Intake air temperatures - actual readings (and why cones aren't the way to go)...
09-26-2004, 09:52 AM
#1
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Intake air temperatures - actual readings (and why cones aren't the way to go)...
Synopsis: Day 1
Difference between ambient air and the inlet of a front mounted air intake duct is less than 2 degrees F in all moving conditions and 5 degrees F when idled.
Difference between ambient and where a cone air filter would go is amazing. Under hood location was hotter than ambient by a minimum of 14 degrees F - even when driving at 75 mph. When stopped it rose up to 72 degrees hotter than ambient, skyrocketing about 5-7 degrees per second stopped. And, when climbing a steep hill about 37 mph, it rose to 30 degrees above ambient.
Those who say under hood temps soon drop once the car is moving are only half right. They still stay a lot hotter than the air that the engine should be breathing! Secondly, launching from a set of traffic lights in a car equipped with an exposed under hood cone intake could be giving the engine very hot inhalations. Third, very high under hood temps are measured under heavy, low-speed load - something usually not mentioned.
Day 2
Temp probe just inside airbox (instead of at intake duct mouth) versus ambient.
Temp very dependent on amount of air flowing through duct. The duct transfers heat to the air flowing through it and the less air passing through the duct, the hotter the air gets.
By driving at a constant speed and then flooring it, even before the car had picked up speed, the intake air temp immediately started to drop! Conversely, decelerating at any speed caused an immediate increase in intake air temp.
The bigger front duct wins!
<img src="http://pictureposter.audiworld.com/20982/a4intakes.jpg"><ul><li><a href="http://www.autospeed.com/cms/A_1337/article.html">Read the blue box towards the end.</a></li></ul>
Difference between ambient air and the inlet of a front mounted air intake duct is less than 2 degrees F in all moving conditions and 5 degrees F when idled.
Difference between ambient and where a cone air filter would go is amazing. Under hood location was hotter than ambient by a minimum of 14 degrees F - even when driving at 75 mph. When stopped it rose up to 72 degrees hotter than ambient, skyrocketing about 5-7 degrees per second stopped. And, when climbing a steep hill about 37 mph, it rose to 30 degrees above ambient.
Those who say under hood temps soon drop once the car is moving are only half right. They still stay a lot hotter than the air that the engine should be breathing! Secondly, launching from a set of traffic lights in a car equipped with an exposed under hood cone intake could be giving the engine very hot inhalations. Third, very high under hood temps are measured under heavy, low-speed load - something usually not mentioned.
Day 2
Temp probe just inside airbox (instead of at intake duct mouth) versus ambient.
Temp very dependent on amount of air flowing through duct. The duct transfers heat to the air flowing through it and the less air passing through the duct, the hotter the air gets.
By driving at a constant speed and then flooring it, even before the car had picked up speed, the intake air temp immediately started to drop! Conversely, decelerating at any speed caused an immediate increase in intake air temp.
The bigger front duct wins!
<img src="http://pictureposter.audiworld.com/20982/a4intakes.jpg"><ul><li><a href="http://www.autospeed.com/cms/A_1337/article.html">Read the blue box towards the end.</a></li></ul>
09-26-2004, 10:02 AM
#2
You have any before and after data from the smaller v. larger intake duct? ...
It's a great idea, id just love to see if it's helping. Heck, for the price, ill probably slap it on regardless. Good article BTW. Cheers! Mike
09-26-2004, 10:08 AM
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Excellent info! Do you have the hard data on the two OEM air ducts?
Even if the tapered air duct was replaced to the larger one, doesn't the air sensor regulate air flow? Or was the intent of the experiment to check air temp?
09-26-2004, 10:12 AM
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Good research Shawn...
Also an excellent find on that 3.0 duct. The Stock box with a few mods is the best IMHO, plenty of airflow, even with a Stage 3 upgrade.
My intake temps never really get above 55C in 100F temps. At night after several hard runs the temps have gotten as low as 23C, cooler than when I initially started the car at times! The OCT FMIC is the biggest reason, but I think the bigger intake and the custom 3" job on the box is supplementing it very nicely. Good job bud.
Best,
Drew
My intake temps never really get above 55C in 100F temps. At night after several hard runs the temps have gotten as low as 23C, cooler than when I initially started the car at times! The OCT FMIC is the biggest reason, but I think the bigger intake and the custom 3" job on the box is supplementing it very nicely. Good job bud.
Best,
Drew
