Exhaust System: Description and Operation
This data covers the various exhaust systems fitted to AJ16 engined vehicles.
Always refer to the Parts Catalogue for parts usage and interchangeability before replacing a component part of the exhaust system.
The low-loss catalytic converter exhaust system for the AJ16 normally aspirated engine comprises of a catalyst/downpipe assembly (1 Fig. 1), an underfloor catalytic converter assembly (2 Fig. 1) complete with heat shield (3 Fig. 1), an intermediate muffler section (4 Fig. 1) and a rear muffler section (5 Fig. 1).
On non-catalytic converter systems the downpipe/catalyst assembly is fitted with conventional twin branch downpipes, hence there are no oxygen sensors or gas temperature sensors.
Conventional mufflers are fitted in place of the underfloor converters.
A simple slip joint or olive seal is used to provide a tight leak free sealed joint between down pipe to under floor catalyst assembly.
Heated oxygen sensors are fitted to the downpipe assembly (1 Fig. 1) which is connected to the manifold (2 Fig. 1). There are two sensors for the ROW and Japan (4 Fig.1) and two additional sensors (3 Fig. 1) for NAS markets.
The sensors are located upstream and downstream of catalytic converters.
Apart from two heated oxygen sensors, the exhaust system for vehicles destined for the Japanese market are also fitted with two exhaust gas temperature sensors (5 Fig. 1).
The exhaust system is held in a predetermined position by a fixing arrangement to the manifold by exhaust centre mountings (6 Fig. 1), by rear axis mountings (7 Fig. 1), and tail pipe mountings (8 Fig. 1).
Only clamps (9 Fig. 1) used on slip joints are welded to the pipes and tightened to a higher torque setting than non- welded clamps. Non-welded clamps are fitted to down pipe / catalyst assemblies with olive seals located between flared joint
The exhaust system must be free of leaks, binding, grounding and excessive vibrations. These conditions are usually caused by loose, broken, or misaligned clamps, shields, brackets, or pipes. Should any of these conditions exist, check the exhaust system components and alignment. Adjust and renew if necessary. Do not attempt to service brackets, clamps and insulators.
The only visible difference between the normally aspirated engine's exhaust system and the supercharged version (Fig. 1) is that the downpipe for the supercharged engine (Fig. 1) is slightly shorter.
The remove & refit procedures are the same as for the AJ16 normally aspirated.
Updates: Exhaust System
Non-catalyst exhaust systems are carried over from the previous model year.
Catalyst exhaust systems are new, as detailed below, to give improved engine performance.
The minimum diameter of the pipes in the catalyst exhaust system is increased from 45 to 50 mm (1.77 to 1.97 inches).
Exhaust Down Pipes And Oxygen Sensors
For tuning purposes, the exhaust manifold outlet pipes have been lengthened. This revision resulted in an increase in overall down pipe length. A slip joint replaces the previous clamp joint between the down pipe and the main catalyst. On vehicles with a supercharged engine, a shorter downpipe is introduced to accommodate the different gearbox installation.
On North American Vehicles two additional upstream oxygen sensors are used with the new engine management system. Refer to Powertrain Management for operating information.
On Japanese vehicles, the temperature sensor at the junction of the outlet pipes is replaced by a separate temperature sensor in each outlet pipe.
Main Catalyst
The main catalyst front connecting pipe has been shortened to accommodate the lengthened down pipe.
Under-floor Catalyst Assembly
The under-floor catalyst assembly is revised to match the new downpipe and to include the larger diameter connecting pipes.
Intermediate Silencers
The intermediate silencers are revised to include the larger diameter connecting pipes.
Rear Silencers
The rear silencers are of a larger volume and include the larger diameter connecting pipes. The rear silencers on vehicles with a supercharged engine are the three-pass silencers. Vehicles with a normally aspirated engine retain the straight-through design of silencer.