An engine test stand is a facility used to develop, characterize and test engines. The facility, often offered as a product to automotive OEMs, allows engine operation in different operating regimes and offers measurement of several physical variables associated with the engine operation. A sophisticated engine test stand houses several sensors (or transducers), data acquisition features and actuators to control the engine state. The sensors would measure several physical variables of interest which typically include:
- crankshaft torque
- angular velocity of crankshaft
- intake air and fuel consumption rates, often detected using volumetric and/or gravimetric measurement methods
- air-fuel ratio for the intake mixture, often detected using an exhaust gas oxygen sensor
- environment pollutant concentrations in the exhaust gas such as carbon monoxide, different configurations of hydrocarbons and nitrogen oxides, sulphur dioxide, and particulate matter
- temperatures and gas pressures at several locations on the engine body such as engine oil temperature, spark plug temperature, exhaust gas temperature, intake manifold pressure
- atmospheric conditions such as temperature, pressure, humidity
Information gathered through the sensors is often processed and logged through data acquisition systems. Actuators allow for attaining a desired engine state (often characterized as a unique combination of engine torque and speed). For gasoline engines, the actuators may include an intake throttle actuator, a loading device for the engine such as an induction motor. The engine test stands are often custom-packaged considering requirements of the OEM customer. They often include a microcontroller based feedback control system with following features:
- closed-loop desired speed operation (useful towards characterization of steady-state or transient engine performance)
- closed-loop desired torque operation (useful towards emulation of in-vehicle, on-road scenarios, thereby enabling an alternate way of characterization of steady-state or transient engine performance)
Engine test stand applications
- Research and Development of engines, typically at an OEM laboratory
- Tuning of in-use engines, typically at service centers or for racing applications
- End of production line at an OEM factory
Engine testing for R&D
Research and Development activities on engines at automobile OEMs have necessitated sophisticated engine test stands. Automobile OEMs are usually interested in developing engines that meet the following three-fold objectives:
- to provide high fuel efficiency
- to improve drivability and durability
- to be in compliance to relevant emission legislation
Consequently, an R&D engine test stands allow for a full-fledged engine development exercise through measurement, control and record of several relevant engine variables. Typical tests include ones that:
- determine fuel efficiency and drivability: torque-speed performance test under steady-state and transient conditions
- determine durability: aging tests, oil and lubrication tests
- determine compliance to relevant emission legislations: volumetric and mass emission tests over stated emission test cycles
- gain further knowledge about the engine itself: engine mapping exercise or development of multidimensional input-output maps among different engine variables. e.g. a map from intake manifold pressure and engine speed to intake air flow rate.
See also
- Air flow meter
- Driveshaft
- Dynamometer
- Emission standard
- Engine cart
- Electromagnetic brake Article about eddy current dynos
