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Old 12-02-2008, 03:57 AM   #46 (permalink)
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Exclamation the proofs in the pudding

Originally Posted by jcantara View Post
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
I am from england and i was looking at your site to see if i could pick up any further tips on fuel economy, when i came across this thread, which i noticed a lot of common mistakes to do with internal combustion operation and principles. i once was on a site that claimed remmaps port polishing freeflow exhausts to name a few would not increase horsepower because the amount of air in the cylinder has not altered (excl turbos of course). first mistake an induction kit allows more air into the engine causing the ECU to administer more petrol FALSE (unless it is exhuast charged ie turbo or a supercharger) a racing filter or induction kit allows the engine to breath without being restrained by a small filter and intake box thus releasing hp, a throttle body is a restriant TRUE for carbuerretors False for EFI becuase the petrol and air is mixed in the cylinders not the intake manifold, has any of you seen a cat conv internals i have its a maze of metal guaze one over the other thats were you lose quite alot of power try this yourself put a thick material over your mouth and try to breath through it and then youll know what the cats doing to your engine like you lot say uneccesary strain on the engine causes loss of power and mpg if you actually to the cat off your car you wouldnt need to do any EOC, who thought of that must be retarded turning the engine off while your in motion you lot might be able to get away with it on your roads (straight wide) try doing that in about 80% of places in england and your gonna get had off probably with your life ie no abs no power steering no vacuum on master brake cylinder (may aswell bite brake disk with teeth). and one last thing have you ever noticed that on a winters morning when you turn the a/c on that the revs arent as high as usual this is becuase the air is colder thus more dense which inturn has more oxygen per litre so the car produces more hp on the same amount of petrol than it does on a summers day.

its good to see you americans starting to think about the enviroment also try to get obama to sign upto the world wide pollution treaty george bush was being an a**ehole about it and one last thing push him for a national health service we have one the amount of money your countrys got and you have to pay for medical treatment thanks for reading this post

all regards
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