Exhaust System: Description and Operation

Introduction
The XK8 sports car has a five-muffler exhaust system fitted. None of the components are carry over from the XJS or XJ sedan ranges. The exhaust arrangement provides a low back-pressure gas flow system which enhances engine performance.

Downpipe assembly







Each engine bank has an exhaust manifold to which is attached a downpipe assembly. For markets which have unleaded fuel, each downpipe has catalytic converter elements. For markets with only leaded fuel, the downpipe elements contain the catalyst components to maintain the exhaust pressure system but they do not have the catalyst coating.

Four threaded studs fitted in the downpipe top mounting flange locate and secure the downpipe to the exhaust manifold. Joint to joint sealing is with a gasket. A heated oxygen sensor is fitted to the upper threaded location of each downpipe which samples the gas prior to the catalytic converter. The lower end of the downpipe is secured by two nuts and bolts to a bracket which is fastened to the engine.

An extra threaded location is provided at the lower end of the downpipe, downstream of the catalytic converter, for the fitting of an oxygen sensor (not heated).

The front exhaust pipes are slip joints to the downpipes and indicator rings on the downpipes provide minimum/maximum and nominal engagement location marks.

Exhaust System Layout







Both front exhaust pipes terminate in a common, centrally positioned, front underfloor muffler. The pipes and muffler are one combined unit, the pipes being welded to the muffler. The front pipes are attached to each other by a bracket welded to each of the pipes and secured together with a strap and two nuts and bolts. The exhaust gases divert on leaving the front underfloor muffler and pass into two intermediate mufflers, through overaxle pipes, into twin rear mufflers and then to the atmosphere. Each intermediate muffler and overaxle pipe are a combined unit and are handed left and right side. All joints are slip joints and have indicator rings providing minimum/maximum and nominal engagement location marks. No gas sealants are needed for any joint. Attachment points for each of the intermediate mufflers and overaxle pipes are made at the overaxle point by a pin welded to each pipe which locates into a bush in a D-shaped, mounting rubber. The two rubbers being bonded into cradles which are bolted to the rear suspension cross member. Rear attachment for the tailpipe and muffler is an arrow head pin welded to the tailpipe, at the rear of each muffler, held in a rubber suspension ring from a body attachment point. Each rear muffler tailpipe has an integral tailpipe finisher and are handed left and right side. All mufflers are the packed absorbtion type. Total system weight is approximately 40 kg (88 lbs).