This was a common arrangement back in the days of carburettors especially in the days just b4 the forced introducction of EFI.
A hot air riser tube would come off a heat shield on the exhaust manifold and either it would mix automatically via a big flap valve with the cool air coming into the air cleaner.
This valve was usually move by a diaphragm powered by vacuum which was switch by a temperature vac valve.
When the car was at full operating temperature the flap would be open all the way and when it cools down again a spring snaps it back.
It worked quite well unless some backyard mechanic had been playing around with the mess of vacuum hoses needed to make it work.
On some cars it was a manual change that needed to be done , by sliding a knob on the side of the air cleaner housing . it was usally marked , ?winter / summer?
Since EFI has come to be the computer is able to auto adjust to give suitable mixtures across a wid range of operating conditions and temperatures , so on many cars this intake preheater has been dropped.
As seen elswhere , warm intakes do have some benifit , but I dont think its the holy grail ,, the hotter the mixture the less air and less power ..its good , but up to a point.
We just need to find the happy compromise intake temperature by solid experimentation.
Hot air / cold air / cold gas / warm gas / & on & on...
To all the tinkerers out there :
Do you realize all this adjusting of the temperatures of the air, the fuel, both together, both different...for whatever reason... is really another way to "fool" the engine's ECU?
I don't deny the effects of all this ... but you must realize the effect you are having on the timing curve (for max. BMEP). Before electronics took over the chore of adjusting the timing, we had to "power time" for each change. Now, the ECU will do this for you...providing you remain within the limiting "window" for change! Some systems have a narrower window than others! You can find out how your timing window changes with an old-fashioned timing light (remember them?) and marks painted on your damper pulley (and some simple math to convert degrees to inches/circumference) for TDC & marks (2 degrees?) away from TDC, for advance.
Assuming you've got a Scanguage (or similar device) for showing the instantaneous MPG...a changeable intake (temp.) system can be activated from the driver's position. Later, the effect can be duplicated in the garage by revving the engine to the highway speed...to note where the timing shift ended up ... advance point. Only by doing this step-by-step approach can you determine if the ECU is within its own limits; ie, you won't be wasting your time with a "maxed out" timing shift(the window limit)!
Remember, too hot is dangerous (detonation) and too cold is bad for MPG ( does anyone remember carburetor ice?). -Ted Hart
For a more professional look you could use a small intercooler sitting directly over the exhaust manifold. You would put one of the cone filters on one side of the intercooler and place the intercooler on top of the manifold then route the other side into the engine. A small intercooler kit like this might work.
intercooler....haha, more like interfooler! anyways. I think the pressure change across an IC would actually increase your "pumping losses." It would take more throttle to pull the air across the IC than gains would show. You'd be better off custom building intake plumbing with radiator fins to absorb ambient air than use a traditional IC.
Perhaps the key is "heat the fuel, cool the air" combo ???
I'm gonna try that...
Gas starts to boil off some of the light end at 95* so if you heat the gas you will possibly start vapor locking very quickly. So I do not think heating the fuel is the answer.
In my drag racing car one of the best things I ever did for performance was to change to a return style regulator so the fuel always kept moving and stayed cooler.
Just a little vapor in the line and it would run lean for a few seconds then rich and never was quite the right mixture. I chased all kinds of problems until one night I saw vapors coming out of the carb when I was putting it on the trailer and the light came on. It was drawing gas and vapors and they are not the same. Changed my fuel system and never had another problem.
Nobody ever told me that and I eventally learned the hard way on my own.
With all due respect, I suppose there is an error in the article concerning the warm air intake...
I have studied physics at college (thermodynamics etc) and worked as a flight dispatcher for 11 years (closely related to meteorology) during all these years I learnt that cold air is much denser than warm, both by means of oxygen and humidity (remember; dew point where humidity densens and becomes fog, is lower than ambient temperature)
I have been told by several saver/misers that cold air intakes improve economy. Furthermore I have been told that chip tuning improves economy given that you do not get tempted to "step on it"
I chenged my filter with a twin venturi cold air direct intake removing the filter box, removed the two mufflers (not the cat) and mounted a Remus glasspack.
Since I habitually do not step on the accelerator pedal, there is no excessive noise and I noticed thru the trip computer that the vehicle started reporting 4.8-5.2 liters / 100 km. from the usual 6.2-6.7 liters/100km. (from 35.10 MPG to 49 MPG) That is an average of a gallon saved every 200 kms (approx 130 miles)
I did not try any flush wheels, skirts and other aerodynamic aides as yet. I plan on getting a complete ground effect kit, lower the vehicle so drag is decreased. I want to prove that fuel saving can also go along with good looks of a car...
changing air flow and availability is going to give you better mpg, but cooling your exhaust system off and youre coolant will keep your engine cool and give it more power I think, plus the way I have mine setup, It's act like a suction pump for the air coming into the car, because I have my front sealed, and deflect air aerodynamically around my car from a few mods, so leave your vent open and with a war air intake that pulls in air from under the car, pulls the car forward, I have also drilled other holes in my air box, so I think I'm getting extra air in(even though I duct taped over it) which reduced pumping losses at high rpms