hot cold air intake

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Joe Hampton

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Just got a K&N intake installed my ST and noticed the piping is hot after running, even for a short period of time. I mean you can't touch it because its that hot. Could this have any adverse effects on the truck and what could be the cause of it. I was thinking that the filter may be too small for it and the engine is starving for air.
 
I also have a k&n intake and yes it does get pretty hot after the engine has been running. I'm thinking it's just due to the normal underhood heat from the engine. Mine's have never gotten so hot to the point where I can't touch it. In fact, when I did the actual installation of the intake, I remember the stock intake tube and box felt way hotter when handling it than I have ever felt the k&n get.



Do you have the 57 series with the plastic intake tube or the 77 series with the aluminum tube?
 
It's from the friction of the air going through it, not ambient engine heat. Nothing to be concerned with.
 
Hey Dingo, I'm trying to figure out how supposedly cool air could heat up the intake. Would the air not need to already be hot for this to occur? If air friction causes the heat, then what purpose would a heat shield serve and just how effective is the zabteck "true CAI"?
 
my zabteck cai stays cool...



possibly cuz of the paint reflecting heat from engine... and havent noticed any due to friction of the air......
 
Not air friction. It is engine compartment heat. Especialy if you filter is still inside engine compartment. Not enough volocity to create heat.
 
The friction is only along the pipe. The surface area of the pipe in comparison to the volume of air entering the engine is negligible.
 
Dingo, at 600 cfm you are not going to generate any noticeable heat from the air flow. It is the pipe soaking up the ambient under hood heat. Since the air coming in through the filter is cooler it is a positive affect on performance. The amount of heat that say a 200 degree piece of plastic can impart on 600 CFM of cooler air is nil.The coefficient of heat of plastic is not that high so little heat will be transfered to the moving air. Dingo if you blow compressed air through a hose, the hose doesn't get hot. The compressor does since it if bound by the PVT laws of compressible fluids.



If you assume a 4 inch diameter inlet you have about 12 square inches or 1/12 of a square foot. With air flowing at say 600 cfm you will have an air velocity of about 120 feet per sec or about 90 mph. If this velocity caused the heat you are referring to then the surface of your car would be warm to the touch after a highway ride.
 
I understand, however, there are some problems with your explanation.



1. My intake tube is metal, not plastic.

2. I insulated it from ambient engine heat and had the same result.

3. An air compressor hose is made of rubber, which is not a conductor.
 
Dingo, why doesn't the outside of your car get hot when you go 90 MPH. As a mechanical engineer I can assure you the friction you are referring to is of little consequence in this application.
 
Captive air going through S shaped bends at high speed is very different than ambient air going over the outside of the vehicle. Also, the increased surface area of the outside of the car dissipates heat faster, as it forms a giant heat sink. Furthermore, due to the aerodynamics of the vehicle, very little of the of the vehicle actually is in contact with the moving air at high speeds. On the pipe, the heat is generated at the bends and it then radiates outward through the metal pipe.
 
First, air friction is air friction whether due to captive air or not. If you had a plastic stone deflector on the front of the TRAC it would be right in the flow of the 90 MPH wind. It is in FULL contact with the air flow and has less surface area of the intake tube. The linear velocity along the deflector is the same as in the intake tubing. The only method of dissipation is to release BTUs into the air stream which is the same temperature as the Air Intake Temperature.

Why is one hot and the other one according to you cool?



With the same air velocity, same ambient air temp, same area, and finally the same material why does one get hotter than the other? My take on it is the under hood engine temperature is driving the surface temperature of the plastic tube.



Dingo a thought came into mind that may convince you. A hand held or back pack leaf blower produces more air velocity through a smaller diameter pipe (more friction). The material is almost the identical plastic as the K&N tube. The leaf blower tubes DO NOT get HOT with air flow velocities over 120 MPH. Try it.
 
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First, mine has a metal tbe. I think you missed that.



Secondly, the temp increase in the pipe can't be released into the passing air, as air is a worse conductor than metal.
 
Joe, when you are running your Trac at speed, the air entering your manifold is nearly the same temp as that entering the filter. You will see a HP performance increase with the CAI but probably a small if any MPG increase. Since your engine can breath freely you can put more gasoline to keep the A/F charge ratio as programmed and have a slightly bigger fuel charge to burn, thus more HP.



The only time the CAI with a metal or other thermally conductive material will harm your performance is at stationary moments when the engine heat can be transfered through the tube and increase the inlet ait temp above ambient. This will be very slight, if noticeable, since most CAI are not true CAI and the air filter will suck up the hot under hood air. When moving the air entering the filter will be closer to outside ambient.



Bottom line...don't worry about it.
 
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