less air intake

[ron]

I built a ram air intake for my 2003 i4 toy techoma . the mileage went up 4mpg and the truck will maintain 35mph with my foot off of the throttle . but the computer found the lean condition and fed more fuel so the botton line is, I went back down to normal mpg

[mechman600]

Volumetric efficiency is not going to change any differently by restricting intake air than doing the same with the throttle plate. A simpler way to do what you are asking is putting a brick under the accelerator so you cannot push it as far - it would accomplish the same thing.

As far as "leaning out the mixture" goes, remember that the O2 sensor is king of the castle. If for a brief moment you are able to alter AF ratio, the O2 sensor will quickly compensate by adjusting fuel trim. If you are able to significantly alter AF ratio, chances are fuel trim will go all the way to the limit and trigger the check engine light, defaulting to open loop. And open loop is bad.

My suggestion is stick to proven mods. As seen in the link above, restricting the intake probably won't work. WAIs sometimes work, but usually only on MAP sensor engines. t vago used an engine coolant WAI that was pretty interesting:
http://ecomodder.com/forum/showthrea...ant-21863.html

[ron]

yep they (o2 sensors) adjusted the trim after the refill and restart, mpg on next 100 mi uninterupted test run went back down to normal of 26 mpg highway @65 mph