Intake air temperature

[aldive]

What do you think the intake air temp is on a very hot da?

I just ran my code scanner in the data mode as I drove around town ( city only driving ) with outside air temp 94F.

I was suprised.....

 

[RTStork]

I'll guess that the temp was around 125.

 

[TDG]

20 questions?

I'd be interested in seeing the answer myself, but some of the reactions are comical as well.

I've ran my code reader in capture mode while drivning around but it only returns a voltage reading from the IAT sensor and not the actual temperature. This probably has a lot to do with the older electronics of the early model and a little bit to do with my code reader being a POS. Either way I haven't gotten around to figureing out the voltage to temperature conversion yet.

It would be interesting to see what effect insulating the intake tube would have, since it sits behind the radiator the engine cooling fan keeps a nice supply of hot air blowing across it.

Tim

 

[leenjen]

i'll guess 98 degrees while moving.

 

[aldive]

Thats right it ranged from 98-99 F during in town driving,

This is much cooler than I thoight it would be.

Thats only a 4-5 F over the surrounding temperature.

Thoughts.......

 

[james t]

about the moving air thing: this is true. at my work it gets very hot inside in summer (110-115). we have these little fans that blow MASSIVE amounts of air. we also have thermometer's up everywere (as if we needed a reminder how hot it is...) so, one day we took a therm. down and moved it over in front of the fan. went from 108 to 99 in front of the fan. all the fan is doing is moving the hot air. but, air in motion will be cooled somewhat. ask anyone in heat/air industry. this is why usually you have a slower speed on the fan on the heat side of your central heat/air. they run a little slower so as not to cool the heated air down as much. hope this helps...

 

[aldive]

This low temperature differential seems to negate the concept of cold air intaj\kes.

Comments........

 

[Robb]

I work in the HVAC industry, and it is true that most direct-drive air handlers do run at a lower speed in heat than when they are in a/c. But exactly why that is leads to various answers. I don't believe there would be any reason why dry-bulb temperature would changed because the air is in motion, but I don't know enough about it to debate with james t who has proven it with a thermometer. In a hot area, air moving across the skin feels cooler, but this has to do with with evaporation removal from the skin.

I have huge books on this subject, I guess I should actually read em.

Robb

 

[Alec]

Aldive, you have an open element filter. Even though you'll pull warmer engine air sometimes, at almost any decent speed (faster than walking), enough "cold" air is coming in to push the warmer air away from the filter. Even though the stock airbox is also fed by this "cold" air, the open filter gets much more, improving power, etc.

I don't find the temps hard to believe at all, outside air is coming in and being heated to a minimum before passing the intake temp sensor.

But, to give you a sense of what air temp can do, my measured 0-60 is .2 seconds slower at 85F than 55F, and my truck always feels better when it's colder outside.

 

[HuiDaddy]

So while stopped at a light or stuck in horrendous traffic, how will that affect my engine? is all the air being taken in just hot air that my engine block is producing? is that bad for the car?

 

[Alec]

Not bad at all for the truck. Maybe an imperceptable drop in mpg at idle, but with a 5.0, it won't make a dent as the mileage tends to be crappy anyway In high heat, low speed offroading situations, an open element can cause the motor to run a bit hotter; but it's nothing a healthy cooling system can't deal with.

 

[RedBeard]

For what it's worth, the other day here in warm sunny (ack) Buffalo, my intake temp was hanging around 92-98 degrees at idle. The temperature that day was only 55 degrees. Obviously when I gave it some throttle and got rolling, the temp goes down instantly as cooler air is sucked in. At the next redlight, back to the high 90's... and actually, rolling to a stop (30 MPH), engine at idle, the temp was going up rapidly... gotta be the heat radiating off the engine and heating the intake assembly.

That ding dang AutoXray code scanner is coming in handy for more than just codes. That realtime data monitoring is fun and useful stuff... and my next project will be to wrap the entire intake with heat reflecting tape to see if that idle intake temp goes down a bit.

Oh, BTW... There are no holes in my airbox... The only thing non-stock on the intake is the K&N drop in filter.

-RB

 

[Robert]

I started runnig all of these tests last summer and even posted my results basically backing up what Al found. Once moving, my IAT was within a few degrees of my outside thermometer. Come to a stop when it is 115 F outside, and the IAT quickly climbs to the 170 F range. The IAT is fairly sensative and starts dropping almost as soon as I start moving. I started doing the tests back when people were claiming that the stock airbox provided as much power as my K&N FIPK since mine was breathing in hot air. The plans were to repeat all of my tests with my factory air-box but when I found that once I was moving, my FIPK was basically pulling in ambient air and not the hot air everyone claimed, I didn't see the point in repeating my measurements with my factory air-box. I'm sure it would have taken a little longer to heat up than my FIPK does, but I don't care what kind of power my engine makes when sitting at a stop light. I only care once I am moving.

By the way Alec, "Maybe an imperceptable drop in mpg at idle ...". You wouldn't even have an imperceptable drop in mpg when at idle since when you are sitting at idle your mpg will always be 0 mpg. BTW I'm back