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Anodizing vs No Anodizing - Thermodynamics -
11-09-2005, 09:25 AM
I had a wild hair, and was going to polish the head on one of my 'scratched to death' VSPEC engines. Then I got to wondering; will the heat radiate better from an anodized head or from a (un-anodized) polished head. Then I found this: Anodized aluminum from a conductive standpoint is pretty much the same as unfinished aluminum. However, its radiative properties are 30-50% higher. Eg unfinished aluminum has an emissivity of 0.3-0.5 anodized aluminum is around 0.8-0.95. That would mean an ano'ed head will allow more heat to radiate into space. So, if I was going to polish it, I would definately re-ano it, but keep the natural shine. Can you chrome aluminum, if so I'm off to FPS.
 
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11-09-2005, 09:33 AM
A polished head tends give false temps on the IR temp gauges due to the emmisivity as you mentioned. It is possible to recalibrate your temp gun but then no one else can take a temp for you except with your gauge. That's kind of a pain.
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11-09-2005, 10:14 AM
The temp gun will give a false reading only if the head is polished on the inside where the plug goes. The center part of the head where you check the temp at. If its polished or has really any type of shiny finish, it tends to make the reading reflect and bounce around not letting it zero in on a particular spot. If you ever want to use a polished head and want to get proper readings, you can always spray some paint in the center so the reflection is gone or reduced. In theory, a colored or ano'd head disapates heat a little better, The darker the better. This also goes for the black cases on some of the motors available. In reality, a real Machined head (like King Headz) cools the motor at a very high rate and much more effectivly than a cast head or stock head.(But thats another story) Sorry for all the info but im bored. Just polish the top fin and it will be just fine on your temp readings.
Also, I have seen some guys using a laser temp gun. These guns can be just as good as a high dollar gun like I have. In order to get a proper read you CANNOT get a good read from just pointing the laser at the head from a few inches away. The laser is just for pointing and not for reading, the temp reader is under the laser and that needs to be lined up and on top of the head at point blank range. Center the big hole on the gun with the plug, forget where the laser is, and this will give you a good reading. When you point the gun with the laser on the plug from a few inches over the head, you just temped the TOP of the head not the plug area. This gives you a false reading and shows a cooler temp. Over all, dont always tune your motor with a temp gun, you dont want to tune for temperature reading. Tune for performance with good smoke, its not uncommon to have a motor run perfect at 260. Hope this helps.  
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11-09-2005, 10:35 AM
If there are any physicists out there, jump into this one, but I think (I said think, but I'm pretty sure) radiation and emmissivity are not the same. Temp guns measure Infrared emmissivity, which is altered by anodizing colors (read the booklet that came with your gun). Radiation, which deals with heat transfer doesn't care what color the metal is, unless the color process/material somehow acts as an insulator.
If you really get into IR emmissivity as a measurement device, you have to take factors such as ambient temperature into account. Our hobby temp guns are just "rough idea" devices, not precision scientific instruments. You get bigger variation in readings based on the accuracy of where you point it at the engine, and how far away you are from it. It's hard to do it exactly the same every time. And to Bruce's point about resetting the E factor, which you can do, you do have to consider if all of your engines are (insert your color here). If not the readings will be off on some of your engines. But the real question will be "By how much?" To learn more, go here: http://www.temperatures.com/eindex.html or your local ITT geek hangout bar.
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11-09-2005, 12:09 PM
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11-09-2005, 12:32 PM
Dave, you an engineer? damn. Good info.
When you take a temp reading its important to move the gun around the plug opening to get a different reading to get the average. I have a Exergen and although it may not be NASA certified it is medical grade. Dont chrome the head as it will make your car top heavy too.
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11-09-2005, 05:10 PM
Yes, you can chrome plate aluminum. Hydrogen enbrittlement is the cause of any loss in strength, but in that application it would probably be minimal. On impact the aluminum will still bend but the chrome & nickle layers would crack.
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11-09-2005, 05:32 PM
Last I checked, chrome retails heat. Doesn't sound like a great idea chroming out a head if you ask me.
"If you cook scallops in a non-stick pan, then they won't stick. That's why they call it NON F@#*$&%G STICK!!!" - Im watching YOU!- roc
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11-09-2005, 05:55 PM
Emissivity and Radiation are essentially describing the same effect.
Emissive Defintions emissivity <physics> The giving off of heat rays; a perfect black body has an emissivity of 1, a highly polished metallic surface may have an emissivity as low as 0.02. emissive |iˈmisiv| adjective technical having the power to radiate something, esp. light, heat, or radiation. Radiation Definitions Radiation n 1: energy that is radiated or transmitted in the form of rays or waves or particles 2: the act of spreading outward from a central source 3: syndrome resulting from exposure to ionizing radiation (e.g., exposure to radioactive chemicals or to nuclear explosions); radiation |ˌrādēˈā sh ən| noun 1 Physics the emission of energy as electromagnetic waves or as moving subatomic particles, esp. high-energy particles that cause ionization. • the energy transmitted in this way, as heat, light, electricity, etc. Article on Emissivity http://www.electro-optical.com/bb_ra...y/emisivty.htm Article on Radiation http://www.efunda.com/formulae/heat_...erview_rad.cfm
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11-09-2005, 06:11 PM
You really want to know what the engine temp is get this gun:
http://www.raytek-northamerica.com/cat.html?cat_id=2.7 Also considering what we payed for some of our temp guns they are pretty accurate.
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11-09-2005, 08:55 PM
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11-11-2005, 12:24 PM
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