Legot

iTrader: (1)

It kind of looks like a hole, but it's more of a divet to keep the plug in contact with the spring plate instead of the thermostat shaft. It's only there so that I didn't strip the thermostat when torquing it down.

These type of thermostats don't have any kind of pressure bypassing since pressure across the cooler is pretty much inconsequential (they are probably safe to a couple thousand psi).

04Green

iTrader: (1)

A couple of the little mushroom things that Legot posted.

Plan is to test what I have, take hot day temps, install one, then see what changes. Cooler temp should actually go up on that one if more hot oil is going through it, and line temps should go down. Today I had oil out line at 185, one cooler at 155, the other at 145, and the oil return line at 165.

04Green

iTrader: (1)

@ Legot,

Missed your post. The pressure relief is the fact that the flat piece on the end (spring plate?) will slide down the shaft if the thermostat has closed off the bypass port.

I am really close to just buying the different thermostats as opposed to trying to modify what I have. The risk of dorking something up to save $100 is too great. I think I will order 1, put it in the second cooler, and take some measurements. If the second cooler, with the lower thermostat, is hotter than the first one, then it is flowing more oil.

04Green

iTrader: (1)

Update:

I ordered the new thermostat. They were out of them. The did "find" one, but it got to me once things got cooler out. All my "hot" measurements were kind of useless for a before an after. However, I can share that the highest temp I saw, after work, in summer, was in the 130s for the first one, with the second one (passenger side) being around 110 to 115. This was on 90 to 95 degree days.

Today, winter, 60 degrees out, with the new thermostat in first cooler position, it was around 155, with the second one still around 110. Yeah, I know, I should have put the new one in the second cooler. I thought the oil flowed the other direction. A few days ago it was 45 degrees out, the temp was 145. Again, significantly hotter.

This is 25 or so degrees hotter with 30 degree cooler temps outside and 45 degrees hotter than the other cooler. To me this means a lot more oil is flowing to get the temp up that high. That was the goal. I would call this a win.

I will be ordering a second one once I finish a brake duct project. Once I get the second one installed, I will flush the oil and see if there is any difference in how the oil looks after a few thousand miles.

I cannot really compare the coolant temps any more to see if this cools the engine. I made a few cooling mods since summer started. I am not sure how a cooler rotor will effect housing temps. But, I like cooler oil and a cooler rotor cannot hurt.

Legot

iTrader: (1)

Overall it might reduce coolant temps, but it probably won't be noticeable. Even though the engine heat is split between the oil and coolant the the temperature of both is practically independent (unless your oil cooler and radiator are stacked).

gwilliams6

Rotary Performance - Oil Cooler Thermostat

This may the same product you are talking about. I put two of these in my RX8 last year. More precaution than anything. I also have the Remedy lower-temp cooling system thermostat, cooling fans lower temp relay switches, and just yesterday a new Koyo radiator with the new Pettit Racing closed AST system, with Racing Beat silicone cooling system hoses. Ready for the probable move to Dallas ,Texas area and its heat this summer.

04Green

iTrader: (1)

@ Legot,

Yeah, the heat transfer from the rotor to housing is pretty slim. But, a cooler rotor may be a happy rotor. I cleaned the garage and found the data from September. Left cooler was running about 10 degrees higher than the right side. Now, I am seeing 45 degrees or so, on a cool day. And, this is after several miles of 45 mph cruise and a mile of 30 mph cruise. At speed, I have no idea.

I ordered the second one. I am not really expecting an overall cooling difference. But, if oil is cooler, engine may be happier. My oil turns dark almost immediately after an oil change. More so than just mixing with dirty oil. Maybe this will help.

04Green

iTrader: (1)

OK,

This just got weird. With one installed, I really could not claim a reduction in water temps. I may have seen a degree, but would not have sworn to it. Cruise temps in cold weather around 180 to 181 degrees at 60 mph. I also stiffened the under tray, so that may have helped. My overall goal was lower oil temps.

I got the second one in and installed it. Um, water temp dropped immediately to 174. I do not think thermostat is all the way open yet (lower temp thermostat, Pettit build). I am at a loss as to how the cooler rotor reduces water temp other than rejecting more heat from the system. Maybe it is just the heat dump to the rotor does not go to the housing.

But, I wanted to share. And if I get another renesis, I will be buying more of these.

dannobre

iTrader: (3)

LOL...not sure why you were surprised it took 2 with only one it wouldn't change the oil flow through the coolers.....

You could do the same thing effectively by disabling one and just using one...would do the same thing

I thought this was discussed YEARS ago.....there are large temp differences with improved oil cooling....you can loose 20+ % more heat if the oil is cooler.

gwilliams6

I have the lower temp oil cooler thermostats installed and working fine.

04Green

iTrader: (1)

Thanks all, I missed the last two responses.

getting into hot weather, sharing the last set of observations..

Car is running way cooler, and does not creep up running the AC on the highway. It used to get to around 200. Now that it is finally warm, I am not seeing much a creep at all. well under 190 on t

So, to close the revival, I think these things work. There are likely cheaper things you could do, and things you could mod, but this engine is a bit expensive. So, $180 is not that bad.

I will be tracking how dirty the oil is with this mod, but need to get into a non-track oil change. If I start getting less cooked oil, there is a benefit there tool.

@ dannobre, I could only get one the first time. But, yeah, it takes 2 to work as planned.

@ gw, yes, thanks. I have recommended these to several folks.

swoope

iTrader: (5)

wow,

just stumbled across this thread. how hard is it to get to the two parts?

beers

ASH8

https://rotaryperformance.com/blogs/...ur-rx-8-engine

Interesting bit about 'double your engine life' published last year.
While I am a little dubious about using the word double, it is interesting to hear someone else ( I guess considered an expert in his field) say how 5W20 oil is basically crap, and how the main e shaft bearings are that from old RE's and have not changed (clearance wise).

I said about 10 years ago that 5W20 was crap and should never be used in any RE, and got poo pooed, glad he thinks like me...

gwilliams6

Yes my dealer (one of the largest volume Mazda dealers on the East Coast) has always used 5W30 (dino oil) in all its RX8 oil changes, and recommends full synthetic for its piston cars owners.

gwilliams6

Swoope, here is the oil cooler diagram, if you didn't have it already, with the thermostat location circled in red. You will have to remove some stuff to get to it.

Steve Dallas

I wish we had a real oil temp sensor. I would love to know how actual oil temps track with the lower temp thermostats installed. The activation temp seems low to me. I think I'd rather see it start to open at 180F. Info on the first page of this thread indicates the OEM opening temp is 194F, which is pretty typical. I wonder where RP got their information that the temp is 220F?

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Legot

iTrader: (1)

I believe that in the workshop manual the temperature that it starts opening at is 194F, and if it's in spec it will be fully open by 220F, so it's mostly vendor BS mixed with sketchy fact. For example the thermostat in my FC cooler cracks open at 149F and is fully open by ~194F.

It's a way of controlling oil temperature without really having to restrict the flow through the system, just through the cooler.

Steve Dallas

I guess that should have been obvious. If he is really comparing the opening temperature of his product to the fully open temperature of the OEM unit, that is more than a little disingenuous.

gwilliams6

The seller's "chart" suggests the lower temp thermostats are fully open at 175 degrees, which is still better than 220 degrees for fully open stock thermostats. My rotary wrench has put these into modded FDs (the exact same part fits FDs) and reports cooler temps. That is partially why I bought them and had my wrench put them in.

I see these as just one part of my total cooling mods, not an end all fix. Your oil along with the coolers contributes around 20% of the RX8's rotary engine cooling.

Steve Dallas

Right. But there is such a thing as running your oil too cool. That's why I would like to see before and after data on oil temps.

The Mocal sandwich plate on my Miata has a thermostat rated at 180F. I have to cover the oil cooler, when ambient temp is below 50F, for example.

Love_Hounds

Is there? Wouldn't that just mean the viscosity rating would be different if it were cooler?

I'm pretty sure in the US, the 'W' number is the cold or "winter" number and the non-W number is the rating at 212 F for multi-grades.

EDIT: Guess I should add that if you knew what temperatures your oil ran, you could then use an oil that would have the right characteristics at that temperature.

Steve Dallas

^ What you wrote is not untrue, but there is another dimension to consider. Oil needs to reach around 220F to burn off deposits and evaporate accumulated water. If that water is not burned off, it mixes with the sulfur and impurities in the oil to create acids.

Of course where that temperature is reached is important. I measure my oil temp at the oil filter, which is a cooler location than some others. At that point, the hot oil returning from the engine has mixed with cooler oil in the pan, before being pumped back to the filter. So a reading of 210F at the filter might mean oil leaving the engine is actually 230F. In that hypothetical situation, I should be fine: not too hot and not too cold. If I am reading 180F at the filter and 200F is the actual peak temperature, things are likely not OK.

212F is commonly cited as an ideal operating temp. 212F where? Also, pure water boils at 212F, but water in solution with other molecules may have a higher boiling point, and it reportedly does in an oily environment.

The bottom line to me is, more data are needed. RP has an opinion. Mazda engineers actually measured oil temps everywhere (surely considering emissions demands) and decided on the higher temperature thermostat. I want to know what is optimal for a car owned by someone who doesn't care much about emissions. In the Miata, I struggle to bring it up to 200F in the winter and down to 200F in the summer (measured at the filter).

Footnote for context: a lot of engine builders use a 75F rule of thumb for the temp of oil leaving the pistons over the temp of oil in the pan. It would be helpful to know that delta for the Renesis. The numbers I used above are completely made up.

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Love_Hounds

I can buy off on that. Of course if there are really big differences in temperatures between two or more locations, wouldn't a faster circulation help, provided it isn't so fast as to not shed heat in the radiators?

I'd also add 212F at see level, the oil in most engines is under some pressure right? You would have to increase the temperature to truly boil it off.

Maybe I should go back to the B@W thread...

9krpmrx8

iTrader: (46)

There are not big differences between the locations, I have measured (for years now in South Texas) from the oil pan, the oil filter housing (both stock and my remote mounted filter) and at the oil cooler feed on the block. The temps are all about the same thru various oil cooler setups. The only place you will see a noticeable difference is at the pan when the car is idling after a hard run, then the temps creep up due to no flow thru the coolers.

Theory is one thing, actual data is another.

Steve Dallas

Faster circulation would help, but circulation rate is a function of volume, pressure, etc. which are things you may not want to increase.

Believe it or not, I was thinking about pressure contributing to boiling point, and somehow it did not travel from my brain to my fingers. You are absolutely right. It factors in as well.

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