Fixed Sleeve Method

Parallel with the development of the Instantaneous IMEP method, a derivative of moveable bore methods termed the Fixed Sleeve method has been developed. To date this has been implemented on a 4.1 liter gasoline engine (7). Figure 13 shows a cross section of the Fixed Sleeve design. The original 4.1 litre engine liner which had an 88 mm bore is fitted with a smaller 80 mm sleeve which is attached to the outer liner by a pair of jam nuts located at the bottom of the assembly. Piano wire in tension is used near the top of the assembly to pilot the inner sleeve so that it does not touch the outer liner. O-rings are used to seed combustion gas, water and oil. Cooling water is permitted to circulate between the two sleeves. Strain gauges are mounted on both inner and outer surfaces of the necked-down section near the bottom of the outer liner.

The outer liner, which is essentially identical to the production liner, is supported in the engine in the conventional way between the top of that liner and the support lip. Thus the inner liner is positioned like a standpipe, the top of which is shortened slightly so that it cannot contact the cylinder head. Acting on the inner sleeve are the sum of the cylinder pressure force acting on the rim and the friction force. These are shown in Figure 14. The upper figure shows cylinder pressure while motoring at 1000 rpm, wide open throttle. The center figure shows the strain gauge signals and the lower figure shows the friction force as a function of crankangle. This is found by differencing the two upper signals.

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