8 replies to this topic

[Alberto]

So I have a blog where I post up lessons learned and other racing stuff.  I like to write and my wife doesn't care much to listen to me talk about racing so the blog is an outlet for me.  Lately, I've been catching up on write-ups and just posted a rather long couple of posts on thermostats that I wanted to share and get some input on.  Some newbies like me find my blog useful but I also use it to document things so I don't forget.    I'm getting old... 

 

You experienced guys will probably not derive much benefit from this but the newbies probably will since this questions comes up regularly at the track during the summers.

First blog post is on the topic of my testing results running different temperature thermostats in race conditions.  I compared the stock 192* vs 180* vs 160*
http://blog.miatarac...spec-miata.html


Second post is just comparing an OE Mazda thermostat to the NAPA thermostats.  Some minor differences between the two but nothing earth shattering supporting that the OE Mazda is a superior unit as some claim on forums.
http://blog.miatarac...em-vs-napa.html
 

 

Hopefully the info is accurate and helpful.  If anyone has any knowledge to share, please do so I and others like me can learn.

 

Thanks.

[Ken SM94]

Nice work, Alberto.  Your article confirmed what I thought I knew...  :^)

[CARacer]

My recent thermostat experience: I had a new thermostat put in in June. On the way to a race in November (I drive the SM to the track), the temp fell almost all the way down on the highway (I still just have the stock temp gauge. Fixing that very soon). At the track it took forever to get up to temp, but once it did everything seemed normal; no overheating, water level fine, no leaks. Seemed like the thermostat was stuck open.

 

I replaced the thermostat before the next event, but the one I pulled out seems fine in the stovetop test. Car seems normal again with the new thermostat. I did not stovetop test the new thermostat before putting it in, which the scientist in me is upset about.

 

The new thermostat I got at O'Reilly's had two valves in it: http://www.oreillyau...ord=thermostats 

What is the small one? Air relief valve?

[Alberto]

^yep

 

small one is referred to a a jiggle pin by the unscientific crowd - cuz it jiggles around  

so nice having a real water temp gauge.  pretty easy to install too.

 

 

thanks Ken

[SaulSpeedwell]

My experience/thoughts/facts/opinions:

1.  FACT/EXPERIENCE:  Where you install your H20 gauge sending unit absolutely matters.  Put it where the ECU's sending unit is if you want to measure your apples the same way the ECU measures its apples.  Putting a sending unit in a heater hose in line-of-sight with the header will give you BOGUS readings.  If you have OBD-2, compare OBD-2 data to your sending unit numbers to convince yourself.  Wrapping the sender in gold foil from Pegasus will make a dramatic difference. 

 

2.  FACT/OPINION (subject to potential memory loss):  The Miata EFI does not *proportionally* alter its WOT control strategy (A/F ratio or timing) based on H20 temp. Other than temporary modes we don't care about like cold start and limphome modes, the Miata ECU breaks the world up into "STILL TOO COLD", "WARMED UP - OK", and "TOO DAMN HOT" (i.e. timing retard).  For most people, the car will tune easiest and run best thinking it is "WARMED UP" - generally north of ~165F and south of ~205F.  In contrast, the Miata EFI *does* proportionally alter it's A/F ratio based on Intake Air Temp.  Hotter IAT (delta from actual ambient) runs leaner, colder IAT (delta from actual ambient) runs richer.  

 

3.  EXPERIENCE:  I also found the 180F thermostats to be ideal for the greatest number of environmental conditions (in Ohio, anyway), on both 1.6 and '99 cars.  I ran the Stant premium units.  The NAPA units were occasionally failing (physically breaking).  The "stock" 192/195F units left me bumping into timing retard more often than the 180F Stants - possibly nothing to do with the thermostat setpoint as much as the equivalent orifice (flow) of the Stant versus the stocker.  Or maybe the nominal setpoints weren't quite what the actual setpoints were.  In any case, timing retard will leave you 3-4 HP weak and you want no part of that if you can help it.

 

4.  EXPERIENCE:  The "coldest" I could ever make the car run was with a gutted thermostat (orifice plate).  But this leaves you running too cool in many situations, and thus is only recommended for days where you are overheating and have tried everything else, or if you are fairly sure you are going to be drafting someone's hot dirty air the whole race. 

 

This isn't gospel, just my experience and opinions, backed up with hundreds of dyno runs, albeit a few years ago ....

[ECOBRAP]

First blog post is on the topic of my testing results running different temperature thermostats in race conditions.  I compared the stock 192* vs 180* vs 160*

http://blog.miatarac...spec-miata.html

 

I am trying to figure out ideal water temperatures for this year and ran into this thread. Thanks for the article, very useful 

 

Last year I would see 175 degrees in the middle of a race (except for The Sahara Desert Thunderhill) by using the 160 degree thermostat. From the article, it would appear that this is good because I never ran into timing issues, but also bad because the engine was not running at max efficiency?

 

Do you have any recommendations on this tradeoff? Is there a difference in ideal temps for 1.6, 1.8, 99, VVT?

 

I will be trying the 180 degree thermostat this weekend to get temps up to 195.

[RazerX]

In August at Thill, you will want that 160...

[SaulSpeedwell]

Seeing my old post above, it is my true experience and still what I would do for my own car in Ohio.  However - based on the "TapeGate" thread and talking to frontrunner friends, they pinky-swear they have had reliability problems with thermostats, and prefer to run tape.

 

If you are in the desert and running too hot, try the gutted thermostat plate and see how cold you can run.  The more you seal up the radiatior perimeter - meaning, the more air you force THROUGH the rad instead of AROUND the rad - the cooler you can run if you don't have a t-stat.

 

At risk of resurrecting a dead horse, a wide open bumper cover inlet WILL flow more than one choked down with "chicken wire".  If you slide all that chicken wire over and up until it all touches each other in a solid sheet, it isn't much different than a strip of tape, is it?  That's why I don't like chicken wire filling the bumper cover inlet, versus having it "hovering" in front of the radiator.

[Tom Sager]

I am trying to figure out ideal water temperatures for this year and ran into this thread. Thanks for the article, very useful 

 

Last year I would see 175 degrees in the middle of a race (except for The Sahara Desert Thunderhill) by using the 160 degree thermostat. From the article, it would appear that this is good because I never ran into timing issues, but also bad because the engine was not running at max efficiency?

 

Do you have any recommendations on this tradeoff? Is there a difference in ideal temps for 1.6, 1.8, 99, VVT?

 

I will be trying the 180 degree thermostat this weekend to get temps up to 195.

Lots of good info in this thread.  My experience with '94/'95 is that they can and will run better cooler than a '99.  The much less sophisticated ECU reaches best map at 160 degrees as I recall.  My '95 seems to run in a very favorable temp range with a 160 degree thermostat or with no thermostat in a wide range of weather.