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  #13  
Old 07-29-2011, 02:32 PM
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Re: Intake air temperature

OK - so I just ordered an OBDLink SX Scan Tool, and will plan on logging data this week on my way back and forth to work. It will log IAT data all week. I will also collect infrared temps of the engine bay as well as the intake at the airbox, midway down the intake, and at the throttle body. I'll do that for a week with the OEM airbox. Next weekend, I'll put on the bwoody intake and do the same.

I'll be more than happy to send you the logs.
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  #14  
Old 07-31-2011, 09:25 AM
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Re: Intake air temperature

How much time does a molecule of air spend in the intake tract absorbing heat?
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  #15  
Old 08-01-2011, 06:18 AM
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Re: Intake air temperature

Hi guys, I've read a lot of debate of Aluminium intakes adding to AIT. one thing you need to consider in your analysis is that Aluminium is a very poor radiator. Polished aluminum radiates only about 5% of it's radiant energy (emissivity is 0.05) and therefore is 95% reflective. Consequently air rushing through the Al tube, unless it is directly in contact with the surface is not being heated by radiant energy. The plastic on the other hand (any organic) has very hi emissivity and radiates very efficiently. Ie it will heat up air more quickly passing through the tube. Yes, Al is a good conductor but it's ability to transfer heat is limited by it's poor radiance. Likewise, it can reflect a good amount of heat being radiated upon it by other high temps in vicinity, like engine block!
I'll admit you don't want to sit AIT sensor against it, but if isolated should be ok. Main thing is, inside of air intake needs to be polished and shiny, otherwise it will have high emittance and all benefits will be lost. If inside of air intake is cast alloy, or dull and highly oxidized then you have 2 problems... Good thermal conductivity and radiance.

Otherwise, Al and plastic should reach same temperature eventually, ie at some point they will reach equilibrium as engine bay temps.
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Old 08-01-2011, 06:36 AM
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Re: Intake air temperature

I'm so glad I'm not the only nerd on here...

btw, I ordered the K&N drop-in to use until someone proves this intake can really make that much more power and not just sound cool.

Maybe we should all get air intercoolers and mount them in front of the radiator. down ATI make a pro charger for the WK2 yet??????
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Old 08-01-2011, 08:54 AM
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Re: Intake air temperature

Quote:
Originally Posted by wardy View Post
Hi guys, I've read a lot of debate of Aluminium intakes adding to AIT. one thing you need to consider in your analysis is that Aluminium is a very poor radiator. Polished aluminum radiates only about 5% of it's radiant energy (emissivity is 0.05) and therefore is 95% reflective. Consequently air rushing through the Al tube, unless it is directly in contact with the surface is not being heated by radiant energy. The plastic on the other hand (any organic) has very hi emissivity and radiates very efficiently. Ie it will heat up air more quickly passing through the tube. Yes, Al is a good conductor but it's ability to transfer heat is limited by it's poor radiance. Likewise, it can reflect a good amount of heat being radiated upon it by other high temps in vicinity, like engine block!
I'll admit you don't want to sit AIT sensor against it, but if isolated should be ok. Main thing is, inside of air intake needs to be polished and shiny, otherwise it will have high emittance and all benefits will be lost. If inside of air intake is cast alloy, or dull and highly oxidized then you have 2 problems... Good thermal conductivity and radiance.

Otherwise, Al and plastic should reach same temperature eventually, ie at some point they will reach equilibrium as engine bay temps.
The measured IATs are at least 30* cooler when cruising and up to 70* cooler when sitting idling for long periods with the IAT located in the inlet of the filter vs the intake pipe itself. The IAT was installed in a rubber grommet in both the filter and the intake pipe.
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Old 08-01-2011, 02:51 PM
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Re: Intake air temperature

Took the first measurement of IAT yesterday afternoon in the OEM location with the OEM intake. When I started the Jeep - temp on the dash thermometer showed 96. IAT started at 98* in my driveway before I started the drive.

Over the course of a combination of stop/go and freeway driving for around 40 minutes, the max temp it got to was 118. Median was 114. So, 50% of the measurements (one per second) were below 114, and 50% above.

My goal is to show that the BWoody either does or does not increase the IAT above OEM.

The simple null hypothesis is that the change from the OEM intake to the BWoody intake has no effect on the measured IAT at the locations of the IAT sensor.
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  #19  
Old 08-02-2011, 06:57 AM
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Re: Intake air temperature

This is good science, my friends. I'm proud, and excited to see the results
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  #20  
Old 08-02-2011, 07:41 PM
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Re: Intake air temperature

Quote:
Originally Posted by wardy View Post
Hi guys, I've read a lot of debate of Aluminium intakes adding to AIT. one thing you need to consider in your analysis is that Aluminium is a very poor radiator. Polished aluminum radiates only about 5% of it's radiant energy (emissivity is 0.05) and therefore is 95% reflective. Consequently air rushing through the Al tube, unless it is directly in contact with the surface is not being heated by radiant energy. The plastic on the other hand (any organic) has very hi emissivity and radiates very efficiently. Ie it will heat up air more quickly passing through the tube. Yes, Al is a good conductor but it's ability to transfer heat is limited by it's poor radiance. Likewise, it can reflect a good amount of heat being radiated upon it by other high temps in vicinity, like engine block!
I'll admit you don't want to sit AIT sensor against it, but if isolated should be ok. Main thing is, inside of air intake needs to be polished and shiny, otherwise it will have high emittance and all benefits will be lost. If inside of air intake is cast alloy, or dull and highly oxidized then you have 2 problems... Good thermal conductivity and radiance.

Otherwise, Al and plastic should reach same temperature eventually, ie at some point they will reach equilibrium as engine bay temps.
Think you'll find that the majority of the heat transfer is by convection, not radiation. Plastic is a poor heat conductor compared to aluminum. However, eventually, they will both get to an equilibrium temperature state in the engine bay. Combustion air gets heated by convective heat transfer from the inside surface of the intake tube. Inside of the tube gets heated by condution across the tube wall. Outside of tube gets heated by convective heat transfer of cooling air flow from radiator exhaust air over the outside surface. Coefficient of convective heat transfer is "h" and a very difficult parameter so most relationships are empirical, rather than rigorous. Depends on relationships like Reynolds number, Prantl number, Nusselt number, etc.

I watch the IAT on the DashDAQ XL on the highway and in town traffic. With just the K&N drop-in, the IAT shows about 10-15 degr F above ambient in steady state highway driving and can be >40 degr F higher in stop-and-go town traffic. Differences also vary by season (Summer / Winter).

For you HEMI dudes, remember, you are using 1/2 the rated air volume when MDS is active. Velocity through the tube will be less, so there is more time for heat gain.....however, the "h" value also decreases with a decrease in velocity, so.....it's not clear which has the greater influence.

A good calculus-based text on heat, mass, and momentum transfer will help you.
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  #21  
Old 08-03-2011, 02:56 PM
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Re: Intake air temperature

Measurements from this morning:

Ambient air temp as measured by the thermometer on the dash: 81

After a 13 mile drive of stop/go and hwy driving:
IAT max was 118, with an average of 111.

Interesting:
Infrared temp measurements once I parked:
Temp at snorkle lip: 100
Temp on the top of the OEM airbox: 105
Temp on the corrugated connecting tube between the airbox and TB: 121
Temp on the box that connects to the throttle body: 110

So, there are parts of the intake that get above what the IAT sensor ever measures.
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Old 08-03-2011, 06:13 PM
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Re: Intake air temperature

My thinking is that if an aluminium intake is designed correctly, conductive, convective and radiant heat transfer to the passing air would ALL be minimised when compared to a material of higher emittance (say plastic/rubber/organic air intake. Without actual data and testing of the individual designs (which may reveal other design flaws) my instinct would be to go with Al ducting.

Inside the Aluminium intake must be smooth and polished to reduce radiant loss. The smooth surface will also reduce convective losses, and improve laminar flow, as oppossed to turbulent flow which will have more air comign into contact with the surface of the hot aluminium. I would argue that with good laminar flow, radiant transfer is a significant contributor.

Aluminium or plastic in that environment will reach equilibrium with engine bays temps (unless directly in contact with a hotter surface, in which case Al will be hotter). While the plastic/rubber materials can be designed to reduce convective transfer, the are still very good emitters and will be responsible for a large amount of radiant transfer.

It is exactly the same principal with aluminium air conditioning ducting in a hot roof atic/ceiling space. In summer, inside your roof it's well over 60C, and yet you are passing refrigerated air through meters (or feet) and meters of ducting and it still comes out relatively cool in the house. The Al is very efficient at minimising both convective and radiant sources of heat transfer.

While i am no expert in all things scientific, i do perform thermal imaging for a living and energy loss on structures is one of our core areas.
If anyone's intersted i can send you images of manifolds/ducting that illustrate the point. I am not sure how to imbed an image here.

If you go to this link and check out the gallery of images i took with one of my cameras you will see an electric kettle that has just boiled. Note the temp scale on the right. the plastic parts of the kettle are showing apparent temps of 90+C.... whereas the chrome/stainless steel portion shows up at around 25C, despite the fact that the vessell is holding boiling water.
http://www.ipi-infrared.com.au/infra...tenance/ipi-r9

Also, just be careful what materials you are measuring if using an infrared spot radiometer, just stick to the organics.

Now of course if your intake is improperly designed, aluminium is not going to help. If you are either already drawing in warmer air because of it's location or position, and/or if you have turbulent air flow or a surface that increases convective heat transfer, and/or dull/oxidised aluminium (inner) that has a high radiance this unit properly won't work that well.

I guess getting back to the original argument... polished aluminium/chrome/stainles steel should be better for getting cool air into your engine if designed properly and i have no doubt the data you are collecting will tell us just that.
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  #23  
Old 08-04-2011, 07:53 PM
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Re: Intake air temperature

Measurements from today:

To Work:
Outside Temp: 77
Snorkel: 97
Airbox: 107
Tube: 117
TB: 107

IAT:
Min: 90
Max: 111
Mean: 101

Work to home:
Outside Temp: 89
Didn't get OEM Airbox temps

IAT:
Min: 95
Max: 114.8
Mean: 101

So, from measurements today it looks like the outside air temp isn't a huge factor in the temp measured at the IAT. 20+ deg difference still resulted in the same average IAT measurement, and just a few degrees hotter at max.
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  #24  
Old 08-05-2011, 06:11 PM
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Re: Intake air temperature

For what it is worth, even with the IAT being read in the intake manifold, my data in another app with a plastic intake tube showed a drop in IAT when header wrap was used. The measurement used was IAT over ambient temp.
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