Oil cooler thermostat? - RX8Club.com



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Old 02-26-2009, 05:42 AM   #1
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Oil cooler thermostat?

Maybe it's already answered, but I found the next sentence in a German RX-8 (SE) service manual. I did not find this info in any other english serv. man.

Quote:
Ein integriertes Thermostatventil führt Öl mit einer Temperatur von über 90C (194F) durch den Ölkühler.
If it means that there is a 194F opening temp thermostat valve in the oil coolers, maybe it could be the reason for some of the overheated engine, and the high oil temps.

Some thoughts:
There is no cell when this thermo valve goes wrong.
If the thermo valve open later (went wrong), the oil temp will be too high and the oil will be too thin (bearing wear).
Who knows when the thermo valve goes wrong, does it stay opened or closed mode?

In winter (europe) my oil coolers are only warm when the engine is on idle for a while and the car is standing. If the car was moving before, the coolers are cold immediate after stopping. I could check it with my hand after stopping. Even in summer my cooler's thermostats are closed a lot of times (checked after stopping), when the engine warm.
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Old 02-26-2009, 06:00 AM   #2
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Oh good find. However Rotarys run hot anyway. Always have.
You know Jeff (MM) can read that stuff (German) really good. PM him.
But why would it be in that book and not the US book???
Keep us posted!
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Old 02-26-2009, 08:10 AM   #3
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MM's post box exceeded the limit, so I sent a mail to him.

Just for confidence, the information comes from the German Mazda RX-8 (SE) Trainingshandbuch 11/2003.
It's a book in my hands, but I don't speak German.
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Old 02-26-2009, 11:54 AM   #4
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Well, German is not my primary language, but this is what it says:

"An integrated thermostat allows oil with a temperature over 90°C (194°F) through the oil cooler."
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Old 02-26-2009, 12:08 PM   #5
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So where is this thermostat or valve?

Has Paul at Mazmart seen a valve on the oil cooler?
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Old 02-26-2009, 12:21 PM   #6
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All RX-8s have them. Its in the oil cooler itself.
IIRC, all of the contemporary rotary Mazdas had thermostats in their oil coolers.
90°C is troubling, though.
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Old 02-26-2009, 12:25 PM   #7
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Then there is Easy answer to running hot.

Correct?
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Old 02-26-2009, 12:38 PM   #8
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Quote:
Originally Posted by Razz1 View Post
Then there is Easy answer to running hot.

Correct?
No, probably not.
His oil temps are never as high as his water temps when he begins to overheat.

I'm in the same boat. (Though my issues are due to the intercooler blocking airflow to the rad.)
Thermostats in the oil coolers is a good thing in most places, I would just like to see it open at 175°F.
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Old 02-27-2009, 05:21 AM   #9
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Is it true, that all of the RX-7 FC-FD oil coolers's thermostat opens at 149F ?

Why the Renesis has so much higher (194F) temp thermostat?
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Old 02-27-2009, 10:40 AM   #10
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dont concern yourself with oil temps---not an issue. the oil temps will follow the coolant temps more or less. address coolant temps. Mazda does not want oil flowing through the coolers at too cool of a temp due to possible plugging.
OD
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Old 02-27-2009, 10:52 AM   #11
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Quote:
Originally Posted by olddragger View Post
dont concern yourself with oil temps---not an issue.
Huh?
Where do you think the water gets half of its heat from?
Oil doesn't follow water - water follows oil!
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Old 02-27-2009, 01:22 PM   #12
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umm... nice 69 avitar!
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Old 02-27-2009, 01:32 PM   #13
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Hmmm, subscribing. Can the oil cooler be upgraded?

Last edited by 9krpmrx8; 02-27-2009 at 01:49 PM.
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Old 02-27-2009, 03:10 PM   #14
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thats why you should pay more attention to the coolant temps---and if you get it down the oil temp will follow!
Oil doesnt play a part in cooling a large part of the engine whereas the coolant does---concentrate on the coolant. If you concentrate on just the oil---well ok go ahead.
olddragger
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Old 02-27-2009, 03:46 PM   #15
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Quote:
Originally Posted by olddragger View Post
thats why you should pay more attention to the coolant temps---and if you get it down the oil temp will follow!
As I said - other way around.
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Old 02-27-2009, 03:47 PM   #16
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Quote:
Originally Posted by ayrton012 View Post
Is it true, that all of the RX-7 FC-FD oil coolers's thermostat opens at 149F ?

Why the Renesis has so much higher (194F) temp thermostat?
FC oil cooler thermostats started opening at between 140F and 149F (60-65C), the same temp that the E-shaft thermo pellet opened on a FC.
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Old 02-27-2009, 03:49 PM   #17
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Quote:
Originally Posted by olddragger View Post
thats why you should pay more attention to the coolant temps---and if you get it down the oil temp will follow!
Oil doesnt play a part in cooling a large part of the engine whereas the coolant does---concentrate on the coolant. If you concentrate on just the oil---well ok go ahead.
olddragger
On the FC, 30% of the cooling was by the oil... is the FE water cooling system that much better that number is reduced?
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Old 02-27-2009, 06:05 PM   #18
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Quote:
Originally Posted by 9krpmrx8 View Post
Hmmm, subscribing. Can the oil cooler be upgraded?
In Japan, some shop has them.

you can always go get universial kit and fit it your self.
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Old 02-27-2009, 06:52 PM   #19
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if the oil is doing 30 % of the cooling then the coolant is doing 70%. which do you think will respond to upgrades better? which will have the most influence on the other?
to see one difference between the engines look at the housings on the earlier models versus the renasis and you will see that the areas around the sparkplugs has a much bigger area for coolant to pass through for example.
the twin oil coolers on the rx8 are pretty good--the oil system has the capacity to cool the oil if it is not asked to cool more than its share. The inadequate coolant system does just that. The coolant temps on a 90+ day on an oem car at low speed can get to 230F easily. the oil will be at around 210F. To get the oil temps down from that you are going to have to create enough cooling capacity to influence the coolant temps--that will be a pretty big job. Now if you add just a little coolant cooling capacity to bring that temp down to 200--then the oil will drop down to 180 easily.
would you rather work on the system that has the lesser impact on the result you are seeking?
And dont forget--the oil will do its job at 250F+ coolant will not!
It does have to be a balance--you dont want much difference between the two.
enough said.
olddragger
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Old 02-28-2009, 12:05 AM   #20
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Quote:
Originally Posted by olddragger View Post
if the oil is doing 30 % of the cooling then the coolant is doing 70%. which do you think will respond to upgrades better? which will have the most influence on the other?
to see one difference between the engines look at the housings on the earlier models versus the renasis and you will see that the areas around the sparkplugs has a much bigger area for coolant to pass through for example.
the twin oil coolers on the rx8 are pretty good--the oil system has the capacity to cool the oil if it is not asked to cool more than its share. The inadequate coolant system does just that. The coolant temps on a 90+ day on an oem car at low speed can get to 230F easily. the oil will be at around 210F. To get the oil temps down from that you are going to have to create enough cooling capacity to influence the coolant temps--that will be a pretty big job. Now if you add just a little coolant cooling capacity to bring that temp down to 200--then the oil will drop down to 180 easily.
would you rather work on the system that has the lesser impact on the result you are seeking?
And dont forget--the oil will do its job at 250F+ coolant will not!
It does have to be a balance--you dont want much difference between the two.
enough said.
olddragger
Think you are missing the point. Modifying the cooling on the car is not a one thing or the other. On a rotary engine it only makes sense that if you are upgrading one, that you also at least look at upgrading the other.

However it makes no sense what so ever to say, "I only want to upgrade the radiator" if you are having temp issues. If you are having temp issues you should look at every thing you can, to help.

Its not like changing the oil cooler thermostat and eshaft thermo valve is going to solve anything, but in conjunction with other modifications it may lead to better coolant, oil and engine life. Now with a piston engine, the oil does not provide even 5% of the cooling, so your comments fit that idea perfect. Why waste the time even looking at oil cooling if you are not affecting anything. On piston engines that use an oil cooler, it is more for oil life than cooling of the engine.

But on a rotary, its not, and this is not a one thing or another issue. Sure if you can solve the issue with a bigger 3 row radiator, then you are done. But if not, if you run the oil temp back down at 180 instead of 210, that might be the extra kick that helps.

Now again, don't get me wrong. If you are having overheating issues, just changing the oil cooler thermostat is not going to solve anything...But how much less viscosity and oil break down.. how much would be reduced by dropping that oil 10 or 20 degrees?
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Old 02-28-2009, 12:49 AM   #21
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and if you are running a h20 thermostat that works right at 180 deg. the with some extra water cooling. both the problems are solved..

that is how olddragger fixed the problem..

beers
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Old 02-28-2009, 03:09 AM   #22
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Hey guys, I asked this before but no one really gave me an answer, What about using a water or oil pool? will that help with cooling? I know some GT and other race cars use them.
-Gil
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Old 02-28-2009, 12:39 PM   #23
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icemark--you are absolutely correct--everything should be looked at. And the full range balance (warm up, wot applications etc) between the oil temps and the coolant temps have to be considered.
In looking at all --i found my solution by simply adding a small secondary radiator placed below the front support member directly in the air flow
https://www.rx8club.com/attachment.p...1&d=1235846259
see pic--this little thing with a couple of other mods will fix the cooling problem(except for the desert guys with no humidity in the air.
olddragger
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Old 03-01-2009, 03:50 AM   #24
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OD can you post a larger pic? or pm it to me and I will post it. I cant see shat in that small attachment.
-Gil
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Old 03-01-2009, 06:43 AM   #25
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Quote:
Originally Posted by olddragger View Post
--i found my solution by simply adding a small secondary radiator placed below the front support member directly in the air flow
You don't say, so are you talking oil or water rad you added? Your pic is not much bigger than an avatar, can you post one a bit larger so we can see what you added?

Quote:
....see pic--this little thing with a couple of other mods will fix the cooling problem(except for the desert guys with no humidity in the air.
olddragger
a couple little other things? Can you pls be a bit more specific?
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