Two Step Performance High Efficiency Downpipe - 22+ Civic & Si, 23+ Integra, 18+ Accord 1.5T

Your 1.5T is breathing through the factory downpipe, and that's the single biggest restriction on the hot side. Free it up and the whole car changes, it spools easier, pulls cleaner, and quits feeling like it's gasping through a straw. This Two Step Performance High Efficiency Downpipe is the one we keep recommending for these cars, and here's the best part: it's EPA compliant, it doesn't need a tune to run, and it won't throw a check engine light. You get the airflow without any of the usual headaches.

EPA Compliant, No Tune, No Check Engine Light

This is what separates this downpipe from the race-pipe crowd. It runs a genuine 400 CPSI GESi G-Sport catalytic converter that's EPA compliant, so you're not gutting your emissions equipment to make power. You can bolt it on with a completely stock ECU, drive off, and never see a CEL. No tune required, no codes to clear, no limp mode, no "check engine light is just part of the build" nonsense you'd have to live with on a catless pipe.

That cat is rated for up to 850 horsepower, which means you'll never outgrow it on a 1.5T, and it's formulated specifically for small displacement direct injection engines. That formulation matters more than people realize, a cat that isn't matched to a small DI engine is where you get the rotten-egg smell and weird drivability gremlins. This one just works, and it still acts like a street car.

Built Around Flow, Not Guesswork

The construction is where Two Step earns it. You get 304 stainless investment cast ends that are CNC pocketed for a clean transition into the 4.5" OD cat body, so exhaust gas isn't slamming into a rough weld or a sharp step. The inlet is a wide casting that blends the turbine outlet and wastegate flow together instead of jamming them into each other, which is exactly where cheap downpipes lose their gains. On the other end, the cast outlet tapers smoothly into your front pipe.

Two Step back purges the welds on site, meaning they flood the inside of the pipe with argon while welding so the welds come out clean and strong instead of scaled and brittle. That's a real durability difference on a part that lives in constant heat, and it's the kind of thing you don't see until a lesser pipe cracks on you.

What You'll Actually Feel

More flow across the entire powerband, less backpressure, and cooler exhaust gas temps, and that EGT drop gets more valuable the more boost you run. The turbo spools easier because it's not fighting to push gas through a restrictive factory pipe, so throttle response sharpens up everywhere. And it does all this without turning your car into a droning, raspy mess, which is the trap a lot of exhaust mods fall into.

Want More? Add A Tune

You don't need a tune to run this, that's the whole point. But if you want to get everything out of it, software is how you do it. The downpipe frees up the airflow, and a tune lets the ECU actually take advantage of it. If that's your plan, look at Hondata FlashPro or KTuner V2.0. Run it bone stock now, tune it later, either way works.

Bolts Up To What You've Got

It's compatible with your factory exhaust and most aftermarket front pipes, and no adapter is necessary. So whether you're keeping the rest of the car stock or you're already running a full system, this drops in. It also fits all variant models, including RHD and international cars.

Common Questions

Does this fit the 11th gen Civic Si?
Yes. The 2022+ Civic Si runs the 1.5T, so this is the correct downpipe for it, same as any other 2022+ Civic 1.5T.

Do I need a tune?
No. It's designed to run on a completely stock ECU with no check engine light. A tune gets you more, but it's optional.

Will it fit my Civic Type R or Integra Type S?
No. Those are 2.0T cars and use a different, larger downpipe with a 5.0" cat. This one is for 1.5T engines only.

Is this catless?
No, and that's deliberate. It uses an EPA compliant 400 CPSI GESi G-Sport cat rated to 850hp, so you get the flow while keeping your emissions equipment intact.

What's included?
Gaskets and stainless hardware come with it, so you've got what you need to install it.

What You Get

• Two Step Performance High Efficiency Downpipe (SKU TSP-DWN-01-02, MPN TSP-HC11-HEDP)
• EPA compliant 400 CPSI GESi G-Sport catalytic converter, 4.5" OD, rated to 850hp
• No tune required and no check engine light
• 304 stainless investment cast ends, CNC pocketed for smooth transitions
• Wide cast inlet that blends turbine and wastegate flow
• Back purged welds for heat tolerance and durability
• Compatible with factory and most aftermarket front pipes, no adapter needed
• Gaskets and stainless hardware included
• 24 month warranty covering welding

Fits These Cars

• 2022+ Honda Civic 1.5T, including the Civic Si
• 2023+ Acura Integra 1.5T
• 2018+ Honda Accord 1.5T
• Fits all variant models, including RHD and international
• Does NOT fit 2.0T models (Civic Type R FK8/FL5, Integra Type S)

Note: Two Step Performance High Efficiency Downpipe, SKU TSP-DWN-01-02 (manufacturer part number TSP-HC11-HEDP), for the 2022 and newer Honda Civic 1.5T including the Civic Si, 2023 and newer Acura Integra 1.5T, and 2018 and newer Honda Accord 1.5T, including all variant models such as RHD and international versions. It does not fit 2.0T models such as the Civic Type R or Integra Type S. The downpipe uses a 4.5" OD, 400 CPSI EPA compliant GESi G-Sport catalytic converter rated for use up to 850 horsepower and formulated for small displacement direct injection engines. No ECU calibration or tune is required and use of this downpipe will not result in a check engine light, though tuning software will maximize gains. Construction includes 304 stainless steel investment cast ends, CNC pocketing for smooth transitions, a wide cast inlet that blends turbine outlet and wastegate flow, and a cast outlet that tapers into the front pipe; all welds are back purged on site for heat tolerance and durability. Compatible with factory and most aftermarket front pipes with no adapter necessary. Includes gaskets and stainless hardware. Carries a 24 month warranty covering welding; damage resulting from coating, heat wrapping, or insulating the downpipe is not covered, as these treatments accelerate material degradation. This product is not CARB legal and is not for sale or shipment to California. One downpipe per order.