41 replies to this topic

[dstevens]

you are correct justin. with some cars the water will pass through the radiator to fast and doesn't get cooled if there's no stat. Run the proper stat for the temp range you want your engine to run at.one more thing please do not open the radiator cap on hot cars again.If that water that splashed on you was 200 degrees you would be a hurtin' right now. don't ask how i know.

The velocity of the coolant (in this case water) is a myth that gets repeated in all forms of racing. It is not correct though it keeps getting passed down from racer to racer. The amount of cooling is determined primarily by the differences in temperature of the heat exchanger. If you rad is hot or ineffective, it doesn't matter if the coolant is stagnant, there will be limited to no heat exchanged.

It's very common in race cars not to run a thermostat though some run restrictors to provide back pressure so there is no cavitation in the water pump. Dave Wheeler says he's not had a cavitation issue in the Miata and I'll go with his experience. In stock cars we did have cavitation issues but the engines were larger and had more water running through them.

On Edit: Opps, didn't see Tom's response. Hammy where you been?

[pitbull113]

The thermostat is simply a valve that measures the temperature of the coolant and, if it is hot enough, opens to allow the coolant to flow through the radiator. If the coolant is not hot enough, the flow to the radiator is blocked and fluid is directed to a bypass system that allows the coolant to return directly back to the engine. The bypass system allows the coolant to keep moving through the engine to balance the temperature and avoid hot spots. Because flow to the radiator is blocked, the engine will reach operating temperature sooner and, on a cold day, will allow the heater to begin supplying hot air to the interior more quickly.
Since the 1970s, thermostats have been calibrated to keep the temperature of the coolant above 192 to 195 degrees. Prior to that, 180 degree thermostats were the norm. It was found that if the engine is allowed to run at these hotter temperatures, emissions are reduced, moisture condensation inside the engine is quickly burned off extending engine life, and combustion is more complete which improves fuel economy.
The heart of a thermostat is a sealed copper cup that contains wax and a metal pellet. As the thermostat heats up, the hot wax expands, pushing a piston against spring pressure to open the valve and allow coolant to circulate.
The thermostat is usually located in the front, top part of the engine in a water outlet housing that also serves as the connection point for the upper radiator hose. The thermostat housing attaches to the engine, usually with two bolts and a gasket to seal it against leaks. The gasket is usually made of a heavy paper or a rubber O ring is used. In some applications, there is no gasket or rubber seal. Instead, a thin bead of special silicone sealer is squeezed from a tube to form a seal.
There is a mistaken belief by some people that if they remove the thermostat, they will be able to solve hard to find overheating problems. This couldn't be further from the truth. Removing the thermostat will allow uncontrolled circulation of the coolant throughout the system. It is possible for the coolant to move so fast, that it will not be properly cooled as it races through the radiator, so the engine can run even hotter than before under certain conditions. Other times, the engine will never reach its operating temperature. On computer controlled vehicles, the computer monitors engine temperatures and regulates fuel usage based on that temperature. If the engine never reaches operating temperatures, fuel economy and performance will suffer considerably.

[davew]

I've said this a bunch of times. Take the stat out, install it in the garbage can. Put car back together.

The purpose of the stat is to warm the car faster. Originally for heater operation, but now-a-days for emmision reasons. We don't care about either. If you are one of those people who think you need the restriction, look at the size of a gutted stat versus the inside diameter of your stat housing. An even smaller hole is at the cylinder head opening into the lower half of the stat housing.

In theroy, water passing through a radiator too fast, will not cool as efficiently. In our cars, too much flow is not possible. So who cares about theory.

To fill the radiator; poor in coolant/water/wetting goo/etc. Start car, top off radiator with water. Install cap. With no stat, you will get instant flow and no air bubbles/pockets to worry about. After bringing to operating temp, allow to cool before removing cap.

On cold days, apply Advanced Autosports stickers to the radiator screen, thus blocking some airflow. FYI, tape is not legal, but stickers are!!!!!!!

Dave

[davew]

Actually, the speed of a fluid flowing through a heat exchanger is very important. The best example is your typical auto A/C system.

Put a thermometer in the dash vent and turn the fan on high speed, record the temp. Now go down with the fan speed one click at a time. The temp will drop at slower speeds. The air is not "in" the evaporator box long enough to get fully chilled at high speed. On a slower fan speed, the air spends a longer time being cooled. Typically the coldest temp is found on the second slowest fan speed. I have seen as much as a 12 degree difference betwwen hi and low fan speeds.

Yes, I spent 25 years fixing street cars and did a lot of A/c work.

Dave

[dstevens]

Actually, the speed of a fluid flowing through a heat exchanger is very important. The best example is your typical auto A/C system.

Yep, the second law of thermodynamics. Velocity is secondary to the exchanger heat differential but an important component. No temp differential, doesn't matter what the velocity is, there won't be an exchange. The exchange pretty much instantaneously. It's physics 101.

[Tom Hampton]

On Edit: Opps, didn't see Tom's response. Hammy where you been?

Been brewing beer! The first 7.5 gallons of porter is about to get split into 3 gallons of chocolate porter, and 3 gallons of coffee porter, and 1.5 gallons of Robust Porter. I'm getting ready for batches 2 and 3. Way more important than this silly season stuff.

Actually, I've been around. Just haven't had much to contribute to the "sky is falling" threads. I'm a techie...shut-up and drive.

The difference between an AC system blower and the cooling system is that the cooling system is a CLOSED, recirculating system. So, while the heat exchanged by a single molecule of water may decrease as it passes through the radiator you're moving more molecules per unit time. Plus there are two halves to this equation:

• Heat from the block going into the water
• Heat from the water going into the air (through the radiator).

The system works to maintain equilibrium between #1 and #2. So, if the water is very cold...heat moves VERY fast from the block into the water...but, because the water is near the air temperature very LITTLE heat moves from the water into the air. This is the situation described above. But, its only temporary. The result of lots of heat IN and none OUT is a rise in water temp. As the water temp comes up, the rate of exchange with the block will decrease, and the rate of exchange with the air will increase. The water temperature will continue to rise until both of these rates are equal: IN = OUT.

The total heat removal capacity (at fixed atmospheric conditions) is limited by the size of the radiator first, and the rate of water flow second.

[Justin Fowler]

Well I have the stat guted and been running it for the past few days and no problems, Think I will just remove the stat when I buy my new Koyo next weekend, yes I have been running stock radiator.

All seems good as of now, just writing up my parts list for my big order and should be ready to get this build fully on its way!

[pitbull113]

glad to hear you got things sorted out

[Justin Fowler]

Thanks SAE! I appreciate everyones help.

Now tell me this, why am I converting this into a racecar again? Just got back from a 3 hour drive, city/highway and only used less than a 1/4 of a tank! I guess these things like the abuse of high rpms

[pitbull113]

don't worry they get great mileage on the track as well

[Tom Hampton]

After I got my alignment at MER, I was getting 29 mpg hwy vice 18 mpg before. Zero toe makes a big difference.

[Justin Fowler]

I am surprised how well these things can take a beating, very eager to get this car on the track. Not much more left, trying to figure out the best way to add my water temp and oil pressure gauges!

[Keith Novak]

Justin...consider a data system. They do cost a few bucks, but sooner or later you'll probably want one. You can put your oil P and water T right there on the dash with your shift lights and other important stuff, complete with idiot lights. Otherwise gauges fit well in the eyeball vents or radio blanking panel. If you go to the Longacre site, they have a link to their refurb page where they sell last years models and the stuff they took out of the box for trade shows for cheap.

[davew]

I know where you can get very nice adapters for water and oil temp gauges

Dave

[Justin Fowler]

I know where advanced autosports would look great on the racecar Dave!

[pitbull113]

I know where advanced autosports would look great on the racecar Dave!

hahahahahaha

[Justin Fowler]

This is not a sponsorship, just an advertisment opportunity!

[Glenn]

I know where advanced autosports would look great on the racecar Dave!

I think he told you where to place is sponsorship stickers......on the radiator! LOL

[Justin Fowler]

more room for advertisements

[Alberto]

If the water pump wasn't working properly, would it leak out of the weep hole? (Assuming the Miata wp has a weep hole like on other Mazdas...)