NoPistons -Mazda Rx7 & Rx8 Rotary Forum

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pete_1979 09-20-2009 04:02 AM

I was just trying to find out if any one knows what the water temp should be at the thermo stat and what temp the coolant should be on the return from the radiator? I have a series 6 and it seams to be running little warm. The temp at the thermo stat stays around 85c to 95c and the return from the radiator is about 50c. I'm not shaw what they should be does any one know?

Signal 2 09-21-2009 10:32 AM

IIRC, the stock T-stat opens at about 82 C. (~180 F.) Since the t-stat doesn't instantly slam open or shut, and the stock water temp thermosensor doesn't activate the fans until 108 C. (or 95 C. with an FC thermosensor replacement)...your temps don't seem unusual IMO. There also might be a little difference in the accuracy of temp readings vs. the t-stat setting.



I've never taken readings from my radiator, but I'm thinking there would likely be alot of variance from one car to another anyway...depending on type of radiator (OEM and any number of aftermarket ones), ducting, ambient temp, AC working, coolant to water ratio, etc.

Signal 2 09-21-2009 02:23 PM

Also.....FWIW, yesterday where I live it was a sunny 82 F. ambient. My car has a SMIC, Fluidyne radiator, stock T-stat, about 30/70 coolant to distilled water ratio, FC themoswitch and I was not using the AC. During cruise my coolant temps sat rock solid at 81 C. on the PFC commander and confirmed with a seperate gauge.

pete_1979 09-23-2009 03:43 AM

Thanks for the reply mate. The thing that is bothering me is that it the temp changes consantly. It will drop from 95 C all the way down to 75 C or less and then jump back up to around 95 C. Sometimes it will go up to 105 C. It doesn't stay at a constant temp. I don't think that this is normal, what do you think?

Signal 2 09-23-2009 06:53 AM

Those are pretty big swings in temps. What ambient temps are you seeing right now where you live? Also, have you checked to make sure you have all three fan speeds? The only other thing I can think of would be if the T-stat is sticking. Most, including the FD, are designed to fail in the open position. But I'm not sure that would account for what your seeing. Still, if it hasn't been replaced in a while, it's not a hard job.

Other things that come to mind to ask are:

Where are you getting the readings, is it from the PFC or an aftermarket gauge? If it's a gauge, where are the sensors placed?

Any cooling mods?

pete_1979 09-23-2009 10:21 PM

Ok ill try not to leave anything out. The ambiant temp here is around 25 C to 30 C. The fans are factory which are now controlled buy an electronic thermo fan controller which is set to turn the fans on at 45 C, this temp is on the return house from the radiator. Can be set to what ever temp i want and they are wired up to there fastest speed. This was my only choice as some idiot put a microtech in it instead of a power FC. And it wasn't set up to control the thermo fans. The gauge is after market and the sensor is in the factory temp sensor location. The thermo stat is new only 1 week old and the radiator is a 3 core alloy big sucker it only just fits in the factory location.



The rest of my engine is only ten months old it was fully rebuilt by Dyson performance in the gold coast Australia. I fitted a new water pump before refitting the engine and most of the hoses are silicone. I should mention that it has been converted to single turbo using an ITS turbo chager. It uses a TO4S rear housing and i'm not to sure on the compressor housing.



This is my car ad it is for sale atm but you can see the engine bay in the photos



http://www.carsales....t=84tty&trecs=1



I have spoken to the guys who rebuilt my engine and they have know idea why its doing this. I would take it to them but they are 4 Hours away and i simply don't have the time.



thanks for your help

Signal 2 09-24-2009 08:04 AM


Originally Posted by pete_1979 (Post 834217)
......

The fans are factory which are now controlled buy an electronic thermo fan controller which is set to turn the fans on at 45 C, this temp is on the return house from the radiator. Can be set to what ever temp i want and they are wired up to there fastest speed.

Well, it's only internet speculation from the other side of the world...so take it for what it's worth. But I suspect that this ^ is behind the big temperature swings.

Again, none of the temps you posted are extreme, so it seems to be keeping things within an acceptable range. But with the fans either ON or OFF at HIGH speed and given the T-stat setting and big radiator...it's giving the bouncing readings.

pete_1979 09-25-2009 05:56 AM

That sounds like you could be on to something there. What temp should i start to get worried ? I don't know what temp a rotary engine starts to over heat.

Signal 2 09-25-2009 07:43 AM


Originally Posted by pete_1979 (Post 834257)
That sounds like you could be on to something there. What temp should i start to get worried ? I don't know what temp a rotary engine starts to over heat.

Opinions will vary some on exactly what the motor will tolerate. In talking to people whose opinions I respect, they say the stock coolant seals will begin to fail at about 115 C. At that point I'm not sure if it's the heat or increased pressure. Probably a combination of both.



FWIW, I don't like to see anything over about 100 C. on my car. And I'd get nervous enough to pull over at 105 C.

pete_1979 09-25-2009 10:04 PM

I was thinking around 100 C. I just took it for a drive this morning and it was all sweet. It seams to be affected buy the ambiant temp queit alot. But it also doesn't like to be driven like a girl. As soon as it gets some reves up the temp drops so I do belive you are right. Thanks for all your help.


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