There is almost no difference between metal and plastic when it comes to how much heat is transferred between the engine bay and the air in the intake pipe, heat soak is also not an issue as the air is not in the intake pipe long enough to affect the temperature.

 

Correct, at this level (on a N/A car) it should not make a notable difference. Once you go F/I the difference is more easily noted. If you go to a larger intake piping you can gain horsepower because of more flow capability but also loose torque because of lower velocity. I have seen this and experienced this first hand.

False! I have had an eBay intake for my 98 GS300 & my SC430 with no CEL. I then used the same intake that I had on the 300, cut the portion of the intake where the meter mounts, and used that with some spare piping to make an intake for my 98 GS400.

A meter is calibrated to work with a specific diameter pipe. As long as your eBay intake uses the same diameter pipe as the factory meter mount (and you hook up all the vacuum lines) the meter will stay calibrated and everything is happy. If you change the pipe size but dont change the calibration of the meter it will read incorrect and you will then get a CEL. Look at the older SC's and 1G GS's. When you buy an intake they still use the factory meter. All I did was make a "meter". I took idea this from my Mustang days. As long as I use the "meter" I made, I can run my intake pipe however I want to.

There are a couple of things I should mention though. You should keep the pipe diameter between the meter and throttle body close to the same size that the pipe is where the meter itself is mounted. (you dont HAVE to but to help avoid any problems later I would recomend it) You should try to keep the distance between the meter and the throttle body close to the same distance it is in factory form to avoid messing with the ECU's timing. If you put a pipe in front of the meter (for cold air or something) try to keep the pipe as straight as possible as it gets closer to the meter. (for some reason I remember 12" but I have had intakes in the past with only 4" or so) If there is a bend directly before the meter that can cause air to "shift" to one side of the pipe as it passes and the meter will not read it accurately. This can also cause a CEL.

Here is a picture of what I tried to make. As long as I use this (and I dont have any bends in the piping close to the front of the meter) I free from CEL's. I'm just trying to state that there are other options out there for people who dont mind a little DIY.

 

Actually there is some difference, as the temp readings were from the maf. However; I can not say if in fact affects performance or not.

There is a thread here about srt (metal) vs k&n (plastic) and there was a significant amount of heat soak from srt vs k&n. Like I said, I don't know if performance is lost, but I would keep it in mind when trying to squeeze every drop of hp from a NA

 

The heat transfer from the engine bay through the pipe whether it be plastic or metal is basically the same. You wont get any advantages/disadvantages to choosing either material for your intake pipe material.

The heat transfer coefficient of plastic and metal are considerably different however, steel is approx 21 W/m-K and Plastic (PP) is .12 W/M-K. That means that considerably less heat will transfer through plastic than metal in the case of thicker walls, though in this case it's thin walled which somewhat negates the difference in heat transfer coefficients for the two materials though they are large.

Since the intake pipe is a thin walled case (roughly 1mm thick ), you can use the ht coeff from above to calculate the difference between the two materials by finding U (Overall heat transfer coefficient). Since air is the fluid on both sides of the wall, Ha and Hb are the same.

U = 1 / (1 / hA + dxw / k + 1 / hB)

(After Calcs) U steel = 24.97 W/M^2-K and U plastic = 20.69 W/M^2-K

As you can see there is hardly any difference between the two materials when it comes to heat transfer through the wall of the pipe at any given point. If we were using a thick material than it would make more of a difference but in thin walled vessels it's roughly the same. Not to mention the air is not in the intake pipe long enough to soak any heat up anyways.

As far as the intake causing heat soak to the MAF, I would be interested to see the testing methods and conditions and actual results. I can see how it would be possible as the metal is a good conductor of heat but the plastic is a poor conductor of heat and that's what the MAF is encased in, not to mention it has a constant flow of "engine bay ambient" air to cool it off.

 

Would it matter if the material was another metal, such as aluminum?
I guess what I am asking is what the heat coefficient is of aluminum?

 

Thin walled Aluminum is the same as steel, it would be lighter than steel and could be polished though

 

Here's the post I was talking about, he used a scan tool, which is how he got air temp readings.

 

U = 1 / (1 / hA + dxw / k + 1 / hB)

(After Calcs) U steel = 24.97 W/M^2-K and U plastic = 20.69 W/M^2-K

^^ wow mac, im definitely coming to u for intake problems.

 

Has anyone tested air temps under normal driving conditions, while moving? I have a feeling the temp difference would not be as great.

 

Reminds me of heat transfer class

Kipod, I dont think anyone out there has both K&N, SRT and a scanner on their hand to test metal vs plastic. sbgs400 was probably the only one who had all 3 combo. I had SRT then switched to K&N, but never had a scanner on hand to read IAT. Seems like sbgs400's SRT (leisure pace) equal that of the K&N's IAT (hard run). Too bad he sold the car so he's not around to elaborate his findings.

 

I have a scanner, my boy Adam has a SRT, now who has a K&N in the DC area and wants to do a test.

 

AEM wrong an interesting article
http://www.aempower.com/ViewNews.aspx?NewsID=7

I was actually thinking about buying header wrap but I don't think it is worth the money.

 

I don't think wrapping the intake will be a possitive thing. Wrapping will keep the heat in the pipe without actually keeping it from getting hot. I think the best solution would be venting the filter area, so it can get cold air from out side the engine bay.

 

I should have clarified, I was going to wrap the exhaust manifold. But I didn't realize how expensive it was until I started looking into it. I might buy some for my other project.

 

Our car has a sensor called "IAT" that goes with the "MAF". The Intake Air Temperature (IAT) will tigger the signal to the ECU and compensate for the heat. So I don't think it matters if you use plastic or metal. No need for the complex formulas. =p
But like mac said, the length of the pipe does matter. =)