Not defending the kit or anything else.

BUT to answer your question. They are talking Rear Wheel Horsepower. Not HP at the rear of the engine. Bottom line for the video is an actual measured gain in HP, and torque to the ground.

 

I didn't hear them say it was SAE corrected numbers...and frankly from the video it is rather confusing as to the HP gain. It was a poorly made video IMO...they should have shown a graph of the gains to make it easy for people to see the results. I do know the difference between brake HP and rear wheel HP

 

My comment was merely based on your comment as to differences in what ford advertises and actual numbers shown on their tests. As you are aware, They are two different readings.

 

Yeah I hear ya...I watched the video again and see it was actually SAE corrected. It's just too confusing the way they talked about the numbers. All dyne numbers are all subjective anyway...and some dyne's get better numbers than another with too many variables that change the results.

The exhaust doesn't sound too bad, however it is hard to really get a feel for it over the internet.

 

It's insane how many times I hear people say that you want the biggest 'pipe' after the turbo to reduce backpressure on a Turbo. LOL

If you size the tubing AFTER THE TURBO properly you will have scavenging, exactly like a non turbo exhaust. If you size the tubing too large, you will have a huge expansion chamber with slow velocity stale exhaust gases polluting it. These stale exhaust gases then have to be pumped out by the engine LOL. Not knocking any particular company or set up.

The exhaust tubing on the stock ecoboost isn't the bottleneck, it's the muffler, and the part of the system that necks down to 2.5" Anytime you go up or down you create turbulence, this turbulence creates slow moving exhaust, aka, backpressure.

Back pressure and scavenging are 2 different things. Unless you have an infinitely variable diameter exhaust system you have to make a trade off. Ford engineers spent literally millions to find that trade off and made the determination that 3" is it. They also invested some of that money into the muffler. To the average enthusiast it would appear that the muffler was a big fail, but to the contrary, it does exactly what it was intended to do.

Federal regulations require a vehicle to meet specific DB levels from a certain distance at a certain speed. If they exceed this DB they fail. The ecoboost muffler makes the truck pass this test and makes for a easily repeatable, cost efficient muffler. They traded flow for money, go figure.

Simply removing this bottleneck cures the problem. But is there a circumstance where you would benefit by going bigger than stock? Heck ya, but you would have to spend thousands of dollars on the bottom end, top end, and turbos for it to make sense.

Here is an article that I wrote. Most guys find it very helpful:
How a properly built exhaust system works