Octane Engine cylinder height values are displayed in two ways, the Digital Counter and the Dial Indicator. Both Dial Indicator reading and C.R. Digital Counter reading are directly correlated to a specific octane value as per ASTM D2699&D2700 methods specifications. (More details about the relationship between cylinder height and fuel octane number. Please see “Octane Engine Cylinder Height Relationship to Octane Number” in our blog).
The octane engine digital counter has two indicating counters. The top counter is the uncompensated digital counter reading. The lower counter can be disengaged from the upper counter for the purpose of off-setting its reading. And thus establish the differential or compensation for prevailing barometric pressure. With the differential set, the two counters can be engaged to move together with the lower counter indicating the measure of cylinder height compensated to standard barometric pressure.
NOTE: Digital counter readings decrease as cylinder height is raised and increase as cylinder height is lowered.
The dial indicator is installed in a bracket on the side of the cylinder clamping sleeve. So that the movable spindle contacts an anvil screw, positioned in a bracket mounted on the cylinder. As the cylinder is raised or lowered, the dial indicator reading measures the cylinder height in thousandths of an inch of travel. When indexed, the dial indicator reading is a measure of cylinder height for engines operating at standard barometric pressure. If the prevailing barometric pressure is other than 760 mm (29.92 in. Hg), correct the actual dial indicator reading, so that it is compensated to standard barometric pressure.
Compensated dial indicator readings apply whenever the reading is pertinent during the rating of sample fuels, or when calibrating the engine using PRF blends.
NOTE: Dial indicator readings decrease as cylinder height is lowered and increase as cylinder height is raised.