Any reason to get 180* t-stat over a stock t-stat for PI headswap?

5spd GT · May 17, 2007

Is there any actual 'con' to getting the stock replacement thermostat (195?) over a 180* t-stat when I do my PI headswap.

10.4-10.5:1 compression.

02 heads, intake, cam.

Would a stock one be fine? Just looking for a 'reason' to get the 180*?

WillDuhhBeast · May 17, 2007

Well.. I bought a 180 thermostat just so I could have a new mod. That was my reason. As far as "needing" it with the swap, thats a definite no. Some are leary of it.. I never had a single problem when I was bolted on.

'01 Steed · May 17, 2007

180 is fine. Stay away from 160's.

If you don't command the fan to come on at a lower temp, changing the t/stat isn't going to do much for you. It may take a little bit longer to warm up, but once it's hot, it's hot. So you have to turn the fans on sooner to keep the temps down.

160 is too low. You'll wear the engine out and foul plugs.

5spd GT · May 18, 2007

So a new stock replacement will be fine, even with the increased compression (pressure/heat).

RandyStinchcomb · May 19, 2007

5spd GT said:
So a new stock replacement will be fine, even with the increased compression (pressure/heat).

sure it will be fine but if your going to-go wth a new 'stat, just get the 180* from Ford, part # is XL3Z-8575-AA and is only @$10.00 which is @ the same price of the 197* stocker

'01 Steed · May 19, 2007

Yep, go with the 180*

5spd GT · May 19, 2007

Sounds good!

What advantage does it have?

the98stang · May 20, 2007

5spd GT said:
Sounds good!

What advantage does it have?

No advantages, really. Your car will probably be slower. The PCM and engine are designed to run the best at normal operating temperature.

'01 Steed · May 20, 2007

the98stang said:
No advantages, really. Your car will probably be slower. The PCM and engine are designed to run the best at normal operating temperature.

That's simply not true. The engines burn cleaner at the higher temps, but performance is best at lower temps. Cooler is always better for performance.

the98stang · May 20, 2007

'01 Steed said:
That's simply not true. The engines burn cleaner at the higher temps, but performance is best at lower temps. Cooler is always better for performance.

This is true for older, non-fuel injected, cars. The PCM is calibrated to work best at normal operating temperatures. When you change the T-stat, you are tricking the computer.

Kilgore Trout · May 20, 2007

the98stang said:
No advantages, really. Your car will probably be slower. The PCM and engine are designed to run the best at normal operating temperature.

+1

WillDuhhBeast · May 20, 2007

It's not noticably slower at all. I don't understand why some people frown upon this. It didnt even feel like it took longer to warm up. Anyway, if you don't have your fans calibrated to turn on sooner, you'll practicablly be running about the same anyway.

Kilgore Trout · May 20, 2007

Well, if I had to change the thermo anyways I would prob put a 180 in there. But I would not change it just to be changing it... I would not go lower than 180.

the98stang · May 20, 2007

WillDuhhBeast said:
I don't understand why some people frown upon this.

Because the car is designed to run best at 197^, not 180

We have fuel injected cars. The PCM controls way more than you think.

5spd GT · May 20, 2007

I'm kind of on the lines of thinking if it isn't broke don't fix it, so I may just go with a stocker.

steveb24 · May 20, 2007

yea but when changing the thermostat you are now changing your "normal" operating temp. The temp guage will still read in the same "normal" location as always, when the car is fully warmed up, and the computer will read "normal" now at 180*, just in reality your acctually running cooler. no tricks, no problems. theres no electrical connections to the t-stat itself, so why would it change anything?? as far as the pcm is concerned, it dont make a darn diff, so slower, no way! just retune the fans and dont go too cold because it even the 12* difference makes it take longer to warm up completely.. which is when the car runs its "new" best.

the98stang · May 21, 2007

steveb24 said:
yea but when changing the thermostat you are now changing your "normal" operating temp. The temp guage will still read in the same "normal" location as always, when the car is fully warmed up, and the computer will read "normal" now at 180*, just in reality your acctually running cooler. no tricks, no problems. theres no electrical connections to the t-stat itself, so why would it change anything?? as far as the pcm is concerned, it dont make a darn diff, so slower, no way! just retune the fans and dont go too cold because it even the 12* difference makes it take longer to warm up completely.. which is when the car runs its "new" best.

Have you ever heard off the coolant temperature sensor? I'm pretty sure that sends signals to the PCM . You are NOT changing the "normal" operating temp buy using the 180^ T-stat. "Normal" for the computer is 197. If you change that, it won't run at optimum performance. Period.

'01 Steed · May 21, 2007

the98stang said:
This is true for older, non-fuel injected, cars. The PCM is calibrated to work best at normal operating temperatures. When you change the T-stat, you are tricking the computer.

The PCM will do what it does based on engine temp. It adds and pulls spark based on coolant and air charge temps. We can consider air charge temps to be a constant in this context. The cooler the engine coolant temp, the more spark your PCM will add, to the tune of (no pun intended) 1* of spark per 10* coolant temp. There's no tricking involved.

So, is that enough to go ahead and swap t/stats on a whim? Probably not. But if you're in there anyhow, you may as well go with the cooler t/stat, because it does pay dividends in the power catagory.

jstreet0204 · May 21, 2007

'01 Steed said:
The PCM will do what it does based on engine temp. It adds and pulls spark based on coolant and air charge temps. We can consider air charge temps to be a constant in this context. The cooler the engine coolant temp, the more spark your PCM will add, to the tune of (no pun intended) 1* of spark per 10* coolant temp. There's no tricking involved.

So, is that enough to go ahead and swap t/stats on a whim? Probably not. But if you're in there anyhow, you may as well go with the cooler t/stat, because it does pay dividends in the power catagory.

+1
This is the correct answer^^. The PCM adjust timing and fuel acordingly. In closed loop, hotter temps adds fuel and pulls timing, both of which degrade performance. Also keep in mind, that a 180* tstat does not mean you are going to run at 180 unless the weather is pretty cool. Also the tune that Kenne Bell shiped with their 1.7L kit was setup for a 160* tstat.

Any reason to get 180* t-stat over a stock t-stat for PI headswap?

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