Test Pipes / Decat for Honda CRX EH

A test pipe, or decat pipe, replaces a catalytic converter with a straight section of pipe. Race catalyst versions put a free-flowing converter in the same place instead. Both are competition parts for use where the rules allow, listed in fixed and adjustable lengths for the car named in the title.

The converter’s honeycomb is one of the main restrictions in a production exhaust, and it adds heat of its own as the reactions run. Taking it out lowers back pressure and the heat under the floor. The cost is that the gas is no longer cleaned, it smells strongly, and the car gets louder, because the converter also damps some noise.

The rear lambda sensor watches how well the converter works. With a straight pipe in its place, the engine management usually stores a catalyst-efficiency fault and lights the warning lamp, so these parts suit cars with a competition calibration.

Check the type and the fit:

• Straight test pipe: plain pipe, listed in polished SUS 304 stainless with gaskets and fixings supplied.
• Race catalyst version: a high-flow 200-cell catalyst in place of the original converter, with a boss and plug for the oxygen sensor.
• Adjustable length: these slide to the length the car needs before the joints are tightened, and the title gives the pipe size, such as 2.5″.
• Decat pipes and downpipes: stainless decat pipes, plus downpipe-and-decat sections for turbo engines, each listed for one model and engine.

Fit the pipe with new gaskets, move the sensors across and refit the heat shields. Keep the original converter, since it is needed to return the car to road use. Expect the car to be noticeably louder, and check the noise limits of the circuits you visit.

Neither type is legal on public roads in Europe. Fitting one to a road car can affect its type approval, inspection and insurance.