Fitment Guide
Fitment is the single most common reason an exhaust order goes wrong, so we make it explicit. Every HMD system is built for one specific chassis and engine — not for a loose year range.
What we need from you
Before ordering, send us:
- Year, make and model — the exact variant, not the family. For example "Audi S6 C7" is not "Audi A6 2019".
- Engine code or VIN — this pins down the powertrain, and therefore whether the catalyst layout and flange positions match.
- Chassis code where you know it (for example G80, F10, W213, 991, C8) — this is the fastest way to an exact match.
Which system should I choose?
Catback replaces everything behind the catalytic converter. It is the usual first upgrade: a large sound gain with the least disruption to the car, and it keeps the emissions hardware in place. Axle-back replaces only the rear section, which is a common choice on super cars where the original catalyst is already removed or already quiet enough. Full system changes the entire route including the downpipe, and is normally chosen when the car is being built rather than improved.
Valved or non-valved?
A valved system gives you a quiet mode for the commute and an open mode for the weekend, controlled by a remote or an OEM-style actuator. A non-valved system has a single, fixed, louder tone and fewer components to install. If you are unsure, tell us how you use the car and we will tell you which one we would fit to it.
Material guidance
Material is decided by the engine, not by the price list. High-revving naturally aspirated and big-turbo engines generally benefit from titanium, because the high-frequency character that makes them exciting is exactly what steel dulls. Turbocharged cars that spend most of their time on boost are often better served by SUS304 stainless steel, where durability and thermal management matter more than the last few decibels. Send us your engine and we will give you a straight recommendation — including when the cheaper material is the better engineering choice.
Installation
Catback and axle-back systems are direct replacements using the factory mounting points. For installation, we recommend a reputable workshop that can supply the correct hangers and clamps and check for leaks after the first heat cycle. Downpipe, header and manifold work normally requires professional installation and, on some vehicles, an ECU tune; this is stated on each product page.
Still not sure? Send us your vehicle details and we will confirm fitment, recommend a material and configuration, and quote lead time.