XForce’s HSV Exhaust System: The Low Restriction Upgrade You Need

Car buffs have always relished the prospect of auto manufacturers joining forces with pedigree racing enterprises to develop their own factory-bred muscle cars. Holden’s HSV subsidiary was one such marriage, and the cars that turned out from 1987 until Holden’s closure in 2017 are the stuff that automotive legends are made of.

Commodore sedans, GTO coupes and Maloo utes have all borne witness to HSV’s willingness to squeeze their most aggressive V8 powerplants under Holden bonnets. And while each model has come to exemplify their 3-decades long saga of tyre-shredding success, there was one area of high performance that HSV was obliged to refrain from: installing high flow exhaust systems. NSW’s XForce knows precisely how to remedy that problem though, which is why today might be the right time for an HSV owner who hasn’t done so already, to seriously consider buying a premium aftermarket system.

Bringing XForce Exhaust Expertise To Holden’s Mighty HSVs

HSV owners understand: with more than 25 years in the business of designing and manufacturing high performance exhaust systems, an upgraded XForce high flow HSV exhaust system is more than just another aftermarket exhaust. No other aftermarket exhaust company in Australia is as committed to actual flow dynamics testing and optimising as XForce; and it’s no secret that optimisation is the key to getting the most from HSV’s supercharged V6s and V8s.

Although the bulk of HSV’s high performance engine development was largely limited to only 3 engine families – GM’s “LS” and Holden’s “Iron Lion” V8s, and GM/Buick V6s – there were multiple versions of each of these engines, many within the same model year. And because torque and output levels also varied dramatically within model years, XForce manufactures a wide selection of header-back, catback and header-only systems and components for a full range of HSV engine/chassis combinations, with emphasis on later model V8s, such as:

• 2004-2006 VZ 6.0L V8 coupes;
• 2006-2013 VE 6.0L V8 sedans and wagons;
• 2008-2017 VE/VF 6.2L V8 utes and SS sedans;
• 2013-2017 VF 5.0L V8 sedans;
• 1997-1999 VT 5.0L V8 sedans;
• 1999-2006 VT/VZ 5.7L LS1 V8 sedans; and,
• 2001-2006 VU/VY 5.7L LS1 V8 utes.

From Commodores and Clubsports, to Senators and Statemen, these are only 7 of the more than 40 different exhaust system configurations XForce offers for Holden’s mighty HSVs. And while each system is unique, they all share the same need for balanced airflow. Not surprisingly though, this is where XForce’s unrivalled exhaust engineering expertise makes the difference.

Characteristics and Configurations That Make XForce HSV Exhausts Shine

Unlike most aftermarket exhaust manufacturers, XForce understands that regardless of their displacement, every engine has its own unique power and torque curves, determined by that engine’s own unique airflow requirements. A 5.7L VZ V8 producing 220kW won’t have the same exhaust flow characteristics as a 6.2L VF V8 grinding out more than 470kW. That’s why XForce dyno tests each HSV configuration to achieve the best balance of the most crucial exhaust flow characteristics, which includes:

• Increasing maximum scavenging. Exhaust scavenging is the process where the vacuum, created by hot spent exhaust gases traveling from high pressure to low pressure, aids in drawing fresh air and fuel into the engine.
• Achieving maximum gas velocity. Gas velocity is the speed that spent exhaust gases are drawn through the system. As spent gases expand, their velocity also increases – a process that has an instantly positive effect on engine scavenging.
• Minimising exhaust backpressure. Whether it’s the result of crush-bent tubing or overly restrictive cats and mufflers, backpressure is caused by any resistance to spent exhaust gases moving through the system. Minimising backpressure is the key to maximising scavenging and gas velocity.

Ideally, XForce exhaust systems are designed to produce the best possible airflow balance that encourages optimal scavenging, while delivering the highest spent gas velocities to keep backpressure low. And because HSV engines are already such efficient breathers, XForce exhausts don’t have to rely on oversized exhaust tubing to encourage better exhaust gas movement; just a solid focus on the basics of heat movement and gas expansion built around the following:

• A choice of 1 3/4″ or 1 7/8″ primary tube to 2.50″ – 3.0″ 201 stainless steel headers with a 3.0″ cat;
• 2.50″ – 3.0″ twin primary tubing configurations, made from fast heat dissipating 409 or 304 stainless steel;
• Flush welded flanges and slip joints that seal and fit perfectly, without leaking or flexing;
• Mandrel bent curves to ensure minimal backpressure throughout the entire system; and,
• A choice of dual centre mufflers or hot-dog style resonators.

Xforce also manufactures an electronically controlled, butterfly-valve equipped muffler called the Varex. It allows drivers to regulate the amount of inline back pressure via Bluetooth, key fob, or from a touchscreen in later model Commodores, Commodore Calais and Senators. The Varex’s independently-mounted Smartbox Controller gives HSV owners a full range of tunable muffler settings, allowing them to maximise airflow according to their precise needs.

Big Benefits From Low Restriction XForce HSV Exhausts

While it may be difficult at first to understand why Holden treaded so carefully when it came to choosing exhaust systems for their highest output behemoths, HSV owners are under no illusions about the reasons. Restrictive systems were selected over factory-engineered HSV performance exhausts to spare the company from a barrage of costly ADR compliance requirements for noise and exhaust gas emissions.

They understood that aftermarket manufacturers like XForce wouldn’t hesitate to pick up the high performance baton, though. And in doing so, they also green-lighted the successful transformation of their most potent performers into timeless street and strip legends.

With the assistance of an XForce upgrade, HSVs are able to get all the high flow/low restriction benefits that drivers expect from a high performance exhaust system had it been built by the factory, to include:

• An unmatched increase in output. With XForce’s dyno-tuned exhausts, an output increase of 5kW – 15kW can be expected just on the improvement in catback airflow and reduced backpressure. A full XForce header-back upgrade, together with the addition of an aftermarket airbox, can expect to see a gain of 40kW – 50kW, or even more.
• A more powerful exhaust note. The low restriction, straight-through design of XForce exhausts allows them to produce an exhaust note that’s befitting of any of the HSV’s heavy breathing V6s and V8s. And with a Varex muffler, the sound can be adjusted from a mild rumble to a powerful roar.
• Improved fuel economy. Fuel economy isn’t ordinarily associated with aftermarket exhaust upgrades, but the easier scavenging and reduced backpressure that’s afforded by an XForce system means an engine doesn’t have to work nearly as hard to put power to the ground. At any speed, that’s a guaranteed improvement in fuel economy.

From their increased airflow, to their impeccable sound management, XForce give HSV owners everything they need to take their vehicle to the next level of legendary performance. And the fact that they’re able to do it with full noise and emissions compliance leaves no question about their ability to dominate the streets as easily as they do the track.

The Final Word

At the end of the day, HSV owners can be proud of knowing that their cars have been equipped with some of the most powerful V6s and V8s ever manufactured in Australia. And they can also be proud that where HSV understandably needed to take their foot off the gas on high performance exhausts, that a company like XForce was prepared to push the pedal to the floor on their own premium exhaust development.

The result is a lineup of high flowing, low restriction HSV exhaust system configurations made especially for HSV’s hottest performers. They’re the systems that give HSV engines the airflow they need to reach their full performance potential.