Quick answer: for most street-driven Commodores, Falcons and Mustangs, a cat-back system is the best starting point. Twin 2.5-inch is the classic choice for a V8 Commodore, a single 2.5-inch suits most V6 and XR6 cars, and 3-inch twin systems make sense on bigger V8s such as the Mustang GT or a modified VE/VF. The muffler or hotdog you choose changes the sound far more than the pipe size does, so pick the sound you want first and the diameter second.
Our blog has leaned heavily towards diesel 4x4s, but a big part of the DEA Performance range is built for Australian performance cars. This guide covers the main decisions when you are choosing an exhaust for a V8 or six-cylinder sedan, ute or coupe.
Single or twin exhaust?
A single system sends both banks of the engine through one pipe after the catalytic converter. A twin system keeps each side separate all the way back, so you get two pipes and, usually, two tips.
Twin systems are the usual choice on V8s because they suit the engine's layout and give the traditional V8 look and sound. A single system is simpler and is common on V6 and straight-six cars such as the XR6.
There is a bit of simple geometry behind the sizing. Two 2.5-inch pipes have a combined cross-section of roughly 9.8 square inches, which is more than a single 3-inch pipe at roughly 7.1 square inches. That is why twin 2.5-inch is such a popular match for a V8: you get plenty of flow without going to a very large single pipe.
See our guide to 2.5-inch vs 3-inch exhaust for how size relates to engine and power.
2.5-inch or 3-inch for a V8?
For a standard or mildly modified V8, 2.5-inch per side is usually enough and tends to keep the tone deep without an overly harsh note. Going to 3-inch makes more sense when the engine is making substantially more flow, for example a bigger-capacity or heavily modified V8, or when the rest of the system (extractors, high-flow cats) has already been upgraded. Bigger is not automatically better, and a larger pipe can change the sound without a useful gain on a stock engine.
Which hotdog or muffler?
This is where most of the sound is decided. In rough terms:
- Straight-through hotdogs give the deepest, freest-flowing sound and are the louder choice. See what they are in our exhaust parts glossary.
- Mufflers make the car quieter and are the safer pick if you want to avoid drone or keep the car comfortable on the highway.
- A combination, such as a front hotdog with a rear muffler, balances the two. Several of our Commodore systems are built this way.
If you want to switch between quiet and loud, a valved muffler is an option: see our VAREX mufflers and universal mufflers. For the difference between a resonator and a muffler, read resonator vs muffler.
Cat-back, extractors or both?
A cat-back system replaces everything behind the catalytic converter and leaves the cat in place. It is the simplest upgrade and usually the one that changes the sound most. Our catback guide explains it in full.
Extractors (headers) replace the factory exhaust manifolds at the engine. They are a bigger job, and they are usually matched with high-flow cats so that the whole system works together. Browse our high-flow cats for extractors and high-flow catalytic converters. If you are doing both, plan the extractors, cats and cat-back as one package.
Systems by model
Commodore VN to VS. The V6 and V8 cars use different systems, so check the listing carefully. For example, the VN/VP/VR V6 and V8 and VS V8 sedan 2.5-inch cat-back covers the VS V8 only, while the VS V6 sedan (live axle) system is a separate listing. For VS Ecotec extractors, see the Genie auto extractors or the Pacemaker extractors.
Commodore VT to VZ. V8 owners can look at the twin 2.5-inch hotdog and tailpipe system. V6 owners have a wide choice of 2.5-inch cat-backs, such as the VT-VY front and rear muffler system. For supercharged V6 cars, see the Pacemaker PH5061 extractors.
Commodore VE and VF. Options include the XPS twin 2.5-inch stainless cat-back, the twin 3-inch cat-back with HDX pipe and straight tips and the XFORCE twin 3-inch polished stainless cat-back (a special order item).
Falcon. The XR6 is well covered, for example the BA/BF XR6 sedan 2.5-inch cat-back. See the full Ford Falcon exhausts range.
Mustang. The FM 5.0L Coyote V8 GT fastback 3-inch twin stainless cat-back has mufflers and black chrome tips. Browse the Mustang exhaust collection.
For everything else, browse Commodore exhausts, Monaro exhausts, Statesman exhausts and the full performance exhaust range.
Finish: tips and material
Tips are the part people see, so it is worth choosing them deliberately. Browse exhaust tips and dual exhaust tips, and read how exhaust tips change the sound. Stainless costs more than aluminised but lasts longer, as we explain in stainless vs mild steel.
Check the fit and the rules
Two things to check before you buy. First, make sure the system matches your exact model, engine and body, because a V6 and a V8 version of the same car can need different systems. Our guide to checking exhaust compatibility shows how. Second, check the noise and emissions rules in your state, which we summarise in our state-by-state legality guide. Keeping the factory catalytic converter in place is the safest road-going approach.
Frequently asked questions
Is twin 2.5-inch or single 3-inch better for a V8 Commodore?
Twin 2.5-inch is the classic V8 setup and has a larger combined cross-section than a single 3-inch pipe. A single 3-inch is simpler but is a different sound and look. Twin 2.5-inch is the usual choice for a street V8.
Will a cat-back make my Commodore or Falcon louder?
Usually yes, mostly because of the hotdog or muffler you choose. A muffler keeps it quieter and a straight-through hotdog makes it louder and deeper.
Do I need extractors with a new exhaust?
No. A cat-back works on its own. Extractors are a separate upgrade and are best planned together with high-flow cats and the cat-back if you want to do the whole system.
Will it drone on the highway?
Drone is a low-pitched hum at cruising revs. A muffler or a resonator is the usual way to reduce it, so choose a combination system if highway comfort matters.
Will it fit my VS V6 or V8?
They can need different systems. Match the listing to your exact engine, and contact us if you are not sure.
Shop performance car exhausts at DEA Performance
Browse Commodore, Falcon and Mustang exhausts, cat-back systems and extractors. Not sure what suits your car? Send us your model, engine and the sound you are after and we will point you to the right system.