[California98Civic]

Originally Posted by Old Mechanic

In November 1969 Nissan built the first 240 Z a car heralded by the automotive media as a revelation of economy reliability and performance. On the air filter of the early Z cars you will see a lever on the side of the intake snorkel. It was marked winter and summer.
A metallic hose ran from the air cleaner down to the exhaust manifold and the flap actuated by the lever closed off the intake snorkel in the front of the air cleaner and forced the air to be drawn from the exhaust manifold.

At the time emissions controls consisted of a PCV, EGR, and air injection.

Anyone here who has been around and driven cars of that era and actually worked on them and understood the operational principles, knows that almost all cars of the era had WAI to mitigate the effects of colder air, in particular air at just above and below freezing temperatures. The variable venturi carburetors of the era were particularly susceptible to "icing", a condition where the higher velocity of the air passing through a variable venturi carburetor would simply not atomize properly, the early Z car was undriveable unless you moved the flap to the winter position.

The same basic design carburetor is used on motorcycles to this day.

While fuel injection vastly improved atomization, it did not change the laws of physics. There is a freezing point of gasoline, and although it is very low temperature wise, you still have the "chill factor" of air at higher velocities making the actual temperature much lower than ambient.

Sentra spent a lot of time and found no benefit with his testing. This is more of a testament to modern fuel injection, than an attempt to defy the laws of physics. Every liquid has properties that change as temperature drop. His testing did not include temperatures that were low enough to freeze salt water, to the extent where you could drive a car across a 4 mile wide river.

I gets much more cold in places more north of here. I've seen 38 below F, some here see that every winter.

I have found that warmer intake air and warmer wintertime coolant exiting the radiator made a difference of about 10 MPG on my Insight and on my VX. I could feel the difference in power, power I didn't need was reduced while efficiency was increased.

regards
Mech

That's a thought I had, because I don't like how hot the IAT is in the summer (140+). Thanks for this posting, one of the most welcomed I have seen in a while. Question: I looked for pics of the intake snorkel you mentioned and did not find one... do you know of any?