Install report: SPD 170 deg thermostat

[importfighter01]

Installed the SPD Performance 170 deg thermostat today. Happy to report not a hard job at all…

Tools:

Just have a magnet handy for when the 2 bolts for the thermostat housing get loose. Having 1/4” ratchet set (vs 3/8) with a 4” and 6” extension is perfect too. The 2 bolts are 8mm and with tight clearance the small 1/4in socket worked well.



Coolant refill:

Refill after burping () was 1.75 gal of 50/50 mix coolant.

Highest temps observed on factory 198 deg thermostat:

Engine - 201
Transmission - 206

Highest temps observed on SPD 170 deg thermostat:

Engine - 183
Transmission - 177

The ECU goes into closed loop mode way earlier than 170 deg (I monitored with the FPP box to confirm) so no issues with running a lil cooler ECU wise. I have bypassed the electronic thermostat for the transmission cooler so coolant is flowing through it at all times, so instead of only cooling the trans at 195 deg it can now take advantage of the colder coolant temps the SPD performance thermostat allows. For my transmission it shifts way better when it’s cooler vs hotter so the cooler temps for the trans are what I was mostly seeking (almost 30 deg temp reduction is a win for me).

Random related thoughts:

The fact that the SPD thermostat keeps engine coolant temps at mid 170s to low 180’s (with A/C on and full temp idle) tells me that’s the lowest temp the radiator can generate based on its own inherent efficiency. If I upgraded to the Mishimoto unit thereby increasing radiator effecincy I’m sure I could keep things in the low 170’s consistently. Plus getting an aluminum transmission fluid pan vs the factory plastic one would prob allow the trans fluid to pull heat out of the coolant and transfer it out via the transmission more too.

I was VERY surprised to see the Ford thermostat using a plastic plunger too. Never seen that in thermostat materials in the past.

Mileage impact update: Some had wondered what impact this thermostat would have on MPG.The last thousand miles have shown no change in MPG. I’m still getting 19mpg avg with a city / highway driving mix.

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[importfighter01]

are you concerned about poorer fuel mileage?

Not at all, meaning if I do see a 1-2 mpg drop I’m good with that.

 

[Frenchy]

As happy as you are with the temp results be aware that the PCM needs to be programmed to be ok with that temperature range. If you dont it may add more fuel to try and warm it up. Even though it is going into close loop before hand you can still run into the issue

 

[JasonTremor]

As happy as you are with the temp results be aware that the PCM needs to be programmed to be ok with that temperature range. If you dont it may add more fuel to try and warm it up. Even though it is going into close loop before hand you can still run into the issue

I second this.

Transient fuel is one of the key fueling parameters coming to mind that is coolant temp based. 190 degrees is generally when the fuel adders for warmup are no longer a factor.

 

[BassRanger]

Colder does not = better. The T-stat is there to warm the engine up. A warmer engine is more efficient than a colder one. What you want is a cold air and a hot combustion chamber. Running the engine at a lower temp than it was designed for will not benefit you anything.

 

[Blmpkn]

The hotter a motor is, the more efficient it is. Efficiency in this case also meaning powerful.

The best thermostat for a motor is in 99% of cases the factory one.

With the temps you posted before/after I really see no logical improvement.

Especially the trans temp. You went from smack dab in the middle of optimal atf temperature to the very low end of acceptable...

 

[importfighter01]

Agreed that factory t-stat is just fine. This thread is not to say “colder is better” just that the install is easy and the part works as desired.

I’m ok with burning more fuel to run colder.

My particular transmission has the 3-4 flair (despite multiple trans relearn cycles) when temps get above 180. Anything above that temp the trans strategy keeps a higher line pressure and zero flair, so my primary goal was lower trans fluid temps to keep out of that temp range and mission accomplished there.

 

[BassRanger]

If you are having a shift flare, why not take the truck to get it fixed? Putting in a lower temperature Tstat seems like a pretty arbitrary and likely temporary fix to a rather serious issue. There's no way you are going to be able to maintain those temperatures as summer rolls around.

 

[importfighter01]

There is no fix unfortunately. If you search Mustang 550 and F-150 owner experiences with the 10R80 many reports of flairs and nothing cures them. However mid-2020 Ford did a torque converter design change and owners after that report much better behavior. Some reports I read have owners driving with it for years. It doesn’t appear to negatively affect the transmission, just super annoying. A quirk if you will…

 

[Doc]

Don’t need new thermostats…

 

[dtech]

Well at least it's not like doing it on an audi 6 cyl . As I do shorter trips now <10 miles, I want the engine to quickly reach operating temp to burn off any contaniments, esp fuel.

 

[importfighter01]

Don’t need new thermostats…

Agreed not “needed”, just reporting for future forum searches.

 

[Gsxrdoug]

At least if we need to replace the factory one for the same we know how to do it now. Thank you.

 

[P. A. Schilke]

Installed the SPD Performance 170 deg thermostat today. Happy to report not a hard job at all…

Tools:

Just have a magnet handy for when the 2 bolts for the thermostat housing get loose. Having 1/4” ratchet set (vs 3/8) with a 4” and 6” extension is perfect too. The 2 bolts are 8mm and with tight clearance the small 1/4in socket worked well.



Coolant refill:

Refill after burping () was 1.75 gal of 50/50 mix coolant.

Highest temps observed on factory 198 deg thermostat:

Engine - 201
Transmission - 206

Highest temps observed on SPD 170 deg thermostat:

Engine - 183
Transmission - 177

The ECU goes into closed loop mode way earlier than 170 deg (I monitored with the FPP box to confirm) so no issues with running a lil cooler ECU wise. I have bypassed the electronic thermostat for the transmission cooler so coolant is flowing through it at all times, so instead of only cooling the trans at 195 deg it can now take advantage of the colder coolant temps the SPD performance thermostat allows. For my transmission it shifts way better when it’s cooler vs hotter so the cooler temps for the trans are what I was mostly seeking (almost 30 deg temp reduction is a win for me).

Random related thoughts:

The fact that the SPD thermostat keeps engine coolant temps at mid 170s to low 180’s (with A/C on and full temp idle) tells me that’s the lowest temp the radiator can generate based on its own inherent efficiency. If I upgraded to the Mishimoto unit thereby increasing radiator effecincy I’m sure I could keep things in the low 170’s consistently. Plus getting an aluminum transmission fluid pan vs the factory plastic one would prob allow the trans fluid to pull heat out of the coolant and transfer it out via the transmission more too.

I was VERY surprised to see the Ford thermostat using a plastic plunger too. Never seen that in thermostat materials in the past.

Hi Folks,

Ford chose a thermostat operating range for a reason and there is a ton of testing behind this choice. Changing to a 170°F thermostat is not a change I would make nor recommend to any forum members... I view this as a move into the unknown with unknown consequences that may occur... Installers beware...

Would not make such a change without factory recommendation.

best,
Phil

 

[Doc]

Hi Folks,

Ford chose a thermostat operating range for a reason and there is a ton of testing behind this choice. Changing to a 170°F thermostat is not a change I would make nor recommend to any forum members... I view this as a move into the unknown with unknown consequences that may occur... Installers beware...

Would not make such a change without factory recommendation.

best,
Phil

Hear Hear …..

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