Warm Air Plenum (rather than WAI) good for Winter

[Thymeclock]

Warm Air Plenum (rather than WAI) good for Winter


This is my latest experimental project, intended to increase warm air provided for the air intake. The car is an ’09 Aveo. It seems to take a long time to reach operating temperature, especially in winter. That’s annoying not only due to reduced fuel economy, but also in waiting to have adequate heat in the car. My primary objective was to get warm air in the cabin ASAP for short trips when the car isn’t up to operating temp.

This idea is not mine, originally; I got the idea from another car I have, an ’89 Galant. The photo shows that my old Galant has a long, sealed duct tube that runs from the air cleaner along the top of the radiator, and it was originally designed with this feature.



I’ve never seen this on any other car. (If anyone has seen this sort of setup, I’d like to know of any other car makers that did likewise.) My old Galant warms up somewhat faster than other cars I’ve owned, and certainly much faster than the Aveo, so the concept seems to be a valid and useful one.


On the Aveo it would be difficult and impractical to try to run the warm air plenum from the lower part of the air box itself, as it is mounted too low and there is no room to route the pipe in the direction it needs to go. For this application I only bought the top of the air box so I could modify it. (I ended up buying it new for about $50, as the entire air box costs much more than that, even as a junkyard part, since it’s a late model car.) In this case when making the hole for the pipe I only needed to trim away minor portions of the top (both inside and outside the box) to create a flat surface for the area where the plenum pipe would be mounted. The plastic fitting is a drain trap for 1 ½ inch PVC pipe that is secured with a threaded nut. I used a rubber gasket to fill the space and provide a good seal when mounting it inside the box wall.

Since it is not exactly a straight run, I initially used a very short piece of pipe out of the fitting into a 1 ½” rubber coupling, to rise from there to the top of the engine; then I ran pipe across the engine, then a 45 degree angle coupling to extend it over the exhaust manifold, towards the radiator. The end was sealed with a removable rubber cap. This is essential, because the pipe that is now mounted in the top of the airbox is bypassing the air filter.




This first version didn’t work too well because the plastic pipe (not a heavy PVC type) I used started to melt from being over the manifold. I revised the setup by using a flexible rubber elbow followed by a short piece of pipe and coupling, a PVC elbow, followed by the long run of PVC pipe over the radiator, ending with a PVC cap. Everything needs to be cemented together, except that last cap, which remains removable. (See photos.) The pipe itself is tied down at the capped end by a piece of wire to the hose that is beneath it.








I found that in spring when the temps are above freezing it was best to remove this rig because otherwise the car will lack acceleration and your MPG’s won’t be any better for it either. In spring, it is very easy to remove the whole thing: simply take that PVC cap off the end of the pipe, undo the clamp on the rubber elbow at the air box fitting and put the PVC cap in its place, at the box end. It’s a fairly tight fit and it won’t vibrate loose.

I found the air intake temp to be higher than usual, particularly after a short run. The plenum continues to retain warmth in the engine compartment after the engine is shut off. If you do a lot of local short trips with the vehicle shut off for an hour or so in between, this modification may be beneficial. The unexpected effect I’m getting is that of having warm air in the cabin long before the temp gauge on the dashboard rises. I’m getting relatively warm air out of the vents with a water temp of about 120 degrees according to my Scangauge, while the dashboard temp gauge has barely risen at all.

It seems to help conserve heat somewhat, if only a bit.

[Pooh Man]

Very clever, although i run a CAI I would say this is the most original intake mod I ve ever seen. This may be better than an episode of McGyver. I love well thought out homemade ideas- awesome work.

[Dustin]

I thought that the sealed tubes on the airboxes were for resonance cancellation. How would having greater filter plenum volume make the car warm up any faster? Sorry, I'm not seeing how this would do anything.....

[Thymeclock]

I thought that the sealed tubes on the airboxes were for resonance cancellation. How would having greater filter plenum volume make the car warm up any faster? Sorry, I'm not seeing how this would do anything.....

The sealed pipe is in effect an extension of the airbox itself. The air in the pipe is now part of the volume capacity of the box. If we could heat the airbox directly it would increase the temperature of the air in it, right? The same concept applies here, but by extension, as an indirect (or remote) application.