calio64

i was wondering if it is ok to run a turbo 2 with no thermostat. will it hurt the car?

thanx for the advice

Rxmfn7

iTrader: (4)

You never want to run a car with no thermostat ( or at least a restrictor plate of some sort). Why were you thinking of doing this?

If you runwithout a thermostat, the coolant will be moving non-stop throughout the system. This does not give enough time for proper heat trasnfer from the engine to the coolant. You will see lower coolant temps, yes, but this is because it is not doing its job and carrying heat away from the engine. You will most likely see a distinct rise in oil temp.

NZConvertible

What he said.

glorthu

Actually, the above is not true. Basics laws of convective heat transfer:

Q = h(T1-T2)

The greater the temperature difference between the fluid (coolant) and the solid (engine block), the greater the energy transfer between them. Also, if the fluid is flowing faster, 'h' tends to be higher due to turbulance (and therefor thinner boundary layers. The fact that any particular bit of coolant doesn't stay long in the engine does not in any way decrease the overall heat transfer, since there is a steady flow.


OTOH, the real reason you don't want to run without a thermostat is that your engine won't warm up as quickly, and may never reach proper operating temperature (in cold weather). Since engine clearances are designed around operating temperatures, this can lead to premature wear.

SureShot

If you really have to run without a stat, plug the bypass hole in the housing that is about 1" below the stat seat.

The stat has a spring loaded disc that sticks down there to cover it.

Icemark

Despite the number of times this subject has been covered your answer is very flawed.

#1 you saidWithout a thermostat there is no steady flow. The flow becomes entirly dependent upon speed of the pump, which is driven by the engine and is only based on engine RPM.

#2 Because of the non restricted and varible speed of the flow, turbulance and cavitation points are considerably lowered. This can mean that the cavitation point of the coolant at the water pump could be as low as 4000-4500 and up instead of the normal stock 6500-7000 point when used with the proper flow restriction. That means you are effectivly throwing out any cooling ability of the coolant at above that cavitation point (as well as lowering the overall pressure of the system- which lowers coolant anti boil ability). A side effect of that is the coolant fails to pick up sufficent heat, as the coolant is now compromised because of that air induced by cavitation. Lowering pump RPM (or replacing the pump with one with an impeller designed for that specific flow rate) will solve it as then the cavitation point also lowers. Of course the additional air in the coolant because of cavitation will provide now a false reading on the actual coolant temp since density has changed as well.

#3 The oil provides about 30-35% of the cooling on a rotary engine, so even if (as you say)the oil will generally reach a sufficent warm temp to provide a warmed engine condition.

neptuneRX

I have a question then, would block of the OMP, and running premix result in higher operating temps then? And if so, are there any safe ways to counter that.... this is regarding

and if so, wouldn't that lead to premature wear on the housing?

Icemark

There should be no difference... The oil that does the cooling runs through the engine and oil cooler, it is not injected at all for cooling.

glorthu

Despite the number of times this has been covered on the forum, I have been here only a short while and have not had time to sort the useful information from the chaffe in even the new posts, much less the forum history.

As for #1, This only increases the cooling effect of removing the thermostat. The thermostat can only decrease flow, thereby decreasing heat transfer (except if it can cause secondary effects as mentioned below).

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#2 Because of the non restricted and varible speed of the flow, turbulance and cavitation points are considerably lowered. This can mean that the cavitation point of the coolant at the water pump could be as low as 4000-4500 and up instead of the normal stock 6500-7000 point when used with the proper flow restriction. That means you are effectivly throwing out any cooling ability of the coolant at above that cavitation point (as well as lowering the overall pressure of the system- which lowers coolant anti boil ability). A side effect of that is the coolant fails to pick up sufficent heat, as the coolant is now compromised because of that air induced by cavitation. Lowering pump RPM (or replacing the pump with one with an impeller designed for that specific flow rate) will solve it as then the cavitation point also lowers. Of course the additional air in the coolant because of cavitation will provide now a false reading on the actual coolant temp since density has changed as well.

Yes, higher speed can lead to turbulence... which can help heat transfer by reducing the boundary layer thickness...

But cavitation at the pump should not be more likely. Without the thermostat there should be a smaller pressure drop accross the pump, which should make cavitation less likely.
But maybe there's something I'm missing here...

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#3 The oil provides about 30-35% of the cooling on a rotary engine, so even if (as you say)
the oil will generally reach a sufficent warm temp to provide a warmed engine condition.

Is there a thermostat in the oil cooler lines somewhere? How would 30-35% of the cooling capacity being provided by oil increase the warm-up rate? I see what you mean about the cooling not being entirely engine coolant dominated, but an engine running without a thermostat in cold weather is not going to warm up any faster because it happens to use an oil cooler! The oil cooler is still exposed to the same outside conditions as the radiator.

NZConvertible

You can argue as much as you want, but the effects of running without a thermostat are well known and have applied to all engines for decades. At low load the engine is overcooled because of the sheer volume of coolant being circulated. At high load the coolant's speed through the engine is too high for sufficient heat transfer to take place so overheating results. Nothing you say is going to change these two facts.
Yes there is, in the oil cooler's left end tank. The oil cooler is bypassed until the oil has warmed up.

Avatar

here's my 2 cents worth...

If the coolant is doing it's job then your engine is going to be running cold all day every day, in which case your going to break stuff when you thrash it.

If the coolant is doing bugger all then your going to have problems

Either way spend the $14 to keep your car healthy, just replace the two bolts as well

SpeedFreak03

Think about it if the car didn't need it then it wouldn't have one...and if it didn't need it then you wouldn't have to replace it as maintenace. Just buy a new one .

glorthu

Assuming you are correct that engines tend to overheat more without a thermostat at high load (I am not a mechanic), that still does NOT mean that increased coolant speed is the reason for it! I might believe something like Icemark said about the pump cavitating (if I can find a reasonable explanation for that happening), but saying that increased coolant flow causes less energy to be transfered to the coolant goes against basic laws of thermodynamics!

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Yes there is, in the oil cooler's left end tank. The oil cooler is bypassed until the oil has warmed up.

Cool, thanks.

Avatar: Right on!

NZConvertible

I studied thermodynamics and heat transfer at university, so I'm not just making this up.

Heat transfer is not an instantaneous process. It takes time. The longer two objects remain in contact (in this case the engine and the coolant), the more heat transfer that will take place. The faster the coolant flows through the engine, the less time each water molecule is in contact with other molecules that are hotter than it (engine parts or other water molecules), so less heat transfer takes place.

As an example from the HVAC industry I work in, if you double the flow of air over a cooling coil, you don't get double the cooling capacity, because there's less time for the air to be cooled down as it flows through the coil. Another more obvious example is holding your finger in a candle flame (not that I'm suggesting you do it). The longer you hold it there, the hotter (and more painful) it gets, because more heat transfer takes place. Sweep your finger through the flame quickly and you barely feel anything.

The coolant flow rate through an engine is a balance of two things. Too slow and even though the heat is being transfered to the coolant, the coolant is not removing that heat faster than the engine can generate more, so the engine gets hotter. Too fast and the coolant doesn't absorb enough heat as it moves through the engine so too much the heat stays where it is, and the engine gets hotter. There is a "sweet spot" where the maximum heat removal rate occurs. Manufacturers balance many factors (like thermostat restriction and pulley sizes) to make sure the engine spends as much time as possible close to that sweet spot.

Removing the thermostat greatly increase coolant flow rate, and moves it far from the sweet spot. The cooling systems capacity has effectively been reduced, so less engine load is required before it can't keep up and the engine overheats.

I hope that explains it.

BrandonDrecksage

FOr everyone who says that running w/o the t-stat will overheat your engine...explain this to me. When you engine gets to the certain temp were the t-stat opens, doesn't that allow the coolant through almost unrestricted? So my point being, if you gut the t-stat housing and put that in, then your car should be fine. You won't have heat when it is freezing cold, but other than that, it will be okay. I've been running w/o a t-stat since july with no problems, my car actually runs better now than it did. I also beat the **** out of my car and it has 145,000 miles on the original engine, so don't you think it would have gone if running w/o the t-stat makes it overheat?

glorthu

Me too. The undergrad and intermediate graduate courses for both.

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Heat transfer is not an instantaneous process. It takes time. The longer two objects remain in contact (in this case the engine and the coolant), the more heat transfer that will take place. The faster the coolant flows through the engine, the less time each water molecule is in contact with other molecules that are hotter than it (engine parts or other water molecules), so less heat transfer takes place.

Everything but the last part is correct. Remember, this is a continuous process. Even though less energy is transfered to each particle, but there are many more particles flowing through. The balance ends up being towards more heat transfer with higher flow, because when you integrate over time the temperature difference is greater. You HAVE to take into account the thermal capacitance of the coolant FLOW.

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As an example from the HVAC industry I work in, if you double the flow of air over a cooling coil, you don't get double the cooling capacity, because there's less time for the air to be cooled down as it flows through the coil.

This is not the same. In the HVAC case, you are concerned about the outlet temperature of the air with respect to room temperature, not the degree to which you change the temperature of the coil. If you look at the different surface temperatures of the coil at different flow rates, it would be a more accurate comparison.

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Another more obvious example is holding your finger in a candle flame (not that I'm suggesting you do it). The longer you hold it there, the hotter (and more painful) it gets, because more heat transfer takes place. Sweep your finger through the flame quickly and you barely feel anything.

Not the same at all. Here you don't even have a flow, just one block with a set thermal capacitance, your finger (unless you count your blood as coolant... )

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There is a "sweet spot" where the maximum heat removal rate occurs. Manufacturers balance many factors (like thermostat restriction and pulley sizes) to make sure the engine spends as much time as possible close to that sweet spot.

The thermostat trys to set a cap on the coolant temperature. It does so by openning whien the temperature exceeds a certain range. This has little to do with heat transfer in the engine, and much to do with heat transfer in the radiator. And pulley sizing is generally determined to provide as much flow as possible accross the operating range without cavitating the pump.

Icemark

Searching on a subject will help you then. The search function is found in the upper right hand corner of the page.

no The coolant can only pick up heat so fast. That is why mixes of coolant and water are used, to lower the transfer time.

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Yes, higher speed can lead to turbulence... which can help heat transfer by reducing the boundary layer thickness...

But cavitation at the pump should not be more likely. Without the thermostat there should be a smaller pressure drop accross the pump, which should make cavitation less likely.
But maybe there's something I'm missing here...

Pump impellers are designed to work with a specific operating speed both for flow, pump volumn, and average operating speed with that flow. If you change the flow rate, the impeller is no longer working in an optimum movement, causing cavitation.

Yes if it was an impeller designed to work at 8000 RPM with no restriction, your suggestion would work. Too bad most water/fluid pumps are not ever designed that way.

This is very very basic and is covered in even basic fluid dynamic engineering (and probably even high school physics).

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Is there a thermostat in the oil cooler lines somewhere? How would 30-35% of the cooling capacity being provided by oil increase the warm-up rate? I see what you mean about the cooling not being entirely engine coolant dominated, but an engine running without a thermostat in cold weather is not going to warm up any faster because it happens to use an oil cooler! The oil cooler is still exposed to the same outside conditions as the radiator.

The oil cooler thermostat is in the oil cooler body. I did not suggest that the 35% of the cooling of the motor helped warm up (other than the oil not being actively cooled until the engine reaches operating temp), but rather that the coolant only controls about 55% of the cooling on a rotary motor. This means that even if you screw up the coolant system, you still have 45% of the cooling on the motor done correctly, which (since the oil cooling of the FC is way over built, and direct air cooling represents around 10% on most internal combustion motors) will help fix/compensate the mistake of what you did by removing the restriction in the coolant flow.

This (of course) does not fix the issue of inconsistent cooling thought the engine leading to hot spots as covered by other members (in this thread and countless others), but rather provides some minor back up to keep the motor from melting down.

Sure there are plenty of newbies to the rotary (BrandonDrecksage comes to mind with his post) that dont understand how a cooling system really works, and say how they have removed their thermostat for increased cooling. But any long term rotary user (including ones that race rotary engines) can tell you how without a restriction (be it a restrictor race plate, or a thermostat) that there are some major internal water cooling issues and hot spots. Hot spots in an engine that has sandwhiched plates will lead to warping and seal failure. Might not happen this week, or even this month, but it will happen.

BrandonDrecksage

Sure there are plenty of newbies to the rotary (BrandonDrecksage comes to mind with his post) that dont understand how a cooling system really works, and say how they have removed their thermostat for increased cooling. But any long term rotary user (including ones that race rotary engines) can tell you how without a restriction (be it a restrictor race plate, or a thermostat) that there are some major internal water cooling issues and hot spots. Hot spots in an engine that has sandwhiched plates will lead to warping and seal failure. Might not happen this week, or even this month, but it will happen. [/B][/QUOTE]


lol...well i guess you missed my point...i gutted the t-stat housing...read the post before you respond....therefore, its like my t-stat is constantly open.....also, i understand how the coolant ssytem works, engine is more efficant at higher temps, but can't go to high because a seal will go, or the housing will warp...so the t-stat is used to keep the engine in it optimun heat range to be the most efficant.also, my oil pressure and oil temps have stayed the same since I removed the t-stat...maybe my engine is just special

glorthu

Fine, but if I find the same answers people are giving here, I will still be inclined to argue. I don't have enough practical knowledge with vehicles to know if the trends you are describing are true, but I do have a good enough theoretical base, to know that at least some of the theory that is being presented to explane these trends is innaccurate.

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no The coolant can only pick up heat so fast.

In a sense, yes, but not the way you seem to be saying. If you set up a free-body diagram of the system, you have a energy source (the engine), mass flow in at T_i (coolant in), and mass flow out at T_o (coolant out). The heat tranfer from the engine to the coolant is a function of the temperature difference between the engine and the coolant, and the heat transfer coefficient, h. h is a function of the surface area and shape (constants), the fluid properties (density, viscosity, thermal conductivity, specific heat: basically constant), and the flow conditions. To simplify, I'll also assume the engine temperature (T_eng) is constant. The heat flow balance for the system includes heat transfer in (mass flow rate times thermal capacitance times T_i) and heat transfer out (mass flow times capacitance times T_o). So the parts of the energy balance equation that are variable are mass flow rate, h (as a function of the flow conditions), T_1 and T_o.

The general equation of convection (which I mentioned before) is Q = h(T_eng-T_coolant), where Q is energy transfer. If the average of T1 and T2 (~T_coolant) are lower, that will increase the heat transfer from the engine, assuming h is the same. But in fact, h is generally increased by increased turbulence (mixing helps heat transfer).

Does this make more sense? I think people here are getting caught thinking of energy (heat) transfer as depending only on the temperature rise of the coolant. There is a bit more to it than that.

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Pump impellers are designed to work with a specific operating speed both for flow, pump volumn, and average operating speed with that flow. If you change the flow rate, the impeller is no longer working in an optimum movement, causing cavitation.

But you aren't changing the speed at which the pump is operating! You're only allowing coolant to flow more freely through it. The pump is mechanically coupled to the driveshaft, and its speed is completely independant of the thermostat.

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This is very very basic and is covered in even basic fluid dynamic engineering (and probably even high school physics).

Careful, I'm new to the forum, not new to the world!

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But any long term rotary user (including ones that race rotary engines) can tell you how without a restriction (be it a restrictor race plate, or a thermostat) that there are some major internal water cooling issues and hot spots. Hot spots in an engine that has sandwhiched plates will lead to warping and seal failure. Might not happen this week, or even this month, but it will happen.

Okay, good to know. I just would like to talk to another engineer who also has experience with rotaries so I can find out the real reason for this. And hot spots says to me it may have to do with coolant channel design. Perhaps under high flow operation, some channels end up not getting much flow due to momentum of the coolant in some other direction (e.g. sharp corners).

Nowhere

Don't forget, when you remove the thermostat, you're altering the flow pattern of the cooling system. More water will flow from the suction on the lower rad to the input on the rad. The thermostat forces the water to move ALL around the engine, getting into everything, keeping the hotter areas under controll. With the thermostat removed, the water has an easier route (it will take it, not ALL of it....) vs being circulated throughout the entire engine.

My 2 bits..

Icemark

No, not at all, I don't think you are getting it. The speed of the pump/impeller is driven based on the speed of the engine. It is always changing (well unless you are idling- but that is only a simple design variable).

Engine (and of course water pump) speed in infinitely variable.

The speed of the coolant flow with a restrictor is more consistent, yes.

Only a electric pump runs at a semi consistent speed.

Crank based pumps run at engine speed (which is why on the stock system despite the great design on the Mazda water pump, still start to cavitate at around 6500).

Icemark

No, originally you said you were running without a thermostat. Your said:
and
A gutted thermostat is still a thermostat and works perfectly fine because of the restriction (other than of course you coolant temp is probably low.

Most people racing a rotary use a restrictor plate or gutted thermostat. This is considerably different than removing the thermostat.

That is why I didn't say anything about your post of :
Because that was correct.

But again you said: not, "I have been running with a gutted thermostat since july with no problems" (which apparently is what you now claim to have meant).

glorthu

Sorry, I should have said "Removing the thermostat does not change the pump speed." Obviously the pump speed changes with engine rpm, but at a given rpm the pump speed does not change between having a thermostat and not.

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Only a electric pump runs at a semi consistent speed.

And an interesting note is that the electic water pump may change speed when you change from having a thermostat to not having one. The decreased restriction may allow the electic pump to run faster.

glorthu

So you're saying that removing the thermostat opens (or widens) a passage that allows coolant to bypass the engine? Do you know where I could find a coolant flow diagram of some sort to check it out?

Thanks!

Icemark

yep, an electric could be tuned for the flow rate you want with or without a thermostat.

There is a company building an electric water pump for the 13B, but because of the high current draw it is designed for drag/burst racing and not for high speed engine operation.