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With Project FC3 fully under way with new suspension and custom ECU tuning, we wanted to start the bolt-ons with an exhaust system. After tuning, the exhaust is the second piece of the power puzzle we’re putting together. I’ve seen a lot of people talk about how exhaust isn’t that important or that it doesn’t gain very much power. I often don’t get a chance to prove this isn’t the case but this is one of those times.

Before we got started on installing any hard parts with Project FC3, our 10th Gen Honda Civic Si coupe, we wanted to see what this thing was capable of right out of the box with just some good ol’ fashioned fuel injection manipulation aka ECU tuning. By way of our KTuner device and custom tuning software which applies changes directly to the factory ECU, we were able to mess with the turbo boost pressure, ignition timing, and fueling to create more power and torque, all with just a computer and a dyno.

If you remember, we bought a 10th gen 2017 Honda Civic Si a little while ago. Around that time, we received the engine for our Focus ST that we were waiting quite a while for. So, the Civic was put on the backburner. A few other priorities crept up and 2 years later, the Civic was still just a regular ol’, stock Civic. Time to change that and get going on this bad boy!

Recently, I’ve had the privilege of tuning three similarly modified Focus ST’s, pretty much one right after the other, with the only real difference between them being the wastegate actuator. All three had the basic bolt-ons, though brands did vary. This alignment of the planets allowed me to get some pretty close back to back data to use in comparison of the different options for modifying the factory wastegate on the Focus ST. Car number one came in with the actuator untouched and unmodified. Car number two came in with the factory wastegate preloaded a little more than stock. Car number three came in with a Turbosmart wastegate actuator installed in place of the stock actuator. When tuning the Focus ST on the stock turbo, you are pretty much just maximizing what the wastegate can do. WGDC (wastegate duty cycle) is going to hit 100%, meaning it's working as hard as it can to keep the wastegate shut, around 4000rpm and hold there to get as much boost as the turbo can give. This may sound harsh, but that's how it works on the Focus ST. Boost pressure on the small stock turbo falls off hard towards redline dropping as low as 10psi (keep in mind I am doing this testing at over 5000ft asl).

When you've finally decided to do an engine build on your Focus ST or other similar EcoBoost 2.0 turbo platform, it can be a little overwhelming once you've started looking for what you need. If all you care about is finding out what you need to bring to your machinist or whoever is assembling your motor, scroll to the bottom and you shall receive. If you're interested in what all this stuff is and checking out an engine tear down, read on.