Oil pressure, temp and viscosity

[Simple_Smith]

sorry about the late reply, my cold oil pressure is around 65-70psi. Since installing the new pressure gauge and sender (80psi instead of 150) I haven't driven the car hard enough to get it to drop the pressure down. Thus far at idle when the engine is at operating temp oil pressure is stable at ~20psi.

Digger, the M21 oil pump, to my knowledge, is a direct Pnp. M21 is very similar to the M20 as you know, but the thumbnail pic on the website isn't working for me anymore just to visually compare it.

Still haven't gotten around to installing my oil temp gauge and sender. I'll update again when that gets put in and I have some data.

[digger]

im also interested in the diesel oil pump and what effect it has and if its PnP. MM sell a modified spray bar to stop the oil being pumped into the head excessively

[digger]

i dont see how deleteing the relief valve helps hot pressure. when cold the pressure is likely 70psi at all rpm inc idle as that sees to be the relief pressure and when cold even 10W-40 is thick enough to set off the relief valve. i havent checked the spring tension to see if that is the true pressure but my gauge reads 65-70psi. as the oil gets thinner the relief valve doesnt get used anymore (except perhaps at WOT high rpm). if the pressure is below the relief valve pressure limit it is dictated by the engine speed and viscosity ( for a given engine). i belive there are more than 1 relief valve so not sure how all those fit into the picture

also ive seen more than 1 broken oil pump drive shaft. thick oil + high rpm + no relief vlave loads up the pump and shaft more as the system has alot of back pressure

[validius]

Reviving an old thread in hopes of some advice/answers

Turbo M20 with a small oil cooler ~7"x5"x1" running castrol 20w-50 in 80+ degrees ambient temp

I've noticed after a few runs (drifting) and idling in grid, my oil pressure drops down uncomfortably low (enough that my idiot light will come on at idle) but if i keep it at ~1000rpm pressure stabilizes around 10 psi. My fear is that I'm cooking my oil and my oil cooler is inadequate. I just ordered an 80psi oil pressure gauge (currently have a 150psi gauge that doesn't give me enough resolution in low pressure situations i.e. idle) and an oil temp sender that I will be installing in the drain plug. I know that isn't the most ideal location to get oil temp, but its the best for me not having to re-engineer a bunch of lines and whatnot to gain a 15 degree more accurate measurement. My other concern is that my m20 with unknown miles is on its last leg and the bearing clearances are getting to be too excessive.

I've been doing as much reading as possible to find answers to bump up the oil pressure for the time being. Some spec e30 guys are saying to delete the Oil Pressure Relief Valve with a M20x1.5 drain plug bolt. Still trying to read into it more and get a better understanding of the m20 oiling system before doing something like that. There is a website selling M21 diesel oil pumps for the m20 as an upgraded flow unit.
http://server.pure-pf.com/webshop2/i...id_lang=1&n=20
Not sure how much I believe that considering thats the only place I've managed to find such information.

Will report back once I get my oil temp readings and a bit more data to get me pointed in the right direction. A bigger oil cooler is definitely in the works, but depending on my numbers I come back here with will be how crazy I need to go with the cooler setup.

Thanks for any input.

You didn't give us a baseline. What is the pressure when cold?

[Simple_Smith]

Reviving an old thread in hopes of some advice/answers

Turbo M20 with a small oil cooler ~7"x5"x1" running castrol 20w-50 in 80+ degrees ambient temp

I've noticed after a few runs (drifting) and idling in grid, my oil pressure drops down uncomfortably low (enough that my idiot light will come on at idle) but if i keep it at ~1000rpm pressure stabilizes around 10 psi. My fear is that I'm cooking my oil and my oil cooler is inadequate. I just ordered an 80psi oil pressure gauge (currently have a 150psi gauge that doesn't give me enough resolution in low pressure situations i.e. idle) and an oil temp sender that I will be installing in the drain plug. I know that isn't the most ideal location to get oil temp, but its the best for me not having to re-engineer a bunch of lines and whatnot to gain a 15 degree more accurate measurement. My other concern is that my m20 with unknown miles is on its last leg and the bearing clearances are getting to be too excessive.

I've been doing as much reading as possible to find answers to bump up the oil pressure for the time being. Some spec e30 guys are saying to delete the Oil Pressure Relief Valve with a M20x1.5 drain plug bolt. Still trying to read into it more and get a better understanding of the m20 oiling system before doing something like that. There is a website selling M21 diesel oil pumps for the m20 as an upgraded flow unit.
http://server.pure-pf.com/webshop2/i...id_lang=1&n=20
Not sure how much I believe that considering thats the only place I've managed to find such information.

Will report back once I get my oil temp readings and a bit more data to get me pointed in the right direction. A bigger oil cooler is definitely in the works, but depending on my numbers I come back here with will be how crazy I need to go with the cooler setup.

Thanks for any input.

[digger]

So I’ve changed over to 10W-40 and the pressures are still good and temps are basically the same. Even on a 30C day with 85-90C oil temp the pressures are still over 20psi at idle.

[digger]

I also tried running sensors in the engine- the problem with anything metal- mounted
is that the conduction heating/cooling of the sensor is significant. I even stuck one in
an AN fitting in front of the radiator- and it ran noticeably cooler (15 deg f, ish)
than when I ran the same assembly BEHIND the radiator.

Currently, I run an 'extended' Autometer sensor with the bulb as high in the
pan as was easy to do without killing myself... and really only worry about
relative temps, as in, "If the oil's not warm, don't flog it yet"

t

that is an excellent point, about the sensor being heat due to conduction and radiation affecting the temperature. this also applies to the IAT. i feel the absolute temps also matter as you want to keep the oil hot to get rid of contaminants. that's why lots of short trips are hard on an engine

[TobyB]

I also tried running sensors in the engine- the problem with anything metal- mounted
is that the conduction heating/cooling of the sensor is significant. I even stuck one in
an AN fitting in front of the radiator- and it ran noticeably cooler (15 deg f, ish)
than when I ran the same assembly BEHIND the radiator.

Currently, I run an 'extended' Autometer sensor with the bulb as high in the
pan as was easy to do without killing myself... and really only worry about
relative temps, as in, "If the oil's not warm, don't flog it yet"

t

[digger]

Hope this helps.

http://www.elephantracing.com/images...erature400.gif

found this to

http://www.viscopedia.com/viscosity-tables/substances/engine-oil/

based on this id say that at 20C 15w-40 has approx same viscosity as 10w-50

10w-40 seems better as from 50C up its the same as 15-40 but its gonna flow more below 50C, that and i can get the same type of oil as i use now in 10w-40...when it starts getting really hot here the 10w-50 might still be the go

[dnguyen1963]

How does the viscosity for 15w-40 at say 40f compare to 10w-50 in general? without seeing graphs vs temp i'd guess it be thicker for cold start but maybe only at extremely low temps

Hope this helps.

http://www.elephantracing.com/images/techtopic/oiltemperature/viscosityvstemperature400.gif

[dnguyen1963]

I'm not a fan of those IR guns. Especially on reflective surfaces - it throws them off.

I have never taken measurement at only one location. It is so quick so you can measure all over the engine and take an average.

[george graves]

An IR temp gun is a cheap and accurate way to measure the oil temp.

I'm not a fan of those IR guns. Especially on reflective surfaces - it throws them off.

[reelizmpro]

Fahrenheit

[digger]

I have both temp sensors in the pan and oil filter housing in the oil flow. The pan temp was cooler by 15 degrees or so.

C or F?

[reelizmpro]

I have both temp sensors in the pan and oil filter housing in the oil flow. The pan temp was cooler by 15 degrees or so.