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Oil Temperature and Viscosity, BWW Data inside


wd6681
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I hope my data will be helpful to some and encourage others to share scientific data and perhaps answer some of my questions. I have run various oils in Our M20B25 power E30 and analyzed their performance with the following measuring sticks.

-Oil analysis from Blackstone

-Oil Pressure Gauge

-Oil Temperature Gauge

Please note the following: We have not experienced engine failure due to oil. All Data and questions I will pose is only related to HOT TEMP AND HOT PRESSURE.

We have run the following oils:

Castrol GTX 20W50

Valvoline VR1 20W50

Mobil 15W50

Pennzoil 25W50

Chevron Delo 15W40

Valvoline VR1 40wt

I only have UOA analysis for the Castrol 20W50 and Mobil 15W50. The GTX 20W50 is non scientific as it was a high milage motor that then lost a rod bearing. The Mobil is a motor that we have since lost to overheating. It was a rebuilt motor and am curious if the high iron is attributed to an engine still breaking in? Or simply racing?

Our water Temp is measured @ the thermostat housing and always reads below 205* with the exception of failure. Typically the car runs around 190* when it is running at its fastest; 205* figure is seen when there is traffic and reduced airflow.

The oil temp Simply DOES NOT GO OVER 200*. Typically they are around 180*. For the 2017 season we removed the Stock oil cooler and have seen no increase in temps. 

Oil Pressure with a 50wt pegs 80psi (pressure relief is 80-85) by 3400-3600RPM

Oil pressure with a 40wt pegs 80psi by 4200-4500

Our Pressure and temperature are both measured at the location of the factory oil pressure switch on an M20.

My questions are, Why does everyone struggle with oil temperature so much? Are my temperatures sound because of the high capacity of oil (overfill to 7qt) supporting a relatively low taxed motor by modern standards? Or are my temperatures low because of where it is measured? For example sump temperatures are higher? My oil pressure leads me to believe I can continue to go down in viscosity as the motor produces well more than 10psi per 1000RPM. Rod and main tolerances are @ factory spec which rule of thumb would put us @ a 30wt but BMW calls for 20W50. Meanwhile I recently raced a Miata to find out that Miatas peak oil pressure is approximately 50-55psi. That means that a motor that makes more HP per liter on smaller rod bearings produces LESS than 10psi per 1000RPM. 

Please everyone keep their opinions as scientific as possible with oil wt temp, pressure, and HRs it has worked. 

UOA.jpg

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80psi pre-filter (stock switch location) is scary.   Puck under the filter for oil pressure should never show more than 60psi warm (post filter pressure).  70psi max cold.   Last time I had 80+psi, it was at the stock oil switch port, and it was indicating a clogged filter with no bypass port.  That engine oil starved and spun bearings.  Monitor your pressure after the filter - that's what the bearings actually see. 

 

FWIW, I see little pressure difference between GTX 20W50 and Mobil1 15W50.  Run GTX when is ambient is below 60F, Mobil1 if above because it handles long term heat a bit better.  Oil temps usually 220-250F depending on ambient temp.  Also M20B25, with stock cooler, WIX 51088 or Mobil1/Bosch equivalent filter.  

 

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Yes my temp and pressure are measured at the stock switch port not at the filter housing. Without a cooler I just run an ETA setup with the stock Mann or Mahle filter on the block with the thread in bung from an ETA. Where do you measure your temp? Why is it so much higher?

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  • Technical Advisory Committee

I see 220-250 like will, I measure by drilling the oil cooler adapter plate bolt and tapping for the sender.

We know the oil cooler works well, we use tape to block it off to maintain oil temps where we want them.

 

water temps are solid at 180 measured at the tstat housing, using the third hole (upper on driver side) of a 4hole housing. Would prefer it got a bit warmer actually...

 

 

i can get data when I'm not on my phone.  

 

What team/car/region are you running ? (Not familiar with your username)

Edited by Huggy
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StepBrothers. We run in North East like WGI but mostly Canada. I wonder if my temperature is low because of the location of my sensor. I believe the stock switch port is a small chamber off of the main oil galley. Because so much water is flowing through this area I wonder if the oil is cooling compared to where it sounds like you guys are measuring which has just been lifted from the sump.

 

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Ran Mobil One 15 50 in the roller 455.  Been a while but I recall 80 pounds cold and 60 hot. Idle. More than it needed by a lot.

 

Flip side, my truck runs about 58 with 5w30 hot.

 

In the end, your oil choice depends on clearances. Stock I'd never go that high.

 

10w30 in the Vortec right now. Will run same.

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I run the same set up as Huggins. 

 

I would question your your location to pull temperature. There is no oil flow there. I would not really trust that reading. 

 

I would suggest running a sandwich plate or drill/tapping the hollow bolt that holds the filter housing to the block. 

 

-Sandwich plate that fits: https://www.glowshiftdirect.com/oil-cooler-sandwich-adapter-3-4-unf-16-thread/ 

Edited by MichaelPal
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Also to the contrary, could reading oil @ a sandwich plate or @ the adaptor/filter or tapping the adaptor bolt get heat soak from being right under the exhaust manifold? Without a question the oil is hotter when it is being wedged through rod, main, and cam bearings. But that should also indicate that pan oil temps should be the most accurate measurement as that oil is the largest mass and was the most recent to be pushed through the circuit. The oil has however had time to cool from running down the block/bitch tube and cooling in the pan. Spec E30 racers without skid plates usually report around a 190 sump temp. The oil temps you guys are reading is oil that has just been picked up from the pump;do you really think the pumping action is adding 50-60 degrees?

Edited by wd6681
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I don't expect heat soak from the exhaust. Air flow in the engine bay would help prevent soak and the oil moving through and around the sensor has thermal mass greater than the thermal mass of the heated air around the exhaust.

 

Oil pan temps depend on where you're picking it from (at the drain location, at surface level). Next time I run, I'll get a surface temp on the bottom of the pan. Now i"m curious. 

 

I don't think the pumping action adds any considerable temperature. I want to know where the spece30 racer took that 190 measurement. Then I searched the google and found this (https://www.engineeringtoolbox.com/pumps-temperature-increase-d_313.html) so I'm now distracted at work finding values. I recently tried running the no oil cooler solution and found temps during a 20min HPDE got to 250F quick (35F ambient). I could see a drop in peak oil pressures and the temps climbed closer to 260F. So back comes the cooler. 

 

Also, did I read that correct in that you are running a full 7 quarts in the m20 motor?! 7 quarts puts the oil in the crank throws which is no bueno. I Usually run the stock fill + about 1 qrt over (4.25 + 1) and that is enough to help with starvation in corners (I also run an oil pan baffle). 

 

I would recommend to take your oil temp in a location where there is appreciable oil flow, not stagnant. Then proceed from there. 

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Hmm maybe I am getting a little forgetful, maybe I do 6 quarts. It is basically stock plus one quart; dipstick reads a pinch over full mark. It probably adds only a pint but I have removed the level sending unit on the driver's side of the pan. Not that I completely know but what makes the area I am measuring low flow? It looks to be right off of the main oil galley that runs front to back on the block. I had a vdo sender leak between the plastic and metal part of the body and the flow was fairly considerable. I think I am going to make a temp probe that sits in the oil sump where that level sender used to be.

 

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18 minutes ago, wd6681 said:

Michaelpal, do you run a 50wt?

 

Valvoline 20w50 synthetic.

 

you got a picture of your set up? 

 

When I say low flow, in reality there is no oil flow at that point. It's a dead end street for the oil. Whereas in the puck, you get a lot of flow. 

Edited by MichaelPal
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That makes more sense now since it is at the end of the galley so it does not have oil flowing through/by it but just too it. That also makes sense with oil pressure too, I believe I am getting good 'signal' from my pressure but should relocate my temp probe. Your pressures likely read lower than mine because it is in or near the largest open volume in the pressurized portion of the oil circuit. I will grab a photo sometime but retail at Christmas is BUSY. Is it Valvoline synthetic vr1 or normal street synthetic?

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2 minutes ago, wd6681 said:

That makes more sense now since it is at the end of the galley so it does not have oil flowing through/by it but just too it. That also makes sense with oil pressure too, I believe I am getting good 'signal' from my pressure but should relocate my temp probe. Your pressures likely read lower than mine because it is in or near the largest open volume in the pressurized portion of the oil circuit. I will grab a photo sometime but retail at Christmas is BUSY. Is it Valvoline synthetic vr1 or normal street synthetic?

 

 

VR1

 

Take the oil temp in high flow

take oil pressure at no flow (keep the stock location) I take oil pressure at the stock switch location. 

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Has anyone run a 30wt in a Chump/ endurance BMW? The fast specE30 cars seem to run a 30wt. I am just concerned that over 7, 14, or 24 hours it would shear too thin. But again I know of Honda's and miatas that on paper are much tougher on their oil that run a 30wt @ chump.

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5 minutes ago, MichaelPal said:

 

 

VR1

 

Take the oil temp in high flow

take oil pressure at no flow (keep the stock location) I take oil pressure at the stock switch location. 

So you would suggest temp @ near the filter rather than sump? I am excited to try some new setups next spring.

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Wow, your water is cold! Do you not run a thermostat? Your oil temp is close to what I had been measuring at the switch port. I find it interesting that the highest oil pressure you see is 65psi but it clearly is generated from the pressure regulator based on how it is reaching that pressure before peak rpm and how consistently it is reaching the same psi. Could your pressure relief spring be adjusted differently? Or do you think this is irregularity between one of our measuring devices?

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12 hours ago, wd6681 said:

Has anyone run a 30wt in a Chump/ endurance BMW? The fast specE30 cars seem to run a 30wt. I am just concerned that over 7, 14, or 24 hours it would shear too thin. But again I know of Honda's and miatas that on paper are much tougher on their oil that run a 30wt @ chump.

Cup cars run 10wt. Pro stock runs lighter at 1900hp. It's clearances you're concerned about.

 

Probably impossible to get that info from the factory however.

 

Trial and error, but in the end don't try to get power in an endurance series with your oil choice.

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