Warm Air Intake

[fifteenwindow]

Nice work. If you insulate that ductwork and seal up the hood gaps, your IATs will go up further. Today I was driving in 4 degrees F and my IAT got up to 156 F, traveling at 60mph.

[alex16]

I still think this mod is super awesome. I know a lot of people don't understand how a warm air intake can help a engine more than a cold air, but I am with you on the warm air!

My idea is to weld a round piece of pipe that is slightly larger than the exhaust manifold heat shield then pipe it to the intake box. I would like to have a thermostat spring setup to close off the warm air once the engine gets to operating temperatures, but that makes things complicated.

[deleted user]

Atmospheric density drops 25% from the freezing to the boiling point of water. I don't want cold air. I want hot air going into my engine at say 85% of the density of freezing air.
Toss some gas on a steel plate and time it until it fully evaporates at the freezing point of water. Now heat up the steel plate to 150 degrees and see how long it takes the fuel to evaporate.

Better atomization
Lower manifold vacuum
Much better warmup times even in warmer weather.

Reducing the "effective" displacement of the engine means the engine is more efficient, because it is more highly "loaded" under normal operating conditions.

A well designed system to provide warm-hot incoming air can also be overcome by throttle opening, beyond the heat delivery capacity of the system, in which case the intake air temperature will fall under higher throttle openings giving the same performance with better efficiency when under lighter throttle loads.

In maybe 100k miles of running WAI systems on many different cars over the last decade, no preignition or any other problem.

Just compare the mileage differences between Florida and places where winter temps drop way below 0 degrees.

regards
mech

[alex16]

Yup! You won't see any issues running a wai and 87 octane, that's a crazy myth I've been told as well! I can see how a turbo car doesn't need as much of a wai but naturally aspirAted cars benefit so much from them. Wai, just one more way for us to catch up to those Prius c guys!

[fifteenwindow]

A well designed system to provide warm-hot incoming air can also be overcome by throttle opening, beyond the heat delivery capacity of the system, in which case the intake air temperature will fall under higher throttle openings giving the same performance with better efficiency when under lighter throttle loads.

Hey there, Mech. Could you explain this part a little further? Does this mean dialing down the WAI inlet to only provide enough hot air for lower RPMs? If I got that right, how do you measure this?

Thanks for sharing your knowledge. I enjoy your posts.

[deleted user]

an engine at 1800 rpm with with manifold vacuum at 15 inches or half atmospheric pressure.

900 induction strokes per cylinder per minute @50% of the displacement.

450 inductions at full displacement per cylinder (.4 liter)

180 liters per cylinder per minute X 3 cylinders

540 liters per minute.

Wide open throttle at 5000 RPM. 0 manifold vacuum.

2500 induction strokes per cylinder per minute

3000 liters per minute.

With the air flow volume increased by 550% the speed and volume of the air flowing past your heat source will easily overwhelm the heat transfer capability of the source.

I would not swear by this math but it seems to be close anyway.

I'm sure someone with a scan gauge can verify this.

Exponentially higher velocity= lower heat transfer per unit of volume.

regards
mech

[alex16]

This is why I am glad your on this board.



Regards
Alex

[owl]

an engine at 1800 rpm with with manifold vacuum at 15 inches or half atmospheric pressure.

Seems to me that standard USA air pressure is 14.7 pounds per square inch. One half of that is 7.35 pounds. The other issues with your math is that rpm is not the sole determining factor of cylinder fill.

The throttle opening can be almost infinitely adjusted from closed to wide open at any given rpm. It takes time for the revs and intake vacuum to adjust to the new steady state.

I have no information as to the volumetric efficiency of this motor. The best cylinder filling probably happens as shown by the torque peaks of the output.

[chris_top_her]

Seems to me that standard USA air pressure is 14.7 pounds per square inch. One half of that is 7.35 pounds. The other issues with your math is that rpm is not the sole determining factor of cylinder fill.

The throttle opening can be almost infinitely adjusted from closed to wide open at any given rpm. It takes time for the revs and intake vacuum to adjust to the new steady state.

I have no information as to the volumetric efficiency of this motor. The best cylinder filling probably happens as shown by the torque peaks of the output.

15"inHg is roughly = to 7.5 psi... When talking about a vacuum (or weather) we typically use inHg in the usa not PSI. PSI when referring to MP is usually reserved for forced induction over the current atmosphere. inhg for vacuum psi for atmosphere.

[owl]

15"inHg is roughly = to 7.5 psi... When talking about a vacuum (or weather) we typically use inHg in the usa not PSI. PSI when referring to MP is usually reserved for forced induction over the current atmosphere. inhg for vacuum psi for atmosphere.

Looks as though I have to learn the difference between inches of mercury and pounds of air pressure.

My biggest concern, other than my obvious lack of reading comprehension, are the statements that smaller engines are more efficient than big ones and that partial cylinder filling is more efficient than 100 percent or more.

An average gas engine is roughly 20 percent efficient. 30 to 35 percent of the fuel is wasted as exhaust heat. Another 30 to 35 percent of the fuel is wasted as heat loss through the cylinder walls and head. Another 5 to 10 percent of the heat is wasted overcoming internal engine friction. Those are all rough numbers and do not consider transmission/cv losses. Basically, it seems you get roughly 15 percent of the fuel actually driving the car.

When you fill only half of a cylinder with the air/fuel mix, you are changing the ratio of cooling area to the volume of combusted fuel. At half fill, you are doubling the cooling effect of the container. That is less efficient than a 100 percent volumetric efficiency.

For small engines, people tend to confuse fuel consumption with efficiency. A tiny model airplane engine uses far less fuel than a car motor. Is it more efficient? Far from it. As a very rough guess, I'd venture to say the smaller engine has 20 Percent of the efficiency of the much larger car motor....and that is assuming good design and manufacture in both...and four stroke setup. Let's not get into two stroke weed whackers and chain saws. Those are just obscene but the Chinese are happy to keep selling them until their last customer dies from cancer. Kind of like the asbestos laced crayons now on the store shelves.