Working on a new theory which I have not heard anyone mention. Reducing the amount of air which enters the intake will increase fuel economy. My theory is that it will decrease performance, but increase FE due to the computer sensing a lower volume of air and running a leaner fuel to air ratio to the ICE. It goes against all that we have learned in the past, especially with the Horse Power dudes. Some time ago I swapped the standard air cleaner in my 2003 Toyota tacoma pu, for a K&N high performance (greater flow) air filter. I noticed immediately that the FE had dropped but the throttle was peppier and seemed to be more aggressive on acceleration. Again it is only one vehicle but is it possible? I have not had a chance to try this on the NAH and am deciding on the best way to restrict airflow. Perhaps a thin layer of some cloth material covering the intake tube inside the air box, or maybe a cloth material covering the air filter (paper element) within the air box. What do you guys think???

 

It would probably be the equivalent of driving around with a dirty air filter...

 

I kinda thought that the conventional wisdom suggested that denser air contributed to better FE...? Denser air suggests more air, no?

I'm about to install an aftermarket air intake, and was planning on experimenting with the results. Should be on mid this week, and will probably try a tank or three to see what the results are. I've been averaging ~35-36 mpg, on 85% highway/15% city driving, with an average speed of 70mph/25mph. That with the stock intake.

 

Correct conventional wisdom states so. Again it is only a theory, lets say you completely remove everything right to the throttle body, it would be safe to assume that more air will enter than any other mod would allow, at this point the ecu would automatically make the adjustment for a richer fuel ratio. There is no doubt that performance (eg acceleration ) would be improved, but my theory is that the opposite would occur in reverse. A restriction in the volume of air would cause the ecu to reduce fuel to the engine. Basically it would be a forced reduction is performance even if you mashed the accelorator. In regards to the dirty filter, the answer is yes, except without the risk of contaminating the TB intake. Let me know how the performance and FE change with the aftermarket intake. By the way is it a K&N intake? I have used the K&N filters in the past but did see a reduction in FE. If our engines could be de-tuned down to say 50 HP, we would probably get 60mpg.

 

I don't buy this logic. We all have the means to use less air, it's called "the pedal on the right." Actually, your gas pedal no longer actually controls gas, it opens the air intake in the throttle body. Want to use less gas? Don't open the throttle body intake as much, and less fuel will be delivered to the cylinders. I don't think you are going to outsmart the engineers who designed the intake, mass air sensors, throttle body sensors, tuned the exhaust, etc. etc. If you restrict the air upstream, you will need to open the throttle body more to produce the same power.

Actually the industry is leaning towards more air being forced into smaller displacements via turbo charging in the next generation of fuel efficient engines.

 

I'm with steved28. Good FE comes from burning the fuel as perfectly as possible. Modern engines measure the mass flow of the air entering the engine and dump out a fairly precise amount of fuel for a good burn. Restricting the air flow produces less power which ultimately means you aren't accelerating or going as fast.

-dan

 

Really, give me one reference which shows that a turbo charged engine is more fuel efficient than the same vehicle with naturally aspirated engine. I think we are getting off point here. The goal is to increase FE. Anyhow, it is easy enough to test.

 

Here's one article on turbocharging, there are many more.

http://www.greencarcongress.com/2008...perc.html#more

But more to the point, that "perfect" air/fuel mixture is called "stoichiometric", it's about a 14.7/1 mixture. In the old days we used to jet carbs to try and reach it, today we have 02 sensors which feed back information to the components feeding the air and fuel. So no matter how much more, or less, air you feed into the intake, the computer is going to try and achieve the best air/fuel mixture. The only reason the K&N filter may provide more power, is because you were able to feed more air to the mixture, the computer reacted with more fuel, and you obviously got worse mileage and more power, same as mashing the throttle. If you provide less air, the computer will not lean out the mixture, it will simply provide less fuel, and less power. The engine management system will simply not allow you to run a leaner or richer mixture.

Lean mixtures produce hotter combustion gases than does a stoichiometric mixture, so much so that pistons can melt as a result. Rich mixtures produces cooler combustion gases than does a stoichiometric mixture, but at the expense of unburnt fuel, higher emissions, and poor FE.

 

You all are making me miss my Audi 5000 Turbo.

I don't think I would recommend trying to trick the computer to gain MPG by fooling around with air flow, but you all are doing something right. I'm down to 36 mpg again, another season and another 38 tops.

 

I've had the Fujita air intake installed on my NAH for about a month now, and it's difficult to judge the fuel economy because the temptation to hear the new growl is always there. Overall I haven't noticed a dramatic difference in fuel economy, up or down.

It's certainly funny to see the looks on peoples faces after they realize that the loud growl they just heard was coming from a hybrid...