jerry507

Running 5-10 degrees cooler isn't going to make a huge difference either way. 190F is likely picked to target some emissions requirement, so if you don't care then knock yourself out.

The biggest problem I've noticed is large swings in coolant temperature. A 190F thermostat should regulate temperature pretty close to 190F under a constant load (cruising down the highway). But I've looked at the voltage output of my ECT sensor which reacts much faster than the temp gauges driven off the sender, and routinely notice 40F swings.

Many people will tell you it's because you need a dual stage thermostat. That isn't correct. You've just got a crappy thermostat which isn't settling down to a constant opening size.

motospeed

I don't have big swings of engine temps. Maybe +/-5º. Which doesn't make a big difference. I use a cheapo t-stat from O'Reilly's. No problems.

snobdds

A dual stage thermostat was never designed or intended to stabilize the engine coolant temperature. It was designed because the 22re did not have a bypass hose for the exit from the heater core. Instead it puts the "cooler" antifreeze back into the system just before the thermostat. This was causing the thermostats to never open when the heater was on...thus causing overheating. The dual stage thermostat was just a quick way to solve the problem, but as an intended consequence, it regulated the engine temperature in a narrower range.

jerry507

First, if you're saying you're not seeing big swings and your source is looking at a temperature gauge, it's not possible to know. Temperature gauges in combo clusters are designed to react slow. The stock gauge for example takes 6-8 seconds to swing over it's entire range. I still need to work out the details on that range, but if you watch the ECT you'll see your el cheapo tstat is not regulating to +/- 5F. Or if it is, let me know because I want to buy that!

Regardless of the original intent of the dual stage thermostat, they are designed to allow more flow through once the engine is warm. Think of them as an improvement over simply drilling a few holes in the body plate. It allows more flow through which gives the wax plug a more accurate sense of engine temperature. The downside is you have more bypass when the engine is cold. Dual stage thermostats simply put another valve on which opens at a lower temp. Now you have more bypass only when the engine is hot and the main valve can provide the bulk of the regulation.

It's not the original purpose, but you commonly see people recommend dual stage thermostats as a cure-all for any temperature related problem regardless of model.

snobdds

You've never actually seen a dual stage have you. Because if you have your claim about them flowing more when the engine is warm is not true and you would not make the claim. The duel stage thermostat larger valve is significantly smaller than the normal size thermostat valve. What it does do is cycle more (open and closes) and allows the coolant to stay in the radiator longer than the normal one would do. This allow the radiator to take more heat out of the system...thus normalizing the range of temperature swings.

Please, make sure what your talking about before you go off on a rant. Newbies reading this will thank you.

jerry507

If you're bypassing more water constantly through the smaller valve when the engine is hot, then the main valve would be smaller to maintain the same flow at the given operating point.

Thermostats don't cycle between open and closed. This is a very common misconception, one you obviously also share. You can relieve yourself of this by checking the FSM for our trucks. The check for the stock thermostat specifies the valve begins to open between 187F and 194F. The valve is open 8mm at 212F.

Water doesn't stop flowing through the radiator after the engine warms up. Before you call someone a noob you should be sure you have a through understanding of the process in question.

snobdds

You can't teach stupid...good luck in life.

jerry507

Urg, really? Personal insults?

I don't blame you if you don't believe me, I'm just a dude on the internet. Here is Stants website, which will hopefully more clearly describe the operation of a wax pellet thermostat for you:

http://www.stant.com/consumer-produc...of-thermostats

I'll quote the relevant part for those that don't want to follow the link:

"This is the temperature the thermostat will start to open, give or take 3 degrees
The thermostat fully open about 15-20 degrees above its rated temperature"

So while the thermostat may swing fully open to fully closed if there is a large step in load (and therefore heat), the STEADY STATE behavior is somewhere in between.

edit Wait no, I'm not playing the insult game. Sorry, can we all be adults here?

xylicon

According to my Autometer temperature gauge you I can see it cycling open and closed about 2 or 3 times before my engine gets to operating temperature, (while using a Toyota OEM thermostat).

After my engine is warmed up it no longer cycles.

rworegon

Maybe this is what should have been quoted from the Stant link under purpose of a thermostat:
"Regulate the engine's operating temperature: By opening and closing in response to specific changes in coolant temperature to keep the engine's temperature within the desired operating range."

jerry507

Let me understand you correctly, because there is some ambiguity in what you said.

When you start cold, you see the temp start to increase. As it's increasing, but before it's hit about 190F, you see the temperature start to go down and then resume going back up?

Or you see it get to 190 and then you see it cycle down and up a few times before it stabilizes???

xylicon

When I cold start in the morning, I'll sit there and warm up my truck for about 3 minutes.

Then I'll start driving and while I'm driving I can see the temperature gauge creep up, when it gets to about 190, the needle will go back down to 150 and sit there for another minute, then it will go back up to 190. It will cycle between 190 and 150 about 2 or 3 times before stablilizing at 190

snobdds

How do you even take someone seriously when they fail to understand the basic principles of a thermostat?

RustBucket

iTrader: (1)

So are we all heat exchanger engineers here? No need to get riled up at each other, it's just physics.

In the fully open position, would the dual tstat be less restrictive than a single stage? Or is the difference negligible?

And again, any more *data* regarding engine temperature that you have to share would be great.

RustBucket

iTrader: (1)

Snodbbs, please read a textbook on heat and mass transfer and then educate us on how radiators and thermostats work rather than belittling people on my thread.

snobdds

I'll do one better for you...my first degree is in mechanical engineering.

To the topic at hand...

The total volume of flow for the dual stage is less than a normal OEM thermostat. Two smaller valves replace the one larger valve. The smaller valve opens at a lower temperature due to the heater core issue. Then the "bigger" valve opens at the normal 195*. The flow is more restrictive due to 2 valves instead of one, meaning the coolant stays longer in the radiator. The radiator is more efficient due to the flow not being as much.

Need more?

RustBucket

iTrader: (1)

Touche!

Good to know about the flow restriction. That would be something to consider.

I would disagree with the statement that slower flow through the radiator is more efficient. Yes your delta T is greater from inlet to outlet, but what you want is to reject heat from the system. Ideally you want as much turbulent flow as possible and for the entire fin surface of the rad to be as hot as possible so you move more heat through delta T vs the ambient air.

jerry507

Wow, now we're throwing around degrees. Electrical and mechanical here, I work on control systems. Does having a degree justify insults?

I have suggested a model of how a thermostat operates and so have you. I'll summarize in my own words so we can tell if it's just a misunderstanding.

You suggest that a wax thermostat operates like a switch. Above the printed temp, it opens fully. Below that temp it closes fully. Did I misunderstand you?

I have said a thermostat has a variable opening between the printed them and about 15-20F higher than that. At the printed temp it's fully closed, 15-20F higher than that it's fully open. Do you disagree with that???

RustBucket

iTrader: (1)

Jerry, you're right that the thermostat has a variable opening. As a controls person, would you say that it is the proportional controller in the system? In other words, the farther the actual temp is from the goal temp the wider tstat opens.

snobdds

The thermostat is mechanical...there is no electrical input to tell it how far to open...