Thats becuase Peugeot specifically tuned this engine for it...
The old Mi16 is a very peaky unit, almost as powerful but needs keeping on the boil and lacks low end grunt, wheras the GTi-6 lump has a very wide spread of power but theres less of a change when it comes on cam.
Some good info here >>>
The XU10 J4RS engine is the latest in the XU engine range. This 4 cylinder unit replaces the XU10J4 ACAV engine in the S16
1998cc capacity and a bore stroke of 86mm. It has a lighter rotating assembly and timing gear, a remodelled cylinder head, specially designed cams and a new inlet and a 4 branch tubular exhaust manifold.
The engine develops a maximum 167bhp at 6500 rpm and maximum torque of 193Nm at 5500 rpm.
The optimised acoustic harmony between inlet and exhaust produces a smooth torque curve.
Cylinder block:
The thin wall cast iron block incorperates the 4 cylinder barrels, at the base of each there is a oil spray nozzle for piston base cooling.
The cast iron crankshaft is fitted with a vibration damper and supports new, lighter con rods. In fact the reduced mass of all the moving parts, by reducing inertia mankes for smoother changes in engine speed (injection cuts out at 7300rpm)
The timing gear is driven by a toothed belt system of hubs and idler wheels keeps the belf tension fully independant of camshaft timing.
Cylinder head
The light alloy (AS7) cylinder head is split into 2 main sections. In the lower section are forked inlet and exhaust pipes, the wedge shaped combustion chambers, the valve gear and coolant reservoir.
Compared with the original cylinder head, the pipes have been re-designed for an improved gas mixture flow. The wedge shaped combustion chamber features as a flush - a special protuberance to improve the permeability of the cylinder head.
The camshafts are of a brand new design and the valve diagrams are specific to this type of engine.
Each cam is individually lubricated and as in the other multi valve engines in the range the cams act directly on the hydraulic zero lash tappets.
The wieght of these tappets has been reduced from 62.5g to 50g to assist speed by limiting inertia. The valves have 2 return springs and are almost identical to the valves found and the XU10J4R except they are:
More permeable because of the alignment of the neck valves and lighter because 1mm has been shaved off the rod diameter thus saving 10g in weight.
Inlet control and exhaust
The air inlet has an aluminium manifold consisting of a chamber or plenum with a composite Helmholtz resonator fitted in parrallel to establish acoustic harmony with the chamber. The resulting smooth torque curve gives the driver the feeling of constant acceleration.
4 pipes run from the manifold to the cylinder headeach one consisting of a primary tube 283mm long coupled to a 37mm trumpet build into the plenum. The manfiold is also fitted with a pressure sensor which keeps the calculator constantly informed of the engine load.
At the front of the manifold is the progressivly acting throttle unit (64mm) There is also a seperate step motor ensuring correct air regulation when engine is idling.
Sequential ignition and injection are controlled by a new Magneti Marelli AP10 control unit fitted with Flash EPROM. Twin jet injectors spray in vapourised fuel while a regulator controls petrol pressure. Ignition is triggered with 1 coil per cylinder and the engine is protected by a pinking sensor.
There is a 4-2-1 tubular dissymmetrical exhaust manifold, precision engineered by ECIA the comprises of 4 stainless steel tubes with an internal diameter of 37mm. The exhaust run into a 1.9 litre catalytic converter and the rear silencer is strengthened.
BE3/6 gearbox
The design and production of this 6 speed gearbox was initially commissioned by Peugeot Sport to satisfy the requirements of customers involved in road/rally competition. This gave birth to the SMAN organization conceived specially for rally connoisseurs.
Peugeot engineers and designers naturally turned to this gearbox in search of a power trian ideally suited to the GTi6.
The 6th gear housing is slightly outside the main gearbox, slightly increasing turing circle to the right.
Of the 6 forward gears only 3rd has pinions specially designed for the BE3/6. The other pinions were selected form the existing range of ratios on the BE5 variations.
The gear stepping obtained from these choices was carefully adjusted to give the lowest possible falls in engine speed to ensure optimal use of the torque and power curves, The gear change diagram reveals that first gear is slightly longer than on the 306 S16.
The other 5 gear are relitivley close although 6th is slightly longer than the old 5th.
Suspension, Steering and brakes
The suspension and steering remain almost unaltered on the GTi6.
The self steering rear axel incorporates rubber blocks of varying hardness and gradual absorbtion which constantly keep it in the best possible position in relation to the struture.
Thats from the original dealer/press pack release from July 1996 before the original Phase 1 cars (like mine) were launched, quite rare and I have a copy of it.
