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The earliest dynamometers use what to absorb engine power?
What are the two general types of dynamometers used?
Hydraulic or electric
How is power dissipated in a water brake dynamometer?
Name three types of electric dynamometers?
- Direct current
- regenerative alternating current
- eddy current.
Which dynamometer offers the greatest flexibility but the highest cost?
What is a motoring dynamometer?
A dynamometer which can spin the engine if the engine isn’t producing power.
What response would be required by a dynamometer to maintain constant speed if the throttle were opened wider on a spark ignition engine?
Apply a larger load.
How is engine speed typically measured in a test engine?
Optical or electrical techniques.
Name at least four instruments used to measure fuel mass flow rate?
- Weight scale
- turbine flow meter
Which flow meters measure mass flow and which measure volume flow rate and must be converted to mass flow?
The weight scale, the coriolis, and the flowtron measure mass flow, and the turbine flow meter measures volume flow.
What type of accuracy can be obtained if the best equipment described in Chapter 4 are used to measure fuel flow?
What are the two reasons listed that exhaust concentration measurements are more accurate than direct measurements of the fuel and air flow rate.
- A. The best instrumentation available can measure air only to an accuracy of ±1%
- B. Air can leak all over the place.
What is used to even out the air flow into a single-cylinder engine?
Larger volume. It acts as a fluid capacitor.
List five instruments used to measure air flow.
- ASME orifice
- Laminar Flow Meter
- Critical Flow Nozzle
- Turbine Meter
- Hot Wire Meter
What does NDIR stand for, what gases can be measured using NDIR, and what is the basic principle used to measure gas concentrations.
Nondispersive infrared analyzers. They can measure methane, hexane, nitric oxide, sulfur dioxide, ethylene, and water. It’s based on the infrared absorption spectrum of gases.
What does FID stand for and how does and FID analyzer work?
Flame ionization detector. When hydrogen gas is burned, and hydrocarbon molecules are introduced, electrons and positive ions are produced. The number produced is directly proportional to the number of carbon atoms. If in an electric field, this produces an ion current, which can be measured.
How is NO measured in a chemiluminescence analyzer?
When ozone reacts with NO, it produces NO2 and chemiluminescence. The light, which is directly proportional to the amount of NO, is detected and measured.
What are the three methods used to measure particulate?
- Light absorption
- Filter discoloration
- Measurement of the total mass of particulates trapped on a filter paper.
What is the purpose of a dilution tunnel when collecting particulate for measurement?
To simulate the effects of exhaust leaving the tail pipe of the car and mixing with the air.
What type of transducer is used to measure cylinder pressure data?
What does FTP stand for and how is it used?
Federal Test Procedure. It’s the simulated speeds that a car goes through in the US when it’s being emissions tested.
How closely is the air-fuel ratio maintained in order to keep a three way catalyst operational?
Within 1% of stoichiometric.
What are the rich and lean voltages produced by an oxygen sensor?
- 800 mV — rich
- 50 mV — lean
Can a Hall Effect sensor work if the engine is not moving?
List different engine parameters which are measured and send information to the engine control unit (ECU).
Torque, Dyno temperature, inlet air temperature across engine, outlet fair temperature across engine, air flow, fuel flow, throttle actuator, throttle position sensor, intake manifold temperature, intake manifold pressure, cylinder presure, oil pressure, crank position, rpm, coolant flow, coolant temperature inlet, etc.
Does the fuel pressure increase in order to increase load?
No. You increase the load by opening the injector longer.
What is memory based and adaptive based when referring to engine control?
Memory based is where optimal timing of various engine parts is determined by fixed table values. Adaptive based is memory based +. It looks at real engine data and adapts the table values to be truly optimal for the given engine and ambient conditions.
If an engine increases in altitude what will happen to the bmep of the engine and why?
It will go down. If there is lower ambient pressure, then the air is less dense, and less of it fits into the engine.
Basic physics used to measure CO2
NDIR (non dispensive IR absorption) is used to measure amount of CO2 in a solution by measuring the amount of IR light absorbed by the solution.
Basic physics used to measure CO
measured by NDIR
Basic physics used to measure NO
Chemiluminesence measures NO by the amount of light it gives off when mixed with Ozone (O3) in this chemical reaction NO+O3 = NO2* → NO2 + photon
Basic physics used to measure O2
A Galvanic Cell reacts with O2 to make electrons
Basic physics used to measure UHC (unburned hydrocarbons)
Four (Three) types of air measurement
- Choke flow orifice
- Calibrated orifice
- Hot wire anemometer
Four (three) types of fuel measurement
- Turbine flow meter
- Gravimetric Scale
friction inside the engine (cylinder walls, bearings, valve train, etc.)
friction or resistance in accessories like, AC, alternator, power steering pump, water pump, etc
not really friction but rather a pressure differential also called pumping work
Typical types of piston rings: Compression and Oil, Their function, what they look like
Two compression rings create an air-tight seal between the piston and the cylinder wall. The oil ring is a honey-comb looking ring that pulls oil up and coats the cylinder walls
ratio of effective flow area to a representative area. If valve seat area used it is flow coefficient (Cf) if valve curtain area used, it is discharge coefficient (Cd)
Choked flow occurs at valve throat if ratio of upstream pressure to downstream pressure exceeds a critical value.