Effect of vehicle speed on IAT

[aldive]

There have been discussions about “cold air intakes” and ways to duct outside air to the intake as long as I can remember.

I have in the past conducted tests on IAT ( Intake Air Temperature ) vs. vehicle speed and have concluded that there was no real advantage to a “cold air intake”. Nevertheless, to further validate my data and claim that there is no need to duct outside air to the intake or to disprove it, I am repeating the testing.

The test parameters were as follows: various truck speeds from 20 to 70 MPH, determined by GPS ( Dead Link Removed ), ambient temperature determined by the vehicle’s outside temperature display, IAT from PCM as reported to OBD II scanner ( http://www.autoxray.com/default.htm ). The truck has a Mac intake ( http://www.explorerforum.com/forums/showthread.php?t=130982&highlight=mac ).

The truck was driven for 10 minutes at each speed on cruise control and then the IAT was noted and recorded.

For all of the trials, the Black Magic Extreme 180 electric fan ( Dead Link Removed ) was on continuously via manual control.

Prior to any of the tests, the engine was warmed up and the coolant temperature was 194 F ( OBD II scanner determined ).

Speed Ambient temperature IAT

20 82 F 85 F
30 82 85
40 82 83
50 83 84
60 83 84
70 84 86

After the highway testing, I took the truck into town and drove in traffic ( stop and go ) for 10 minutes and then recorded IAT.

Stop and go traffic: ambient temperature- 86 F, IAT – 146 F

Finally, I let the truck run while parked in my driveway for 10 minutes and then recorded IAT and was repeated with the hood open.

Running in Park: ambient temperature – 88 F, IAT – 181 F
Running in Park with open hood: ambient temperature - 88 F, IAT - 138 F

Conclusions: IAT soars with the engine running with little or no air moving ( other than fan ). At speeds of 20 MPH and above, there is little difference in ambient air temperature and IAT. Based on this data ( supported by previous testing ) I see no reason to try to have a so called “cold air intake”. The only difference in these evaluations and the previous ones is that the bumper cover and air dam were not installed ( http://www.explorerforum.com/forums/showthread.php?t=143230&page=1&pp=20 ).

Before you attempt to fab a cold air intake system, try the above test with your truck.

 

[briwayjones]

Just to add a comment. Since getting my Scanguage I did a little comparing of the IAT versus ambient air temp. I have a KKM intake. In my case I noticed that with the outside air temp. around 80d and traveling less than 70mph the IAT would be around 20d hotter than the outside air temp. And once you got below 30mph or so it would get even hotter. At 70mph or over it would come down within about 10d of outside air temp.

 

[410Fortune]

Aldive but have you tested a truck that is sucking in hot underhood air, and then one that actually has a shielded element & airflow to the element?

The main advantage to a "cold air intake" is to remove the factory restrictions that are built into the stock intake. Even this does not, as I understand it add a bunch of horse power, but it does effect throttle response and allow you to pump more air through the engine with more intake and take full advantage of additional exhaust mods/or restriction removals.

I would be curious to see a truck with a simple open element sitting under the hood,,a stock style intake, and then a truck like mine (shielded open element, large intake tube, and large cold air feed from grill)

Your truck has alot of cooling and mileage mods, I expect your underhood temp is much lower than say a factory truck? And your oil, water, and trans temps are lower then said truck?


I can tell you a factory intake at altitude is not the same as an intake like mine at altitude, espcially during the winter when its really cold up there.

So the IAT sensor will send a similar signal through a large range of intake charge air temps, it's not a picky picky sensor it seems.

That scanner is cool. Thoughts on this?

 

[aldive]

Just to add a comment. Since getting my Scanguage I did a little comparing of the IAT versus ambient air temp. I have a KKM intake. In my case I noticed that with the outside air temp. around 80d and traveling less than 70mph the IAT would be around 20d hotter than the outside air temp. And once you got below 30mph or so it would get even hotter. At 70mph or over it would come down within about 10d of outside air temp.

Wow, those numbers seem really high to me.

 

[aldive]

Aldive but have you tested a truck that is sucking in hot underhood air, and then one that actually has a shielded element & airflow to the element?

I would be curious to see a truck with a simple open element sitting under the hood,,a stock style intake, and then a truck like mine (shielded open element, large intake tube, and large cold air feed from grill)

Your truck has alot of cooling and mileage mods, I expect your underhood temp is much lower than say a factory truck? And your oil, water, and trans temps are lower then said truck?


I can tell you a factory intake at altitude is not the same as an intake like mine at altitude, espcially during the winter when its really cold up there.

What do you mean by shielded element? One such as a K & N or Volant?

Maybe its semantics, but the term “cold air” and open element ( shielded or not ) are not the same to me. Cold air intake to me means something like the “ram air” systems of the 60-70s.

My contention is that ducting outside air to the intake does not significantly lower IAT if it lowers it at all.

Nobody is stopping YOU from such an experiment; I would love to see your data.

I seriously doubt that; I shall soon do an evaluation of under hood temperature at various speeds. My oil and water temperatures run comparable numbers to a stock truck; my ATF does run cooler. These facts have nothing to do with this experiment.

I would not have a clue; to me altitude is anything over 50 feet and really cold is any temperature below 50 F .

 

[Rhett]

What do you mean by shielded element? One such as a K & N or Volant?

Maybe its semantics, but the term ?cold air? and open element ( shielded or not ) are not the same to me. Cold air intake to me means something like the ?ram air? systems of the 60-70s.

My contention is that ducting outside air to the intake does not significantly lower IAT if it lowers it at all.

Al, your truck has a MAC intake. My understanding of the MAC Intake is that it DOES NOT bring in outside air. It brings in air from under the hood.

How would your test look if you had outside air getting ducted into the MAC?

 

[aldive]

Al, your truck has a MAC intake. My understanding of the MAC Intake is that it DOES NOT bring in outside air. It brings in air from under the hood.

How would your test look if you had outside air getting ducted into the MAC?

Yes I have a Mac and yes, it draws air from under the hood.

Thats the point in this test; the IAT is not much different than the ambient air temperature at speed. There is no reason to duct for outside air; you cannot get it colder than ambient ( with out some refrigeration ).

 

[Mbrooks420]

Stop and go traffic: ambient temperature- 86 F, IAT ? 146 F

That seems like quite a jump. A cold air intake may lower this quite a bit.

 

[410Fortune]

Cold air = some sort of air duct.
ram air = scoop to help force air over filter
open element = no shield from underhood air

There is a reason you dont see car companies sucking air for the air filter from under the hood w/o some sort of duct I am guessing

There are also turbulance issues that can occur under the hood that can starve your intake. Some sort of shield should be fabricated to protect the filter from hit exhaust air, fan turbulence, spilling fluids, what have you....IMO. And if you're going to shield it it should have a duct to outside air IMO, esentially building a factory airbox, only without the restrictions......

I have never seen proof that a "ram air" setup actually creates boost, I have also never seen proof that lowering the underhood temps, or shooting outside air at your filter actually increase RWHP, But I do know drag racers run ice boxes on the intake, ram air setups with cold air style intakes, so I am guessing there is something to it, especially in high performance engines (not likely us) where every possible CFM and drop in intake charge temp = more power.

I know its a little off topic, your data stuff just always gets me thinking....


Now our trucks are not exactly high performance machines that will be effected by slight changes in ambient air temp and ram air, but every little bit helps.

When its cold enough here in CO the throttle body can ice over, I bet you see a change in IAT readings on that day

I would love to see my data too silly, I dont have the tools/ability (yet)

 

[IAmTodd]

So in this case, the stock box would be better because it pulls from more or less, outside the engine compartment?

 

[410Fortune]

as long as the opening is large enough and the filter is free flowing enough to allow as much air through as the engine wants to draw at WOT, yes.

Somehow I doubt the factory setup does this, especially once you start adding other intake and exhaust mods.

I have a 4" hole in my rad support, right where the factory 88 intake took air from (was about 1.5 x 2.5") with a 4" tube running directly into the shrouded (cut off from ambient air sitting near exhaust header and sealed off to hood/inner fender) area under my hood where my KKM sits.

 

[spindlecone]

Very interesting 410 about the turbulance starving the intake, last dyno run I had the dyno guy hit the intake direct with one of the fans they use (3rd pull) it killed the engine,why?

 

[410Fortune]

freak incident? I dunnop but I am guessing the air was flowing over the filter and not into it? the filter sitting in a pocket, and cannot draw enough air to feed the engine? I dunno, just a guess.
Did it do it every time or just that once? Would have been fun to play with some cardboard in that situation.

 

[spindlecone]

freak incident? I dunnop but I am guessing the air was flowing over the filter and not into it? the filter sitting in a pocket, and cannot draw enough air to feed the engine? I dunno, just a guess.
Did it do it every time or just that once? Would have been fun to play with some cardboard in that situation.

Just the one time, dyno guy thought it was due to hitting the MAF with cool air.
But starving the filter as you say is a good possibilty, makes sense

 

[410Fortune]

My MAF gets cold air here in CO, never shut it down, in fact the 4.0L always loved the super cold temps (ran like a bat out of hell)

 

[aldive]

Stop and go traffic: ambient temperature- 86 F, IAT ? 146 F

That seems like quite a jump. A cold air intake may lower this quite a bit.

Please explain how this would work.

In stop and go traffic, max speed about 15 MPH, there is verry little air flow, ducted or not.

 

[aldive]

So in this case, the stock box would be better because it pulls from more or less, outside the engine compartment?

Better for what? These data show that the IAT is basically the same as the amvient outside air temperature ( on my truck which has NO outside air ducting ).

 

[410Fortune]

there is more airflow then you might think, even sitting at idle.
I know if I put my hand over my intake opening it starts sucking around my hand

Naturally aspirated engines suck the air they need, they are not fed it.

and sorry if it seems like I am trying to discount any claims, I am not, I just want to add to this... I am not sure how relaint the PCM really is on the IAT anyways. It would be interesting to effect the voltage sent to the PCM from the IAT and see how the timing/air/fuel changes. or like that IAT resistor mod effects it (run rich at all times I am guessing)

 

[spindlecone]

My MAF gets cold air here in CO, never shut it down, in fact the 4.0L always loved the super cold temps (ran like a bat out of hell)

On the other hand in your case all temps are cooler, ambiant, intake air etc.
If your on a dyno running hot with outside temps say 80, and you hit the maf with 80deg air when maybe it needs underhood temps, wonder if it would have a bad effect.
Think as you said, it somehow starved airflow

 

[Rhett]

Yes I have a Mac and yes, it draws air from under the hood.

Thats the point in this test; the IAT is not much different than the ambient air temperature at speed. There is no reason to duct for outside air; you cannot get it colder than ambient ( with out some refrigeration ).

But don't you find that, except at highway speed, your underhood air temps are higher than the outside air temps? I did.

I did a test a few years ago with my Explorer, with the idea toward setting up a ducted cold air setup. I set a remote thermometer under my hood, and a remote thermometer outside. Consistently, the under hood air was warmer...as high as 140 degF on an 80 degF ambient day. When driving at 70 mph, under hood air temp was about 90 degF; still warmer than the ambient.

At normal town driving speeds, (20-50 mph) underhood air was typically in the 100 to 120 degF day while ambient/outside air was 80 degF.

I should do this test again.

You do not get similar results with your 2nd gen front end? Maybe the 2nd gen front end cools under the hood differently. You were measuring IAT's, not underhood air.