N/A res/muffler delete 5th gen mpg issues?

I'm relatively new to the car scene as well as this forum and honestly just wanted to make my 2014 legacy sound a little more like a subie, so I bought the nameless performance axleback exhaust but still wanted more sound. I've got a good 112k miles on the car and have been getting around 18mpg city 20+ highway, but I just recently removed my resonator/intermediate pipe with the intent to weld flanges and make it swappable, and I wanted to test the sound so have been driving it without the intermediate pipe. It hasn't thrown any codes, my air fuel is fine and MAP and whatnot which I can check with an OBD2 scanner, but for some reason I dropped to 8mpg and its a lil scary, I can't find any info on why this may be happening, does anyone have some insight? Sorry if this is a stupid question or stupid thing to do, again I'm kinda a newbie and just trying to get into the car scene

Wouldn't have expected such a drastic drop in fuel economy, if you put the intermediate pipe back to stock configuration is the issue resolved?

 

I'd be worried that you have another problem like a faulty injector dumping fuel to have that much of a loss in fuel economy.

 

Sure if you go with a free flowing exhaust on an NA motor you could lose low end torque and that would be detrimental to fuel economy, but I can't imagine it would be as much of a loss as you see here going from 18 to 8 mpg.

Sure if you go with a free flowing exhaust on an NA motor you could lose low end torque...

 

Can't lose what was never there.

i have a resonator delete and dual vibrant mufflers on mine...2013, 110K miles and still very easily get 30-35mpg

Have you changed your spark plugs, AFR and/or O2 sensor(s), cleaned you air filter, cleaned for MAF sensor? Could the drop in MPG be due to you goosing it around with your new found sound?

 

Are you referring to MAP as in Manifold Absolute Pressure or something else?

Thanks all for the replies, I haven't got to put the intermediate pipe back yet as it's currently back in the shop, I was in an accident a bit ago and the airbox may be an issue currently as there is a big hole in it they never noticed lol but once that's fixed I'll test with the pipe again. Also, 18 is definitely bad to begin with so I'm going to take it to a local dean team I think and get it checked out further because I definitely should be getting better mileage. The air/fuel has also been off normal numbers so hopefully this is the main issue, will post more as I work out the problem. Appreciate all your help

Update: After getting the airbox fixed everything seems normal! back to 18mpg city and hit 25 on the highway today

While I’m glad it’s back to where it was, those numbers still sound pretty low. You’re getting the kind of mileage I get on my 3.6R in the winter.

 

 

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