37 replies to this topic

[Keith Novak]

Actually neither are entirely correct. Why does sweating cool you on a hot day? Why do you feel cooler in a breeze than still air? Evaporation pulls heat from you. Moving air speeds evaporation and cools you faster. If you drive or trailer a car when it's bone dry, once everything is the same temp, it's the same temp. It doesn't matter if the air is moving or not. Everything is at the same temp. When you introduce moisture, the moving air will reduce temps by speeding evaporation.

I forget the mechanics of it all but I think that's still how it works.

[Rob Burgoon]

Moving air still matters some. Suppose the engine block is at 60* and metal conducts heat well (which it does). The 25*F air molecules next to the engine get a boost of speed from the molecules in the metal, bringing up the temp of the surrounding air to be closer to the temperature of the engine block. If the air isn't moving, this is kind of like wearing a wetsuit. The temperature of the air around the engine comes up and the engine doesn't cool as fast until that air leaves by convection or it gives that heat energy to colder air.

If you put this engine in 30mph wind, it never gets a chance to warm up its engine bay and sit in an insulating layer of warm air, since the air around it is always getting replaced with fresh 25*F air almost instantly. So the engine in the wind cools faster.

[Keith Novak]

This is true. Getting back to the original question about how to not let your engine freeze...moist air and moving air will make your engine colder. On an open trailer with no heat going into the engine, it can freeze faster because heat will leave faster and it can get colder than the ambient temp. When in doubt use antifreeze, dump it in a container you can reuse when you want to run water. Antifreeze doesn't go bad like mayonnaise. You can reuse it later. The 1 gallon jugs that Arizona Ice Tea come in are great cuz you can drink it, and then have a super durable 1 gallon jug for water or coolant.

When your car is sitting after a race, straight water doesn't cool down right away and putting a cover over it will make it cool slower due to less moving air. It has to be pretty cold for it to freeze over night. Still worried about it freezing? Hang out for about an hour and it will be cool enough to dump out and refill with your antifreeze for the night. Reuse your distilled/water wetter or suck up the $6.50 for 2 gallons of distilled and half a bottle of water wetter.

[SaulSpeedwell]

I don't get it. The fear of coolant being on the track is WILDLY overblown compared to all the other "dangers" of racing. Yeah, I know it is slippery. Yeah, I know it doesn't clean up nice. The fact remains it doesn't happen often, and when it does, it isn't much different than the MUCH more common oil slick laid down in a turn. If you are first on the scene, you fly off the track either way. Everyone else tiptoes around it while the debris flag waves.

If the zero tolerance attitude towards coolant was warranted in terms of the actual risk it presents, then there would be a zero tolerance for contact, leaving the racing surface, we wouldn't race in the rain, and there would be a "3 strikes" rules for over-strung engines blowing Redline all over the track. If you cause a debris flag, you get points on your license. If you hit someone, you get points on your license.

Boneheaded moves, divebombs, pinch moves down the straight, people "racing" out of class, people making aggressive moves for 12th place in a Regional, people threatening each other in the paddock (ahem, 2009 Runoffs) ... all are "dangerous" and all should be punished. Or not.

The most dangerous part of racing is the starts and restarts - should we write in a rule that all starts are single file, with 1 second between cars, and no passing before the flag station? I'M ALL FOR IT!!! Suddenly "Qualifying" might actually matter

At the end of the day, an engine relieving coolant on the track happens almost never. It only takes 10-15% antifreeze to protect down to 0 deg F, and that isn't much more slippery than rain on a green track, and certainly not as slick as oil. The normal "not very green looking" Prestone, at 10-15% it still looks clear unless you pour a bunch of it into a clear container.

But, if you want to run a generator all night, or stay 1 hour later and get there 1 hour earlier doing a coolant replacement, you can do that too

[ChrisA]

Wind chill is described as the "feel" the wind creates on human skin in relation to the actual temp. Wind will do a lot of things but it will never lower the temperature of an object lower that the temperature of the wind. In other words if the outside air is 25 and your car on the trailer is traveling through a 50 mph wind(towing), its still 25! But of course the wind blowing across the car will cool it quicker if it started at 50 degrees in your garage!

We are saying the same thing...you are just using the words "wind chill" which is not the correct term. "Wind Chill" is a term which only applies to humans. At least this is how I've always understood it

Using the given example, once the wind has exchanged the human's body temperature to the 25° ambient, the person will no longer feel colder than 25 no matter the wind speed, just like any non-living object.

[SaulSpeedwell]

Using the given example, once the wind has exchanged the human's body temperature to the 25° ambient, the person will no longer feel colder than 25 no matter the wind speed, just like any non-living object.

I've always felt wind chill was subjective BS invented by "meteorologists". Yeah, humans are "radiators", but some of us have more natural insulation than others ... and some of us don't wear miniskirts and UGG boots at the same time - or at all .

I'd love to read a scientific paper asking a broad spectrum of people how they "felt" standing naked in a refrigerator, versus standing naked in a refrigerator with 5, 10, and 25 mph winds blowing over them. Did the Russian guy "feel" as cold as the girl from Florida?

What about the effect of the sun's warming rays? Why don't we have a BS term for that?

[CruzanTom]

What about the effect of the sun's warming rays? Why don't we have a BS term for that?

Well, there is a "heat index" based on humidity and temperature. This is how it feels:

[ChrisA]

I'd love to read a scientific paper asking a broad spectrum of people how they "felt" standing naked in a refrigerator, versus standing naked in a refrigerator with 5, 10, and 25 mph winds blowing over them. Did the Russian guy "feel" as cold as the girl from Florida?

The Russian guy actually may have felt colder... I've had Florida girls leave me feeling rather cold.

[fishguyaz]

I don't get it. The fear of coolant being on the track is WILDLY overblown compared to all the other "dangers" of racing. Yeah, I know it is slippery. Yeah, I know it doesn't clean up nice. The fact remains it doesn't happen often, and when it does, it isn't much different than the MUCH more common oil slick laid down in a turn.

when i roadraced motorcycles with AMACCS 25 years back they would have us remove the radiator cap and look at tech to see NO antifreeze was being used. water wetter was OK. if you dumped antifreeze on the track you were in trouble as this would have meant you went through tech w/o it, then added it before going out on track knowing it was not OK.


wish it were the same rules for cars.

[Bench Racer]

I would suggest that in the SCCA Spec Miata class one may not drain the antifreeze (OEM from the factory) and refill with water because there is no written rule that specs it as being legal to do so.

[Randy Thieme]

I would suggest that in the SCCA Spec Miata class one may not drain the antifreeze (OEM from the factory) and refill with water because there is no written rule that specs it as being legal to do so.

Bwah-ha-ha-ha-ha!!!!

[Flyntgr]

Thanks everyone!

[SaulSpeedwell]

when i roadraced motorcycles with AMACCS 25 years back they would have us remove the radiator cap and look at tech to see NO antifreeze was being used. water wetter was OK. if you dumped antifreeze on the track you were in trouble as this would have meant you went through tech w/o it, then added it before going out on track knowing it was not OK.


wish it were the same rules for cars.

I think the situation with motorcycles is entirely different, and if you were still in Arizona back then, it is WAY different

Photos below: NASA Mid-Ohio, a few years ago.

[SaulSpeedwell]

Well, there is a "heat index" based on humidity and temperature. This is how it feels:

I hear ya, but if their "model" is valid, then there should be a "breeze index" in the summer, and a "sun radiation index" in the winter, or they should be able to lump the parameters together. In reality, I don't know that anyone changes their behavior as a result of wind chill or heat index - they just talk about it at the water cooler like it matters.

Meanwhile, even dogs know that the best they can do is be naked, pant, and find shade and water, depending on how they "feel"!

[Keith Novak]

Look up wet bulb temperature. It is the temp taking evaporation into account. Wind chill takes wet bulb temp and factors in the moving air effect on the evaporation.

After frostbitten ears from a few minutes riding my bike to work in college, not wearing a hat when it was a bit over 32* snowing big wet flakes, I can assure you some people change their behavior due to wind chill.

[SaulSpeedwell]

Look up wet bulb temperature. It is the temp taking evaporation into account. Wind chill takes wet bulb temp and factors in the moving air effect on the evaporation.

After frostbitten ears from a few minutes riding my bike to work in college, not wearing a hat when it was a bit over 32* snowing big wet flakes, I can assure you some people change their behavior due to wind chill.

Oh, I know how it works, and so does the dog - I've been freezing my ass off wet and naked a few minutes of every morning of every winter for 38 years. (Please do not misconstrue this as my frequently or ever showering with the dog). And, at risk of being labelled a sexist when I am really just anti-Business-major, even my lovely wife has figured out that her car does it best heating with a fan speed of "2", but she fearlessly goes to "4" in the summer! (I'm still awaiting an automatic climate control system that is as smart as me, the wife, or the dog).

My claim wasn't challenging whether airspeed affects evaporation affects human comfort. My claim is the weatherman giving a title to the effect and attempting to quantify it (e.g. "wind chill") is more subjective BS than not, is dominated by other variables in many situations for which the weatherman doesn't have a folksy fudge factor for, and doesn't change people's behavior except for a tendency for them to annoyingly repeat whatever the weatherman said while we are standing at the coffee pot in 73 degree bliss!

It was kind of a pointless point, but those are always the most fun to discuss. When I get dressed to snowblow to the West with no windbreak, I end up wearing safety glasses and cinching my hood closed until I can barely see out. This is because I have determined that snow melting directly on my face really sucks, regardless of what the guy in the skyscraper 30 miles away says when he he pointing at his map on TV.

[Qik Nip]

Brian:
About that snow picture .... How well I remember that April Sunday morning at Mid-Ohio and the snow plows clearing the track (so NASA wouldn't have to issue a refund)!
Rick
P.S. Old Silver 17 looked a might fresher back then!

[Rob Burgoon]

And, at risk of being labelled a sexist when I am really just anti-Business-major, even my lovely wife has figured out that her car does it best heating with a fan speed of "2", but she fearlessly goes to "4" in the summer! (I'm still awaiting an automatic climate control system that is as smart as me, the wife, or the dog).

Hah! If the air is hotter than you are and you're not sweating it's not wind chill, it's wind roast! Don't convection ovens do that?

If you put your car into circulate, it's mostly a question of whether you want the air in the whole car heated faster, or slower moving hotter air out of the vents.