UnknownJinX

The relay requires less effort to put in.

Seriously, though, my S2 is sitting at ~48k miles rn, so I still have time. Doesn't hurt to change it a bit earlier, though.

The thermostat also doesn't require any splicing or cutting, so that's also a plus.

dannobre

iTrader: (3)

I'm going to try and explain this again. The thermostat does NOTHING to change the fan on/off temperature. It only changes the temperature that the coolant flows from the engine into the radiator.

Ideally if you want to get maximum benefit you would change both the thermostat and add the relay kit that changes the fan on temperature so the fans come on earlier. Either that or you can use a flash tuner to change the fan temps.

The relay kit actually is an elegant solution to turn the fans on sooner...

Depending on your environment the thermostat may not change things much.
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gwilliams6

I have both the Mazmart thermostat and the fan relay kit. I chose to do these and also added lower temp oil cooler thermostats
,with a new aluminum Koyo V-core radiator and new Racing Beat hoses. . All part of major upgrades to my cooling system on my 2008 40th Anniversary Edition.

https://rotaryperformance.com/produc...ler-thermostat

Tho mas

Thanks for clarifying, that makes sense. I'll add the fan relay to my list, too (and potentially the oil cooler thermostat) .

But if I'm understanding that correctly, the water thermostat and fan relay should only help in combination, because having the radiator fan on earlier but not having water pumped through the radiator (or vice versa, to a somewhat lesser extent) shouldn't help much for cooling, right?

dannobre

iTrader: (3)

The fan on temp is above where the thermostat opens...so basically turning the fan on earlier cools the air going through the radiator sooner. Especially at low speeds where the amount of air moving through the radiator is lower than at speed, where a lot of air is pushed through the rad anyway

Having a lower temp for the thermostat to open is good up to a point. If it is too low then the engine operates at a temperature that is less efficient.....and the problem is to a large extent the ideal temp is a lot hotter than is ideal when the car is being pushed to maximum performance. Lowering the thermostat temp will give you more "gap" between steady state temp with the thermostat fully open and the "too hot" temp where you have to lower the engine load to reduce heat buildup

There is some controversy that this does much...but in real life in my case at least it does work. In a dedicated race car there often isn't a thermostat. Altering airflow into the radiator is used as a means to allow the engine to come to operating temps and to keep it at the ideal temp during the race

Tho mas

Thanks for the good explanation!

UnknownJinX

With the limited engine tuning options for S2, I am definitely going to get the cooling fan relay, just to have some room for safety.

The oil thermostats sound like a good idea. The only real concern I have with the 5W-20 oil I have is really the fact that the rotary's high running temperature may make it less stable. Kinda expensive, though, as a pair will run me more than CAN$200... Each one is US$88, and obviously, I need 2 for the 2 coolers.

Do you have any before and after comparisons for the water temp? I will still run the factory rad, but I just want to have an idea of the change we are talking about here.

Ramart

[QUOTE=dannobre;4835106]...The thermostat does NOTHING to change the fan on/off temperature. It only changes the temperature that the coolant flows from the engine into the radiator...

Please explain once more. Exactly how can a thermostat itself change the temperature of anything? It's merely a sensor-regulated switch. The thermo-activated fan, and heat dissipation through oil cooling and the critically important radiator component of the coolant-circulating system, are the only mechanisms that affect the engine's operating temperature. Except for some aftermarket mods, of course.

If the coolant's temperature as it flows from the engine to the radiator indeed is changed by some system, that would have to be the cooperative, reciprocating system of fan activation, coolant-oil circulation and heat dissipation - with the integral fan element dependent on the thermostat's instructions, no?

dannobre

iTrader: (3)

[QUOTE=Ramart;4835434]I'm going to answer this as a serious question...even though I have a difficult time believing it is 😐
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The thermostat allows the coolant to flow into the radiator when it is open. After the coolant in the engine gets hot enough to open the thermostat it flows into the radiator so that heat can be shed into the airflow. If the thermostat doesn't open there is almost no cooling capacity and the engine would overheat very quickly

It is a very simple system to allow mechanical control over the operating temperature of the engine coolant system overall.

The cooling fan can be as simple as a mechanical fan attached to a pulley or the water pump that turns at a constant speed..or a viscous drive that has a speed reducing mechanism. In most new cars the fan is totally electric and it is triggered by a thermosensor that tells the ECU what the coolant temp is...and the ECU decides when and how fast it wants the fans on dependant on a number of factors...including vehicle speed as that effects the amount of airflow over the rad even if the fan isn't on

I hope that explains things well enough for you

gwilliams6

There are cooling mod threads where folks talked, debated and argued about the temp differences with various cooling mods. Everyone drives differently, and there are huge differences in climate ambient temp in various places the RX8s are owned around the world, SO I can only speak for myself and my car and the load and heat I generate by the way I drive and where I live and drive.

With the lower temp coolant thermostat and fan relay kit ( I read the temp with an OBD2 dongle and using bluetooth Torque Pro app on my android phone) I often read up to 15 degrees F or more cooler at high engine heat load in the heat of summer than before with a working well stock radiator. Please take all this with a grain of salt, again this is me, and others may never see this much difference with the same setup. The oil cooler thermostats were added when I changed the radiator so their added help may partially show as the better efficiency of the Koyo V-Core aluminum radiator.

Your oil coolers provide up to 20% of your engine cooling on a RX8, so there is some benefit to the lower temp thermostats allowing fuller oil cooler flow sooner.

My purpose was to get the high load/high heat engine coolant temps below approaching dangerous territory, even when I push the car in the summer, and for my setup I am pleased. I am moving to Texas, so I will need all the cooling I can have on my budget. There are even more expensive dual-core custom radiators and other cooling mods that many Turbo and Supercharged RX8 owners have used.

If you plan on using your stock radiator (in good shape hopefully, and with less than 100k miles on it) for now then I don't think you need the oil cooler thermostats (they are a pricey addition, and its work to get to where they install, if you do it yourself), but yes I do recommend the lower temp coolant thermostat and some fan relay control. Most RX8 club owners that have done one or both of these mods have seen some benefit.

I have also added a closed-system AST coolant recovery mod from Pettit Racing to remove any trapped air from my cooling system and add a better overflow sensor than the stock coolant reservoir bottle sensor which is problematic over time. http://shop.pettitracing.com/aluminu...-p-120224.html
Not at all necessary for most, but I did this when I changed radiators.

We don't really want to get into any argumentative and/or long debates here about cooling mods in this new owner's thread. There were other threads for that.

Moderator Dannobre has done a great job in explaining it all. Thanks !

UnknownJinX

So I just got the cooling fan control kit today, along with Mazmart REmedy thermostat.

One thing that slightly confusing is that on a S2, they label what was cooling fan relay 3 as cooling fan relay 2, and vice versa. The fuse box layout is still the same, though, so the S2 relay 2/S1 relay 3 is still the blue one to the right.

So I am guessing I just install it like S1, right?

gwilliams6

yes

UnknownJinX

Just got the cooling fan control kit done today. Wanted to do the thermostat, but it's kind of a pain on an S2... Might have a mechanic do it.

Engine was running between 91~98 C(196~206 F) before, now it's running between 82~86 C(180~187 F). Definitely an improvement.

This begs the question: why is the factory fan-on temperature set so high?

dannobre

iTrader: (3)

Higher Coolant temps are more thermally efficient....but there is fine line. Mazda likely was trying to get every inch of mileage out of the engine

UnknownJinX

Makes sense, but given how people would overheat with the factory cooling settings in hotter climates, I must wonder if there was enough testing...

gwilliams6

I think dannobre has got it, Mazda was trying to squeeze every last bit of mileage and emissions numbers out of the car. But in the long run, you and your engine are better off with a lower trigger temp for the fans.

Steve Dallas

Hotter engines produce fewer emissions, and Mazda was right on the edge of what was acceptable with this car. Whatever they do to pass testing has to go into production (except for VW, of course), so they pushed it right to the edge of what would survive in the wild. That is my working theory at least.

I don't think you need to worry about the thermostat. It is already 180F, which is widely accepted to be the minimum oil temp. Coolant heats up much more quickly than oil, and coolant is used to heat oil as a result. Too low is as bad as too hot, so record some data under different conditions in different seasons and make an informed decision about the thermostat.

eric45mchs

My 06 rx8 has a rough idle and sometimes dies at a stop. I need some tips on what I could do to solve it. I have a new air filter and there is new coil packs and throttle body on the car .

UnknownJinX

Did you get a rotary-specific compression check for the car before purchase?

gwilliams6

Engine Power Loss
• chokes as revs increase
o O2 sensor failure (too rich)
o MAF failure
o MAF disconnected
o e-shaft sensor fouled
o accessory belt fraying
• high end power loss (hard fuel cut)
o Rev limit reached
• high end power loss (jerky and stumbling)
o Ignition failure
o fuel pressure loss
o e-shaft sensor fouled
• high end power loss (smooth)
o Catalytic converter clog
o air filter clog
• low end power loss (smooth)
o Engine compression loss
• low end power loss (stumbles)
o Ignition failure
o front O2 sensor failure
• revs slowly but smoothly
o O2 sensor failure (too lean)
o catalytic converter clog
o air filter clog
• sudden power drop at a specific rpm
o Intake valving actuation problem
• trouble getting to redline
o Ignition failure
o front O2 sensor failure
o catalytic converter clog
o air filter clog
o e-shaft sensor fouled
o fuel pressure loss
o MAF failure

Eric Layne

I have replaced air filter coil packs and throttle body. Any other solutions out there?

Dave04

Have your compression check at a MAZDA dealer, check for proper fuel pressure, clean the MAF sensor. Did you check your plugs and wires?

UnknownJinX

Are you the same guy?

Like said, check compression first. If you have an engine with low compression, NOTHING will help short of a rebuild.

Eric Layne

yeah. I'm same guy. Forgot password to other one 😂

Eric Layne

the guy before me had cat conv gutted . If I replaced it, could that help?