MazdaSpeed B-Spec. Low Temp thermostat installed!

[TheMAN]

I just installed the MazdaSpeed low temp thermostat yesterday while I was doing my timing belt... this thermostat is designed to reduce the engine operating temperature so that it will less likely be heat soaked during hard driving while also being emissions legal (in Japan). This thermostat is very expensive (overpriced), it retails for 80 bucks in Japan!

The stock thermostat starts to open at 82 degrees celcius, while the ms one starts to open at 68 degrees celcius... a difference of 14 degrees!

The thermostat I installed was obviously QBJ1-15-171 since I have the FS engine. It is compatible with the FS, FP, K series, and RF diesel engines (both turbo and non-turbo). There's another thermostat MazdaSpeed sells that is compatible (part number QNB1-15-171, it is a bit cheaper... by 10 bucks) with the B series engines (they do not recommend using it with the B3 engine since it doesn't make all that much heat to begin with, so you'll end up overcooling it!), Z5, ZM, and ZL engines.

After I installed it, I did some data logging through the OBD-II port to see what the coolant temps are now at.... ambient temperature is about 35 degrees celcius today... the data logging starts from cold starting the engine and waiting for it to be in the, "operating temperature" range (temp gauge at middle), the coolant sensor is reading at a steady 75 degrees celcius even with some driving in the first 10 minutes of start up. This shows the thermostat is just at the threshold point (it's regulating the coolant temp to that level) while the coolant sensor is seeing 75 degrees at the hottest point of the cooling system. After waiting for the engine to be truely warmed up (through some highway cruising), the temperature peaks out to about 85 degrees at idle (with A/C on). Driving around streets, the temperature stays steady between 80 to 81 degrees. Highway cruising between 65-75mph results in a steady 83 degrees. Hard "spirited" driving bumps the coolant temperatures up to 87 degrees. Not bad!

So what is the real result? The engine bogs less now in the "spring" 95 degree fahrenheit texas heat, its making power at the upper RPM ranges like it should, and the engine does *not* run "too cold".

Compared with before (back when the car was still pretty stock):
-about 25 degrees celcius ambient temperature (guessing)
-Intake temp sensor reading about 40 degrees celcius
-50mph crusing... about 95 degrees celcius
-sitting at idle at the light.... about 100 degrees celcius (for you people still in the stone ages, that's 212 degrees fahrenheit, which is boiling at sea level... but that's not boiling in the radiator since its pressurized to 16psi)
So while the engine wasn't overheating, it was already heat soaking and reducing optimal power. This will get worse when you add more load to the cooling system obviously, especially a turbo!

As for extra info, using 93 octane gas and ZFR6F-11 extended reach plugs (just installed), the timing advance peaks out at 63.5 degrees (it would be less with lower octane gas from what I saw a few years ago when I last data logged)... and with my HKS intake and FS-ZE parts, the MAF reading peaks out at about 82 grams per second airflow. The intake temp averages about 60 degrees celcius since 1) it's not 100% accurate, 2) the intake sits in the engine bay and is not a "cold air intake"


So was it worth paying so much money for this thermostat? Hell yeah! Is it overpriced? Of course it is! But this thermostat has proven that the stock radiator can still adequately cool in hot weather which makes this thermostat a "cheap" cooling system upgrade (yeah a $400 radiator is not cheap and most people don't need it).

Hopefully this data will discern any skeptics about installing a lower temperature thermostat (that's Mazda approved) increasing emissions, reducing efficiency, engine running richer (in fact it doesn't, the fuel trim level is about the same as before), etc.

But this thread is worthless without pics right?

 

[TheMAN]

Here's a comparison between the stock thermostat and the ms one... you can see that there's more coils in the ms thermostat's springs, which means it will close more gradually than the stock one.

stock one is at the left, and ms one is at the right

 

[TheMAN]

on the ms thermostat, there are 2 notches on the sealing rubber that when the themostat is opened slightly, coolant flow will be increased, thus making the operating temperature lower.

 

[Chilledboost]

where did you get it? im very intrested in one

 

[Glowspeedp5]

Here's a comparison between the stock thermostat and the ms one... you can see that there's more coils in the ms thermostat's springs, which means it will close more gradually than the stock one.

stock one is at the left, and ms one is at the right

Where did you get it from.....The dealer you work for>

 

[TheMAN]

straight from japan

 

[Puckpimp71]

Nice to know, especially since FL is juat as bad as Texas. Since the the car's not running much richer, do you think this would worth it for us MSPers?

 

[Glowspeedp5]

straight from japan

You can read Japenes Grasshopper......

 

[Glowspeedp5]

straight from japan

With old V8's I ran thermstat list. Can you do this with the fs motor.

I also did this with My BP powered escort GT...

 

[TheMAN]

Nice to know, especially since FL is juat as bad as Texas. Since the the car's not running much richer, do you think this would worth it for us MSPers?

of course! if it worked for me, it'll work for you!

 

[TheMAN]

With old V8's I ran thermstat list. Can you do this with the fs motor.

I also did this with My BP powered escort GT...

you what?

 

[Puckpimp71]

Now what's the easy to order this???

 

[TheMAN]

I can get more where they came from, but like I said, they ain't cheap! PM me if you're interested

 

[Glowspeedp5]

you what?

Sorry,

I ran the car with no thermstat........

Also how long did it take you to get this......

 

[ChopstickHero]

Nice write up Edwin.

Would this have similar results in a MSP with a smaller radiator? PM me some info, i'm interested in getting one.

 

[P-Funk!]

Nah. Better overall results from a thermobloker[tm] keeping the intake manifold cooler/less heat soak.

The engine is essentially a thermo-air pump. It is the high heat in the cylinder (as high as design can allow it with cuurent metalurgy technology) that meets cool air that produces power. The difference in temp (expansion) between cool/ambient and fire-heated pushes the piston.

Higher temps are how better combustion reduces NOx output.

Now, heat is the enemy of durability. Over the long run a cooler engine goes through less extreme heat cycles (metal fatigue).
So.
Cooler thermostat is better (maginally) for durability - but does not contribute to improved performance.

(I do jet fighter propulsion engineering with a Masters... But the principles apply to reciprocating engines as well). I am confident an SAE engine designer would agree.

I plan to keep the thermostat as designed.

 

[TheMAN]

Sorry,

I ran the car with no thermstat........

Also how long did it take you to get this......

it is stupid to run the car without a thermostat... your engine will be overcooled leading to less efficiency and increased wear, or the other possibility is it won't get cooled well enough because the coolant flows too fast in the system for it to have time to heat exchange at the radiator and heater core

 

[TheMAN]

Nah. Better overall results from a thermobloker[tm] keeping the intake manifold cooler/less heat soak.

The engine is essentially a thermo-air pump. It is the high heat in the cylinder (as high as design can allow it with cuurent metalurgy technology) that meets cool air that produces power. The difference in temp (expansion) between cool/ambient and fire-heated pushes the piston.

Higher temps are how better combustion reduces NOx output.

Now, heat is the enemy of durability. Over the long run a cooler engine goes through less extreme heat cycles (metal fatigue).
So.
Cooler thermostat is better (maginally) for durability - but does not contribute to improved performance.

(I do jet fighter propulsion engineering with a Masters... But the principles apply to reciprocating engines as well). I am confident an SAE engine designer would agree.

I plan to keep the thermostat as designed.

high combustion temperatures is what *produces* NOx... hence why EGR valves exist, so that they can help lower combustion temperatures

while all engines are the "same", they're all a bit different as far as combustion efficiency (which all relates to piston dwell time, cam timing, cylinder head flow, etc), coolant routing and cooling system performance goes (I'm talking about all the stock components)... so my point is, on THIS particular engine with a STOCK radiator, it DID increase efficiency... in the past week its been over 104 here and the car does NOT bog like it would before... sure its running in the extreme heat, but at least its running a bit cooler... I've also noticed I've been getting very high MPGs even in this weather compared to before.... if that's not "proof" that it does improve efficiency for THIS engine, I don't know what is

look, this thermostat isn't no crackshot halfassed "engineered" part... it was designed AND produced by MAZDA themselves... it's a properly engineered part meant FOR the engine, tested to conform to japanese emissions standards, and tested for optimal engine efficnecy.... if it was something that is bad/not street legal, they wouldn't sell it and even if it's a "good" part that's not meant for the street, they would've labeled it so to begin with!

this thermostat was released in 2001, two years after mazda bought out the mazdaspeed company.... so you can't say it's not a mazda produced/engineered part... also because mazda has bought them out, almost all of the "race only" mazdaspeed parts have been discontinued due to lack of interest, so saying this part maybe a "race only part" doesn't hold either.... saying mazdaspeed motorsports here in the US selling race parts doesn't hold either because they do NOT sell japanese mazdaspeed parts anymore, and they don't sell mazdaspeed branded race parts... they ONLY sell stock parts, non-branded race parts, race parts from select companies (such as AWR), and mazdaspeed USA parts

 

[Dimitrios]

(I do jet fighter propulsion engineering with a Masters... But the principles apply to reciprocating engines as well). I am confident an SAE engine designer would agree.

...and it shows! Kudos!

 

[Gaboost]

If one is available for the bp engine in my msm(I'm guessing the other part # will fit), would you recommend it? It seems to make a big difference from the way you are describing it.