MPG improvement with modifying?

[Fnjeep314]

I am curious to see if anyone has noticed any increase in mpg with the addition of a cat-less up-pipe or a downpipe. I know that it can be possible. On my 95.5 Audi S6 went from 21~22 mpg on the highway with MTM software to 24~26 with my full turbo back exhaust w/ MTM software. I as averaging 21.x on my trip from GA to CA fully loaded with 2 roof boxes traveling 70-80mph. In CO I had my exhaust put on and in my first tank got a hand calculated 24.5mpg with the exact same load at the same speed. Empty, I am getting almost 26mpg. All on a 15 year old car with 175K. I didnt know if there is a possible unlock for better mpg by opening up the exhaust and maybe the intake too? Anyone know?

 

Thanks on advance!

[wpmarky]

When I installed my Cobb stg. 2 OTS, my mpg went up also.

 

My theory about that is you might be getting better MPG because by opening up the flow, you might be getting more air, but your fuel is staying the same, thus leaning out your AFR. It might be good for your MPG, but it's not good for the longevity of your engine. I'm still a beginner with tuning, but it's my understanding that being too lean under WOT conditions could lead to a dangerous situation.

 

This is why a custom tune is highly recommended. It will maximize your power with the safest AFR's and timing etc. for your engine.

[rockle3]

Its not the fact that your leaning out that makes you get better mpgs. Your car is just more efficient without any chokes in you system (cats). Why would using the same amount of fuel lead to a better mpg.

[Fnjeep314]

I am a pretty versed in tuning as I had a 425 crankHP Audi A4 1.8T Quattro with a GT28RS and all supporting mods, with a custom tune, so I am good there. Now I am thinking along the same lines as rockle3 in that opening up restricted areas like the DP and exhaust, and opening up the intake, I could find more power to move the car along thus needing to be in the peddle as much. I would of course go with some sort of tune, like Cobb or others of the like(I cant think of names right now). I am curious to know if people are or have been able to increase mpg's with opening up some of the cars choke points.

[Strizzy]

With my stage 2 opensource tune, I can get around 28-29+ MPGs (from what the computer says) cruising around 65-70 on the highway. My highway/city combined MPGs are 22 and I my driving is about 50/50.