Little background:
The car is a 91 Vert with street ported 13B-RE, GT35R, FMIC, Power FC, etc. Car is making 450rwhp @ 15psi

Every part of the coolant system is brand new: S4 Water pump and housing, sensors, Koyo N-Flo, 18" Flex-a-lite 3300cfm Extreme Fan with full shroud, Samco hoses, and multi-rib pulley kit. Running the underbelly tray and the Signal cooling panel.

The problem was that while driving the temps would climb out of control with the A/C on, and it would always be hovering in the mid 90C's even on cool days with the A/C off.

One solution would have potentially been to remove the A/C to increase the amount of air flow to the radiator a small amount, but we really wanted to keep it functional. This was also the reason for not configuring the system as a V-mount.

As a final attempt to keep the temps in check, before ditching the A/C, I spec'd out a 160F thermostat for the S4 housing. The results were incredible, the temps never climb over 87C with the A/C on and typically sit at 84-85C while driving in summer heat with the A/C off.

Needless to say I was pleased with the performance. I have added them to our website: Thermostats

 

Really don't see any overheating issue as 90C is only 194F which I would say is about normal temps if using the OE 'stat. The stat is to open in the 80.5C to 83.5C range and be fully opened at 95C.
IMHO, if the car is destined to overheat, a lower stat won't change that condition as it will only open sooner, but will not stop overheating as the temp will still continue to rise.

 

anytime you can run cooler is nice, especially with nothing more then a stat change.

 

I said mid 90C's that means 94C-96C (201F-205F) that is far too hot for my liking. That was with an 82C thermostat and every cooling mods including Redline water wetter. With the A/C on it would climb to 105C+ (221F), then turn the A/C off for it to drop back down.

All that has been cured with the 71C thermostat so obviously it was not "destined" to overheat. A lower opening thermostat allows the coolant into the radiator sooner, this allows the cooling process to happen prior to reaching the higher temps. This also allows the N-flo to function at a lower temp. The lower temp thermostat changed the entire condition.

Your opinion is noted, too bad it does not have any data to back it up.

 

If you look you will find all the data that you'll need that a lower stat will not cure an overheating problem. How could it? If the stat is fully opened at 95C and the temp still shoots up to105C and higher, why would it not climb with a lower stat? You'll need to explain that one to me as both stats are fully opened and yet you're stating that it won't rise with the lower stat, impossible.

 

This is not rocket science nor is it new territory. Not to mention that I am far too busy to be starting threads with useless/false information. I have no reason to lie about the temps.

The thermostat is rated 11C lower, temps 95C-11C=84C nothing magical just simple math.

There are numerous forum members that have found lower opening thermostat to solve there cooling issues. Here is one that installed the Mishimoto 61C thermostat. https://www.rx7club.com/20b-forum-95...-pump-1001907/

This is what prompted me to source and try out the lower temp stat for the S4 in the first place.

I understand that there are members of this forum that have the uncontollable urge to argue in every thread, so now run along and crap in someone elses thread.

 

Touchy aren't we!
Been around a long time and I certainly don't post crap and your math is flawed:
95C open climb to 105C=+10C
84C open climb to 84C=0 increase?

Yup, it certainly did do something never heard of before, constant temp no increase.

I'm done

 

Not touchy at all, however you wanting to insist that myself, David Hayes and any other member that has installed a thermostat are liars, I find ignorant and offensive.

Your abilty to read is flawed and I am not going to bash my head on a wall to teach you both reading and math.

If you think that your join date adds credibilty to your post you are hugely mistaken. Good to hear you done, since posting about something you have never tested is nothing but crap.

 

the thermostat opens earlier allowing the cooling system to do its job sooner.
All that matters is that the car is RUNNING COOLER now with nothing more then a thermostat change

all the guy did was change his thermostat and the car runs cooler across the board- why is there a need to question this he knows his car.

 

Banzai: "it works"
Turbonut: "why?"

Maybe the 'racing' stat has a larger opening, allowing more flow? At steady-state, 2 open stats with the same flow characteristics should equlibrate the engine/cooling system at the same temp, regardless of what temp they first opened at. This is a little concept called enegy balance. If the only thing that changed is the stat, and the engine/cooling system now equlibrates at much lower temp, the flow must have changed as well. Since it's pretty tough to measure coolant flow, it would be interesting to see deltaT across the rad with the different t-stats.

 

^ bingo, we have a winner.

Just measured the openings, they are the same about 29mm, however the racing thermostat has a different plunger design. The racing version is flat, where as the standard thermostat is about 4mm thick, impeding coolant flow considerably.

So earlier opening and increased flow equates to much lower coolant temps across the board.

Racing thermostat



Standard

 

OE thermostats never run the engine at their rated temperature, figured this was common knowledge. while the plunger opening is smaller on the OEM thermostat the intake is larger. on the "racing" thermostat the intake is smaller but the plunger area is larger. i bet the flow characteristics of both are actually very similar.

 

well I ordered one, will see how it works for me

 

I saw your order, do you have the S5 water pump assembly?

 

I believe so, using a S5 thermostat housing

 

No problem, just making sure the correct one was ordered since the S4 is 54mm and comes with a gasket and the S5/FD is 52mm and comes with an o-ring.

 

swapping out housings soon so plan on changing the stat at the same time

or I might get anxious and swap it out earlier. I also have AC, its not working right now but I have it, and realize how it greatly changes things when it IS running

 

I think you may have the thermostats confused. Intakes are the same size, the pluger diameter is the same, the opening depth is much smaller due to plunger on the standard (as seen above). Racing flows more.

Racing thermostat on right

 

You are swapping it for another S5 with the 3 bolt thermostat housing?

 

yes, aluminum s5 aftermarket one and using a -20 hose

 

The lower temperature isn't the winning factor in this.

It's the flow of the new t-stat.

If the flow was the same between the two, then lower temp opening only adds time before you over heat again. If a system cannot remove all the heat, then opening it earlier will do nothing but take it a little longer to get to the critical point again.

Increasing flow can also be detrimental dependent on the cooling system make up.
Cooling is all about the time the fluid is in contact with the engine/radiator and how much heat it can take or remove.

Increasing flow speeds up the coolant so it will have less time to remove heat from the engine block and less time to release it through the radiator.

This can cause false results when only monitoring coolant temps. The engine could be unable to give out all it's heat to the fast coolant. This is why removing a thermostat completely is a bad idea.

The larger core radiator will help remove heat by it's size and possible flow stagnation. Your larger flow T-stat can better utilize the radiator now.

This isn't to say your T-Stat that you're selling will not solve issues. It' just that it is one piece in a larger cooling puzzle.

 

hm, ill certainly have to keep an eye on my temps after i finish my setup.
basically, im copying yalls build, unintentionally of course
do you think that adding AI, you could pull more power out of the engine with more boost?

Lloyd

 

The lower temps are the winning factor, for that matter it was the entire goal. I never said it would solve everyones problems only that it solved ours. It is pretty obvious that we have a very well built cooling system covering all the bases. The N-flo keeps the coolant in the radiator longer allowing it to see more ambient temps, the issue seems to be that there was not enough flow to the radiator due to the restrictive thermostat opening at a much higher temp..

Lloyd, Yes we could easily add water/meth and see 500+whp, but really that was not the goal for the car. 450whp is a lot for a vert and seeing that I already have a 600+whp 20B FD, it really was not necessary to build another car that just spins the tires all the time.

 

nice ull be seeing a order from me monday

 

This seems logical but is in fact wrong.

Picture each water molecule as a dump truck, as it travels through the engine, it loads up on heat which it dumps in the radiator.
Now increase the flow and yes, it'll absorb and disperse less heat per cycle but you've also increased the number of cycles per "x" amount of time.
The net result is the same.

The trick with flow rate is to make sure the molecule/dumptruck is still capable of absorbing heat as it leaves the block, too slow and it's not absorbing through the last part of the journey through the block (it's boiling/the truck is already full).

If the big advantage of the "racing" stat is it's increased flow rate, then the early opening temp is actually irrelevant, the same sized part that opened at the factory spec should work just as well (and improve heater performance, if you care).