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Frequently asked questions

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Sport exhaust system and manifold - what is their effect on the fuel consumption?

A sport exhaust manifold after the catalytic converter usually decreases the fuel consumption just a little bit, but it produces a better sound.
When changing the catalytic converters with free flowing resonators and sport exhaust system, the consumption can decrease with up to 2-3 liters depending on the engine's displacement. The factory tuning settings remain the same, but the resistance in the mufflers is decreasing.

On the other hand, adding a sport exhaust manifold and an exhaust system is often related to more power, new tuning settings, and more engine improvements. People who do that are aware that the actual fuel consumption will increase in order to get the best result from the tuning.
When determining the dimensions of the manifolds and the exhaust system we take some facts into consideration including the current modifications and the desired effect.

The information published above is a product of the observations of the Extreme Tuning team.

Random diameters and badly designed manifolds can actually make the things worse.

 

Should we wrap the exhaust manifold?

Wrapping of tubular manifolds with heat wrap is extremely useful because of number of factors.

The most important thing is to keep the temperature of the exhaust gasses and their velocity. With tubular manifolds, the walls of the runners exchange heat very fast and if they are not thermically isolated, micro vortices will appear around and the exhaust gasses will decrease the velocity (their kinetic energy) when overcoming these vortices.

The faster heat exchange leads to greater fluctuations in the walls temperature for short periods which causes the material to shrink and expand multiple times. In the time, bending causes mechanical stress and very small cracks that can result in a visible crack in the manifold. Expand/shrink frequency decreases thanks to the thermal isolation. This leads to smooth transition between the temperature amplitudes.

Another important effect of using the heat wrap is keeping the heat in the engine bay under control. For tuned cars and especially these having a turbocharger, the manifold is often exposed to temperatures of approximately 700 degrees Celsium which makes it potentially dangerous for the surrounding components. The heat wrap will also prevent melting of tubes and cables.

Extreme Tuning team suggests that you always use a heat wrap for a tubular manifold.