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The neverending thermostat debate.

Discussion in 'The Hokey Ass Message Board' started by Bort62, Mar 28, 2007.

  1. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Doesn't the thermostat or restrictor plate increase pressure within the engine to prevent localized boiling? If you have a pump that will flow X and then put a restrictor so that it cannot flow X, but something less, I think one or two things will happen - you will increase system pressure between the pump & the restriction (thermostat or restrictor plate) & this WILL prevent SOME of the localized boiling around hot spots (boyles gas law). The other thing this could do is create cavitation (let's not argue the engineering definition of cavitation) around the pump impeller introducing bubbles into the system that will reduce heat transfer some. I think there's a balancing act here...

    If you have a system that is suceptible to localized boiling & hot spots, removing the thermostat can result in overheating if the rest of your system cannot compensate.

    I do not believe you can move the water too quickly, or so quickly the radiator can't remove the heat. I think in the cases where removing the thermostat results in overheating (many flatheads), it is because of localized hot spots & boiling that go away under pump pressure created with restrictors (thermostats or restrictor plates).

    I'm no engineer, but I did stay at a holiday inn express once.
     
  2. fun factors involved
    now do the math !!!!!
    boiling temps of water vs mixed coolant

    speed of water through the system .. t stats(with -without) .. rad size .. water pump speed air flow thru rad and around engine

    coolant system pressure

    the ability for the engine to remove its own exhaust heat

    engine materials that dissapate heat or contain it . aluminum vs steel

    the oiling systems ... heat/friction reduction

    fuel type and air fuel mixtures

    engine timing

    engine pulling against a force lugging with load

    wheeew

    i say use a stat that will keep the temp at 190 -205 and the water should stay in th system....
    slow driving on hot days are the hardest to overcome with any performance engine...

    paperdog
     
  3. i hope this is not solved so we can still be called HOT RODDERS ....
    not Kool engineneers
    kinda like when harleys drip oil most rods puke a lttle coolent when parked after a hard run....
    mmmmmm
    the smell of a hot engine .high octane fuel..... oil... a-f ...and burned rubber

    paperdog
     
  4. chuckspeed
    Joined: Sep 13, 2005
    Posts: 1,643

    chuckspeed
    Member

    this is a HUGE pet peeve of mine. Here's what it is:

    1) Q= GPM x Delta T X 500.

    The amount of heat rejected to the radiator from the motor is a relative constant at constant speed; it's roughly 1/3rd of the heat value of the fuel, or roughly equivalent to the amount of power going to the ground. If you pull the stat and the flow increases 2X - the delta T, or temperature differential, decreases by a factor of 2, as HEAT TRANSFER IS CONSTANT.

    Experiments? been there done that; had to bet a Chrysler engineer a $1500 service contract once that his system was overpumping, as he 'interpreted' lack of residence time the same way folks on this board do.

    2) Thermostats exist to bring the engine to operating temp - and maintain it there. Operating temp is critical to maintain correct piston -to-cylinder clearances; if you run too fat on the clearance, you scuff cylinder walls - and lose HP.

    3) glycol (as an additive) is there to extend freezing and boiling points of the cooling system on an engine; it has the unfortunate side effect of REDUCING heat rejection capacity of the system.

    4) The highest pressure drop item in the cooling circuit is the thermostat, followed by the radiator. Engine is literally a wide spot in the pipe - which presents a problem....

    Here's the reason engines overheat W/O a stat, and it's gonna get techie, so hang on:

    Pumps don't suck - they blow. there's a lower limit to their ability to suck water out of the radiator and push it into the wide spot in the pipe - the motor - and it's called the Net Positive Suction Head Required (NPSHR). When the Net Positive Suction Head Available (NPSHA) is less than NPSHR, the PUMP STOPS PUMPING - it's literally spinning in a bubble of water vapor.

    unfortunately, as you heat water up, it becomes less willing to be pumped B4 turning into water vapor. Adding to the misery is the fact that an automotive water pump spins at some pretty high speeds as compared to most centrifugal pumps, and this causes the NPSHR to skyrocket.

    Soo...when you pull the t-stat, you remove the one restriction in the system which prevents water from changing phase (turning to steam) in the waterpump as the engine approaches operating temp. Once it does that - Bam! water flow comes to a virtual halt, and the engine starts makin' steam in the block - and the engine overheats.

    Guys - I have patents in this sorta stuff; it's what's REALLY going on in the system. the entire explanation takes about 20+ pages - honest. Do a Google search on Net Positive Suction Head if ya don't believe me...
     
  5. Scrumpy
    Joined: May 31, 2006
    Posts: 85

    Scrumpy
    Member
    from NH93 Exit1

    Yes, To bring the temp of the engine UP to the correct operating temp and to keep it there.

    Scrump
     
  6. chuckspeed
    Joined: Sep 13, 2005
    Posts: 1,643

    chuckspeed
    Member

    That's pretty good!

    There are these things called Reynolds Numbers and Prandtl Numbers which (skipping the sordid detail) basically state that the faster a heat transfer fluid moves, the more turbulent it becomes - and the more effective the heat transfer fluid is in transferring heat. If cavitation is left out of the equation for the time being, then yes - removing the stat should increase the amount of heat being transferred.
     
  7. This may stray from "traditional hot rod" application, but for the sake of argument, the EFI Camaro and Mustang guys put lower (160 degree) thermostats in to "make the car run cooler/faster". Is that bullshit?
     
  8. Vicious_Cycle
    Joined: Mar 27, 2006
    Posts: 107

    Vicious_Cycle
    Member

    I like that answer, chuckspeed. Bort62's first post precisely describes my mindset on this debate. You have given me something to think about.
     
  9. Vicious_Cycle
    Joined: Mar 27, 2006
    Posts: 107

    Vicious_Cycle
    Member

    I think they are tricking their ECU's into dumping more fuel into the cylinders.
     
  10. chuckspeed
    Joined: Sep 13, 2005
    Posts: 1,643

    chuckspeed
    Member

    Richard -

    the 160 degree stat is there to bypass closed loop operation in the Powertrain Control Module (PCM). By keeping the engine at 160 degrees, it's in perpetual 'warm-up' mode (as seen by the computer) so the fuel and ignition maps are a bit more aggressive, which translate into a few extra ponies over closed loop (where 02 is monitored off the exhaust and A/F ratios are adjusted) operation.
     
  11. They also put bags of ice on the intake between runs.
     
  12. Damn, I'm glad I gave up on those complicated-ass computer cars! I'll stick with six simple carburetors, thank you.:D
     
  13. chuckspeed
    Joined: Sep 13, 2005
    Posts: 1,643

    chuckspeed
    Member

    I dunno...27 MPG and 110 MPH traps are a nice combo; you don't get that with carbies...
     
  14. SinisterCustom
    Joined: Feb 18, 2004
    Posts: 8,277

    SinisterCustom
    Member

    Cooler intake charge=denser air mix=more power......
     
  15. HotRodFreak
    Joined: Mar 25, 2005
    Posts: 1,935

    HotRodFreak
    Member

    Forget all the theoretical empirical calculation BS for a real moving hot rod scenario with significant variables!
    There are normally accepted thermostat options but bottom line is whatever works in your ride....Sometimes trial and error produces the best solution.
     
  16. Road Runner
    Joined: Feb 7, 2007
    Posts: 1,256

    Road Runner
    Member

    I agree - these old cars and especially the early engines don't require nearly as much theory to make them stay cool.
    Safe experimetation always does the trick.
    And you learn a lot more that way, than any other...
     
  17. 31whitey
    Joined: Jan 2, 2007
    Posts: 2,214

    31whitey
    Member

    thank you hot rod freak...its whatever works for your specific application...DO IT ,dont think about it or think you get it with out actually trying...ignorance is thinking you know how to do something with out bothering to try it
     
  18. chaos10meter
    Joined: Feb 21, 2007
    Posts: 2,191

    chaos10meter
    Member
    from PA.

    What about heat soak?
     
  19. T-Time
    Joined: Jan 5, 2007
    Posts: 1,627

    T-Time
    Member
    from USA

    Several of my cars came from the factory with no thermostat and no waterpump, either. I guess that the engineers didn't think there was a reason for having them. Hmmmm. ;) Thermosyphon 4ever! As I think HF said one time, "If a Model T doesn't have it, a car doesn't need it.":D
     
  20. DrJ
    Joined: Mar 3, 2001
    Posts: 9,419

    DrJ
    Member

    Maybe if the car thermostat was called a "Coolant Temperature Regulator" it wouldn't cause such debate?

    Why does the Heater/Air conditioning system in a house have a thermostat?
    To keep it near a desired temperature, right?
    In a car, it is assumed the radiator is (or should be) designed with enough heat transfer ability to handle at least slightly more heat than the engine can slough off to it at any time under any output level.
    So, since it is desired that the radiator NEVER run at or past maximum cooling capacity it can be assumed that without a thermostat/"Coolant Temperature Regulator" it would get too cold, under less than aximum heat transfer, just like your house would if you turned on the air conditioning full blast and just let it run all year without a preset thermostat to tell it when it's cold enough.
    Right?


    But look at the source of the inquest...
    Rocket Scientist?
    What used to be a "slide rule boy", an engineer... ;)
    (Just ribbin' Ya.) :cool:
    I actually have an Abacus... ;)

    The reasonings used so far are mostly semantical and we might as well be debating whether we have points and condenser in our traditional distributors or what engineers have always insisted on calling them, points and Capacitor!
    My Fender DeLuxe Reverb Amplifier has Capacitors in it but my truck MOTOR has a Condenser! :D
     
  21. CB_Chief
    Joined: Aug 17, 2006
    Posts: 775

    CB_Chief
    Member
    from Oklahoma

    We had a SBC one time in an industrial application that had a hose clamp on the upper hose (not at a connection point) and I asked the shop mechanic about it. The motor ran constant speed 24/7 except for maintenance downtimes. He explained that instead of a thermostat they used the clamp to restrict coolant flow from the engine to regulate the operating temperature of the engine. Anyone else ever heard or seen anything like that?
     
  22. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    Totally True!

    What works for one will not necessarily work for another!

    Different radiator sizes and fan packages and frontal areas mean different heat exchange capabilities.

    Different climates and road conditions and traffic densities means every car is in a different situation.

    Different water pumps, pulley ratios, and cruise RPMs mean different GPHs for every car.

    Let's not forget different heat sources as well. You've got iron engine versus aluminum engines, high compression versus low, agressive or lazy spark, 200hp or 400hp.

    We all operate on the same planet, thus share laws of thermodynamics. There is no denying that. But some of us run closer to the edge of those laws than others, thus some can get away with things others can't.
     
  23. noboD
    Joined: Jan 29, 2004
    Posts: 8,926

    noboD
    Member

    Yes, some tractors use this method.
     
  24. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,697

    theHIGHLANDER
    Member

    Chuckspeed has it dead-on correct. His scenarios may not take place in all combinations which is why some get away with certain cooling system get-ups. The "do whatever works" ideas are just a way of saying you don't care. There's times when you sometimes should care like designing something new or upgrading major performance components. Heat is our friend not our enemy. Heat is the energy in the fuel. The more control you have over it the more power and efficiency you'll see, or stated another way, the hotter you can run the engine and still maintain the same friction factors and air/fuel ratios the more power it will make. Now, before that starts another debate within this discussion most of us know that there are limits to that idea and let's just leave it at that.
     
  25. Chuckles Garage
    Joined: Jun 10, 2006
    Posts: 2,365

    Chuckles Garage
    Alliance Vendor

    I actually experimented without a thermostat in my 460 ford. Without the thermostat it never would reach normal operating temperature. Not even with the fan off sitting still with zero airflow through the radiator.

    With the thermostat, it worked as it should.
     
  26. I've had ski boats that restrict the flow of water to regulate the temp. But, that's on an unlimited supply of water/open system (the lake itself). It don't compare to the "closed" system on a car
     
  27. thecockeyedwallaby
    Joined: Feb 27, 2007
    Posts: 262

    thecockeyedwallaby
    Member
    from Kelowna

    I'm not sure if the thermostats are there to cool the engine better or help keep the engine at a better running temperature. After all an engine may run more efficiently when hot, but not too hot. So you don't want water running through the rad cooling the engine until it needs cooling. As well if you cool the engine too fast you can crack the block, so I would think the thermostats would help protect against this. I know that in my 51 merc pickup the original rad was so good at cooling that if you went down a hill or by a lake where the air was cooler, you'd notice the water temp drop very fast, and could potentially crack a block I would think.

    As for your comments of people running without thermostates, I haven't heard of that, and I wouldn't do it myself, but I have heard of people replacing the thermostates with washers to act as restrictors.


     
  28. thecockeyedwallaby
    Joined: Feb 27, 2007
    Posts: 262

    thecockeyedwallaby
    Member
    from Kelowna

    That's a pretty silly view, I mean everything works based on the laws of physics, hot rods are no exception.

     
  29. beetlejuice55
    Joined: Feb 18, 2007
    Posts: 738

    beetlejuice55
    Member

    i ran a very built 396 in a 70 nova, which ran hot (it would go well over 200 degrees if i got caught in traffic, and eventually i'd have to shut the engine off).
    (the car ran 11.90 in the 1/4 mile) it had a 3 core radiator, and a 195 t-stat. what i did was remove the center of the t-stat, and then put the rest back in as a restrictor. from that day on, no matter what the outside temp was...the engine ran at 190-200 degrees, all the time. i was using a flex fan on the engine, and no electric fan. this worked good for the 2 years that i owned the car....and it never overheated.
     

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