This is a discussion on Exhaust Diameter within the Focus RS Performance forums, part of the Focus RS Garage category; Does anyone happen to know what the stock diameter of the exhaust is on the RS?...
Does anyone happen to know what the stock diameter of the exhaust is on the RS?
resurrecting to say thanks
only resonated exhausts are legal here, if stock was already 3" I would not have bothered but +0.25" is worth having for a future tune
2002 SVT Focus - Jackson Racing Supercharger ---SOLD---and miss it
2016 RS - I waited longer than you did! 452 days
2017 Ford Fusion Sport
Blog : Focus RS Turboback Exhaust Results : Stratified Automotive Controls
This is the write up that up that you want, explains everything you'd want to know about if you should or shouldn't upgrade the exhaust . Best of luck!
2018 LE Nitrous Blue
From the article/blog, I think it has to do with the fact stratified is comparing tune to tune, ie. not the off the factory tune. By having torque targets be more aggressive in the stratified tune, the car adds fuel which nets you the extra horsepower. Most manufacturers quote gains on the stock tune so it's apples to apples. the stratified blog post is specific to understanding the bottlenecks within the car when building for power. Edit: Want to be clear, stratified used the same tune for both runs, but it was their tune, not the factory...a 3" exhaust simply helps lessen the pumping loss of the engine, freeing up the horsepower. I'm sure any 3 inch exhaust with any bit of good design would net a similar increase under any tuner.The torque targets, timing, charge air temperatures, and fueling were the same between these runs. However fuel trims tell us a little bit more about what is going on. They indicated that the ECU had to add 1-2% more fuel to achieve the same air fuel ratios with the catback versus the bone stock car. This means the catback actually improved the volumetric efficiency of the engine. This means more air was entering the cylinders and producing more power. This, along with a drop in pumping losses accounts for the performance gains.
Last edited by monkey302; 04-10-2018 at 11:25 PM. Reason: added some clarity