View Single Post
Old 04-05-2012, 12:58 PM   #18 (permalink)
Saturn Driver
Nels's Avatar
Join Date: Jan 2010
Location: Manitowoc WI
Posts: 30

Peanut - '96 Saturn SL
90 day: 37.27 mpg (US)
Thanks: 3
Thanked 6 Times in 4 Posts
I think another point that needs to be considered is the diameter of the tubing. Not just for clearance issues with other hoses, etc., but because of the low air volume being used in economy driving. In my picture above you can just see the large (4") feeder tube going between the air filter box and the throttle body. The high volume of air that this large pipe holds is counterproductive to what we are trying to accomplish, in that the air has time to cool again before it actually gets into the cylinders. It seems to me that the smaller cross section would help keep the velocity of the airstream high enough to avoid heat losses, thus requiring less insulation. The way I figure it, the throttle body on my car has an opening of around 2", so anything larger than that is overkill on the intake diameter. Of course, this line of thinking is in opposition to conventional theories, but we're not concerned with horsepower. I am willing to tolerate slight performance sacrifices (within safety margins) in trade for fuel economy. And of course, not to be too restrictive so as to starve it for air.

And it may not matter that much on the Saturn. The main thing as far as the Saturn engine management system is concerned is to achieve a higher temperature at the IAT so the ECU leans out the mix accordingly. To do that, you need to get the warm air from the heat source to the IAT before it cools significantly. To me this means tubing no larger than is practical. I know I could do some plenum and insulation work on mine to bring it up some, but this is a low budget operation, and I have no scanguage or anything to monitor the actual intake air temp. The last thing I want to do is lean it to the point of some kind of internal damage. Since I can't monitor it, I am staying conservative on my mods.
Manitowoc WI
1996 Saturn SL, 5-sp manual

2011 Fiesta SFE sedan, 6-sp dual dry clutch Powershift transmission
  Reply With Quote