Recovering lost heat energy in engine coolant...
 

In other words, a coolant-based hot air intake.

I have removed the cold-air intake tube from my truck, and have re-installed the stock induction setup. I purchased the smallest transmission oil cooler I could find, and have mounted it to the filter box, after the filter element. This will be the intake heater. I decided against placing the intake heater before the filter element, as I do not think that the intake heater should serve as a pre-filter, nor do I think that the intake element would like being heated up to well above ambient.

The coolant lines have been routed out of the intake box, but they have not yet been connected to the coolant system. I plan to use a 4-way heater valve to connect the intake heater to the supply heater hose. When disengaged, the heater supply will go directly to the heater core as normal. When engaged, the heater supply will be re-routed to go through the intake heater first, then go to the heater core as before. The heater valve is controlled by engine vacuum - I will use a vacuum solenoid, controlled from the cabin, to switch the intake heater on or off.

The above setup is for demonstration purposes; once I have seen a satisfactory A-B-A result set, I will probably do a Y branch instead, in order to have full heat capacity to both the heater core and the intake heater.

I plan to have the hoses and control circuit hooked up tomorrow, prior to my work commute.

This is really creative, but are there any advantages over pulling in warm air from exhaust side area? I guess if nothing else ur bay will look more clean and stock.

It's a lot easier to route a couple of heater hoses, than it would be to fabricate something that could take usable heat off my ceramic coated headers. Besides, with the way my stock induction system is set up, I think it'd be next to impossible to route hot exhaust-heated air from the left bank and still have it be kept warm enough to do anything meaningful. The filter sits on the front of the right fender.

I also consider coolant to be a more stable source of heat.

"stable source"

best I can tell, the constant temp is the key to further tuning.

If you want to further control the airbox heat, you can use a thermal switch and an electronic valve. Place the thermal switch somewhere in the intake tubing to monitor air temps, wire it to a controller on the valve you already have in place. In this way, the valve will shut off at X temp, and open back up below X temp, keeping a close range of temps in the intake tract. Different switches will allow you to fine tune for the best IAT for FE.

I had a similar idea quite awhile ago, wherein I'd use a small heater core mounted in the airbox. I never got around to doing it, but at least someone is... if it works for you, I might also give it a shot.

I'm a bit puzzled why you would want hot air in the intake.

The adiabatic expansion implies the colder the air you can use, the more delta T you get.

The greater the delta T, the more effiicent the 4 stroke engine?

I guess I'm curious why you would want a hot air intake.

Here's my solution:

http://i12.photobucket.com/albums/a2...n/IMG_0883.jpg

The stock filter sits off to the driver's side more, in front of the battery. It also pulls cool air from the fender well and is blocked off from the exhaust heat. To build the one in the pic, I simply purchased a cheap "racing" intake, cut the pipe and rotated it 180 deg.

Next step is using a exhaust cutout, an rpm window switch, and a temp sensor with a Y that goes to cold air as well. Above a certain temp, cold air will be let in, and also above a certain RPM. For now, this seems to work just fine, though the loss of power is quite noticeable.

Nice setup!

Do you have temperature measurements from inside your intake manifold?

No, only temp sensor is the one right behind the filter. I don't even have any instrumentation.

There are some well-documented setups on Saturnfans.com that are much closer to the exhaust manifold and produce higher temp air. Apparently the point at which the stock pcm starts to retard timing is quite high for most operation (around 150+ F). I may borrow my roommates scangauge/OBD2 reader/whatever to verify I'm not in the crazy temp range, but I'm in no rush.

Unfortunately, there is really no reliable way to A-B-A test anything around here since the nearest traffic free section of road is probably over an hour away, unless I feel like doing my testing at 3:00AM. I'm happy with just logging my mileage as usual for now - after all, its gas usage that I'm really after. Even if its a placebo that makes me subconsciously drive better... I'll take it :)

Your post did make me think about the intake manifold a bit... the stock manifold does have a coolant line coming into/out of it. It would be quite easy to add another heat exchanger in-line to extract more of this energy if I so desired. Although, as I pointed out above, the only intake air temp sensor is near the filter, so the computer compensation wouldn't be as accurate.

The intake coolant line is there to provide warmth to the intake air and prevent sonic freeze at high air velocities. It doesn't do much, but removing it creates a traceable increase in power when tuning. At least it did on my Civic, 3hp avg over 5 runs on a chassis dyno at 3k rpm. I never had a problem with sonic freeze, either.