TECH TALK: HJS 200 Cell Catalytic Converters

Soul Performance Products chooses HJS Emission Technology for premium catalytic converter solutions for our customers looking to enhance sound and flow – all without a check engine light. Let’s dive into a quick explanation of how catalytic converters work and how HJS perform compared to OEM.

How Do They Work?

The job of a catalytic converter is to convert pollutants through a combination of high heat and precious metals into harmless water vapor and carbon dioxide. The catalyst components of a catalytic converter are mainly platinum (Pt), along with palladium (Pd), and rhodium (Rh).

Nitrogen oxide is split up through the chemical process of reduction into nitrogen and oxygen. Carbon monoxide is oxidized into carbon dioxide. Unburned hydrocarbons are also converted into carbon dioxide and water. You’ll know when your catalytic converter is failing or your car is running rich as you’ll smell unconverted hydrogen sulfide as a result of sulfur in gasoline. Modern vehicles are designed to quickly raise the operating temperature of the catalytic converters into their operating temperature of around 1,000 to 1,500 degrees Fahrenheit. Most modern OBD2 cars will have an o2 sensor pre and post catalytic converter to monitor effectiveness – for example your car can tell if it is running rich by detecting an increase in temperature between the two points.


French chemical engineer Eugene Houdry patented what seems to have been the very first catalytic converter in the United States in 1950. Houdry had previously invented catalytic cracking, the industrial process by which the many complex chemicals in petroleum are separated into dozens of useful products, including gasoline. After that he experimented with making different kinds of vehicle fuels and making them cleaner. Early catalytic converters were held back by the lead in fuel (used to raise the octane rating / reduce engine knock) – it would reduce the effectiveness of the process and ultimately ruin the converters ability to act as a catalyst. In the 1970’s the EPA recognized the dangers of leaded fuel and a need to reduce harmful emissions with catalytic converters becoming standard equipment on new vehicles.

Enter HJS

HJS Motorsport and Tuning has been developing premium catalytic converters since 1990 for Motorsports use having cooperated with the German Motorsport Federation and FIA. Using this experience, they carried technology over to craft tuning catalysts for road-going cars. For Motorsports use, HJS primarily uses 100 cell catalytic converters for non-controlled racing cars, and offers various cats to meet Euro specs – but you will commonly see the 200 cell HF and HD variants for use in aftermarket components like our exhausts. HJS aims for a “zero defect quality” standard and manufacture under strict ISO certified tolerances. They’re also focused on recycling as much as possible – trying to reduce environmental effects on both street and race cars alike.

Premium Performance

Replacing the restrictive OEM catalytic converters can yield gains in not only power but sound as well. You’ll hear the engine and turbo(s) much more. How does HJS achieve an increase in flow while still catalytizing effectively and not throwing a check engine light? A premium wash coat of precious metals of higher density than OEM allows for catalyzation to effectively occur in spite of a decrease in surface area and increase in flow. The downside is an increase in cost – Palladium is worth more than gold! This wash coat elevates the performance of HJS cats to a higher level than your average, unbranded aftermarket catalytic converter. By selecting the right length and width of the cats we’re able to defeat the chances of a check engine light while making your car more enjoyable to drive. Compared to catless components, HJS cat equipped components offer a similar increase in flow without emitting obnoxious toxic fumes which can be unbearable to some at stoplights or in the garage.

You’ll notice the HJS core on the left looks much different than the factory 991.2 GT2 RS unit, not only in cell count but in construction. HJS HD cats have a triple foil winding metal matrix. This design increases durability and rigidity with the use of larger sized cells. It can also prevent failure of the structure of the matrix – you may have experienced a failing catalytic converter that breaks into chunks in your exhaust system.


HD variants have a brazing stripe which is an indent that locks the core into the shell. This increases the durability of the matrix which receives a constant beating of pressure wave and pulses that can be brutal from higher horsepower engines.

Due to their extreme durability and our belief that you should be able to truly enjoy your upgrades, we warranty HJS catalytic converters for 3 years including both street and track use. We’re proud to incorporate them into our exhausts and enhance your driving pleasure.

Further reading:

HJS Website

Questions? Comments? Let us know!

– Mike Spock / Marketing Manager