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Hi there! I've got a 2005 4 port 6 speed manual(not a USDM car, swapped the 5spd to 6spd myself) with about 25k total miles, with the last 7k miles done by me. The car has nearly all possible mods done to it, and will include a list if needed.
I have installed an oil sandwich plate and mounted an oil temp sensor there. I have switched around 5 types of sensors untill I found one I like. The sensor is linked to an arduino and a screen in the ashtray, so I can change the type of sensor as needed. Currently its a digital thermometer, LM19CIZ from Texas Instruments. Its error is given as 3F over -67F to 266F. Its mounted inside a 1/8NPT adapter. I have switched 3 NTC type sensors thinking my calibration of them is bad or something but...
The issue is that the oil never seems to heat up past 130F during light highway cruising@3000-4000 rpm. The water stays at a solid 180F. The ambient temp is 55-65F.
During city driving the oil heats up to 145-150F, but cools down as soon as I give it some speed. To have any chance of bringing the oil temp past 160F I must drive on the street as if I'm on a track which I'd rather not.
I know the temperature measurement is not wrong since if I touch a water hose with one hand and with the other hand an oil pipe, the temp. difference is clear. The oil does not heat up...
The oil pressure at 1250rpm is about 30psi(raised the idle with mazdaedit). By 3000rpm the pressure is steady in the 60-65psi range. Can't recall the pressure at redline. Oil weight is 5w40.
I've also tried to block airflow over both oil coolers and it did nothing, so I can say that the oil thermostats inside the oil coolers is not the issue here.
Is this any reason for concern ? Should I suspect that the oil pellet/thermostat in the e-shaft is stuck open and the oil jets don't work, thus not cooling the rotors and the oil stays cold ? Given the ultra low mileage(25k) is this to be expected?
Last edited by ciprianrx8; 10-18-2020 at 04:07 AM.
Reason: typo
Oil comes to the filter and your sandwich plate from the coolers, and then goes to the engine, so it's not a great place for hot oil temp. Same as measuring water temp after the radiator wouldn't be.
Then where is the oil shedding so much heat, if any? Those oil pipes can't amount for more than 5-10 degrees. The rads don't get any airflow, so the temp in the sump should be within 5-10 degrees to what I am measuring. If anything I'll raise the car and warm my hands on the sump to confirm.
You would be surprised, the oil lines are quite long and in the wind. Think about it, they carry oil to one corner of the car, then the other corner, then to the back of the engine. It's like 3 meters of pipe. Also what's more likely: that the temperature reading is correct and somehow the same engine is keeping coolant at 180 while oil is at 140, or that the oil temp reading is measured in the wrong place and oil and coolant are actually at roughly the same temperature? How would the first scenario even be possible?
At 50F ambient it doesn't take much to cool this car, you may not be using the oil coolers at all.
May want to get a remote thermometer before putting your hand on the 180F oil pan
Allrighty then. I shall try to relocate the sensor in one of 2 places: the banjo bolt before the left oil cooler, straight out of the engine, or directly in the oil sump. 1st option is easier but may leak due to the pressure there, 2nd requires me to somehow run 3 waterproof wires to the sump. Was thinking to run it down the oil fill tube via an adapter...lol.
Reason I'm so paranoid about this is that the roads around my corner of the world just don't allow me to redline past 2nd gear and I usually drive long distances with this car.
S1's max oil pressure is, according to the service manual, 64-71 PSI. Seeing your OP I would recommand that you either upgrade your OP regulator to the Mazmart one or use a lower viscosity oil or you will suffer from lack of lubrication at higher revs.
Personal thoughts below, might not be accurate:
If your oil temp is only about 130-150f, I believe that even 0w-16 oil can be used due to the excessively low oil temp. 0w-16.
At 104f (40c), 0w16(39mm²/s) is thicker than 10w-60 (23.717mm²/s) at 212f(100c).
I already have 65psi from 3000rpm, so pressure is not the issue here. Its that I find it hard to believe that some unvented oil pipes can shed down the oil temp from 180F to 130F. I will have to relocate the oil temp sensor so that I read the highest oil temp possible and go from there.
I already have 65psi from 3000rpm, so pressure is not the issue here. Its that I find it hard to believe that some unvented oil pipes can shed down the oil temp from 180F to 130F. I will have to relocate the oil temp sensor so that I read the highest oil temp possible and go from there.
I mean if you are having 65psi at 3000rpm, you will also have 65psi all the way up to 9000rpm redline. Sure 65psi might be sufficient at 3000rpm, but not 9000. 65psi is where the oil pressure regulator starts to bypass oil. Thought the pressure is the same, the oil flow is reduced.
I mean if you are having 65psi at 3000rpm, you will also have 65psi all the way up to 9000rpm redline. Sure 65psi might be sufficient at 3000rpm, but not 9000. 65psi is where the oil pressure regulator starts to bypass oil. Thought the pressure is the same, the oil flow is reduced.
Oil flow remains the same. Flow is determined by rpm since the oil pump is driven by the crank. Oil is not compressible so constant pressure = constant flow. Said another way, if you didn't have the reg you would pump ever more oil with more rpm and create drag on the engine. Or raise pressure to the point that seals start to fail. The reg causes the "extra" oil beyond the 3000rpm requirement to return to the pan. You don't need more oil with more rpm, it's not a linear relationship.
Oil flow remains the same. Flow is determined by rpm since the oil pump is driven by the crank. Oil is not compressible so constant pressure = constant flow. Said another way, if you didn't have the reg you would pump ever more oil with more rpm and create drag on the engine. Or raise pressure to the point that seals start to fail. The reg causes the "extra" oil beyond the 3000rpm requirement to return to the pan. You don't need more oil with more rpm, it's not a linear relationship.
The above statement isn't clear, like at all. I'll put them in bullet points.
Low oil temp = Higher viscosity
Higher viscosity = Harder to pump (Before OP regulator moves this does not matter)
Harder to pump = higher oil pressure
Higher oil pressure after the OP regulator moves(65-70psi) = reduced flow.
Here's what I really wanna say. Also the S2 has increased oil pressure up to 140 psi compare to S1's 65 psi, we also have seen lots of bearing wear in club.
Also to thread starter, if your oil temp remains low, not only I am concerned about the problem I stated about OP and oil flow, gas dilution is also something you should address.
S2's max oil pressure is 115. Operating is roughly around 90. S1 max pressure is 85 or so. Increased, sure, but let's not go crazy.
I agree with what you're saying except the last part. In any fixed configuration liquid pumping system constant pressure means constant flow. If the reg is maintaining 65psi it's also maintaining whatever flow rate 65 psi corresponds to. At no point is flow reduced, it just stops increasing. The pressure is set such that the oil can adequately fill the bearings and do its job, regardless of engine rpm.
The bearing failure stories seems associated with fuel dilution and low load low speed driving, at lower pressure than the reg is set to. For any given engine an used oil analysis will tell you whether bearings are wearing and actual presence of fuel.
Those temps sound very realistic to me for around 50 degrees high speed low rpm cruising. Mine does settle at 160 or so though at those ambient temps. Do you have lower temp t-stats on the coolers by any chance? Heavier oil (10w & 20w) increased the minimum temps for me as well.
No, all thermostats are stock and both oil coolers do not see any airflow.
Also on a more recent drive I could see the oil pellet in the e shaft closing as the oil pressure jumped up slightly while cruising at the same rpm.
Yeah I witness the thermal pellet closing as well around 110-120F at the pedestal. I blocked off my oil coolers with some cardboard but it still cools fast when I drop rpms and the engine bay cools very quickly regardless how I drive. I can get the oil up to about 180 if I drive a bit hard but it will still drop back down rapidly. Eventually I'm doing an oil filter relocation with a kit that includes oil cooler ports and a changeable thermostat. Try using your water temp gauge and sensor in the oil to double check. I'm not fully convinced that you are having an actual problem but I am aware that these cars are very temperature sensitive. In one week I can go from close to the upper limit on a 90 degree day of slow driving to 40 degrees driving on the highway and the oil won't even get up to a temperature that I like.
I don't use an external water gauge, just the stock one and reading its value off the can bus. Next oil change I'm relocating the oil sensor in the driver side banjo bolt before the oil cooler, this should give closer readings to the sump temperature.
OK - relocated the temp sensor on the oil pipe that leaves the motor, before the first/driver side oil cooler. The oil temp is identical to the one measured before/under the filter. My oil simply is not warming up, and keeping one hand on the coolant bottle and another on said oil pipe confirms the measurements.
No more than 130F for my oil while coolant is at 180F rock solid.
Last edited by ciprianrx8; 02-14-2021 at 01:09 PM.
OK - relocated the temp sensor on the oil pipe that leaves the motor, before the first/driver side oil cooler. The oil temp is identical to the one measured before/under the filter. My oil simply is not warming up, and keeping one hand on the coolant bottle and another on said oil pipe confirms the measurements.
No more than 130F for my oil while coolant is at 180F rock solid.
Any consideration switching to 0W16 or 0W8 during this season?
Is your car LHD or RHD? If LHD, the drivers side should be the return from the coolers, and it goes straight to the filter.
If RHD, I don't really have any theories about why it's not warming up. Your engine isn't producing any less heat than normal, so if for some reason your oil isn't making it through the bearings and rotors, you would have noticed those welding themselves together by now. Are these readings after a drive or just idling in the driveway?
I can believe it not getting hot when idling but as soon as you set off, it should see more heat load.
not unusual for an RX8 to run cool in colder weather. Didn’t have oil temp then, but remember the the coolant not getting to 170 with a 170 Tstat for about the same ambient temp.
been thinking about you blocking both coolers off and it not changing, pretty stumped myself.
Let me state clearly about my car:
- left hand drive, left cooler is driver side, oil temp sensor is placed here:
- ambient temp about freezing
- car maintains 130F oil temp even after a few runs while boosting (car has a turbocharger fitted...) so not even the f'in turbo seems to heat it up much
- idling or bumper to bumper traffic does not seem to bump up oil temps, 140F if even that, coolant temps remain at 180F at all times
- both oil coolers airflow is blocked off using some rubber mats
Honestly stumped if my oil temp never gets past boiling temp to evaporate condensation. I should let my car overheat a bit(200-210F) and see if that helps... at least every few hundred miles.
Yeah you're right, didn't realize it was backwards to the older 13b's.
How is your turbo oil plumbed in? Possible it's creating some kind of bypass that prevents the oil from going to the coolers correctly?
Where are you picking up oil pressure?
Turbo oil feed comes from under the oil filter via a sandwich plate, thats where the pressure is monitored too. That oil already passed by the coolers. Oil drain is straight to pan - by the drain plug.
The turbo came after I've noticed the oil never warming up.
10-18-2020, 04:06 AM
Oil remains cold
