From 15s to 11s: The Journey of a 8th gen Honda Civic Si Sedan

In 2021, we started an exciting project with a 2008 Honda Civic Si sedan, a popular platform due to its K-series engine, specifically the K20Z3, paired with a factory 6-speed transmission and LSD. This car already had a solid foundation, and the customer wanted us to help him optimize its performance.

When the car arrived at our shop in Lake City, FL, it had some basic bolt-ons like a cold air intake, header, exhaust, and RDX injectors. However, it was running rich and didn’t perform well despite making 201whp on our dyno. After installing a Hondata Flashpro, we dialed the car in, and it responded with over 20whp and 20ft-lbs of torque, making a solid 215whp and 152tq at the wheels. The car was running better than ever, and the customer was ready to take it to the dragstrip.

First Dragstrip Experience: A Pleasant Surprise

The customer had never been to a dragstrip before, so we invited him to a test and tune at Gainesville Raceway. He quickly took a liking to the track and drag racing, and on his very first attempt, he managed to run a 14.5 @ 98mph, an impressive feat for a full-weight Civic on all-season tires. His enthusiasm for the sport grew, and he was eager to take things to the next level.

Adding More Power: PRL Motorsports Turbo Kit

The customer was ready to push for more power while keeping the car streetable. We recommended the PRL Motorsports turbo kit, paired with a Precision 6262 turbo, Fuel Injector Clinic 1200cc injectors, and an AEM 340lph fuel pump. To display critical data, we chose the AEM CD5 Carbon Dash instead of the usual gauges. Additionally, we upgraded to a Competition Clutch Stage 4 and a **Competition Clutch Lightweight flywheel.

Turbo Dyno Results: 335whp on 93 Octane

When we hit the dyno with the new setup, the car made 335whp on just 5.6 psi of boost, running on 93 octane fuel. The car was clearly a force to be reckoned with, and it was ready to head back to the dragstrip.

Mileage and Boost: Playing It Safe

With the car having 249,000+ miles and still using the original engine, we played it cautious, opting to bump the boost to 7 psi for a final figure of 357whp. This gave the car plenty of power without pushing it too far, maintaining reliability.

Suspension and Dragstrip Performance

After the turbo upgrades, we took the car back to the track. With street tires, the car ran 13.86 @ 111.76mph, followed by 13.31 @ 113.17mph. While the times were impressive, we quickly realized that the 60-foot times could be improved. Despite the added power, we couldn’t get the 60-foot time below 1.9.

Tire Upgrade: Slicks for Improved Traction

In 2022, we made the decision to upgrade to slick tires on Jegs 15” wheels with MH tires (24.5” tall). The goal was to improve traction, especially with the added power. After the change, the car’s performance showed immediate improvement: a 12.87 followed by a 12.62 in the quarter-mile. However, the 60-foot times still weren’t where we wanted them to be, and upon reviewing the videos, we noticed the right rear tire was squatting during launches. After further investigation, we confirmed that the coilover was bad.

Suspension Overhaul and Further Upgrades

To address the suspension issues, we ordered custom-rate rear springs and new rear shocks. With the suspension sorted, we also upgraded the car’s engine management from the OEM ECU with Hondata Flashpro to a Motec M150 PNP standalone system. Additionally, we added a Magnus Clutch Slipper Valve to improve clutch engagement. All these upgrades were aimed at ensuring reliability and consistency in the car’s performance.

New PBs at the Track: 11s Are Here

With the new suspension, standalone system, and slick tires in place, we returned to the track. The car’s first pass after the upgrades was a 11.7 with a 1.68 60-foot. On the second pass, it improved to a 11.59 with a 1.702 60-foot. These numbers showed significant progress, but we weren’t done yet.

Import Face Off 2025: A Record-Breaking Run

In February 2025, we took the car to the Import Face Off event. Driving it to the track and switching to the slicks, we had a little more than half a tank of 93 octane fuel. We decided to add 5 gallons of 110 octane fuel to ensure the fuel system could keep up with the car’s power output (the car’s fuel system, with 1200cc injectors, can’t run E85 and support the current power levels).

First Pass: 11.47 @ 128mph

On the first pass, the car set a new personal best with a 11.47 @ 128mph on 18 psi of boost. The performance was outstanding, but the best was yet to come.

Second Pass: 11.31 @ 128mph

On the second pass, we bumped the boost to 20 psi, and the car ran a 11.31 @ 128mph, showing consistent improvement.

Final Pass: 11.19 @ 128mph

For the last pass, we achieved a new 8th gen stock engine/stock transmission record with a 11.19 @ 128mph. This was a huge milestone for the project, and we couldn’t be more pleased with the results.

Unbroken Engine and Transmission: A Testament to Reliability

What makes this even more remarkable is that the engine and transmission have never been broken or damaged since we began this journey in 2021. Despite the added power and abuse of the track, the Civic Si has remained reliable and strong.

Looking Forward: What’s Next?

This project has come a long way, and we’re excited about what the future holds. The car has proven itself to be a capable and reliable machine, capable of running with some of the best. With more refinements, especially to the suspension and tire setup, we’re confident there’s still more to extract from this build.