Most people probably know that cool intake air makes more power because it is denser, and that using the exhaust to preheat the intake air is more efficient because it wastes less of the thermal energy.
I propose a system that can do both! It would include both an inter-cooler and a heat exchanger. The intake would be connected to a “Y” valve, with one side connected to an inter-cooler, and the other side connected to a heat exchanger on the exhaust manifold, each side would have its own air filter. The exhaust from the engine will also be connected to a “Y” valve, with one side connected to the heat exchanger and regular exhaust system, and the other side connected to a high performance exhaust pipe.
The valves would be electronically controlled.
The Temperature between the relative high and low temperatures can be more controlled by having the intake valve partially opened to both intake sources.
Feel free to add any refinements or corrections. It’s late/early and I’m tired so something might not be right.-- BJS, Jan 25 2008 I thought of the main part of this idea probably about 2 years ago...-- BJS, Jan 25 2008 I like it, [+]. Would it still need a throttle?-- acurafan07, Jan 25 2008 If you read this as an idea for a pair of "Y" fronts underwear, it's hilarious (in a juvenile sort of way) - have this croissant + [BJS] for tolerating my off topic intrusion.-- xenzag, Jan 25 2008 Most older vehicles have a thermostatic valve in the intake assembly that upon a cold start would draw the intake air through an "oven" that was constructed around the exhaust manifolds, once the engine coolant warmed to a high enough temperature the valve would open to emit cooler air to the engine.
To be honest with you for a car this really wouldnt do much of anything. The difference in power between a Cold intake and a hot intake is minute. You simply cant heat the air enough to see any real difference. Also the only time that the difference would show would be under conditions of Wide Open Throttle. The reason for this is that engines use as their primary control mechanism the oxygen sensor. This sensor monitors the amount of oxygen in the exhaust gases alowing the engine to maintain the optimal fuel air mixture at all times.
What this means to your idea is that the engine will optimize the fuel applied to the engine to exactly match the available oxygen in the cylinder. It also monitors the temperature and the Mass of the air entering the engine.
So bottom line this really wont do anything at all to adjust performance or efficiency, its just a boondoggle with no benefit.-- jhomrighaus, Jan 25 2008 I also worked on this idea, but it was about 20 years ago. The throttle is a necessary yet vile device of inefficiency. The problem with the idea is as mentioned PV=nRT. To half the amount of air using heat, you need to double the temperature in Kelvin. Assuming you could get room temperature air to the engine it would be 22+273= 295 degrees K. Doubled would be 590K or 317C (602F) which is hotter than burning paper 451F. Needless to say, that is a bad idea. The other problem is that even within the usable ranges it causes preignition issues. Smokey Yunick tried to solve these with water injection but memory fails to give me his results. So sorry, (-) purely on bad physics.
PS My next idea on this vein was exhaust gas recirc. Basically allow in inert gas instead of throttling regular air. It also will raise the temp.-- MisterQED, Jan 25 2008 // Basically allow in inert gas //
But that will drop the partial pressure of oxygen , and change the stoichometry.-- 8th of 7, Jan 25 2008 //But that will drop the partial pressure of oxygen , and change the stoichometry// Not if it occurs after the mass airflow sensor and even if you didn't the oxygen sensor would self correct. The first weird part would come from unburned fuel and unused oxygen in the exhaust. The really weird part would come if you got a hot ember back into the intake track.-- MisterQED, Jan 25 2008 Is this merely an issue of programming?-- BJS, Jan 25 2008 *everything" is merely an issue of programming .....-- 8th of 7, Jan 25 2008 random, halfbakery