{"product_id":"hks-sport-cat-back-exhaust-for-89-91-honda-civic-si","title":"HKS Sport Cat-Back Exhaust for 89-91 Honda Civic Si","description":"\u003cul\u003e\n\u003cli\u003eFits 89-91 Civic Si Hatchback ONLY \u003c\/li\u003e\n\u003cli\u003e50mm Piping Diameter \u003c\/li\u003e\n\u003cli\u003eDesigned for the D16A6 Engine \u003c\/li\u003e\n\u003cli\u003e60mm Tip Diameter \u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c!-- split --\u003e\n\u003cul class=\"tabs\"\u003e\n\u003cli\u003e\u003ca class=\"active\" href=\"#Description\"\u003eDescription\u003c\/a\u003e\u003c\/li\u003e\n \u003cli\u003e\u003ca href=\"#VehicleFitment\"\u003eVehicle Fitment\u003c\/a\u003e\u003c\/li\u003e  \u003cli\u003e\u003ca href=\"#TechnicalData\"\u003eTechnical Data\u003c\/a\u003e\u003c\/li\u003e  \u003cli\u003e\u003ca href=\"#InstallGuide\"\u003eInstall Guide\u003c\/a\u003e\u003c\/li\u003e \u003c\/ul\u003e\n\u003cul class=\"tabs-content\"\u003e\n\n\n\u003cli class=\"active\" id=\"Description\"\u003e\n\u003ch3\u003eHKS Sport Cat-Back Exhaust (LES-H05) - 1989-1991 Honda Civic Si (D16A6)\u003c\/h3\u003e\n\n\u003cp\u003eThe EF Si is a light car with a modest engine, which means the exhaust has a specific job: get gases out without killing the velocity that makes a small D-series feel alive. HKS sized this system for exactly that. 50mm piping into a 60mm R-2 tip, with a muffler designed to broaden the torque band rather than just chase a peak number.\u003c\/p\u003e\n\n\u003ch4\u003e50mm Is The Right Size, Not The Small Size\u003c\/h4\u003e\n\n\u003cp\u003eWorth explaining, because people see the number and assume bigger would be better.\u003c\/p\u003e\n\n\u003cp\u003eExhaust gas needs velocity as well as volume. Velocity is what creates the scavenging effect that helps pull spent gases out of the cylinder, and it's what keeps a small naturally aspirated engine responsive down low.\u003c\/p\u003e\n\n\u003cp\u003eOversize the piping on a 1.6 liter and that velocity drops. What you get is a car that might show a marginally higher peak number on a dyno and feels worse everywhere you actually drive, with a hollow note to match.\u003c\/p\u003e\n\n\u003cp\u003e50mm keeps velocity where the D16A6 lives while still flowing considerably better than the restrictive factory system. HKS sizes these per application rather than applying one pipe diameter across their range, and that's why.\u003c\/p\u003e\n\n\u003ch4\u003eWider Torque Band, Not Just Peak Power\u003c\/h4\u003e\n\n\u003cp\u003eThe muffler design matters as much as the piping.\u003c\/p\u003e\n\n\u003cp\u003eHKS builds the Sport series around reducing backpressure while maintaining the characteristics that make a car pleasant to drive. That means low-end torque stays intact while the top end opens up, rather than trading one for the other.\u003c\/p\u003e\n\n\u003cp\u003eOn an EF, that's the right priority. These cars weigh nothing, so usable torque through the midrange is what makes them quick on a back road. A system that only helps above 6,000 rpm isn't helping much of the time.\u003c\/p\u003e\n\n\u003ch4\u003eThe Gains Build With Your Build\u003c\/h4\u003e\n\n\u003cp\u003eHonest framing on what to expect.\u003c\/p\u003e\n\n\u003cp\u003eOn a completely stock D16A6, a cat-back is a modest improvement. The engine isn't producing enough exhaust volume to fully use a freer system, and anyone promising big numbers from an exhaust alone on a 1.6 is overselling it.\u003c\/p\u003e\n\n\u003cp\u003eWhere it earns its keep is as the build progresses. Add an intake, a header, or cams, and the exhaust goes from adequate to the limiting factor. This has the capacity ready for that, which is why it's the sort of system people keep as the car develops rather than outgrowing.\u003c\/p\u003e\n\n\u003cp\u003eAnd in the meantime, the car sounds considerably better than it did.\u003c\/p\u003e\n\n\u003ch4\u003eFitment\u003c\/h4\u003e\n\n\u003cp\u003e1989-1991 Honda Civic Si hatchback (D16A6)\u003c\/p\u003e\n\n\u003cp\u003ePart number LES-H05.\u003c\/p\u003e\n\n\u003ch4\u003eWho Should Run This Exhaust\u003c\/h4\u003e\n\n\u003cp\u003eThis is for the EF owner who wants a real name-brand system rather than a generic cat-back, and who appreciates that sizing matters more than size. HKS has been building these since these cars were new, the 50mm piping is correct for the engine rather than the biggest pipe that fits, and the tone suits the car. Bolt it on and enjoy it.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eFits:\u003c\/strong\u003e 1989-1991 Honda Civic Si hatchback (D16A6). \u003cstrong\u003ePart number:\u003c\/strong\u003e LES-H05. \u003cstrong\u003eType:\u003c\/strong\u003e cat-back exhaust system. \u003cstrong\u003ePiping:\u003c\/strong\u003e 50mm. \u003cstrong\u003eTip:\u003c\/strong\u003e 60mm, R-2 style.\u003c\/p\u003e\n\u003c\/li\u003e\n\n \n\u003cli id=\"VehicleFitment\"\u003e\n \u003cp\u003e\u003cspan class=\"tag\"\u003e1989-1991 Honda Civic Si Hatchback\u003c\/span\u003e\u003c\/p\u003e\n\u003cbr\u003e \n\u003c\/li\u003e\n\n\n\n\n\u003cli id=\"TechnicalData\"\u003e\n\n\u003c\/li\u003e\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\u003cli id=\"InstallGuide\"\u003e\n\n\u003c\/li\u003e\n\n\n\u003c\/ul\u003e\n","brand":"HKS","offers":[{"title":"Default Title","offer_id":47603531579426,"sku":"HKS-LES-H05","price":1150.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/2218\/5701\/files\/6a210119ab42f0ae32d9598c026a2a06.jpg?v=1789488063","url":"https:\/\/www.hybrid-racing.com\/products\/hks-sport-cat-back-exhaust-for-89-91-honda-civic-si","provider":"Hybrid Racing","version":"1.0","type":"link"}