I need a lower than stock thermostat. I have a koyo n-flow, and the pettit fan switch which is turning the fans on at 185 before the stock thermostat is fully open. My temps never get above 185 and I feel like because the thermostat is not fully open the fans are running when they otherwise might not need to. During the fall, winter and spring here in San Antonio I think the Koyo and a lower temp thermostat will easily keep the temps below 185 (fan switch on) during normal driving.

 

I went with the FC switch and set my fans for 188. They turn off when temps drop back to 185. My new OEM stat opens at 180 and fully opens by 185. If you don't find what you are looking for, I'd get a new OEM one.

Or ask Pettit what they suggest.

 

Thermostats

 

I wanted a cooler one for the Houston area as summer traffic even with a Koyo "N" pass is brutal. Most optional thermostats are too cold.
SARD Low Temperature Thermostat - SST12 Mazda

I bought a SARD.
Product: Low Temperature Thermostat - SST12 Mazda
SPECIFICATION:
3rd Part Code: SST12
Opening Temperature: 75°C

Lower than stock but higher then a race thermostat.
So far this winter it keeps the temps for normal driving (no boosting) between 76-79 C.
My stock unit with my fans setting at 86C ran 83-85C.
So it runs about 7C lower.

Got mine from:
Sard SST12 Cooling Thermo MAZDA RX7 (FD3S) beat deal at ShutokoEngineering.com

 

Don't run a colder tstat. The stock t stat is fully open at 185, if you have the fans come on at 188 you really have a tolerance problem and will be constantly opening and closing the t stat. Turn fans on around 200 which is plenty early.

If your car overheats a lower temp t stat won't help.

 

if you have a pfc, cant you just see if someone around you has a dataloggit and change when the fans kick in

 

I don't have a PFC. My car does not over heat, it seems like because the fans come on a 185 the stock thermostat never has chance to fully open and allow the radiator to work without the fans. I suspect the fans would not come on as easily if the t-stat opened fully a little earlier. What I'm trying to say is that I thinks the fans are keeping the stock t-stat in the partially opened position.

 

Thanks for the information. Have you been happy with it?

Is there any reason that the engine needs to run at the stock t-stat operation temperature? I remember reading that the US FD was set to run hot for emissions, so are there any other drawbacks to running the car a little cooler?

 

What is up with everyone's obsession with making their car run as cold as possible? What is wrong with 85-89 degree temps?

76 Celsius is only 168.8 Fahrenheit. That is not even warmed up.

 

Nobody is talking about overheating. It is easier to prevent heat buildup than to let it happen then try to reduce it.

A thermostat is not a quick acting open/close system but a gradual orifice size slow mudulating system.


In stop and go Texas driving with air temps above 90 and the AC on, keeping the temps cooler helps the AC to work better.

 

Once again we have exaggeration.

 

I am using a 180F thermostat made by Beck Arnley. I think I purchased it for $4 from rockauto a while ago. I bought (2) of them when they went on clearance. I have one in my car right now and it works fantastic. I think the quality from Beck Arnley is great.

My car is running great. I also suggest picking up a new radiator cap as well if yours is old.

 

FWIW, I'm also using a SARD thermostat. However, my car is mainly a track car. I honestly don't really see a reason for one on a street car, but the SARD unit works well for my track usage. I bought it many years ago before vendors were selling them here in the US. I'd probably grab the Banzai one if I were buy one today, but again my need is a little different.

 

Yes, thanks, I meant to comment earlier. It is not an obsession, at least not for me. I guess I can see how some mechanical neophytes might think since overheating=bad, cooler=good but that is not what I'm getting at.

I'm simply trying to get the t-stat fully open before the pettit fan switch turns on at 185. In hindsight I wish I had bought the FC switch because the pettit switch does not use the factory wire harness plug. Of course I threw the original plug away 3 years ago and now I've been stuck with the pettit switch ever since. I also still have the fan recall so my fans are more likely to stay on at shutdown as it is.

Pettit apparently carries one....I understand they're in the business to sell parts so of course they're going to recommend it but I would think it would be a harmless change that would solve my problem.

PR 180deg Thermostat - Pettit Racing - RX-7,RX-8 & Rotary Performance - Racing - Engines - Rebuilds - Parts

 

It scares me that pettits is only $16.

I'll probably just go with the sard unit and have something that opens at 167 rather than 142 on the Mishimoto.

 

Our cars run better when temps are over 80 degrees (aka fully warm), trying to get it below that seems kinda backwards. A colder thermostat isn't fixing any problems, only creating. Stock thermostat starts opening at 82 degrees and with age starts to open even earlier, the way you have it setup is perfectly fine. If it ain't broke, don't fix it. When I see my temps below 80 degrees in cold weather, I change the thermostat to make it run hotter, not colder.

Also, the thermoswitch is only activating one of the fan speeds, its not a big deal and its still doing work as the coolant is already flowing.

thewird

 

My thought is that there should be a larger range between when the t-stat begins to open and when the fans start. My thermostat is OEM but relatively new, I replaced it in 2010 so I have to assume it's functioning like a new one. If the pettit thermostat opens at 180f (82 c) and my fans kick on a 185f (85 c) there would at least be about a 5-6 deg. range in there where the fans would not be on. Right now the fans are coming on before the stock t-stat is fully open which defeats the purpose of a larger more efficient radiator. At least that is what I'm thinking.

 

The Pettit thermostat doesn't sound too bad but I wonder when it starts to open. The whole point of a thermostat is to get the engine to full operating temperature as quick as possible. If the Pettit one is opening in the 70's causing it to strangle there or possibly never get over 80 degrees, then this is backwards of what you want out of a thermostat. A rad exists to keep your engine from overheating, a larger rad will do this better and faster. You don't really need to worry about any cooling until like 190-200*F. Maybe the solution to your problem would be to instead not have your fans come on so soon, although I think your current setup is perfectly fine IMO. No matter what you do, the fans are still going to be coming on similar intervals, what you would be changing is the temperature ranges.

thewird

 

From the coolant thread in the FAQ:
https://www.rx7club.com/3rd-generati...thread-571088/

7. Optimum Temps
65C (150F): too cold. According to service manual, EGR valve is non-operational below 150F, "to improve drivability when cold."
82C (180F): getting warm. Thermostat begins to open, circulating coolant through the radiator. Some coolant is still bypassing the radiator.
95C (203F): fully warm. Thermostat is fully open, not bypassing the radiator at all.
100C (212F): boiling point of pure water at atmospheric pressure.
105C (221F): getting hot. Stock ECU will activate fans to cool the car down. Fan speed will be low, or medium (if A/C is already on).
108C (226F): hot. Stock 93-95 coolant thermoswitch activates, changing fan speeds from low>> medium (or med>>high if A/C is already on) (switching to an FC thermoswitch will change this temp to 203F)
115C (240F): getting dangerous. OEM temp gauge begins to rise.
117C (243F): dangerous. boiling point of pure water with 13psi pressure cap.
121C (250F): too hot. OEM temp gauge will point to white line. Boiling point of pure water with 16psi pressure cap.
124C (256F): way too hot. Boiling point of pure water with 19psi pressure cap. Boiling point of 50/50 coolant mix with 13psi pressure cap.
127C (260F): way too hot. OEM temp gauge will point to red line.


I burned out 3 sets of fans when I used to run a FMIC as I had to power on the fans around 95*C in order to control temps. With my v-mount, I now have them set to power on around 91* for the low fan and 95* for the high fan. Things are mild here in my area of CA. The fans only engage during the hot days of summer 80*+ when in stop-n-go traffic. I rarely break 85-89* operating temps. Normal Operating temps for most cars of our era is 85-99*C. My old Mercedes would engage the fans at 99*C for reference. I'm on an OEM thermostat that shipped with my reman.

I'm not sure if that 95*C temp listed in the FAQ is accurate. My car acts like the t-stat is fully open at 85*C...


FWIW, I've been using a generic 2 1/2" NAPA thermostat in 180* temp in my Spec Miata race car. The t-stat is the same style and fitment as the OEM stat. It has proven reliable in 2 years of racing. With that t-stat and a Koyo, the Miata runs too cold. That is an odd problem to have after years of dealing with the FD's cooling system.

Hope my rambling was helpful...

 

Very helpful input. I'd like to put in an FC thermoswitch and solve this problem but I don't think I can get the original mazda plug that I had to cut off to install the pettit switch. I think I could run the pettit t-stat and not be running too cold. If anybody knows how to get the original plug that connected to an OEM mazda fan thermoswitch, please let me know.

 

What fan temperature setting are people with the SARD SST12 using on the PFC for street driving? I live in north Alabama with temps in the 90's throughout the summer. I just installed the thermostat and previously had all three settings at 86C with my old 180F thermostat. Thanks.

 

I ve also been using the sard thermostat. I also used arc

They are both 76 77 degrees celcius and my coolant is never less than 81degrees

 

given the fact that technology has upgraded in the aftermarket ECU department like for example "Adaptronic PNP" that I plan on getting; my question is:

would the need of a "Low Temp Thermostat" or the "FC Fan Switch" be irrelevant if you have an Adaptronic ECU where you can and I presume change the settings for when the fans to turn on.

My application would be for an FD going single turbo, V-Mount (current rebuild project)

if the answer to my question happens to be true (yes). then would the optimal combination for the "SWEET SPOT" in water temperature as per "The Big Fat FD3S Cooling Thread" be:

New stock OEM FD thermostat (with a small drill hole or not) to bring temps up to performance level (180*) and set the ECU to turn the fans on at (195*-205*) as to keep it away from anywhere near overheating temperatures.

also, on a side note, I already have an FC Fan Switch in my possession.

I live in Southern California and temps over here on a annual average range from,
Max: 75.4* F
Min: 53.4* F

 

Bump... I have this same question for the same ECU also. Have you figured this out yourself or can anyone else answer this?

 

It isn't an ECU issue, it's a wiring issue. Read my thread on fan control for more.

Quick answer, the ECU only has one wire going to the fan relays to bump the fan speed up one. An aftermarket ECU with multiple outputs could be configured to run the stock relays totally but you'd have to do some re-wiring, it's not plug and play.

Dale