Oil pressure range

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MikeG

MikeG

Mikeg
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Can anyone tell me the average oil pressure range of a healthy Commando engine? Looking for normal PSI at idle and running speeds, also the absolute DO NOT RUN PSI. I'm building an idiot light system and need to calibrate the sender.
Thanks
 
Per Bob Raber, of Raber's Parts Mart, the Commando should have approximately 10 psi for every 1000 rpm. My experience has been that with hot oil, say after a high speed run, the pressure at idle will drop well below that mark. The inverse is true at startup, very high oil pressure until the oil reaches operating temperature. In fact, with a stuck OPRV I read oil pressure well over 100 psi. IIRC, somewhere near 200 psi. This reading was taken with a pressure test gauge I have with 0-200 range. I'm not overly concerned with 2 or 3 psi at idle with hot oil, but I would be concerned if say, there were only 10 psi at 3000 rpm.
 
10 per 1000 is a industry (engine ) standard . as is 20 at idle on a fresh engine . So a race motor runs a 15 or 20 lb In switch , and a big light on top of dash .
only time my TRIUMPH oilpressure indicator button wasnt well out on the Commando was when I dropped the timing cover seal .went for spin, glanced down .

Looked at 30 ft of wood shaveings .Fudge . Rang about , no luck. Had coffe , walked along , stopped & looked down . AND PICKED IT UP . Very good I thought .
Our top quality Pre unit ' oil pressure indicator ' srews onto the C'do press. relief valve . fit a new rubber tbe seal in it if fitting .10c . Cant kick it into gear
( bend ) on a Norton , too. and its visable seated .

Below 10 psi at Idle ? .bleedy apalling , in my book . Oilpump at 1 thou side clearance & good nick holds pressure , though if stinking hot ? fit a bigger oil tank .
3/4 gal. oil .
 
I installed an Old britts oil gauge assembly on my fresh build and i get........................

- 25 psi to 30psi cold start up and cold idle
- 35psi to 40psi at hot run 3500 to 4000 RPM
- Greater than 40psi hot run above 4000 RPM

Oil pressure range
 
I'm not using a simple on/off switch. I'm going to take a switch normally used with an electric oil pressure guage on a GM. Once I know the rate of resistance vs pressure input of the switch I'll have an LED display tailored to it, 0-10psi=red light, 10 to20 psi=yellow light ect. Not as exact as a guage but it will take up lots less space. Same setup for the volts since my assimilator won't work with the Sparx regulator. Two green lights means good to go. Thats why I'd like to know what normal pressure is at say 3000 to 5000 RPM, so I know when to turn on the green. My 71 Triumph runs 75/80 PSI hot at anything above 2500 RPM, but it seems a Cdo is somewhat less?
 
MikeG said:
I'm not using a simple on/off switch. I'm going to take a switch normally used with an electric oil pressure guage on a GM. Once I know the rate of resistance vs pressure input of the switch I'll have an LED display tailored to it, 0-10psi=red light, 10 to20 psi=yellow light ect. Not as exact as a guage but it will take up lots less space. Same setup for the volts since my assimilator won't work with the Sparx regulator. Two green lights means good to go. Thats why I'd like to know what normal pressure is at say 3000 to 5000 RPM, so I know when to turn on the green. My 71 Triumph runs 75/80 PSI hot at anything above 2500 RPM, but it seems a Cdo is somewhat less?
Click to expand...

were in the system are you planning on installing the pressure switch, as the pressure would be different from right after the pump to after its 2nd or 3rd drop point.
I think most people hook up there gauge after the left side rocker connection.
Not sure where your connection to switch or gauge is on your triumph, but it may be before any drop points which may lead to a much greater pressure then most reported Cdo pressures.
Just a theory.

Cheers..................... 8)
 
Pressure pickup point will be between the timing chest and the rocker feed, right off the pump. Lots of room there to mount things up.
 
MikeG said:
Pressure pickup point will be between the timing chest and the rocker feed, right off the pump. Lots of room there to mount things up.
Click to expand...

In that case you may have to direct your question to a member who has tested pressures at or has a gauge hooked up at that location, I would assume the pressure averages at that location to be higher then the more common hookup location of after the left side rocker.
 
staticmoves said:
MikeG said:
Pressure pickup point will be between the timing chest and the rocker feed, right off the pump. Lots of room there to mount things up.
Click to expand...

In that case you may have to direct your question to a member who has tested pressures at or has a gauge hooked up at that location, I would assume the pressure averages at that location to be higher then the more common hookup location of after the left side rocker.
Click to expand...

There is just not enough flow to the rockers to cause a significant measurable pressure loss. This issue was discussed and tested time and time again starting over 10 years ago...The pressure at the left top rocker feed is not different from the timing cover outlet ....even when using large calibration quality pressure meters. These large calibrated meters are now the basis for my oil pump test fixture.
 
Yes supply to head is essentially a restricted bleed hi pressure volume.

I'm not overly concerned with 2 or 3 psi at idle with hot oil, but I would be concerned if say, there were only 10 psi at 3000 rpm.
Click to expand...

At that pressure I wonder if rod shells being fed well even by spin sling and for sure not surfing the lifters on cam, so be pensive on hot slow idle, but not for heat reasons of oil or engine.
 
I'm not happy with 2, 3 psi at idle, but I and my Norton live with it. Bear in mind, this low pressure is after a hard, 80+ mph freeway run in Florida. I've seen this pressure with a fresh engine and a new Andover oil pump. Never checked the new pump for clearances. Under normal street cruising the oil pressure at idle returns to 10 psi. Obviously, the oil is thinning out considerably with a high speed run.
 
It's 82 right now in GR and I go to kick the cold bike over and it will idle at 1000 and show around 60 psi. When criuzing It will 80 to 90 until warm then be about 50 when warmed up. If 95 outside, this number will drop to 20 to 30psi. When warmed up and hot, my needle will be either be just up off the stop or bouncing off it.

I am not so concerned with the range in psi as much as I am with the fact that i have psi.

I would also submit that lower pressure when hot, should NOT suggest a decrease in volume. A positive displacement pump should distrute the same amount of oil hot, cold, thin or thick if the pump is in good shape.
Just a thought.
 
OK so I can figure that:
0-5 PSI= RED: Don't want to see this except with the key on engine off or at a very hot idle
5-15 PSI= YELLOW What you would really like to see at a normal temp idle
15-30 PSI= BLUE Cold idle and maybe low/moderate RPM speed running
30 PSI up= GREEN you're A-OK
It would be easy enough to add other colors and ranges but why complicate it? As nice as a guage would be you can't see them at night and a light will catch your eye quicker than a guage scan might.
Thanks
 
pvisseriii said:
It's 82 right now in GR and I go to kick the cold bike over and it will idle at 1000 and show around 60 psi. When criuzing It will 80 to 90 until warm then be about 50 when warmed up. If 95 outside, this number will drop to 20 to 30psi. When warmed up and hot, my needle will be either be just up off the stop or bouncing off it.
Click to expand...
If your cold reading is 80 to 90 psi you can take out 1 or 2 shims from the OPRV until it reaches 60 psi as the OPRV only regulates top pressure your minimum reading will remain the same.
 
nortonspeed said:
pvisseriii said:
It's 82 right now in GR and I go to kick the cold bike over and it will idle at 1000 and show around 60 psi. When criuzing It will 80 to 90 until warm then be about 50 when warmed up. If 95 outside, this number will drop to 20 to 30psi. When warmed up and hot, my needle will be either be just up off the stop or bouncing off it.
Click to expand...
If your cold reading is 80 to 90 psi you can take out 1 or 2 shims from the OPRV until it reaches 60 psi as the OPRV only regulates top pressure your minimum reading will remain the same.
Click to expand...
I do not think have any shims in but I see what you saying and will look into it. If no shim, would you change the spring with a lighter compression?
 
pvisseriii said:
nortonspeed said:
pvisseriii said:
It's 82 right now in GR and I go to kick the cold bike over and it will idle at 1000 and show around 60 psi. When criuzing It will 80 to 90 until warm then be about 50 when warmed up. If 95 outside, this number will drop to 20 to 30psi. When warmed up and hot, my needle will be either be just up off the stop or bouncing off it.
Click to expand...
If your cold reading is 80 to 90 psi you can take out 1 or 2 shims from the OPRV until it reaches 60 psi as the OPRV only regulates top pressure your minimum reading will remain the same.
Click to expand...
I do not think have any shims in but I see what you saying and will look into it. If no shim, would you change the spring with a lighter compression?
Click to expand...
As far as I know there is only one type of spring available for the OPRV. You could add a thicker (double) copper washer under the domed valve cap. Or leave it like it is as Matt Spencer mentioned it just might leak more.
 
Humph , Higher pressure SHOULD force more oil around the works , therefore a worn engine , while maintaining Oil Pressure , will have more oil in it .
Therefore more goes down the guides & past the rings.IF its worn .
Raceing , a optimum supply would be only amount required , to minimise losses .However MMORE is BBetter than TToo LLittle , :( .

Metred feed to Valves in Vins . Big Issue is oil quantity. Any of these 24 hour thrashers had one gall capacity , and filled to requirements .
Usually about 5/8 imp. Gal. for short scratch races . More for longer ones. Alloy Oil tank is a Cooler , of sorts .

Commandos they were whineing about oil centrifuged from crank matching supply rate , so therefore the PRESSURE supply to the top end starving
in late ( 1973 / ) I.o.M. machines . This meant oil press. READING at s f all , but CENTRIFUGE EFFFECT meant the 80 + psi AT the Big Ends , :?

SO , one thing leads to another . . .

Oil pressure range


Cop THAT for an OIL PUMP , alledgedly they liked to see something on the Guage . These things reputedly ran 174 mph .
 
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