WAI better fuel economy?

Wow. Anyone on here who lives in Salt Lake City should go knock on Rick Harrell's house and slap him.

Yes, sucking in hot air will improve your gas mileage... but at the cost of power and potentially causing detonation. Ever notice how your gas mileage goes up in the summer time, and is crappy in the winter? In the 97GT, I could normally get 24-25mpg during the hot months of summer, and it dropped to 19-20mpg in the winter, with the same driving habits and route.

Hot air will better atomize the fuel and help more of the fuel vaporize as it is going into the cylinder. Of course, better atomization and mixing results in a more complete burn for better efficiency. Another effect may be causing the engine to work harder and reducing the losses from throttling. An engine working harder is more efficient (long as you don't go to open loop).

So yes, your mileage will be better... but you are going to loose a lot of power unless design the system to suck in cold air at full throttle. Also, hot air is more likely to cause detonation. Most modern cars will reduce the spark timing to prevent detonation when they see hot air, which isn't helpful for gas mileage.

On a side note, my 88 2.3 had a ford factory origional system to suck in hot air in certain conditions. It had a metal sleeve around the exhaust manifold, with a tube going to the air box. There was a vacuum controlled door which could open and supply the engine with pre-heated air from the exhaust manifold. I think it was mostly used when the engine was cold, to reduce emissions. And yes, I lost mileage when it was removed.

It can work on a carb or EFI engine, but the carb would probably need to be re-tuned for optimal results.

Hopefully a few of the old guys will chime in about EGV's, lean burn, and Fred number one and how lucky you younger guys have it without stepper motors and temperature controlled vacuum switches.

Smokey's design was based off of a hot lean/atomized mix to increase mpg as well; all part of history now. Honda ran with stratified charges and now, to my understanding, Ford is using a similiar set up with their direct injection approach for cleaner burns resulting in less emissions and greater power.

The biggest reservation with under-the-hood air is that it fluctuates a great deal unlike a constant source of ambient from the fenderwell.

bhuff30 said:

Yes, sucking in hot air will improve your gas mileage... but at the cost of power and potentially causing detonation. Ever notice how your gas mileage goes up in the summer time, and is crappy in the winter? In the 97GT, I could normally get 24-25mpg during the hot months of summer, and it dropped to 19-20mpg in the winter, with the same driving habits and route.

Click to expand...

Huh, and all these years I thought it was because of the fuel addatives they used to keep the fuel from freezing during the winter months.
Learn something new every day.

didn't old chevrolet's do this? I may be wrong of course, but seems that I remember a setup on my mom's old van, that directed warm air from the manifolds to the TB. hmmm, can't remember exactly.

edit: ooops, sorry. didn't see bhuff30 said this already.