Verboden

Saw this exhaust manifold and was wondering if anyone can explain the use of the flex tubing on one of the pipes. This is off of a Ferrari. The flange looks hard mounted as does the end of the pipe, so I am confused about the need for flex. I have seen these flex couplers used in turbo installs which I assumed was for maintenance. Thanks in advance.

Scooby921

Speculation:

Tuning of the exhaust gas flow. That one runner is a lot straighter than the others. In theory the gas flows faster through it. The rougher interior of that flex coupling should build a little thicker boundary layer (exhaust gas flowing slower at the outer walls due to friction with the walls). The ever-so-slight reduction in laminar flow may create a tiny increase in back pressure for the cylinder. The tiny venturi effect may also help change the speed and pressure as it blends with other pulses in the collector.

Alternatively, that one runner might see more total heat build-up due to its location in the engine bay. If it gets hotter and expands too much the flex section might be there to allow that runner to change more than the others and avoid cracked welds.

spdracerut

The bellows joint on that one straight runner allow for thermal expansion/contraction. The other 3 runners all have multiple bends. Those bends basically act as springs to absorb the expansion/contraction of the runners; ex. paperclip. On the straight runner, the 'spring' is in the form of that bellows joint