2004-2007 Cadillac CTS-V Performance Mods Discussion, Intake Replumb in Cadillac CTS-V Series Forum - 2004 - 2007; For fathers dayI finally took off the squeeze pipe. Came out pretty good. I just had to trim the elbow. ...
It looks very neat. Where did you get the throttle body elbow?
EDIT: Didn't see you included that info.
Na, I added it rather than adding another post. I had 2 elbows, one was rubber like CVP33 has, its a smoother transition. The one I used is reinforced silicone but its a hard 90, gives a little more room. Still better than the divided squeeze pipe.
The exterior of the metal tubing picks up a lot of heat. Polishing, in addition to looking nice, does reflect some of that heat. I haven't measured the inside air temp, but I did measure the exterior of my unpolished aluminum tubing. It was running 125-135 degrees as measured with an hand-held infared thermometer. This was about the same temp as the throttle body (with the water connectin detached). Then, I wrapped the tubing with simple and cheap pipe insulation "tape". This reduced the outer wall temp of the tubing to 90 degrees.
Another thought is that the path of the intake makes it a secondary radiator shroud, the primary being the fan shrouds themselves. I am thinking that some sort of simple heat shield between the fan shrouds and the intake tube would be helpful. Alternatively, perhaps some small extenders on the fan shrouds might work.
I suspect that these Gen III motors are oversensitive to intake air temps because I suspect that GM is very aggressive in retarding ignition as intake air temps rise - like retarding the ignition well before knock sensors are activated.
It would be an interesting experiment to see what effect icing the intake manifold would have on a dyno run. It is simple to do, just dump a bag of ice onto the top of the intake manifold and wait five minutes for a cool down.
I have read a lot of that stuff. The pipe is 9" long. The 'residence' time of the air thru that pipe is negligeable. The heat given off by 'skin effect' is also small. If it were a tank holding compressed air and we were cooking it for an hour it might be an issue. Pulling air from around the nose of the car is more of a problem than materials. With the hood closed all parts normalize to the surrounding temp.
While I agree with Lasstss that the residence time of air passing through the metal tubing is negligible, in real city driving where there is stop and go, heat soak will be a big factor in intake air temperature. I did some simple testing using digital thermometers attached to the outside of the grill and the inside of the stock plastic intake just at the airbox. Generally, I found about a 20 degree temp differential; but when the car sat for as short as five minutes the differential soared. I saw as much as a 75 degree differential. Once driving again, the heat differential decreased, but it took more than five miles of highway driving for the differential to stabilize to 20 degrees.
Just covering the stock intake with mylar home dryer ducting as a heat shield brought the differential down to about 8 degrees; and the heat soak differential was more in the range of 40-50 degrees.
All this doesn't make much difference on a long trip/road race or on a dyno run. But it does make a material difference in city driving.