. Well done.
smile.gif


Whatever the relative viscosities of the two fluids, the higher viscosity fluid requires higher pressure in order to flow the same volume through an orifice, even if you're now marginalizing your own incorrect application of the initial principle.


Sorry, we were posting at the same time...hope that the above helps your confusion.

Bear in mid that it's the bearing's draw from the oil supply that controls the backpressure.
 
Originally Posted By: BusyLittleShop
Originally Posted By: digitalSniperX1
BLS just to be clear I don't race the zx14r. It is my street bike. Sees all kinds of traffic including idling in long congested traffic stops here in Florida. I used 15w50 for that reason. I've swutched to 10w40 and noticed about 2 mpg improvement in highway fuel economy and a slight increase in power, as you'd indicated the positives of using lower weight oil.


Not racing??? boy is my face red... post a photo of your prized zx14r so Shannow can see
what we are talking about... he's a cager that doesn't ride or own a motorcycle...


Come on BLS, it is completely and utterly irrelevant whether or not Shannow does or doesn't own a motorcycle, it's the knowledge and factual information that one brings to the table that determines their relevancy in this forum (of which Shannow consistently does). It would be like stating that since a member owns three motorcycles over another members only motorcycle that he could somehow offer more knowledge and contribute more (which I'm sure we've all met someone who has been riding for decades or owns multiple motorcycles, yet knows very little on the subject of engine design and tribological concepts of oil).

In regards to temperature/viscosity chart you posted in response to LoneRanger's Ducati, it happens to be a "temperature/viscosity chart" in that order for a particular reason. Based off the average ambient temperature you are to utilize the described oil, not any of the given viscosities shown. I know you personally favor Mobil's 0W30, but nowhere does your Honda Manual condone the use of a 0WXX oil, and neither does the Ducati manual or any other motorcycle manual I've ever come across. Ducati's philosophy is extremely biased towards ultimate engine performance and power, and yet they continue to prescribe the use of 15W50...even in their liquid cooled engines! KTM and their RC8 also recommends the use of 10W50, or at the very lowest a 40 grade engine oil in the coldest temperatures, nothing else (including any 30 grade oil) would meet their warranty requirements and is even recommended!

KTM RC8 Manual

Then of course on the cager side of things, BMW's M5 recommends 10W60, Ford's Mustang with the Track Pack requires the use of 5W50, and the infamous Bugatti Veyron also requires a 10W60, along with many Ferrari's using the same viscosity. These are all notorious performance vehicles using "syrup" for engine oil, could their engineers have been misguided and not considered Mobil's AFE 0W30 to provide all their requirements of engine performance, longevity?

Regardless, I do agree with you BLS as far as shifting feel goes and the given viscosity. I personally believe it has to do more with proper shifting/clutch engagement along with clutch cable adjustment at the lever and clutch basket. I would also agree that most wouldn't be able to indicate a difference between the same bike ridden back to back with fresh oil of both 30 and 40 grade; but again, this is my personal opinion without any scientific proof and is merely speculation.
 
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