Low Temp Thermostat

[Ross]

I have seen a number of posts about using a cooler thermostat, and I have a couple of questions about it. I understand the concept of cooler air being denser and better for combustion, and that's the reason a lot of guys are getting cold air intakes. Is this related to the cooler thermostat? It seems like the internal temp of the engine (as controlled by the thermostat) wouldn't make the incoming air any cooler or denser. Whatever air comes in is already as dense as it's going to be, regardless of what thermostat you have, right? So it seems that the cooler thermostat must have some other function. What benefit does the cooler thermostat give? Also, if it's better for the engine to run cool, why not take out the thermostat altogether, at least during hot weather? We used to do this decades ago, just because cars get so hot down here in Texas, and we didn't need any help getting the engine to warm up, at least until it was time that we needed to use the heater. Also, I have heard of thermostats that lock open, rather than closed, when they fail. This sounds like a wonderful safety measure to keep an engine from overheating in case of failure. Any suggestions about this? What brand, where to buy one, etc.? As usual, thanks. Ross

[RF Overlord]

Ross:

The thermostat issue has nothing to do with the intake air temp. Actually, a hotter engine is more efficient, so keeping it as warm as possible, while supplying as cool an air charge as possible, is "better"...

However... (you KNEW there'd be a "however" :D)

A hot engine is also more prone to pre-ignition. A cooler thermostat by itself will generally not produce any benefit, and removing it completely would not keep the engine temp stable. The primary reason for installing a slightly cooler thermostat is when it's recommended by a chip programmer, like Dennis, for use with his chip's programming specifically, or by a dyno-tuner like FordChip, again for use with their programming. The more aggressive spark advance and fuel tables in the above programming makes the engine even more prone to preignition, which due to the presence of the knock sensor on our motors, would simply retard the timing, negating some of the benefit of the chip. A cooler thermostat helps mitigate this. It's generally not recommended to install one unless specified by your programmer.

[TAF]

Originally posted by RF Overlord
It's generally not recommended to install one unless specified by your programmer.

And certainly not to remove it entirely...unless you are looking for some real trouble.

^^^Well said, RF!!!

[Ross]

Makes sense to me. Thanks for the explanation. Now about that thermostat that locks open when it fails, heard anything about that?

[SergntMac]

Originally posted by Ross
I have seen a number of posts about using a cooler thermostat, and I have a couple of questions about it. What benefit does the cooler thermostat give? Also, if it's better for the engine to run cool, why not take out the thermostat altogether, at least during hot weather? We used to do this decades ago, just because cars get so hot down here in Texas, and we didn't need any help getting the engine to warm up, at least until it was time that we needed to use the heater. As usual, thanks. Ross

Well, I see my friends beat me to the 411 already, but let me add my .02c too.

Dennis Reinhart suggest a change in t-stat and spark plugs to cooler settings, in order to "fine tune" the combustion cycle under his RPC chip. Reinhart also suggests that you DO NOT make these changes without his chip. They would not show any value alone, and may cause damage over the long term. The chip will work just fine alone, but it works better with the suggested cooler t-stat and colder spark plug range.

The T-stat recommended is a 180 degree, standard FMC/NAPA part and not a significant drop in temps from the factory settings. It is an all-season t-stat and very functional in winter. Here in Chicago over the past winter, my engine reached proper operating temps in 7-8 minutes of normal driving, in zero temps.

The recommended plug has changed over time, and it's now the Denso IT-20, cooler than OEM plugs, and also with improved threading. Denso's seem pricey for spark plugs, but they do perform well. Life span is predicted to be 60K miles.

With respect to you questions about open/no stat, the ECM does some things here that I don't fully understand, but it's been suggested that the MM has a "cripple" system that detects overheating and disables some motor function until you can limp to safety. Not knowing more, I'll shut up. Hope this helps...

[drobin]

Ross,

No one should ever remove a thermostat in a normal working coolant system, because this would increase the circulation speed of the water, thereby making it impossible to radiate it's head and cool down while circulating through the radiator.
This is definitely a No-No.

[Menace]

I think the stat. adds as much to the box it came in as it does to the car.

[jgc61sr2002]

This thread sounds familiar, didn't we have one prior.? The purpose of the thermostat is also to regulate the flow of coolant. No thermostat can cause overheating because the coolent doesn't spend enough time in the radiator to cool properly. IMHO.