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With these larger coolers how is anyone getting enough heat into the oil to actually start getting reasonable pressures / temperatures?
Having some issues after dual 25 row oil cooler and remote thermostat install. Everything works and runs great issue is with excessive oil pressure after warm-up. Seems like an oil temperature issue as prior to install all pressures were perfect to the manual (90psi at WOT warm etc.).
I'm having an issue thinking it's anything with anything in the coolers as all other pressures seem perfect, as well as where the oil sender is located AFTER the oil coolers, I would think a blockage would have lower pressures in the sender as more pressure drop would be in the cooler portion of the circuit.
Current pressures after dual oil coolers using 10W-30
Cold Start Pressures
~60psi @ 1100 RPM
~110psi @ 3k RPM
Warmed up pressures
~30psi @ 900rpm
~60psi @ 3500rpm
POTENTIAL PROBLEM ~120 psi @ 4k - 6k and shows that it will continue to rise until internal engine regulator will be hit. This is all being done light throttle. Does seem to get better as I keep driving which keeps leading me down oil that is not warm enough. (reason for the range...I have not been able to get higher than 6K, but during initial warm-up I can't push past 4.5k without getting to 120psi)
Don't feel comfortable just sending it at this point to try and get more heat into the oil as doing so pressures are getting too high. I did look at the Mocal thermostat again just to make sure I put it in the correct orientation and everything looks good there, also coolers and lines are warm to the touch after driving so oil seems to be circulating through there.
1) Are these pressures actually an issue?
2) Am I going to have to block off a cooler during warmup?
3) Is something else going on?
Currently running 10w 30 and this is a fresh broken in engine so clearances are still tight I had never heard of running an oil that thin in a rotary. I would be open to running a lighter oil if that provides enough film strength for the bearings.
Thermostat is the standard mocal unit starts opening at 160 full open at 180.
I have read plenty of comments of long warm up times but is this common to just never get to 180 - 190f heading into the engine? This should he a common problem whether the car has 1000hp or 300hp as its all during warmup time.
Remember that the factory cooling system opens the thermostat at 82C which is about 180F. There is also a thermostat for the rotor oil cooling jets, which people delete, a mod I don't agree with. Hence my thread a long time ago about it. https://www.rx7club.com/2nd-generati...tupid-1017659/
Put the stock coolant thermostat back in, and after that the next step would be to put the stock oil jet thermostat (oil thermal pellet) back in. Of course use brand new OEM parts in both cases. Is it any wonder your engine is running so cold when you've drastically increased the heat exchanging and you're spraying cold oil on to cold rotors with cold coolant flowing through? There's tons of friction from everything being cold. Friction is by the way not good for power (too much heat isn't good either, which is why cooling systems need to balance friction vs temperature).
Sorry I misinterpreted your question about thermostat thinking you meant the oil thermostatic switch. Coolant thermostat is still the factory unit opening at 82C, I do need to get in and change the fan settings with a dataloggit as they come on at 85, 86, and 87 currently which isn't helping the situation at all, coolant doesn't break 86C currently.
more of what the direction I wanted to get some discussion is if this is really an overcooling issue or if something else could be hiding. I strongly believe the oil is over 60C so the thermowax shouldn't be in play, and getting the idle to 30psi really only takes a couple of minutes of driving. I'm assuming the oil is staying right at ~70C ( 160F ) once the thermostat starts opening. need another 10-15 degrees C to get to optimal temps.
Wanted some extra opinions as the pressure directly follows RPM but idle and cruising pressures are perfect. Thanks for the additional points,
Short term I will probably just cover the 2nd cooler to check the theory and pit in and remove the cover once I get oil temps up to where I'm more comfortable for now, Long term I will probably look into an oil thermostatic switch that cracks at 180F instead of the lower 160F, as well as trying to get coolant a few degrees warmer with moving fan on temps up. I wasn't planning on monitoring oil temps at all because of the amount of cooling, but now I'm thinking that will have to be on the list also, for this issue and to ensure the oil thermostatic switch is actually working in the future.
why not just drive the car hard until oil temperature is presumably (or actually measured) to be at least the temperature of the coolant? Really 97C (fully opened coolant thermostat) is where you should run the car, at least for now. Then you know the oil is hot and thinned out. So go do a fun back roads drive, or if necessary, drive down the road at 5000rpm for a few minutes in 2nd gear just to get it hot.
If you're worried about reaching the regulator pressure by doing it that way (which may not be a big deal), then turn on the A/C and drive in stop and go, or kick on the fans at 100C. If getting the oil up to a higher oil temperature drops the oil pressure then you know you've got a temperature related issue.
That's what I have been trying, cruising at 5000RPM, and going 75%+ throttle up to cruising to try and get heat in. just can't get there. last drive was about 25 miles of trying this, final attempt to pull above 6000RPM still had the same result of 120psi. I'm just concerned about the regulator dumping oil flow back into the pan and starving the turbo at the end of the circuit.
Original plan was to "monitor" temp by watching pressure as I have plenty of oil cooling, i would watch pressure for health of the thermostatic switch etc. as well as the issue I'm seeing right now of excessive pressure means oil viscosity that is still too thick (cold). Would end up being easier in the long run just to still have an oil temp gauge, so that's back on the list. As well as running fan temps ~10C hotter
The amount of pressure and flow turbos require is pretty minor. I'd be hard pressed to believe that you'll be starving it unless youve got some very odd and convoluted oil path. Personally I AIM for 100-120 psi.
there's a higher temperature mocal oil thermostat, 95C that I believe sakebomb uses with their kit.
with larger coolers being faster at shedding heat the higher temp thermostat may be a good solution to help with warmup and normal operating temps without overcooling
I didn't really understand "your rotary is running too cool" until I started playing around with tuning a little. I saw all the settings regarding temps. Although you can adjust them, I haven't gotten into that portion yet. I know I had a pain in the *** time trying to get the car to run cool enough to even tune it when I had my 76°c thermo in. The car had a hard time getting over 80. Therefore the map was enriched. I had to swap back to the 83 oem thermo.
So many say the thermo will not make a difference in you ultimate temp, but in my car I definitely disagree. Lower thermo in... can only get car over 80 if driving hard and slow only have it cool back down. OEM thermo it will run hotter period.
I bet of one wants to play with the settings it may be beneficial to run cooler ... 80 or sub, as it was probably all emissions BS anyway. Sorry of this is off topic, I believe there is a lot written about it.
That could be an option, looks like cracking temps are ~10C hotter (80C).
The 95C value is full open, however it is dangerously close to the 205F (~96C) that oil should never go into the engine at ( Racing Beat Oil Recommendations ) . I've read posts that go both ways on this topic that that switch is too dangerous to run in a rotary as wont get full flow to the coolers until right at that danger point. I know that temp number isn't necessarily gospel and has other factors such as oil type (10w-30 vs 20w-50) but that is getting uncomfortable close to that temperature.
The 95C value is full open, however it is dangerously close to the 205F (~96C) that oil should never go into the engine at ( Racing Beat Oil Recommendations ) . I've read posts that go both ways on this topic that that switch is too dangerous to run in a rotary as wont get full flow to the coolers until right at that danger point. I know that temp number isn't necessarily gospel and has other factors such as oil type (10w-30 vs 20w-50) but that is getting uncomfortable close to that temperature.
205F oil is silly, you don't think these cars ran way hotter than that stock?
Put a reasonable thermostat back in. 95C for the oil coolers is good, and I still think deleting the oil squirter thermostat (thermal pellet) that so many people do instead of replacing it with a new OEM one is dumb.
This is a street car that needs to operate in a variety of conditions. A 60C thermostat makes sense if you literally run it on a race track only.
…and I still think deleting the oil squirter thermostat (thermal pellet) that so many people do instead of replacing it with a new OEM one is dumb….
If the OP’s wax thermopellet has been changed out for the plug, then the difficult replacement of it with the engine in the car, and risking the front stack with an accidental slip, is dumb. And the ‘varied conditions’ likely aren’t as varied as they used to be since these cars aren’t much daily’d and rarely if ever driven in cold conditions. It’s purpose was just to warm the engine faster, by stopping the oil’s spray to the rotors. And while rare they CAN fail closed. And maybe most importantly for this thread, i can’t see it do anything for the OP’s issue.
Just clarifying a few things
-The coolant thermostat is OEM @ 82C cracking
-The 205F number just came from Racing Beat which is a respected source, unfortunately sounds like the info is either outdated or way too conservative
It sounds like the best thing to do is to move up to the HT version of the same thermostat as that gets extra heat in and the 205F is not a real number, even so the oil thermostat would be full open below this temperature anyway, ~$180 to swap out, but really not bad in the long run.
As far as the oil squirter thermopellet, I unfortunately don't know for sure if it's in there, but based on the time to get from 60psi idle pressure to 30psi oil pressure I would bet that it is still in there.
There was a guy that ran turbocharged ported rotaries in power boats who dyno cell tuned the engines, so had control of all heat exchange systems (these see far higher duty cycles than any road or track engine), people were asking about best target coolant temps on guild of efi tuners, his peak power was with low 70 Celsius coolant temps and oil temperatures around 120 Celsius.
Running higher thermostat/thermo fan trigger points instead of setting you coolant corrections appropriately is retarded.
-The 205F number just came from Racing Beat which is a respected source, unfortunately sounds like the info is either outdated or way too conservative.
my friend asked Jim (RIP) in person about this, and he said Delta T, when the oil gets hot it can't remove enough heat from the rotor. which is fine, the part that the catalog doesn't say is that this is for an endurance race engine, so ~8500rpm for 24 hours, and not your street car. so racing beat's number lacks context. IMO in a street car having the oil temp a little higher will evaporate the "crap" out (water vapors etc)
just to summarize, the engine likes oil that is cool, but the oil itself is ok to be much hotter (most oil is ok to 280-300f), which is nice.
07-03-21, 07:52 PM
