National Instruments Direct Injector Driver System Manual
© 2013 National Instruments. All rights reserved.
EPT function. This would cause the crank encoder
pattern to effectively generate twice the teeth between
each reference tooth seen by the EPT function.
Table 4.6.a, Supported EPT Patterns
Brief Glossary of EPT Function Terms
CAD:
Crank Angle Degrees. There are 360 CAD per two stroke cycle or one crankshaft rotation. There are 720 CAD
per 4-stroke cycle, or two crankshaft rotations. In a 4-stroke engine, the camshaft completes exactly one rotation per
two rotations of the crankshaft. There are two strokes of the piston (up and down) within the cylinder during a single
rotation of the crankshaft. A single stroke of the piston covers 180 CAD.
EXTRAP:
The single numerical digit suffix of each EPT function selection refers to the level of EPT Position
Extrapolation. This is a fixed power of two by which the angular resolution of tracked crankshaft position is improved
over the physical teeth alone. For example, if the EPT function has a fixed extrapolation level of 7, then the crank
angle resolution between each physical tooth is improved by a factor of 2^7 = 128. Each individual extrapolated
angle unit between the physical crank teeth is called a Crank Angle Tick (CAT)
CAT:
Crank Angle Ticks. Single unit of angular measure of the EPT function. Reported as a power-of-two angular
ticks of crank position travel, having a resolution dependent on EXTRAP and the number of physical teeth per
crankshaft rotation. For example, if using the N-M EPT VI, which has an extrapolation of 7, the number of CAT per
crank tooth would be 2^7=128, and angular position would be evenly incremented by 128 CAT from one physical
tooth to the next. If a 60-2 pattern were used, the maximum number of CAT per crankshaft rotation would be
60*128=7680. If the engine was a 4-stroke, the total number of CAT per engine cycle would be 2*60*128=15360.
MAX_CAT:
Maximum Crank Angle Ticks per engine cycle.
EPT Function Commonality
EPT Input Signals
All EPT functions have a common internal core that tracks angular position. The supporting internal logic around the
core interprets the incoming crank and cam position pulses according to an expected pattern. Each EPT function
has a Boolean crankshaft and camshaft input. These signals may be connected via any available NI 9411 digital
input source within the DI Driver System. The pattern input signals are named according to the most common
engine applications, such that there is a crankshaft trigger wheel and an optional 4-stroke camshaft trigger wheel.
However, it is also possible to operate with a single trigger wheel mounted to a camshaft of a 4-stroke engine. This
would require routing the physical camshaft trigger wheel sensor signal into the Crank_DigChanAsn of the DI Driver
window description for assigning NI 9411 digital inputs to internal signals.
Digital Signal Filtering