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Old 06-29-2011, 08:46 PM
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Intake air temperature

Ok, so I do engineering for a living, so bear with me. I've been contemplating purchasing the Bwoody intake for my HEMI (or maybe the mopar cai), and was doing some snooping around under the hood today. After driving home from dinner, I noticed how HOT the HEMI gets, as well as everything around it, stock air box included. I was wondering if there any other dorks like me out there that have measured the temp of their air intake charge at the throttle body while driving, and if there was a difference between stock and with one of these aftermarket intakes. I know it's probably a longshot, and I'll probably end up borrowing a thermocouple from work and trying it myself, but I figured I'd ask first. Just curious if the air from the Bwoody is any hotter than the stock setup, which could somewhat limit it's effect. Lots more of hotter air isn't necessarily better, ya know. Discuss...
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Old 06-29-2011, 10:01 PM
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Re: Intake air temperature

those values should be available from the obdII port OR has the wk2 moved on from OBDII?

I know aerofroce gauges in my wk can tke 2 diff air intake temps:

1. INTAKE AIR- Intake Air Temperature taken at the throttle body inlet
2. AMBIENT AIR TEMPERATURE – air temperature at the air filter

then its just a matter of install and testing/
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Old 07-08-2011, 10:42 PM
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Re: Intake air temperature

Metal tube from the aftermarket Bwoody gets way too hot and I lost lots of performance, OEM is going back on. Engine bay is sealed up oo tight, no air flow. Hood needs luvers.
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Old 07-09-2011, 07:29 AM
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Re: Intake air temperature

See this thread, there may be others.

http://www.jeepforum.com/forum/f309/...5-7-a-1236020/

Bottom line, I think, is there is no easy way to get cold outside air into the motor. The IAT sensor is affected by the temperature of the housing it is mounted on. CAIs with metal housing get hotter than plastic (stock) housings, as a result the computer thinks the air is hotter than it actually is and makes adjustments that degrade performance.
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Old 07-09-2011, 08:18 AM
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Re: Intake air temperature

Quote:
Originally Posted by phisch View Post
Ok, so I do engineering for a living, so bear with me. I've been contemplating purchasing the Bwoody intake for my HEMI (or maybe the mopar cai), and was doing some snooping around under the hood today. After driving home from dinner, I noticed how HOT the HEMI gets, as well as everything around it, stock air box included. I was wondering if there any other dorks like me out there that have measured the temp of their air intake charge at the throttle body while driving, and if there was a difference between stock and with one of these aftermarket intakes. I know it's probably a longshot, and I'll probably end up borrowing a thermocouple from work and trying it myself, but I figured I'd ask first. Just curious if the air from the Bwoody is any hotter than the stock setup, which could somewhat limit it's effect. Lots more of hotter air isn't necessarily better, ya know. Discuss...
I'm an engineer also. I measure IAT all the time with my DashDAQ XL. Intake is stock, but with K&N drop-in element.

Intake Air Temperature (IAT) sensor on mine is in the cross box silencer on passenger side. Fresh air intake is through the radiator support, forward of the radiator, so it is somewhat colder than under-hood.

Typical IAT is 5-10 degrees F over ambient when I'm underway at 55-60 mph. In traffic, I've seen it at 122F when ambient was 87F.

The only thing I would change in the air intake system is that huge cross box noise silencer. It's everywhere and a PITA to work around. However, a metal one will heat soak and cause the incoming charge to be less dense. Tough to locate a piece of plastic tubing to substitute for it. I didn't want to spend $200 for an entire system and use only the 2ft tube. Incoming air charge probably receives more heat from the intake manifold than from the cross box.

I removed the "beauty cover" on top of the HEMI to allow more air circulation. Don't know if it worked, but it is easier to get to everything for servicing now.
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Old 07-09-2011, 11:43 AM
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Re: Intake air temperature

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Originally Posted by Walt View Post
Tough to locate a piece of plastic tubing to substitute for it. I didn't want to spend $200 for an entire system and use only the 2ft tube. .
I've read of some that cobbled together combinations of standard PVC pipe and elbows, perhaps a rubber pipe connector. Works, if not the best of aesthetics. I haven't heard of anyone actually getting dramatic performance increases, but some like the look and sound. There is not much airflow through that slit above the radiator.
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Old 07-09-2011, 01:49 PM
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Re: Intake air temperature

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Originally Posted by ColdCase View Post
....I haven't heard of anyone actually getting dramatic performance increases, but some like the look and sound. There is not much airflow through that slit above the radiator.
As a curious engineer, I'd really like to see one of the cold air advocates do a dyno run with the stock air intake, install the aftermarket CAI, then do another dyno run.

I would be surprised to see anything significant in the rpm range that I drive. Since I typically run in the 1800-3000 rpm range, the volumetric air flow through the stock design is adequate.

Sound is another matter: That's an individual taste issue.
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Old 07-09-2011, 10:55 PM
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Re: Intake air temperature

Good stuff, guys.

So I have three thoughts:
1) Even with the more restrictive stock airbox, could the K&N drop-in actually yield better performance than the aftermarket intakes due to the lesser heatsoak and the cooler AIT?

2) Has anyone attempted using the stock intake box and deleting the intake silencer, using pvc to go directly from the intake box to the throttle body?

3) Would using exhaust header wrap on the metal tubing of the aftermarket AI give any benefit, or is the air under the hood just so damn hot from the HEMI that isn't just not going to make a difference?

Side note story about AIT: My previous car as some may know was a 2004 Subaru Impreza WRX. We used to like taking our cars down to the Indianapolis Raceway Park and hit the drag strip on test-and-tune nights for fun. Having an intercooled turbo, and understanding how AIT affects performance (and being an engineering dorks), we would bring down a cooler of dry ice (−78.5 C). I would do a run, then chill my intercooler with dry ice for 15min, then do another run. Being the consistent shifter that I am, I cut 0.7 seconds off my quarter mile time (14.09 was my best). Intercooler was so cold it was generating frost on the outside. Fun times
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Old 07-10-2011, 06:16 AM
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Re: Intake air temperature

Wow, you guys are having some serious talk here and I would like to know where this goes to. Unfortunately, I can't get Hemi here in Korea, so I'm waiting for Mopar CAI. But I also worry about loosing HP due to lack of chamber and excess heat.
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Old 07-28-2011, 09:33 PM
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Re: Intake air temperature

OK - so just to bump this back to the top, I'm really, really curious over this. I 'm a statistician by education, but more of an architect in occupation. I ordered a BWoody, but haven't gotten it yet.

Take a look here: http://www.engineeringtoolbox.com/th...ity-d_429.html

Thermal conductivity is the quantity of heat transmitted through a unit thickness in a direction normal to a surface of unit area, due to a unit temperature gradient under steady state conditions.

Aluminum is 250.
PVC is .19.
Air is .024.
Rubber is .13
Silicone is .22

Aluminum is a better heat conductor than PVC, and PVC is better than air.

There are two sources of heat that are heating the intakes:
1) the actual throttle body itself, but that it realistically isolated by the silicone/pvc elbow that connects to the throttle body.
2) ambient temp of the engine bay.

The other factor to consider is the airflow moving through the intake - either one.

There are actual formulas that could be used to determine the conductive heat transfer that the BWoody ram air intake imparts to the air moving past it. I'm too lazy to do all that math and will go on the base assumption that after a period of time that the BWoody intake is as hot as the engine bay. Given a long enough run, the PVC intake would be as well. The BWoody (and any other aluminum CAI setup) will reach the ambient temp of the engine bay much faster than the PVC, though.

Stay with me.

The air moving through the intake won't absorb heat more from one intake or the other. However, the air moving through the BWoody aluminum intake has a flow rate that's 1.77x the OEM flow rate. So, by extension, the air has that much less time to absorb heat from the intake.

Again - a bit of an assumption here, but in a given amount of time if say one cubic foot of air was passed by the same point at one temp vs one that was 1.77x hotter in 1.77x less time, the heat that would be transferred would be the same. Probably not correct to the decimal, but I'll go with it.

Base conclusion on my part - the flow rate makes up for the difference in temp in the actual intake. I don't think that the OEM intake itself is 77% cooler than the BWoody one will be.

If it were an issue, I would bet that it could be nullified entirely with a header wrap on the BWoody intake.

The IAT sensor is metal, but there is a rubber grommet that the sensor resides in. That rubber grommet will somewhat isolate the sensor itself from the heat of the intake. Again, I'll make the assumption that the thing was meant to be used in an engine bay, so the temp of the sensor itself may not be that big of a deal and the grommet probably isolates it.

Now comes the airflow and source of air.

OEM pulls air from outside of the engine bay. No disputing that that air will be colder than air sucked in from the inside of the engine bay. However, as others have asserted, if the engine bay is sealed tight, 1.77x the volume of air is still being sucked into the engine bay with the BWoody.

Now, that air is being mixed with ambient engine bay air and then taken into the intake.It's going to be hotter than air sucked into the OEM airbox. No doubt about it. How much hotter? No idea.

What we really need to get to the bottom of this is a few measurements:

1) Ambient temps of the engine bay pre/post BWoody install.
2) IR/Thermocouple Temps of the EOM airbox and the BWoody intake
3) IAT measurements from the OEM system and the BWoody intake.

Since I ordered the BWoody and I'm obviously a bit geeked up over it, I'm going to try to get the 3 and put this to rest. No more of this feeling and emotion about it.

I would Dyno test it if I had the time/inclination to do so. Or knew where there was a dyno that I could test with.

Now - can anyone help me out whit a bit of knowledge about how to collect IAT?
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Old 07-28-2011, 09:50 PM
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Re: Intake air temperature

Nice post - i just cant understand 1/2 of it I just bought an OBD2 reader off ebay. It works and collects data. I too want to know some info about it. I'll try to post some info when i get around to doing some tests. I want to see the stock intake, my Airaid and possible wrap to see if there's a diff in temp. My current intake tube is wrapped in foil tape and painted. I found the reader on eBay for $12.
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Old 07-29-2011, 07:51 AM
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Re: Intake air temperature

Quote:
Originally Posted by elvisisdead View Post
OK - so just to bump this back to the top, I'm really, really curious over this. I 'm a statistician by education, but more of an architect in occupation. I ordered a BWoody, but haven't gotten it yet.

Take a look here: http://www.engineeringtoolbox.com/th...ity-d_429.html

Thermal conductivity is the quantity of heat transmitted through a unit thickness in a direction normal to a surface of unit area, due to a unit temperature gradient under steady state conditions.

Aluminum is 250.
PVC is .19.
Air is .024.
Rubber is .13
Silicone is .22

Aluminum is a better heat conductor than PVC, and PVC is better than air.

There are two sources of heat that are heating the intakes:
1) the actual throttle body itself, but that it realistically isolated by the silicone/pvc elbow that connects to the throttle body.
2) ambient temp of the engine bay.

The other factor to consider is the airflow moving through the intake - either one.

There are actual formulas that could be used to determine the conductive heat transfer that the BWoody ram air intake imparts to the air moving past it. I'm too lazy to do all that math and will go on the base assumption that after a period of time that the BWoody intake is as hot as the engine bay. Given a long enough run, the PVC intake would be as well. The BWoody (and any other aluminum CAI setup) will reach the ambient temp of the engine bay much faster than the PVC, though.

Stay with me.

The air moving through the intake won't absorb heat more from one intake or the other. However, the air moving through the BWoody aluminum intake has a flow rate that's 1.77x the OEM flow rate. So, by extension, the air has that much less time to absorb heat from the intake.

Again - a bit of an assumption here, but in a given amount of time if say one cubic foot of air was passed by the same point at one temp vs one that was 1.77x hotter in 1.77x less time, the heat that would be transferred would be the same. Probably not correct to the decimal, but I'll go with it.

Base conclusion on my part - the flow rate makes up for the difference in temp in the actual intake. I don't think that the OEM intake itself is 77% cooler than the BWoody one will be.

If it were an issue, I would bet that it could be nullified entirely with a header wrap on the BWoody intake.

The IAT sensor is metal, but there is a rubber grommet that the sensor resides in. That rubber grommet will somewhat isolate the sensor itself from the heat of the intake. Again, I'll make the assumption that the thing was meant to be used in an engine bay, so the temp of the sensor itself may not be that big of a deal and the grommet probably isolates it.

Now comes the airflow and source of air.

OEM pulls air from outside of the engine bay. No disputing that that air will be colder than air sucked in from the inside of the engine bay. However, as others have asserted, if the engine bay is sealed tight, 1.77x the volume of air is still being sucked into the engine bay with the BWoody.

Now, that air is being mixed with ambient engine bay air and then taken into the intake.It's going to be hotter than air sucked into the OEM airbox. No doubt about it. How much hotter? No idea.

What we really need to get to the bottom of this is a few measurements:

1) Ambient temps of the engine bay pre/post BWoody install.
2) IR/Thermocouple Temps of the EOM airbox and the BWoody intake
3) IAT measurements from the OEM system and the BWoody intake.

Since I ordered the BWoody and I'm obviously a bit geeked up over it, I'm going to try to get the 3 and put this to rest. No more of this feeling and emotion about it.

I would Dyno test it if I had the time/inclination to do so. Or knew where there was a dyno that I could test with.

Now - can anyone help me out whit a bit of knowledge about how to collect IAT?
The air is not moving 1.77 times faster (1.77 times the airmass the stock airbox can handle (~620 CFM)) through the Bwoody or any intake setup unless the engine magically is able to move over 1200 CFM of air all of a sudden. This motor moves about 500 CFM at 360 bhp. 1200 CFM will be inhaled by a motor that makes over 800 bhp. Heat soak happens mainly due to the underhood temps especially the WK2 which has a very well sealed engine bay and also the closer the filter and the IAT sensor are to the radiator (bwoody puts the filter right next to the radiator) that will cause the true inlet air temps as measured at the filter to be up to 203* (ECT is 203*). The filter needs to be moved as far away as possible from the engine (keeping it safe from water ingestion of course) and the IAT sensor should never be put into a metal intake pipe right behind the radiator as this will cause heat soak at the IAT (pipe gets 200* sensor gets hot as a result). With that setup the measured IATs are much higher than the actual inlet air temps at the filter. You will be shocked at how hot the IATs will be with an intake made like bwoody's (metal pipe with IAT in metal pipe with IAT and filter right behind the radiator). You will see 150* IATs after just a few minutes of driving and up to 205* sitting idling for a minute with the engine hot. I have tested 4 different custom intake configurations on my jeep until I found the ideal setup for a short ram intake as I do not want to risk water ingestion. (different filter and IAT sensor locations). I tune for a living so I have really good data logging software but sadly no tuning support for this ECM/TCM yet.
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