Bad fuel mileage and boost control valve problem

[jasonz28camaro]

Wondering why my wife's 2014 sport gets bad fuel mileage. She drives 80% highway and only gets 14.5mpg. We took it on a trip once and got 17 somehow highway only.

Recently I purchased a CAI for the car and I just drove it for the first time and noticed a strange sound like the BOVs opening under boost right away. With the stock intake I could not hear this noise but the car is no faster or slower with the CAI so I'm assuming the noise has always been happening. I ran the car with my phone app and OBD2 to monitor MAP levels and it spiked and fell off fast (up to 180kpi then around 100kpi) . Turns out under the engine cover (I have never removed it) there was a vacuum / boost hose disconnected from the pressure side piping to the Pierburg boost controller valve PA6-GF30. The valves were in fact bleeding down the pressure right away and might have been doing this since day one.

I fixed the problem, no more noise and it holds around 10-12psi (170-185kpi). The car now drives good and has a good amount of power now, still not a racecar but better for sure.

Now my question, would this be the cause for crummy fuel mileage? I'm assuming ecoboost means better fuel economy and I didn't use the turbos hardly with the disconnected hose but at the same time more air means more fuel.

 

[peterk9]

Members seem to be installing a CAI to get a little more 'growl' from the engine. A CAI doesn't do much if anything to increase mileage or power. An Ecoboost engine can replace a larger N/A engine while retaining the same power and fuel mileage. For example replacing a normal V8 with a smaller V6 Ecoboost and maintaining the power of the V8. Here are the figures from the Ford website.
3.5L V6, 16 city / 23 hwy / 19 combined
3.5L Ecoboost V6, 16 city / 22 hwy / 18 combined

Peter