cover8

Yes, I searched (for the "search" ***** that now plague this forum), very little info on doing this.

First, I understand the benefits of bypassing the function of the thermostat so that if it fails it still wont blow your motor. But what are the cons of this mod?

Some say remove the stat while others say gut it.

Is "running to cold" a problem on the highway?

Is this a good mod? If so, what does gutting/drilling holes mean exactly.

Pics/feedback would be great!

thanks

Trexthe3rd

Removing/gutting the t-stat will slow down your engine warmup time quite a bit, especially if you live in a colder climate. If you don't mind waiting for the warm up then there isn't any real down side to it. Many racing applications do not use any t-stat, because it will actually restrict coolant flow.
Now for removing verses gutting. The thermostat and the o-ring together provides a seal between the filler neck and the engine. Gutting the t-stat wil leave that seal along to prevent coolant leaks or blowouts under high pressure. Gutting is simply removing all the moving mechanism and leaving just themetal housing and the rubber o-ring. Complete removal can be done but additional sealing in addition to the rubber o-ring should be provided to prevent coolant leaks.
Drilling is done by placing small holes on the flat part of the t-stat metal housing. This will allow some coolant to flow even when the t-stat is closed.
Keep in mind the following. If the t-stat is removed, the coolant will flow freely through the system, however if your cooling capacity is insufficient (ie. radiator cooling capacity) it will actually have the negative effect. This is due to the fact that the free flowing coolant does not have sufficient dwell time in the radiator for the necessary temperature drop. Race cars without t-stats have quite a large radiator to promote rapid cool down.
There is a fine balance created in the cooling system, unless you know the btu rating of the radiator and the btu generated by the engine under different loads, it's best to stick with the t-stat (get a lower temp one) and maybe drilling it.
If you are not racing, no it is not a good mod.

paw140

I've seen people say this before. It makes absolutely no sense, whatsoever, from a thermodynamics standpoint. Could someone explain this to me? I think it is BS. You are basically saying that slowing down coolant flow through the system will decrease its overall temperature?

turbojeff

iTrader: (30)

Agreed. The coolant does NOT need to "slow down" through the engine to pick up heat.

If you remove the T-stat completely I think that the waterpump tends to recirculate the water (like it does before T-stat opens) and not much makes it to the radiator. The car will overheat without the T-stat.

Otherwise I wouldn't run with a gutted T-stat either. It will run to cold on the highway, even in ~80F weather. In the fall and spring it will never even get close to warming up. The car will run rich, there will be a big change in temp everytime you get on it. This will cause all the parts to expand and contract more often.

Jeff

Brad

cover8

"they" also mentioned using a 18mm "freeze plug" on the pump bypass.

Just wondered all the race guy seem to prioritize removing this first.

thank you all for your feedback.

btw, the only thermodynamic adversity is bypassing the radiator. Maybe this is the function of the freeze plug, no?

The greater the increase in log mean delta T the greater the convective heat transfer rate. Remember from your equilibrium thermodynamics class? "...q, heat transfer rate (btu)/hr is directly proportional the the negative temperature gradient..." (Fourier's Law et al)

by inspection:

q = hA(DeltaT)

Backpressure is necessary in a heat exchange unit operation to utilize the heat exchange surface and to avoid two phase flow. Two phase implies cavitation producing compressible flow...boiling and pumping issues blah blah...need more coffee.

Now the flow rate (Re=Reynold's number) is important only because temp gradients improve heat exchange and turbulent flow has improved heat transfer ability than laminar flow. Calculating the Re number of a fluid will indicate wether it is laminar or turbulent.

paw140

I'm not sure if I agree with this. The difference between having an open thermostat, and no thermostat, will just be slightly less restriction for the coolant to flow into the radiator. I don't see how removing the thermostat will cause less coolant to circulate through the radiator. But I have seen someone on this forum (was it you, jeff?) who said their car overheated when they removed the t-stat. This doesn't really make sense to me, but I don't want to be the guinea pig who finds out for sure.

rx7ofmine

There seems to be some kind of misunderstanding here. If the t-stat is completely removed, MORE coolant will be flowing through the radiator FASTER. The increase in flow rate is higher than the heat transfer rate of a regular radiator. Similar principle applies applies to turbo intercoolers as well. When you upgrade the turbos (ie. increase flow) a larger intercooler is required to achieve equivelant or better cooling.
In race conditions, the engine will be in a constant high output state, the heat generated along with the higher water pump speed will not allow the coolant sufficient time to pickup the heat from the engine and to thansfer the heat through the radiator. I have experimented with this a while back. It takes too long to warm up and when racing, the temperature will slowly creep up and continue to go up pass 240F.

midasp

does anybody know it there is a replacement t-stat that runs like 20'f cooler than the stock

paw140

This is BS. You do not have to flow a coolant slowly to allow it to pick up heat. If you flow faster, you still have a constant blanket of coolant around your cooling channels. If anything, flowing faster will be better for cooling, because faster flows promote turbulent flow, which is good for optimal cooling.

cover8

hmmm...yes definitely some BS floatin' around 'ere.

Thermostats do no increase your overall cooling ability. maybe temporarily, when more fluid is exposed to coling surfaces but eventually this will reach steady state:

dq/dt = 0

Unless more heat is created than can be cooled...but this has nothing to do with the thermostat once it has opened. If you produce more heat than can be cooled by your system that temps will sail...but this is independent of the thermostat and its function.

The only adverse effect of thermostat removal that I can think of theoretically, of course is reduction is necessary head pressure to efficiently operate the water pump. Either "deadheading" or operating a pump without particular resistance head can cause cavitation or two phase flow. Maybe removing the thermostat reduces the differentail pressure and causes the pump to cavitate?

Remember that heat exchage is reversible...so improved flow/ lower retention time to the cooling surfaces has the same affect as similar retention time in the heat sources of the engine.

As stated before heat exchange is an energy transfer. Any transfer needs a "driving force". Driving force is a direct function of the gradient--steeper the gradient the faster the energy transfer (law of entropy =s). This is why heating energy is transferred optimally with greater delta T accross the boundary. As the boundary temps get closer and the gradient decreases, the thermal exchange is less and thereby less efficient.

This fact can be proven by comparing co-current with counter-current exchange. Counter-current exchange maintains the temp gradient and reflect a more efficient heat transfer.

apexkw

if the coolant is flowing too fast, then it wont be able to dissappate the heat in the radiator. it just keeps getting hotter because it never has a chance to exchange the heat. how does a radiator work??? it works by allowing the coolant to come in contact with it right....so for example if you have a ice cube and you just tap it with your finger ...is your finger cold or did it just get cold for a split second? now if you take that same ice cube and hold it in your hand, does you hand get cold for a split second or does it get cold and feel cold for a while after you remove it? now i am not saying that having the coolant sit is a good idea. what i am saying is that you dont want it to be in contact for a split second because it is moving to fast. you need it to be in contact just enough to relase some heat.

cover8

apekw:

Your point is well taken...but since the transfers is reversible, the heating source (engine) does not get the amount of time to heat either.

The flowrate will apply to both exchange areas...if flow is fast the heating source will not have much time to heat as the cooling source will not have much time to cool. In reality this benefits the cooling surface since it is designed to be an efficienct heat exchanger and the engine is not. But btu's are btu's and if the engine produces more that can be removed overall temps increase. But this has nothing to do with the thermostat. Maybe terminal pressure loss over the orifice hinders pump performance decreasing flow rate to the cooling surface.

The resistance head and running too cool would be my concerns.

Brad

I don't see how removing the thermostat would negatively affect anything except warm-up time.

I know you all know how the thermostat works, so think about it. When the coolant temperature is below 180 degrees F, the thermostat is closed, which does not allow coolant to pass to the radiator. It simply circulates within the coolant passages in the motor. When the coolant temperature gets above 180 degrees F, it opens up, allowing coolant to pass to the radiator. As long as the coolant temperature stays above 180 degrees F, the thermostat WILL NOT close. I have tested my thermostat as outlined in the shop manual. Placed the thermostat in a jar of water with a thermometer in it, and gradually heated the water up to 180 degrees F. Sure enough, the thermostat opened up at 180, and stayed open.

I don't know about you guys, but I have never seen my completely warmed up FD get below 85 degrees C. That's 185 degrees F. So assuming we have an engine at normal operating temperature, let's say 87 degrees C, and it never goes below that while in operation, the thermostat will stay open.

What's the difference between a thermostat that stays open ALL THE TIME, while an engine is at operating temperature, and no thermostat at all?? Someone please enlighten me.

And is removing the thermostat going to increase coolant flow to a point where it moves too fast through the radiator? I highly doubt it.

KevinK2

T-stat also functions as an orifice, increasing pressure in engine at higher flows. For EGW cooling, this raises boiling point, suppressing dnb ( departure from good controlled boiling ) at hot points near combustion chamber. Don't eliminate it. Replace often.

The stock T-stat appears to be of 3-way type, where the bypass is closed at higher temps.

FWIW, worked with guy on plastic intake manifold desgn. the design pressure for coolant port was over 40 psi, for that engine.

Brad

Ah, I completely forgot about pressure. Good point Kevin. So removing the thermostat would lower the pressure of the cooling system, which would lower the boiling point of the coolant.

What if you used a higher pressure cap? Or what if you we're using a zero pressure NPG system, like Evans NPG+? The NPG already has a much higher boiling point than water.

RonKMiller

Engines like steady state oil temperatures. Oil works best at the median temperature it was designed for, no matter what viscosity or type of oil you prefer. If for no other reason KEEP the T-stat. If you have other cooling issues you need to find them instead of taking a shorcut in hopes of a miracle cure. The T-stat also helps to buffer shock cooling/heating, which is devastating and can actually cause an engine to sieze.

One thing I find ALL the time when cooling problems arise (especially in older vehicles) is the radiator fins are coated with dirt, insect parts, dust, plant parts, pollen, etc. This microscopic debris dramatically reduces heat transfer - it forms an insulating barrier. This happens more frequently than internally clogged radiators which is pretty much a thing of the past if you put in fresh coolant every few years.

You can look at it and you'll swear it is as clean as a whistle. You can try to backwash this crap out of it, but usually all you do is end up bending fins, especially with aluminum. This stuff gets baked on over time and will not come off. Buy a new radiator to fix the problem.

When you hear hoofbeats, don't go looking for Zebras.

turbojeff

iTrader: (30)

Really your wrong.

Ice cube example doesn't really apply. Imagine if you had a CHAIN of icecubes, such that the icecube was always in contact with your skin. Do you think if the chain moved faster or slower your hand would get warmer or colder (ignore friction from fast moving icecubes).

OR stick your tongue to something in the freezer, tell me how long it will take for you to become attached to it.

You see the radiator will always have coolant in it, moving the coolant faster doesn't decrease it's ability to transfer heat, it actually can increase it since the temps could be higher in the coolant.

massflowrate*specific heat(delta T)= amount of heat you transfer from the coolant. If the coolant is hotter the heat transfer will be higher.

Jeff

spurvo

On top of all this, the engine doesn't get out of cold run mode until 177F, and peak HP is typically seen at 195F. Loss of T-stat will result in the car running well below 177F on the freeway, TOTALLY ******* your gas mileage and power. Unless you have a full engine management system and have dyno tuned at these temps... what was the point of doing this again?

Sorry... flame away!

KevinK2

cruising with t-stat in cold weather means cycling from closed to just cracked open, to maintain min op temp of 180F. yank it with cold weather and coolant temp will drop below 180F into warm-up zone, cruising .... may loose closed loop, will be overrich, will not not vaporize water that works into oil from blow-by.

on a race track, with or w/o t-stat, will not be too cold after some hard laps.

paw140

Good point Jeff.

According to the above logic, if I had some really hot water, and flowed it through a pipe REALLY REALLY fast, it would never get any colder, since it wouldn't have 'time' to cool off Actually, if the coolant was flowing through the engine too fast, it wouldn't pick up any heat from the engine, and also would not dissipate any heat through the radiator. The coolant would remain at ambient temperature and the engine would overheat!

The point you have to understand is that cooling rate is a function of the difference in temperature between the two bodies. There are many other factors, like surface area and thermal conductivities of the materials, but in our case these remain constant. Flowing the coolant through the radiator faster will not change the difference in temp between the coolant and ambient air.

I think the only valid points that have been made about removing the T-stat is 1) it may affect the head pressure of the water pump and may cause pumping problems, 2) it will take your car longer to reach operating temperature.

cover8

If you have other cooling issues you need to find them instead of taking a shorcut in hopes of a miracle cure.

When you hear hoofbeats, don't go looking for Zebras.
[/B][/QUOTE]

What the hell does this mean?

Who is taking shortcuts?

My car doesnt have cooling problems...but I do have my motor out to rebuild...so good time to do the mods.

In my efforts to read more and post less, I found many competitive drivers were gutting out the thermostats in their cars so I thought I'd post a question. Question is, why do they do that?

Frankly, if warming up the car longer is the only downfall then its a nobrainer w/ one less part that can fail...but you all have brought out some insight that I must evaluate.

We all know the thermostat can fail and it is a "fail close device" or a "fail open device"? If an unecessary headache can be alleviated, then now is the time when everything is out.

Thanks for the feedback...from the less pretentious.

Redrotor

I ve seen post from Knight sport web site.

that said FD thermostat is not simple on/off valve because it has another valve at the back this one coltrols bypass coolant this valve suppose to shut off the bypass flow when thermo stat is open.
so if thermostat is removed it can cause overheat.

so I checked when I took my thermostat out it was true it has another valve at the back and there was hole on the waterpump housing.

turbojeff

iTrader: (30)

cover8,

this might help. While cruising on the freeway in outside temps up to about ~85F the SPI temp guage sits solidly on 182-185F (could be some inaccuracy in the guage). This means that the T-stat is barely open, or opening and closing. Imagine if you have a free flowing coolant system, the coolant will not even get up to the 180F operating temp. I'd bet in weather around 50-60F which is normal summer mornings around here the car wouldn't get above 130-150F. This is bad for the car like others stated. It will run in warm up mode, always rich. Funky internal engine temps (hot and cold spots), weird coolant and oil temps. When you "get on it" the car will actually be cold still. It isn't just a matter of longer warm-up times, rather sometimes the car just WON'T GET WARM. This isn't just in cold weather either.

For competition only gutting the T-stat is probably simple and cheap way to eliminate it from failing. Since the car is always running close to WOT it doesn't close in normal operation.

Keep in mind, and many people on the forum should keep this in mind:

Just because it is fast on the track doesn't mean it is fast on the street. Race cars are tuned specifically for certain conditions, when those conditions change they can become incredibly slow. Cold hard race tires are dangerous, race engines are tempermental in stop-and-go traffic, alignments make them darty to drive on the freeway, etc, etc, etc.

Jeff

Air-Rex

cover8,T-stats can fail open or closed, or somewhere inbetween. they can stick and open late also. Most commonly they fail closed. As a Boiler Tech, I get into quite a bit of work on pumps and heat exchangers, and it can get complicated. enough so that I would'nt want to get into this one.( I'm no expert). But I will say that pumps can cavitate if operated at to low a pressure, (off its curve) But not a auto water pump IMO. Otherwise they'd be cavitating every time you start the car from cold, (cavitation runs pumps)
Also the system pressure isnt set by the oriface or opening in the T-stat.