I know Mugen and Spoon make a lower temp thermostat and you need a fan temp switch to match.

What I don't know are the differences between the 2 and are there any other manufacturers of lower temp thermostats out there? The Stant Super Stat doesn't make one.

Has anyone compared the 2? Does one have a larger &/or wider opening than the other? How does the opening size compare to the stock thermo?

Are either of these anywhere near a temp that the stock ecu will decide the car is not fully warmed up and try to run too rich?

What's different about our Tstat that won't let you use another brand? (obviously I haven't taken mine out yet or seen anyone else's)

Where's the best place to buy?

 

The Mugen tstat, at least (and probably Spoon), is identical to stock except it opens at a lower temp. It's not strictly necessary to use a tswitch with the tstat.

As for how the ECU reacts, I don't know if any rigorous testing (e.g. with an OBD2 tool and wideband O2 sensor) has been done.

 

Since the two are identical except for temp then obviously the cheaper is the better buy. Who sells them the cheapest?

I understand that the switch might not be totally neccesary, but since I live in Dallas I want as much cooling as is possible. If the fan kicks on earlier I have longer I can run hard in hot weather.

Ultimately you will run into the limits of the efficiencies of the system so I have made sure ALL the air flows thru the radiator to help extend the stock limits. Time will tell if I would be better served to add a bigger radiator also.

 

I think the Spoon setup is calibrated a little colder, and is slightly cheaper. Several board sponsors sell Spoon stuff.

Also consider the radiator cap, which is what will really extend how long you can run hard (by increasing the pressure at which overflow occurs).

 

There are pros and cons to a higher pressure radiator cap.

I personally believe it is a band-aid that needs to be applied at the end of your quest instead of at the beginning.

The higher pressure should extract more heat from the engine since it will not allow boiling at the hot spots as quickly and it raises the boiling temp, but you will definitely blow hoses more often and sooner and I would rather control the heat so that I don't need the higher pressure cap.

If you find the limits of your stock system and maximize it's potential first then if you need a little help get a cap, but it you are still far from where you need to be then upgrade either in the shroud area (control the air flow better) or get a bigger radiator. Pushing any system to the ragged edge makes for much worse failures.

My car has not come close to the limits yet. But I haven't had it long and I haven't had a track day when temps are above 90 yet. I have 3 scheduled in the next 2 months so I would rather be safe.

I have worked on the air flow to ensure that all the air goes thru the radiator. I have never seen a car with so many and so large of holes to allow the air to go around the radiator than the S2K. If overheating is not an issue in hot climes or on the track then I will be very surprised.

In the Miata world people have seen 10 C drop in temps just by more effective use of shrouding so I started there.

Now it 's time for a thermostat. I just want to make sure I get the best (operational) Tstat and of course I want it for the cheapest price.

The reason I asked which vendors sold it for the best price is I have had trouble searching and comparing. It seems that not many vendors carry them and usually they are usually buried deep in their product list so I am afraid I have missed someone. I also haven't had much experience with S2K vendors so don't know who really delivers and who overcharges and still doesn't deliver. I am open to any suggestions and help.

 

David b,

I'd be interested if you would share some of your air flow modifications, especially pictures and any measured results.

I bought the Mugen radiator cap and thermostat from King Motorsports, and the Spoon thermoswitch (not sure where I bought that, maybe Import Development?). I've had the rad cap and tstat on for 17 months, and the tswitch on for 10 months, with no problems. I recently did two track days at Thunderhill in 90

 

Let's be clear:
When running hard on a hot day, the tstat will be fully open and the fan will run, just as with the stock system. Therefore, the tstat and tswitch don't increase the ultimate cooling capacity of the system. Rather, they lower the quiescent operating temp of the coolant when the engine load is relatively light.

Similarly, the high-pressure rad cap does not inherently change the cooling capability of the system. However, it allows the coolant to reach a higher pressure (temperature) without boiling over, and can therefore be said to increase the operating range of the system (assuming, as you pointed out, that all the hoses hold!).

Things that can change the cooling capability of the system (as measured by the steady-state coolant temp under heavy engine load, and at a given ambient temp):
- Coolant type/mixture
- Radiator size
- Air flow

Known fact: the 3rd bar lights at about 120F; the 4th bar lights at about 220F.

Some personal experiences:
- I ran a track day in 90+ F weather with the stock system and never saw 4 bars.
- I ran a track day in ~110 F weather with the Mugen tstat and rad cap and never saw 4 bars. At the same event, though, C3's car saw 4 bars and his stock system boiled over, but only after two consecutive 30-minute track sessions.
- Overall, I've never seen 4 bars!

So the stock system's pretty good, even at the track, but "beefing it up" a bit won't hurt.

 

I agree, a hot track day will have you running with the stat open and fan going but the system seems to be adequate. I have had a number of sessions with the ambient over 105F without problem.

The two situations that seems to prompt higher coolant temps are an airflow restriction (dense grill or obstruction in the flow), or inadequate cool down laps between heavy running and gridding the car for more laps.

I have the tstat, switch, cap mods and would like a slightly larger radiator capacity but since I have not seen over three bars it is hard to see the payoff for that many dollars.

 

David - I would also like to hear more about the modifications that you made to the shrouding around your radiator.

 

I will post some pics soon. They are in the camera, just haven't downloaded them.

I don't have any test data as I just plugged the holes as I noticed them.

It is nothing great, I just sealed all the holes I could find with foam. It doesn't take a fancy shroud or exotic materials to direct the air flow. Air flows thru the place of least resistance, I just made sure it was easier to go THRU the radiator than around it.

Place a screen door in a flowing stream (which in this analogy is like your radiator) and you will see what I mean. It will build up a big front wave and very little water will flow thru the screen. It will all go around. Even if you direct the flow of water so that there is only an inch or so of space around the screen the majority of the water will still flow around the screen door. Keep in mind a screen door flows much better than a radiator.

One of the guys on the Miata list made a shroud out of cardboard and dropped 10C on the track.

On either side of the radiator are 2 great big open areas. They are of a uniform size so they are easy. I used a piece of foam about 1.5" wide and placed it firmly in the gap. It looks factory.

At the top right and left are irregular openings which took just stuffing the foam in them. This doesn't look factory, but unless you are looking for it you don't even see it.

At the bottom of the radiator is a thin opening that allows the air to flow under the rediator thru what looks to be amounting channel. I filled this with 1/2" strips of foam. You can't even see this when it is installed.

Since I added the AEM CAI I have no need to allow air to flow over the top of the radiator so I have ordered a Coastal Metals Front Engine Bay Accessory to further control the flow. I have ordered it without the cut out that directs the flow to the stock air box opening. I have also ordered it un-powdercoated and will be custom coating it to match my accent color so it should look good when you open the hood.

Were you aware there is a great big sealed compartment behind the front wheels and in front of the doors? (nice place for an amp) If I could find a nice looking vent you could vent the underhood air out the side like the old 60's Ferraris or the vettes. That would give you a lower pressure area behind the radiator which would make you flow even more air!

How do I post pics on this list?