Exhaust Kits

Exhaust Kits Overview

It’s well established throughout the 4WD community that large capacity, high flow exhausts are of great benefit to the modern 4WD. Increased torque over a wider RPM range result in a more flexible engine with improved economy

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Why does it Work so well in Turbo Diesel:

The Law of Adiabatics – as a gas cools it expands, as the exhaust gases move away from combustion they are expanding at the greatest rate, as they are cooling at the greatest rate. The turbine spins earlier due to the greater space for the hot exhaust gases to expand into.

It’s the expansion of the gases that make the turbo spin, as they rush past the turbine into the greater space provided by the larger exhaust.

The earlier spinning leads to earlier boost pressure which leads to improved efficiency, hence improved economy and lower down torque.

Mandrel bends do not have reduced diameter like factory compression bends, but this is a minor improvement compared with muffler design and the fundamental improvement gained by the increased pipe diameter.

Pre-DPF kits come with a dump pipe, Post-DPF fit onto the rear of the DPF. From there a kit should have a  flex joint, hi-flow mandrel bends, mount to the original mounting points with a choice of muffler, straight through pipe or hotdog. They can be as quiet as the factory system or as noisey as a drag car.

Note, more noise does not equate to greater flow.

The reason? Remember, diesel fuel detonates due to the compression of the air-fuel mixture on the compression stroke, and it is the compression that lifts the temperature of the fuel to ignition. If there is not enough ‘back pressure’, the exhaust gas flow out is so fast that upper cylinder temperatures reduce to the point where more compression energy is required to cause combustion. More energy is used from the other ‘firing’ cylinders to force the piston higher (to get compression), hence energy is being absorbed, overall power output is reduced. Timing of the piston position vs fuel delivery is also altered, reducing power output further.

For more low down torque for 4WDing, better towing and safer overtaking on-road, with improved economy, the hi-flow exhaust will make a noticeable difference, up to 15%.


  • Available in Turbo Back and DPF back
  • Stainless Steel Braided Flex Joint
  • Available in a variety of noise levels: straight pipe, hot-dog or hi-flow Stainless Steel muffler
  • 409 Stainless with 3” Mandrel Bends
  • 10mm Thick 409 Stainless Steel flanges
  • Fix to OE mounting points
  • DIY Kit gaskets, high tensile zinc plated nuts, bolts & washers
  • Manufactured in Australia
  • Guaranteed Fit Well

High flow exhausts are of great benefit to the modern 4WD. Increased torque over a wider RPM range result in a more flexible engine with improved economy.

For an in depth discussion about 4×4 Exhaust Systems, read this 4×4 School article

3 Year Unlimited KM Warranty

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For all enquiries to arrange a fitting, international freight costs or specific product information, please complete the form below or call 04999 85209

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