Well the experiment is on. Removed the cold air induction, but its not that cold here now so may take a while to find out. Physics, my 20 years of racing experience and 32 years of working on cars professionaly says this should work.

 

I have a 1988 Dodge Pickup with fuel injection.
It does pull the intake air over the exhaust system for a "hot air intake".
There is a "blend door" that can mix ambient air too.

It is a 4-liter V6 and gets about 22-24 MPG Hwy.
Of course empty it does not weigh much...

With 500 pounds in the bed, and towing a tandem axle 5000 pound trailer, it gets about 12 MPG Hwy!

I think ambient air is fine, when ambient air is 72 degrees.
I think a hot air intake will improve things a lot when it is zero degrees.
If nothing else, it will allow the car to have more regen and more EV.

 

Wow these FEH ICEs are LOUD with the cold air pipe off. I am getting 87-95 IAT now but its 65 outside right now. Hope it will stay up there when its 45 outside.

My thinking, only might be benefits when outside air is in the 50s.

GPSMAN maybe you could test this up where you are, Im not a good tester as I havenot established a base mpg yet. You have to remove the airfilter housing, the battery tray and one bolt that attaches the snorkle to the radiator core support. Though you dont have to remove the battery if you have a helper to hold it out of the way. If you do remove the battery keep the cicuit powered so you dont loose the KAM.

 

Check this thread out over at cleanmpg

http://www.cleanmpg.com/forums/fuel-...help-3320.html

 

I'm not saying "hot air", but "warm air".
Our experiment show the 35C(95F) intake air temperature is the best for fuel economy on Prius.

Ken@Japan

 

Okay, let me get this straight. Toyota spends who-knows-how-much researching and developing a system whereby hot coolant is pumped from the engine into an insulated container on shut down, to be stored in a NASA-class thermal container before being pumped back into the engine's head later. And they spend who-knows-how-much more money to so-equip hundreds of thousands of cars with this complex arrangement. All in the interest of gaining a tiny MPG and emissions advantage for cold starts.

Yet apparently neither they nor the armies of engineers at any other manufacturer ever figured out that 95° intake air "is the best for fuel economy".

A thermostatic valve to regulate the temperature of intake air when it's cold outside by drawing all or part of it across a hot intake manifold would cost a few dollars per car. My mom's 1970 Chevy had one, and it seems they still used them on Dodge trucks in '88. Yet they don't have one on the Prius.

I try to be open minded here, but I really need some explanation for this one.

 

The main purpose about Prius thermos is to improve the EPA emission test results. The EU and JP Prius does not come with the thermos where the emission tests are different.
Anyway, it's up to you.
I just would like to tell readers that Japanese Prius hypermilers don't like cold intake air.

Ken@Japan

 

It's pretty much down to physics. We can't change the fact that air density depends on altitude, temperature and humidity and that hot air is always less dense due to it having a higher level of molecular activity.

It's most likely that people who have done this just drive slower, since their car's performance is "de-tuned" by the computer in its effort to make up for the bad air. This de-tuning results in less output but also burns less fuel, more than compensating for the inefficiencies of using hot air vs cold air for combustion. In other words, tricking the computer by feeding the engine hot air lowers performance and less fuel is used. Toyota could certainly have de-tuned the vehicle for us at the factory by fitting a smaller engine, increasing mileage significantly, but then few people would have bought them because they wouldn't have enough power to deal with real-world driving. They're slow enough as it is.

Maybe Toyota should produce a hypermiler version of the Prius. It would have less features to save wieght, even harder tires, and a 990cc lean burn ICE. They could call it the Prius HM.

These aren't "always" or "never" situations, but it's safe to say that hot air entering an engine always hinders efficiency.

BTW Toyota used the warming of the intake area for emissions purposes to satisfy the State of California, not the EPA. It allowed the car to go from ULEV to SULEV. The Prius far exceeds all EPA emissions standards.

 

Terry, I think you answered your own question, about why didn't engineers who had years of research and millions of dollars ( Yen ) to spend, equip the Prius with a warm air intake:

They need to design an average car, for the average driver, in average conditions.

Those of us in colder than average weather, who want better than average MPG can perhaps benefit from a warm(er) air intake.

I'm not a design engineer, but I know from real-world experience over the road this helps.

Mark, I wanted to do this Mod Winter of '05 but it did not look easy so I gave up. This winter I got the block heater and battery heater and that has helped already. My fabric grille cover is on order and will be here soon.

I've been able to keep a 37 MPG average on 10 mile trips at 10'F with just the plug-in heater and no grille cover.

 

I just would like to say it seems Prius likes an adequate warm, not hot, intake air.
Again, it's up to you. If you like cold intake air, go for it.

Ken@Japan