Stock Thermostat Versus Low-temp Thermostat

[cowboybinkz71]

OK I may be showing my ignorance here, but I was wondering what is the advantage of running a low temp thermostat versus the stock one. When I got my basic tune a few years ago I replaced the stocker with a Hypertech low-temp 160* unit. In my mind, the advantage is that the engine will run cooler which would seem an advantage. I'm wondering if this may be part of the reason for my lower fuel mileage. So, what really are the advantages and disadvantages of running a lower temp thermostat?

 

Any thoughts?

[Matt_]

Running cooler is not always a good thing. That just means less energy is being converted to mechanical power and more energy is being dissipated through the cooling system.

 

The best cooling system is one that keeps the engine at nominal operating temps without a large fluctuation in temperature.

[cerbomark]

you may be able to put more timing in the tune if you run a cooler T-Stat... It s a good point and I don t know but it may hurt fuel economy by not runnnig the higher temp the engine was designed for?

[Matt_]

you may be able to put more timing in the tune if you run a cooler T-Stat...

 

Yea they're really for modified engines, or when utilizing forced induction which increases pressures and thus temps as well. For a naturally aspirated engine, I'd run at the designed temp range IMO

[Stevens03]

The idea of running a cooler stat is to make the computer dump more gas and timing. The PCM needs to be set for the temp range that you stick in otherwise will try and compensate for the difference and negate the performance gain. Your best bet as mentioned is to run the stock stat unless your highly modified.

[txab]

The idea of running a cooler stat is to make the computer dump more gas and timing. The PCM needs to be set for the temp range that you stick in otherwise will try and compensate for the difference and negate the performance gain. Your best bet as mentioned is to run the stock stat unless your highly modified.

 

+1

 

You would need to tune for the temp difference

[cowboybinkz71]

Well now that I know that, here's another question to throw in the mix. I had a basic PCM tun from Thunder Racing down here in Baton Rouge. Fueling was advanced, TM reduced, etc. When I did that I also had them install the low-temp t-stat at the same time. I've just got to wonder if they programmed in that variable when they tuned the truck.

 

The main reason I'm bringing this question up is because the truck fuel mileage decreased (regardless of how it's driven) with the tune by 1-2 mpg. I'm wondering if the t-stat is part of that problem by not allowing the fuel to get full combustion and/or the tune did not take it into account. I think I know where the stocker one is and I may try to swap it out in the next few weeks to see if I can see a difference.

 

Everything else has been changed with the exception of the stock cats so I've just got to imagine that the computer programming has something to do with the poor mileage.

[Stevens03]

It's easy enough to swap the stat and do a test. Seems like a no brainer to me. Put the stock one back in and run it for a few weeks. If the mileage improves, then theirs your issue. If not, then its most likely in your tuning and a re-tune for mileage would be inorder.

[Rons05z71]

Do you know what temp stat they put in?. On another car I owned it came with a 195 degree stat. I swapped in a 180 and ran like that for 90000 miles. It probably saved the engine because of the plastic intake manifold and leaks that developed on some of the coolant pipes. That is neither here nor there. Point is if they put in a 160 degree it is way too cold, and it is effecting your mileage. Especially not being blown or turbo. A switch from a 195 to a 180 will not (in my opinion) do anything to hurt your engine, you will still have a heater, A/C ETC. you will lose a little mileage but you might get a little throttle response too out of it. I might try it eventually when I have some time to do some research on it.

[cowboybinkz71]

IIRC it was a Hypertech 160* t-stat that replaced the stocker. What is the stock t-stat temperature? I'm thinking it's a 195*

[bossier62guy]

IIRC it was a Hypertech 160* t-stat that replaced the stocker. What is the stock t-stat temperature? I'm thinking it's a 195*

 

186*

[superjim]

IIRC it was a Hypertech 160* t-stat that replaced the stocker. What is the stock t-stat temperature? I'm thinking it's a 195*

 

 

 

Not absolutely sure of the original temp t-stat, but...the engine runs in two different modes.

 

Open loop and closed loop.

 

It is in OPEN LOOP when you first start it and while warming up to operating temp.

When in OPEN LOOP, the computers run it a little on the rich side to facilitate smooth idle and proper operation all the while bypassing most of the sensors that tell the computer what is going on.

 

On reaching operating temp, it goes into CLOSED LOOP.

When in closed loop, the engine computer takes reading from the oxygen sensors, MAF, MAP and others and adjusts your air/fuel ratio, timing, etc..etc.. accordingly.

 

If it never reaches what the computer thinks is NORMAL OPERATING TEMPERATURE... it will stay in CLOSED LOOP forever.

 

And probably burn more gas.

 

I would put the stock T-stat back in and see what happens.