Oil pressure gauge accuracy

[97tiger885]

The oil pressure gauge is installed and tested.  It seems fine.  Now, how do I know if it is accurate?  Not that it matters really...I am mainly interested in using it as guard against total failure; so, an absolute reading isn't critical.

In temps of approx 30-45F (-1 to 4C), it is between 60 and 80 psi when running between 4000 and 5000 rpms.  Is this  accurate?

I bought a liquid-filled gauge from Grainger.  The instructions-in six languages-didn't tell me much other than installing in an improper orientation might result in inaccurate readings.  The proper orientation was not specified.  The gauge is at a 45 degree angle-about the same as the clock.  

One oddity was the gauge had a rubber cap with a tip.  A decal on the side stated that the tip was to be cut off after installation.  I did so.  The result was a small amount of liquid from inside the gauge began to leak out.  I let it do this a few times and then I taped the hole shut.  I was tired of seeing more leakage from the mc after the water pump and clutch master cylinder.

What is the purpose of this hole?  Is it a means of self-leveling the liquid inside the gauge according to the orientation in which the gauge is mounted?  Does the gauge require a breather to operate properly?   Is it some sort of protection against gauge damage in very high pressure situations?  And should I leave the hole open?

I suspect I should have gotten a gauge that did not have liquid inside, but it seemed a cool thing at the time.

[Sin_Tiger]

The fluid inside is generally a glycerin based fluid, the main purpose is to damp the needle movement. The rubber nipple should be fitted so that it points upward, it will keep leaking until it finds a level at the angle you have fitted it. You will eventually see an air ' bubble' at the top of the scale. It will keep leaking past the tape, glycerin is no respecter of adhesive and will find every crack.

[97tiger885]

The fluid inside is generally a glycerin based fluid, the main purpose is to damp the needle movement. The rubber nipple should be fitted so that it points upward, it will keep leaking until it finds a level at the angle you have fitted it. You will eventually see an air ' bubble' at the top of the scale. It will keep leaking past the tape, glycerin is no respecter of adhesive and will find every crack.

Thanks for the info.  Does it matter if most or all of the glycerin leaks out at some point?

[Mustang]

In temps of approx 30-45F (-1 to 4C), it is between 60 and 80 psi when running between 4000 and 5000 rpms.  Is this  accurate?

yep thats about the normal spread I get on my autometer gauge thats made for cars, mine goes down to 40 psi on a hot summer day when you lug her down under 3k rpm

I suspect I should have gotten a gauge that did not have liquid inside, but it seemed a cool thing at the time.

the 35-50 dollar auto meter gauges(not liquid filled ) available from any good auto store or mail order like Summit racing work fine . yours will be fine also
the glycerin filled gauges are more for machinery and the liquid absorbs the vibrations for more accurate readings

one thing I did find out in searching was that the glycerin filled gauges need to have the liquid as it is part of the calibration of the gauge , if you lose the liquid you need to refill or replace the gauge .
they do need the breather hole which is what you provided when you cut the nipple , usually a liquid filled gauge is mounted vertically , so that the vent is at the top and the glycerin stays in the gauge . mounted where the clock was on your steamer  your are likely going to lose most of the glycerin .

[Sin_Tiger]

As Mustang says, there may be a slight accuracy issue if it all leaks out but so long as the quadrant and pinion are in oil most of the time I wouldn't worry too much about accuracy per say, use it more as a trend or relative indication rather than an absolute instrument.

The reason for snipping the nipple is to open the case to allow for expansion and contraction of the fluid, you only need to snip a tiny bit off the end, just enough to allow air to pass, only needs to be a pin prick hole really. I didn't mention this before as I guessed that horse had already bolted and you probably snipped it right off down to near the casing already  :oops:

As well as damping the needle and mechanism from mechanical vibration transmitted throught the mounting structure, it is intended to prevent accelerated wear and blurred needles without resorting to restricting the inlet which can get blocked or reduce the response speed.

The inline pulses are not really an issue with an engine oil system and structural vibartion, even on the Steamer, should never be a concern, it will probably outlast the bike.

Leaked Glycerine can eventually affect both paint, plastic insulation tape and some 'rubbers', just wash it off with some warm soapy water before it dries up leaving a gooey stain.

[97tiger885]

the 35-50 dollar auto meter gauges(not liquid filled ) available from any good auto store or mail order like Summit racing work fine . yours will be fine also.

The auto part stores-and even the hight performance shops-only carried gauges that had 100psi maximums.  

one thing I did find out in searching was that the glycerin filled gauges need to have the liquid as it is part of the calibration of the gauge , if you lose the liquid you need to refill or replace the gauge . they do need the breather hole which is what you provided when you cut the nipple , usually a liquid filled gauge is mounted vertically , so that the vent is at the top and the glycerin stays in the gauge . mounted where the clock was on your steamer  your are likely going to lose most of the glycerin .

I can rotate the gauge so that the cap is at the high point.  The dial won't be as easy to read, but that isn't a serious problem.  That may save enough fluid.  Today and tomorrow are hitting the high 40sF;so, working outside won't be too bad.

The reason for snipping the nipple is to open the case to allow for expansion and contraction of the fluid, you only need to snip a tiny bit off the end, just enough to allow air to pass, only needs to be a pin prick hole really. I didn't mention this before as I guessed that horse had already bolted and you probably snipped it right off down to near the casing already .

The horse is long gone.  The instructions were typical.  The writer assumed the buyer knew what he was doing and provided mostly technical specs.  Fools leap in...

I can buy another industrial guage that maxes out at 160psi w/o fluid and w/o numbers for about $US11.  So, as educations go, this is a rather inexpensive one.

[Mustang]

this is what I have in my clock hole ..........



http://www.summitracing.com/parts/ATM-2605/?rtype=10

$49.95 at summit racing comes with everything you need to install

they have 1-150 psi ones too

and yeah the 0-100 psi is the most common and I am not surprised that the parts stores didn't go higher as most autos don't need it