Big mpg jump!
 

So I spent Friday and the weekend re-constructing my exhaust for better flow and velocity. I decided to gut the pre-cats and install a wideband O2 sensor (For the engine to be able to give me an exact fuel trim readout) to go along with the other upgrades. Considering the pre-cats we never installed as part of the original emissions system I felt fine gutting them....though I still kinda feel bad about killing two high-flow cats but I wasn't about to do THAT much welding lol!

Anyhow I reset my ECU at 2pm today prior to the test drive and WOW! My MPG on my normal route went from 10.4 to 12.7! The ECU still hasn't fully gotten used to the new setup but preliminary readings from the tuner are showing a 20% fuel trim reduction over the old setup that is definitely reflected in the MPG.

As a side benefit the power is up slightly and the sound of the cam is much more clear and angry without the pre-cats in the stream anymore. Main cat is still providing more than enough emissions filtering to be both legal and safe, well to be honest its about 17% better according to the voltage variance compared to the stock one. Not bad for a High-flow "racing only" Cat!

interested if those numbers hold up. More noise usually goes hand-in-hand with bad MPG because people like to hear how awesome their car, or truck, is and make sure to let everyone know as well lol. Keep your foot out of the gas and see if there is a definite advantage.

The engine is a supercharged 408 anyway lol! I know how fast it is already so I don't normally get into it when I'm not at the strip. I'm extremely pleased with the increased MPG though.

Several things changed all at once; wouldn't give much if any credit to the cat-gutting unless they were plugged.

True, the sensor shouldn't have changed anything but the pre-cat elimination and piping redo did have an effect.

Pre-cats were not at all plugged, I just wanted them gone and was too lazy to un-weld them.

Drove around quite a bit today (48 miles) and it's holding steady at 12.4. I didn't use any driving techniques that I normally do and also hit it pretty hard a few times so the mileage increase is not just something I'm imagining!