XS650 Top End Oil Pressure Gauge

[retiredgentleman]

DogBunny................."high oil pressure equals low volume" and vice versa! Well spoken!
I use a very simple way to check if the top end has oil flow. When I start a cold engine, I put my ear down next to the top end. For the first 8 or 10 seconds, I can hear metal on metal clatter. Then as soon as the oil flow reaches the tappets and rocker arms, the clatter stops. Its a very positive check.

I think its extremely difficult to damage these engines from a loss of correct oil flow.
Only ways I can think to do that:
Engine burns and leaks a lot of oil, and owner never adds oil so the oil level gets very low.
Gasoline from the tank leaks into the oil sump and dilutes the oil.
Sump strainer never inspected and oil never changed, so strainer becomes plugged up with sludge etc.
(The right side filter can plug up, but is not fatal to the engine because the relief valve will lift and pass enough oil)
Disconnect and remove the tachometer drive shaft and gear that drives the oil pump. One lad did that and still drove for 200 miles before the engine blew up!!

 

[TwoManyXS1Bs]

Assuming that the oil pump is in good shape, the trochoid pump is a positive displacement pump, with a fixed flowrate relative to rpm, pumping about 1gpm at 3,000rpm. Pumps of this design are robust, and are also used in 2,000psi systems. Our pumps (late '71-on) have no pressure relief valve to dump oilflow.

Since the delivery orifices aren't changing, differences in oil pressures are more indicative of changing oil viscosities, high pressures when cold, low pressures when hot.

But, the delivery rate remains the same. Unless something's wrong.

The concept of highpressure = lower flowrate, applies to relief-valved pumps, and non-positive displacement pumps.

I have 2 of these 0-15 psi gauges, and tested them using mouth pressure, which can produce 1-2 psi readings, enuff to confirm that the gauge can display small pressures.

Looking again at DogBunny's video, I'm thinking that it's reacting like a 0-60psi gauge, similar to the gauge I first installed back in '74.

Otherwise, why would his show such markedly different readings from mine?
Viscosity? I'm running 20w50...

Edit: At the low nominal pressures of our systems, the power losses from the 12mm high- volume pump are on the order of milli-hp. Anybody want the math?

 

[Michaelo]

Hey 2M differences in viscosities will change flow rates when you look at the fluid dynamics of the densities when the oil temp rises.....

 

[TwoManyXS1Bs]

Hey Mick, differences in viscosities will change flow rates when the pressure is constant. But, as described above, the flowrate is a constant relative to rpm. So, what changes is the relative pressures.

On that chart, using typical temps 10-100C, density changes from 0.885 to 0.830 are small enuff to be dismissed.

 

[Michaelo]

I would have thought, from my experience, when pumping a liquid with a SG of 1.42 then changed to 1.415 the flow rate (delivery) changed significantly. With oil however when you heat it your adding a further dimensional change.....agree?

 

[TwoManyXS1Bs]

Absolutely. Since the volumetric delivery is the same, with a density change you get a different mass delivery. There's some wacky perpetual motion machines that depend on this...

 

[XSLeo]

I found that an oil cooler plumbed in and out of the side cover works very well. It drops oil temps where it returns to the engine by around 50 degrees. This extra oil cooling dropped head temps by about the same amount. This wasn't very hard to do and you don't have to worry about altering the orifice for oil to the head.
This cooler oil will maintain a bit more pressure throughout the oil system.
On the HP oil pump, As Ivan Hoey mentioned it can consume horsepower. The stock pump moves X amount of oil and consumes Y amount of horsepower, The HP pump moves 30 % more oil, it has to consume possibly 30% more Horsepower.
I recall that a lot of performance cars used a much smaller alternator for the same reason. A 15 amp alternator draws less horsepower than a 105 amp alternator. It will run the ignition and will charge a battery very slowly.
Leo

 

[ihaxs650]

So, does the 50 degree drop in oil temperature and higher pressure allow you to find neutral at a dead stop when the engine is warmed up?

 

[MaxPete]

No....it still an XS650 fer cryin' out loud.

 

[retiredgentleman]

Several posts keep mentioning higher pressure in the oil system to be a desirable thing, but that is just not true. The XS650 engine was designed for a specific oil flow rate. The oil galleries and orifices were sized for that flow rate. The oil pump was sized for that same flow rate. It does not matter whether the pressure is 1 psig or 15 psig. As long as the path through the filters and galleries is clear, the design oil flow rate will occur.

With cold oil, the oil pressure will be high, and that is fine. If the pressure goes too high due to a plugged filter on the right side, then a relief valve will lift, but design flow rate will still occur. When the engine is hot and the oil is thinner, the oil pressure will be very low, and that is fine as well, as design flow rate will still be happening. The engine will receive the same amount of lubrication regardless of oil pressure.

With an XS650 engine you can forget about oil pressure, as it is meaningless.

 

[Michaelo]

Well put, it's not rocket science, well unless you start buggering around with synthetic oil, but as I've seen on the forum it's a touchy issue. Bikes that are 40 plus years love mineral oil...I'll hang on to that until proven wrong ha!

 

[TwoManyXS1Bs]

The first XS1s came with an oil pump utilizing 4mm thick rotors.

Apparently not enuff oil, as Yamaha upgraded that to 6mm thick rotors in mid-1970.

Apparently not enuff oil, as Yamaha upgraded that to 8mm thick rotors in mid-1971.
The oil pump rotors remained at 8mm to end of production.

It appears that the pump provides adequate top-end oiling at normal engine speeds, and at racing speeds.

My personal objective is to have more than just adequate oiling during times of extended hot weather idling. If a main gallery tapped pressure gauge shows 0psi at idle, it's likely that nothing is reaching the top-end, hence the reason for monitoring top-end oil pressure.

I have these concepts, questions, and thresholds in mind:
- At idle, the 8mm pump should be delivering 23cc of oil per second.
- Having no flowmeter, I have to derive flowrates (somehow) from pressure readings.
With hot, low viscosity oil:
- How much of that flow will easily drain at the bottom, to the crank bearings, crank squirters, then thru the left gallery to the transmission? Anything left for the top-end?
- 0 psi at the mains means nothing to the top-end.
- 1/2 psi at the mains means some oil is reaching the top-end, maybe just a dribble.
- 1 psi at the mains means that the top-end delivery should be more than just a dribble.
- How much more oil to the top-end to ensure that oil is actually squirting out the rockers to lubricate the cam and rocker pads?

This pic, courtesy of RetiredGentleman, shows the oil delivery path (red wires) thru the rocker shafts and rocker, emanating to an oil squirter orifice aimed at the cam/pad juncture.



With 4 rockers to lubricate, what percentage of that hot 23cc/second oil delivery would be enuff to get all 4 squirters to actually squirt the cam/pad zone?

I'd like to have a bit of over-oiling up there (at idle), to reduce clatter, and to enhance top-end cooling. But, not at the expense of reducing delivery down below. With the +50% high-volume pump, every delivery orifice should receive it's own individual 50% increase. I'd like to divert most of that increase to the top-end, leaving about 10-20% increase to the bottom end. Simply done by enlarging the front tube's restrictor. But, I haven't enuff data yet to determine this new orifice size.

 

[TwoManyXS1Bs]

How much horsepower is used by the oil pump?
How much additional horsepower is used by the +50% oil pump?

Let's use a simple scenario of crusing at 60 mph, 4000 rpm, summertime.

At 4000 rpm, the stock 8mm pump will be delivering about 1.3 gpm,
Probably at a minimum of 3 psi outlet pressure.
At 4000 rpm, the +50% 12mm pump will be delivering about 2 gpm,
Probably at a minimum of 7 psi outlet pressure.

Doing it the easy way, Googling: "hydraulic horsepower" yields several calculators.
Formula: HP = PSI * GPM / 1714
PSI is gauge pressure in pounds per square inch.
GPM is oil flow in gallons per minutes.

1.3 gpm @ 3 psi requires: 0.002 hp
2.0 gpm @ 7 psi requires: 0.008 hp <-(updated)

An additional demand of 0.006 HorsePower to run the high-volume pump...

 

[TwoManyXS1Bs]

For those folks that might find all this interesting, Google:

"High school physics fluid mechanics"

One of my favorites is Torricelli's law.
Numerous interesting documents, including on-line courses...

 

[retiredgentleman]

Lots of good research 2M...............well worth the effort.
If someone wants better cooling, XSLeo has shown that a full flow oil cooler is a big improvement. Now for the lads that live in the really hot areas (Texas, Arizona etc.), they would receive the most benefit by using both a full flow oil cooler and the high volume oil pump.

For the high flow pump, Mikesxs states it produces 100% flow increase,XSLeo mentioned 30% flow increase, and 2M mentioned 50% flow increase, however I think its less than those numbers. 2M said he found that the pressure increased by 30% when he changed from the stock pump to the high flow pump.
When you make the square root calculation;
30% pressure increase or 1.3 ...........................square root of 1.3 = 1.14 flow rate increase
1.14 means the flow rate increased 14%.

Anyone using the high volume pump should use caution when the engine is first started and oil is thick. If the pressure at the right side oil strainer (filter) goes very high (>15 psig), the relief valve can lift and any large particles or debris caught in the strainer could then move into the various oil galleries within the engine and cause a blockage.

If the high flow pump actually increased the flow by 50%, that means the pressure increase would have been 2.25 times.
Again, the square root of 2.25 = 1.5 or 50% .

So with 14 % increase in flow, increasing the size of the orifice going to the camshaft area, might be a good idea, but hard to say how much larger the orifice should be. Maybe XSJohn's data for the orifice size knows the answer.

 

[TwoManyXS1Bs]

Hey, RG! Good input there. It helped me to clarify my thinking. Thanx.

...If the high flow pump actually increased the flow by 50%, that means the pressure increase would have been 2.25 times.
Again, the square root of 2.25 = 1.5 or 50% .

Yes, the bernoulli equations show the squares relationship of Q to pressure. That means that the mains pressure would be a little more than double of the original pressures. (Updated post #33 to reflect that) The guys that marketed the high-vol pump may have seen that doubled pressure, and thought it meant that the pump was putting out a 100% increase in volume.

...For the high flow pump, ... 2M mentioned 50% flow increase, ... 2M said he found that the pressure increased by 30% when he changed from the stock pump to the high flow pump.
When you make the square root calculation;
30% pressure increase or 1.3 ...........................square root of 1.3 = 1.14 flow rate increase
1.14 means the flow rate increased 14%.

Yes, that pressure increase was measured at the top of the oil tube, AFTER the banjo restrictor. So, that means that the top end is NOT receiving its fair share of the new pump's additional volume. I ran some numbers (flow/pressure/orifice stuff), and confirmed that the 3mm banjo restriction (0.116" per XSJohn) would indeed produce that non-proportional flow distribution.

...So with 14 % increase in flow, increasing the size of the orifice going to the camshaft area, might be a good idea, but hard to say how much larger the orifice should be. Maybe XSJohn's data for the orifice size knows the answer.

Yes, that's it. Thankyew. Grinding thru XSJohn's 8-10 year old posts, getting his banjo restrictor data, and re-running those flow/pressure/orifice calcs, I get a new restrictor value of 0.142"-0.145" (from the original 0.116" - 3mm) to recover the parity 50% increase in flow to the top end.

I only have my one old OEM banjo/restrictor to play with. I need to order another one. Then I can do restrictor mods, and try to confirm, using the top-end pressure gauge...

 

[retiredgentleman]

Mikesxs is very typical of the aftermarket sellers. The marketing BS needs to be recognized, but many of the newer lads actually believe what the advertising tells them. Double the oil flow, that Mikesxs states, sounds like an attractive thing, and makes for much higher sales numbers than saying the pump has approximately 14% to 20% increase in flow. I would like to see Mikesxs produce the actual test data that shows a doubling of oil flow on these engines. I suspect the only people that ever actually measured the oil flow, was the original Yamaha engineering section.

Certainly a 14% to 20% flow increase going up to the camshaft area is a worthwhile improvement. How much flow increase occurs via the main oil gallery into the remainder of the engine, is unknown. Pressure measurements would have to be made at the main oil gallery with both the stock pump and the high flow pump.

 

[TwoManyXS1Bs]

Thread update.

...Pressure measurements would have to be made at the main oil gallery with both the stock pump and the high flow pump.

I added a high-volume oil pump and a 2nd pressure gauge to monitor main pump pressures, as noted in this thread:

http://www.xs650.com/threads/hp-oil-pump-from-mikes.40991/page-3#post-477090

Spoiler alert. After I'm satisfied with the data I'm getting from the oil pressure gauge pair, I plan to remove those 2 gauges and redesign the instrument layout to accomodate a smaller 1" diameter 0-15psi top-end pressure mini-gauge.

A Spectre performance gauge.


The clear cover easily pops off of the gauge.
I've already installed LED lighting in the thing...

 

[xjwmx]

I would rather know volume of oil rather than pressure, If pressure is resistance to flow because the oil is thick, then low pressure is fine if it translates to thin oil squirting into the head in in gallon buckets. Would be more appropriate to have a flow meter of some kind. Then it occurs to me flow is directly related to oil pump speed, unless the bypass is open. And since the oil pump is always turning if it isn't broken you don't need a flow meter. You just need something to tell you if the pump is turning and the bypass is closed. You could eliminate the bypass and just need to know the pump was turning. Then tach is already a marginally good indicaor that the pump is turning.

 

[TwoManyXS1Bs]

If the pump is in good condition, the tach can actually be used as the flowmeter. I had thought about marking my tach to show the flowrates, like using a decal or applique, but decided no, don't ruin vintage parts.

Anyway, the markings would've looked like these:

For the OEM 8mm oilpump, in Imperial and Metric.


For the high-volume 12mm oilpump, in Imperial and Metric.



FYI, the flowrate remains the same irregardless of bypass valve...