Quote:
Originally Posted by Winston
It is interesting reading about the contrasting theories of "increased Hp/efficiency results in better mpg" ie less restrictive intake or exhaust, or the "reduced hp = greater throttle opening req'd which reduces pumping losses and results in better mpg" ie warm air intake.
As noted, some of those intake and exhaust mods only work with old school, non computerized engines. Less restriction on intake or exhaust does not always equal better efficiency on modern computer controlled engines.
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Here's what I've learned / thought about regarding this:
On a normal gasoline engine, increasing the efficiency of the intake/exhaust is going to have limited success (if any) with MPG improvement. The reason why is because of the way gasoline engines work: The ECU (or carburetor) in a very simplified form, just tries to inject the appropriate amount of fuel for the measured amount of incoming air, usually 14:1 ratio of air:fuel. If you increase the efficiency of the intake, that would allow more air into the engine, and more fuel, and make more power, and you'd accelerate. However... you may just want to cruise, so you close the throttle a little bit to compensate and... all your efficiencies from improving the intake go out the window, because the throttle body is (by design and operation) a restriction, and inefficient. This is one of the main reasons why diesels do so well, no throttle plate. If you improve the path of the intake, you end up having to compensate out the improvement with the throttle any, because you would accelerate too fast otherwise. Any improvements seen from optimizing the intake/exhaust are probably more happenstance and involve running slightly leaner, because the ECU (or carburetor) are injecting slightly less fuel due to one reason or another.
These are just my thoughts and opinions and real-world observations. Feel free to disagree
