The Aim of this whole task is to simulate Different Types of Ignition system setup. But before that, we were introduced to analyze some popular devices which are responsible for Crank/ Cam Position/ RPM.
The Distributor came first as it is inevitable in a Conventional Ignition System. Not just a cap, the whole device houses a Reluctor Magnetic Pickups, the first to pick up Engine Position and spark timing. The pickup coils and the reluctor tip are 2 main things to check: their distance and how fine the teeth on the reluctor rotor are crucial to how clear the G and NE signal will be. Without these signals being clear, ECU has a hell of a hard time to start the car since it doesn't know what stroke each cylinder is in.
Because the Reluctor's signal is not as good as it is in high RPM, more advance signal sensors are available, ensuring these is NE and G signal whatever the engine speed, by giving only Digital Signal not Analog like the Reluctor Magnetic Pickup one.
Hall-effect sensor, instead of getting close to the magnetic pickups coil, the rotor is now capped with a steel chopper plate, that squarely cuts through the magnetic field, which will bring in Digital signal. This gets more electronic because the signal generated is processed by the Hall integrated Circuit.
Optical Distributor offers Digital signal with a different method, instead of magnetic, this is photo-sensitive. And Infra-red diode sending light beams to a photo electric cell, and there is also a steel chopper plate to interrupt the receiver squarely, giving digital waveform.
Testing Ignition coils
Important step in diagnosing Ignition system. But only in Conventional, the Primary coil is exposed. In more electronically integrated system, coil packs are likely to be combined with the Ignition Module housing. So checking Primary's resistance, waveforms etc... is almost virtually impossible. So only 2nd winding can be checked, since there are still high tension cords to the spark plugs.
Ballast resistor is a method to current-control the primary coil from overheating. In electronic system, that won't be necessary since we have advanced current control circuit integrated in Ignition Module.
First, simulating the Conventional Ignition System: This encountered difficulty because it requires Point Breaker mechanism which is manually primitive, must be on a timed engine to work fine. So we'd rather step on to Electronic Distributed Ignition: This consists of: 12V battery, a 2k2 resistor, a coil pack, an Igniter, a Distributor, High Voltage Cord, and a spark plug. This simulation emphasizes the idea that in Integrated Distribution Electronic Ignition, coil pack is integrated into distributor housing, and the Breaker/Points is now replaced by a grounding Igniter, which uses power transistor and on/off signal to ground the primary current:
(Image + Video)
In this experiment, we had to manually turn the distributor rotor, which was normally turned by a timed cam gear.
Next, same setup, but we use a Function generator to create on/off signal, simulating the processed signals from the ECU, from the NE/G, rpm sensors. There is NO distributor from this point on, this we called Distributor-less Ignition (DIS)
(Image + Video)
3rd, the Wasted Spark Ignition, the idea is that the Ignition Module houses 2 coil packs, which are responsible for 4 spark plugs, by a mean of 2 discharge circuits. In this test, at least 2 spark plugs are used. One must receive the spark and transfer that spark into its companion spark plug as a reversed spark.
(Image + Video) This only works for even numbers of cylinder.
Finally the most advanced we know so far, the coil on plug, we just need to hook it up with the function generator, which were currently simulating the on/off switch command from the ECU, after it's very intricate advance timing, current controlling processes from various sensors( Crank/ Cam/ RPM/ O2/ TPS etc...)
(image+ video)
The thing is coil on plug virtually eliminates every moving parts(Point/Breaker; Distributor Rotor) and distant components( high tension cords, less wiring overall), significantly improving coil saturation, timing, emission, fuel economy, and the Ignition system itself is more reliable overall.
Wednesday, November 16, 2011
Tuesday, November 1, 2011
All about the ignition system part 1
Different types of Ignition System
1. How induction works?
2. What is a transformer?
3. And Explain why lightning happens?
Lets start with the ignition switch, you switch on to start the engine also mean you are starting the ignition system. Ignition switch opens the path for battery to reach the primary coil. The ground side of the primary is through the Breaker point mechanism, which is brought connected, disconnected by a rotor cam lobe.
Where do we get that amazingly high voltage? One word: Induction. The coils & Breaker points mechanism are the key for this miracle to happen. In a circuit where battery voltage is to power a coil, its maximum current does not immediately reached. And while it takes a little time for the current to build up on a coil, it induces a voltage so called Electromotive Force (EMF). Next, imagine if you have another coil nearby positioned appropriately, that voltage will get induced into it, we call it "mutual inductance". This law of physic is also applied in the invention of the transformer - namely our primary and secondary coil.
Through the core, a sudden change in current in primary leads to a huge change in magnetic flux and travels to the secondary winding and gets amplified into multiple times larger. As a result, a very short but enormous voltage discharge from 20000V+ through the gap of the spark plug. Yet, this voltage would never be achieved without what had mentioned: a sudden change of current/ magnetic flux. It seems that the time it takes to maximize the current in primary is not as small as the time it collapses. And the less time it takes for change, the more voltage induced. A conventional mechanism that was very good at this is the Breaker Point with its Cam Follower. Each cam lobe angle(no. angle = no. cylinder) rotate to open/close the primary grounding, leading to the build-ups and collapses.
Yet, the timing is a BIG issue. For best compression/power output/emission, the spark must be at the right places when it comes different engine condition. Hence we had vacuum advance, and centrifugal advance to overcome this in the past. Sure fuel burns @ roughly constant rate, but as RPM increases there is less time to burn, so spark is advanced. And when at lean idle/ low load cruise, mixture doesn't burn as fast as rich mixture so timing also needs to be advanced, so there is more burn time. And when the engine runs rich on cold starting, in low RPM, fuel burns even quicker than engine speed so retarding the timing is also necessary. Vacuum advance does advance the spark when there is high vacuum in the intake so it is made for idle/ cruising speed but lean mixture, while centrifugal advance is does more advancing at higher speed.
Nowadays that we have electronic/ distributorless/ integrated ignition systems, the principal of delivering the spark is virtually exactly the same, after about 80 years of "evolution". Instead of having a rotor that spins around all the time to distribute very high voltage/material corrosive spark, why not having ECU ground each single spark plug at the exact time we want? Why bother having a spinning cam follower that pushes on the point breaker suffering the spark and corrosion, when we can use ECU to switch on, off the primary etc... Virtually, making mechanism to handle electrical function is mostly not the best idea, but using electrical processor and circuitry itself, and that the way engineers have been thinking.
Isn't it when electricity can't get through air, then a huge voltage one just might do it for fractions of a second? Isn't it lightning is just simple as so many positive charges trying to get down to its grounding? Obviously if lightning can make a 10Mega Volt up to 120k Amps jumping a "gap" of sky high in just 30 nanoseconds, then we might as well can create a spark of just 40kV jumping a few milimeters. But why some engine sparks just 20000V while some spark even up to 100000V? Will it affect the burn rate of the mixture? Or make the exhaust gas hotter? etc... One thing for sure, engines that run higher Octane fuel will need bigger Voltage sparks, because they require hotter sparks to ignite.
Also, we can't forget the condenser, which is actually a coil of wire that "catches" any voltage spike or surges when the breaker point opens and closes. This little device is very important because the real "spike" that we want belongs to the 2nd winding, not the intermittent, lousy surge that residue after primary collapses, which will gradually destroy the points. Plus, all that surges are stored and sent back to the primary when the dwell period starts( points close) again, results in longer, hotter spark, which is better for performance of course.
Enough about level 3 Physics, lets move on to the real deal: more advanced ignition systems. But before we do, I need to address that the conventional ignition system is not just another method of delivering a spark, it is actually THE ONLY WAY yet to deliver a spark. Even if we have some fancy Coil-on plugs, Wasted spark, or Electronic etc...the circuit's principal stays the same, especially there are as many FUNCTIONS, or PROCESSES in the conventional as there are many in either Distributor less, Wasted Spark or Electronic etc... My point is the new ignition systems is just new materials, new modifications, not new methods, NOT a car with a N/A engine and a hybrid car calling themselves a real difference.
Lets review all the "compulsory" functions inside any ignition system: battery supplying, current-controlled ballast resisting, points contact closing: Dwell period, opening: EMF discharged, residual voltage spike absorbing(Condenser), the amplification and inductance of 2 coils, and finally, the spark grounding(delivering) for each cylinder(simultaneous; grouped; sequential). These are must-occur processes, if one of these fails, the spark is considered malfunction, that means the engine will NOT run properly. And each and every single one of these processes will occur one way or another inside the other types of ignition system.
Electronic Ignition System
Oops! Where is the Breaker points and it's Condenser? Instead, this system has a power transistor inside a module that receives converted digital ON/OFF signal from the ECU, (or from distributor). The reason the ECU can decide when to switch ON or OFF the power transistor WITHOUT a Breaker point mechanism is that it receives signals from NE(speed sensor) and G(crank position sensor) and process it to work out the right cylinder and the right time, using its intricate microprocessor.
The main difference in structure between electronic and mechanical is the Ignition module or so called "IGniter". When the On/OFF signal is sent, the power transistor will get turn on or off, allowing primary current to build up and cut it, leading to voltage inductance into secondary coil. The picture above shows the earliest Electronic Ignition System, which only replaced the Mechanical by its Breaker points mechanism. And still, it received Digital Signal from a mechanis (Pickups Coil, Hall-effect, Photo sensitive etc...)
The fact that this small change was called Electronic Ignition makes it sounds like there is a WHOLE new way of delivering spark. But really, this is just a new way to switch between building up and collapsing primary current. The rest of the system: 100% similar to the Conventional.
Disadvantages started to disappear as there is less mechanical part, hence destruction from voltage spikes to Points is eliminated, enduring the performance and reliability of components.
But the BIGGEST advantage of electronic Ignition is the fact that ADDONS are now easier to develop because instead of being considered as an additional device of chunky mechanical pieces, it is only a matter of a little bit more programing, chip, circuitry etc...which might be more sophisticated in development but production, installment and maintenance are much more comfortable and reliable to achieve.
For example, would we need a vacuum advance and a mechanical advance anymore when the computer is deciding when to spark? and it is not only an open loop computer it is closed loop: it means all the sensors' data is continuously fed and processed to give out best actuation...ALL the time. Ignition timing can be compacted into just some additional circuitry, like the ESA or integrated chip- VAST from Toyota:
Also, circuit breaker/ protector like the Darlington's circuit; Primary & Secondary coils etc... can also be integrated into 1 unit, making it easier for installment & replacement. And we call these Integrated Electronic Ignition system. It's really nothing but a more convenient Electronic Ignition System. But still, these system compares to the Electronic Ignition System with no computerized switch signal, is a real big leap.
Integrated Electronic Ignition System
Any Ignition System that uses the same method of delivering spark but is more advanced in structure layouts, circuitry, modification etc... can all be considered an Integrated Electronic Ignition System. With Integrated, there is mainly no DIY modification on the system to improve any sort of performance but the spark plugs. It is in fact most manufacturers' intention to integrate all the important components into 1 unit for ease of manufacturing, reducing cost, maintenance and usage. This also means that if there is a fault in the ignition system for which doesn't deliver a spark in just 1 cylinder, I'm afraid you will have to replace the WHOLE unit, as well as you will be fine if you have insurance for the unit. IF you are keen for a little bit of science, stick around a little bit more because there are still some disclosures from manufacturers, wanting to explain to their auto electricians how their magic boxes work so they don't look ridiculous in front of customers.
Distributor-less Ignition
There are 2 common types of distributor-less Ignition System: Wasted-Spark EIS and Coil-on Plugs EIS, which of course don't have any distributor-like mechanism. Instead, they can fire induced voltage directly from secondary coil to the right spark plug, at the right time. How?
Wasted-spark
This is quite a special lay-out, can only be used on engines with even number of cylinders, preferably 6. The main components are consist of: CAM or Crank sensor; Igniter, and The Coils...and there are 3 coil packs inside since there are 6 cylinders.
The key operation of this type lies in the sophisticated Igniter and the "Discharge circuit".
The Igniter, in this case for 6 cylinders, will have 3 Drive circuits each responsible for "driving" 2 spark plugs, giving that the positions of the chosen pair gives the engine the best vibration balance: 1-6; 3-4; 2-5 etc...The rest of the control circuit is still controlled by the ECU. There are 4 types of signal that makes this EIS a complete Closed-Loop Ignition system:
IGdA & IGdB for the 3 "spark-driving" circuits: these 2 give the Cylinder Identification Circuit some sort of Binary codes to work out which is the right cylinder to fire. For example, from 0 and 1, there are 4 "permutation" possible like 00, 01,10,11. So for each out come, the CIC will tell which drive circuit will fire. However, IGdA is out-of-phase with IGdB so that they will never give out "11", because that means 2 drive circuits will fire at the same time- impossible for the crankshaft position to be right.
The discharge circuit is what defines Waste Spark Ignition. For each pair of spark plug for eg: 1 and 6, they are in series so that when the first one fires, the spark travels through ground and goes back to the companion spark plug, creating another spark. This is timed so that one fires @ TDC of compression one fires at TDC of the exhaust stroke. This has an advantage of burning off unburnt fuel from the main combustion, creating a little more power when the piston is about to go down.
Coil-on Plugs(COP)
The latest advance in Electronic Ignition, the COP system minimizes mechanical appearance at maximum level:
No distributor, no condenser, no Breaker Points, and very very short secondary HIGH TENSION CORD.
Because, everything that makes the COP looks mystical, sophisticated but surprisingly & extremely reliable: The Igniter and coils pack and all the timing advance circuits are all CRAMPED, in other word, integrated into one single unit, and each cylinder has 1 unit that we call this is the Direct Ignition System.
This is the most reliable, advanced set up of EIS that is popularly available on the market. Comparing to its friend, the Wasted Spark, the Igniter or Ignition Module are basically similar since all the basic process like Cylinder selection circuit, current limiting, Ignition Identification Feedback, Dwell Timing Advance circuit...But this time, each Spark plug will have its own Power transistor/ Darlington, and coils pack, this means there is a big leap from the Wasted spark here. Not only the Waste spark "wastes" a spark on Exhaust stroke, which can bring a small benefit but it is mainly a disadvantage. As spark plug gets damaged faster, the high tension cord will get corroded faster leading to current leak, which in time will weaken the spark. And yes, there are still quite a length of secondary high voltage delivering cord here, so Electrical 101, less wire length, less resistance, less time travel.
Talking about timing, if high voltage takes less to get to the spark plug, it means there is more time for spark "saturation", thus more powerful spark is achieved making it possible for the engine to run leaner with significantly less chance of miss-firing, all in the favor of having a few micro seconds more.
Still, this is a mortal's creation which is not 100% immune to all the ignition problems, but its capability of narrowing all trouble down to 1% keeping us moving forward.
Wednesday, October 26, 2011
Oxygen sensor - EGR system - Exhaust System Part 1
1. Oxygen sensor:
Talking about Oxygen sensor, we are talking about the "mixture": rich or lean. Rich means less oxygen, lean will have more oxygen, and the O2 sensor must be placed to measure the gas in the exhaust manifold.
Oxygen sensor can be considered to be more complex and more advance comparing to other types of sensor. Instead of position, air flow, pressure etc... this senses only one type of gas: oxygen. So how do they do this? Answer: Must be a special material and some configurations.
Narrow band O2 sensor: 1-4 wires. Most advanced narrow band is the one with 4 wires: 2 heater wires, one positive one ground; 1 signal wire, one signal ground. Signal wire is normally with "live" colors, ground wire is often brown or black, 2 heater wires are the same, white or black etc...
Two common alternative materials are zirconium and titanium. These materials need to be in operating temperature in order to sense and conduct signal therefore having a 4-wire will save the car from having trouble waiting to be warmed up. The heater wires heat the material up quickly as soon as the car start to minimize the lack of oxygen sensing at the beginning minutes, which will eventually save some fuel, "healthier" emission and engine components.
This is how it works:
Taking the outside air as reference, the zirconium is sensitive to any incoming O++ molecules from the combustion. Then, the O++ molecules difference between the exhaust gas and reference air is balanced out when O++ from air churns through the zirconium sensor to the lacking O++ gas that the exterior platinum electrode is experience. Basically, this means that the interior platinum has more contact with O++ while the exterior has less contact with O++. Because zirconium is conductive when hot, and in term of positive/negative charges the interior is always more positive than the exterior, so here goes our voltage signal generated by this difference.
When the mixture is rich, less Oxygen left out the exhaust, hence chances of O++ is less, the difference is GREATER, the zirconium conducts a greater voltage signal. When the mixture is lean, more Oxygen left out means more O++ likeliness, the O++ difference is lessened, hence smaller voltage signal.
(An example of narrow band O2 sensor's signal behaviors in different load conditions will soon be added)
Oxygen sensor on vehicle:
First, locate the oxygen sensor. Old cars usually have 1 oxygen sensor and that is before the catalytic converter, so the raw, toxic exhaust gas is accurately measured. Plus, they also have narrowband O2 sensors as common, and this one on a 1993 Daihatsu by Toyota is 4 wired, black-black-white-blue for heater+_heater-_GroundE2_Signal+. Oxygen sensor like this, is pretty old and the signal will be slow and inaccurate. Although, a 4-wire narrow band can heat up faster until it reaches its operating temperature. With an oscilloscope, we can still determine the signal's behaviors at different engine loads which bring different mixtures to the test.
Setting up the oscilloscope is as simple as setting up a multimeter. But there is some configs need to be adjusted like time range, voltage range, because what it gives us not only voltage signal but also the behavior graph.
As we all now aware, the high signal indicates rich mixture/low 02 and low signal is lean mixture/high 02. But in reality, what streaming through the O2 contact layer is not clearly rich or lean, it is fluctuating from rich to lean rapidly and normally about 8-10 fluctuations per 10 seconds. It is also hard to tell if it's zirconia or titania, since their signals behave slightly different:
Zirconia signal is cycling just like titania, same basic amplitude and frequency, but their shapes are different:
Zirconia:
Titania
Talking about Oxygen sensor, we are talking about the "mixture": rich or lean. Rich means less oxygen, lean will have more oxygen, and the O2 sensor must be placed to measure the gas in the exhaust manifold.
Oxygen sensor can be considered to be more complex and more advance comparing to other types of sensor. Instead of position, air flow, pressure etc... this senses only one type of gas: oxygen. So how do they do this? Answer: Must be a special material and some configurations.
Narrow band O2 sensor: 1-4 wires. Most advanced narrow band is the one with 4 wires: 2 heater wires, one positive one ground; 1 signal wire, one signal ground. Signal wire is normally with "live" colors, ground wire is often brown or black, 2 heater wires are the same, white or black etc...
Two common alternative materials are zirconium and titanium. These materials need to be in operating temperature in order to sense and conduct signal therefore having a 4-wire will save the car from having trouble waiting to be warmed up. The heater wires heat the material up quickly as soon as the car start to minimize the lack of oxygen sensing at the beginning minutes, which will eventually save some fuel, "healthier" emission and engine components.
This is how it works:
When the mixture is rich, less Oxygen left out the exhaust, hence chances of O++ is less, the difference is GREATER, the zirconium conducts a greater voltage signal. When the mixture is lean, more Oxygen left out means more O++ likeliness, the O++ difference is lessened, hence smaller voltage signal.
(An example of narrow band O2 sensor's signal behaviors in different load conditions will soon be added)
Oxygen sensor on vehicle:
First, locate the oxygen sensor. Old cars usually have 1 oxygen sensor and that is before the catalytic converter, so the raw, toxic exhaust gas is accurately measured. Plus, they also have narrowband O2 sensors as common, and this one on a 1993 Daihatsu by Toyota is 4 wired, black-black-white-blue for heater+_heater-_GroundE2_Signal+. Oxygen sensor like this, is pretty old and the signal will be slow and inaccurate. Although, a 4-wire narrow band can heat up faster until it reaches its operating temperature. With an oscilloscope, we can still determine the signal's behaviors at different engine loads which bring different mixtures to the test.
Setting up the oscilloscope is as simple as setting up a multimeter. But there is some configs need to be adjusted like time range, voltage range, because what it gives us not only voltage signal but also the behavior graph.
As we all now aware, the high signal indicates rich mixture/low 02 and low signal is lean mixture/high 02. But in reality, what streaming through the O2 contact layer is not clearly rich or lean, it is fluctuating from rich to lean rapidly and normally about 8-10 fluctuations per 10 seconds. It is also hard to tell if it's zirconia or titania, since their signals behave slightly different:
Zirconia signal is cycling just like titania, same basic amplitude and frequency, but their shapes are different:
Zirconia:
This is the signal recorded at warmed idle:
Note that the amplitude varies between 0-1 V, and the shape is more likely sharp ended, not as clear and digital likeliness as titiania. So we can conclude this one as an old little inefficient zirconia O2 sensor. In 10 seconds there are only 4 cross counts, so the data is not rapid enough for the ECU to decide quicker and more accurate, hence efficiency is loss. Plus the shapes are irrational, harder for ECU to cross-counts.
Warming up at 2500rpm: this is the condition that the engine is not fully warmed up and not completely into closed loop, intermittent O2 reading experienced:
Note that there is a high cross count that reaches nearly 1V that lasted about 2 seconds, this is the fast flow of mixture that helps increase the engine speed to 2500 rpm, then it doesn't take much because the engine stop accelerating. The rest of the pattern seems acceptable but low amplitude suggests that the engine is not fully in closed loop, meanwhile there are about 15 cross counts in 10s.
Reving up several times after warm idle:
While range of amplitude is not much different that what of idling, the cross counts seem to accumulate much faster in 2 seconds. This indicates that the mixture reaches maximum voltage more frequently hence the engine is putting more fuel to burn. The average voltage will also be much higher than what of ilding, as we can see the minimum voltage gradually increases as we keep this up. This behavior is different than keeping the engine @ 2500 rpm because we rapidly accelerate, hence the load is more frequently pressed.
Sudden deceleration from 3000rpm
@ 3000rpm, the waves look similar to 2500rpm, except for the higher minimum. The recession gap in between,note that the minimum goes as low as 0V, is the sudden deceleration indicating that the ECU has sensed this and put suddenly less fuel for that moment, then the reading is back to its long moment of recovery. And soon enough the graph will shape like warm idle.
Sensor respond time: should be <100 ms (almost instantly)
This shows that the sensor's respond to sudden load change is still acceptably quick
Overall, this oxygen sensor has still been able to shown at least the basic characteristics of each load condition, although it lacks a lot of accuracy and consistency as data is quite intermittent in general.
Saturday, October 15, 2011
Oxygen sensor - EGR system - Exhaust System Part 1
1. Oxygen sensor:
Talking about Oxygen sensor, we are talking about the "mixture": rich or lean. Rich means less oxygen, lean will have more oxygen, and the O2 sensor must be placed to measure the gas in the exhaust manifold.
Oxygen sensor can be considered to be more complex and more advance comparing to other types of sensor. Instead of position, air flow, pressure etc... this senses only one type of gas: oxygen. So how do they do this? Answer: Must be a special material and some configurations.
Narrow band O2 sensor: 1-4 wires. Most advance narrow band is the one with 4 wires: 2 heater wires, one positive one ground; 1 signal wire, one signal ground. Signal wire is normally with "live" colors, ground wire is often brown or black, 2 heater wires are the same, white or black etc...
2 common alternative materials are zirconium and titanium. These materials need to be in operating temperature in order to sense and conduct signal therefore having a 4-wire will save the car from having trouble waiting to be warmed up. The heater wires heat the material up quickly as soon as the car start to minimize the lack of oxygen sensing at the beginning minutes, which will eventually save some fuel, "healthier" emission and engine components.
This is how it works:
Talking about Oxygen sensor, we are talking about the "mixture": rich or lean. Rich means less oxygen, lean will have more oxygen, and the O2 sensor must be placed to measure the gas in the exhaust manifold.
Oxygen sensor can be considered to be more complex and more advance comparing to other types of sensor. Instead of position, air flow, pressure etc... this senses only one type of gas: oxygen. So how do they do this? Answer: Must be a special material and some configurations.
Narrow band O2 sensor: 1-4 wires. Most advance narrow band is the one with 4 wires: 2 heater wires, one positive one ground; 1 signal wire, one signal ground. Signal wire is normally with "live" colors, ground wire is often brown or black, 2 heater wires are the same, white or black etc...
2 common alternative materials are zirconium and titanium. These materials need to be in operating temperature in order to sense and conduct signal therefore having a 4-wire will save the car from having trouble waiting to be warmed up. The heater wires heat the material up quickly as soon as the car start to minimize the lack of oxygen sensing at the beginning minutes, which will eventually save some fuel, "healthier" emission and engine components.
Friday, September 30, 2011
Thermistor air, thermistor water & thermal fan switch.
Thermistor air, or thermistor water are just the same name for 2 different purpose, one senses the temperature of intake air, one measures the heat of the coolant that flows in all the coolant jacket. These heats will affect the amount of voltage signal generated by these sensors, hence when sent to the ECU, it will know what temperature the air or engine is at.
Temperature affects conductivity of materials, gradually though. Therefore the very basic principal of these thermistors are using materials that have conductivities susceptible to change of temperature. In terms of electrical, conductivity means resistance, and hence depending on different materials, resistance can rise or sink when temperature increases or decrease.
In that case, we know have 2 well know types of thermistor: Positive Coefficient(POT) and Negative Coefficient Thermistor.
POT: Material resistance is proportional to rise of temperature & vice versa.
NOT: Material resistance is inversely proportional to rise of temperature & vice versa.
Because resistance change means voltage drop and available voltage in a fixed reference voltage circuit can be affected as well. Hence this opens up for some type of configuration of thermistor circuit. But generally, all these configurations are again, basically application of voltage divider law.
When searching for thermistor coefficients, there are 2: temperature/resistance and voltage output/resistance. In a circuit, voltage output can either be available voltage or voltage drop, as the two complement but in the same time contradict each other, therefore its definition should depend on situation.
For example:
A positive coefficient will have resistance rises as temperature rises, as resistance rises, the voltage drop across the thermistor proportionally rises as well. This configuration allows the signal to the ECU is equivalent to the voltage drop across the thermistor.
In reality, the temperature and resistance are not always proportional.
However, this does not alter the signal going to the ECU as well as the thermistor as a whole. Because these are figures tested in boiling water environment. In real engine condition, the heat generated by combustion is ideally constant enough to keep a heating power on the coolant, thus raising the temperature rapidly. Average engine temperature varies from car to car, but hottest is always the exhaust manifold and coolant is counted as average engine temperature.
Coolant temperature sensor can usually be found as a plug on the side of the cylinder head, where a hole on the head is. There is 2 wires leading away one is a signal wire(red) the other one must be ground. The 5V feed is ECU internal. This makes testing the ECT simple, just by back probing the signal wire and ground the multimeter, start the engine and the temperature will change in accordance with specification, if not, you know what to do. Simplicity in design and function doesn't mean it's not important to check the ECT when the engine is starting cold or idling warm. Because, the signal makes the ECU "thinks" of how the engine is warm or cold. If the engine is warm and the ECT reads cold, the ECU will make the mixture rich and retard the spark timing, making a warm idle for your car, for example. This of course leads to bad CO and severe fuel consumption.
As you notice, after a while, the car's fan turns on as it reaches a certain level of temperature, blowing all the really hot air in your face. That is certainly for "cooling the coolant". Because the engine temperature and the coolant's temperature balance out, the coolant can't really cool the engine so good anymore. Hence the fan will turn on to blow air temperature in-through the radiator to balance out the coolant's temperature. This whole function is packed into what we call a thermal fan switch. Sometime it is ECU controlled, most of the time it senses temperature by itself, which I think is more reliable because when other thermistor fails it will fail this thermal fan switch from the ECU.
Thermal fan switch is kind of "backwards". The input is a mechanical change, and output is an electrical trigger. All it does is when temperature reaches a level which will eventually close the circuit of the fan's motor to battery. When the coolant decrease back to the ideal temperature, the temperature sensed @ the coolant switch material makes the contact retracted, or opened, in a few second the fan will turn off.
Checking this switch is simple, heat it up and check for continuity, or available voltage.
Temperature affects conductivity of materials, gradually though. Therefore the very basic principal of these thermistors are using materials that have conductivities susceptible to change of temperature. In terms of electrical, conductivity means resistance, and hence depending on different materials, resistance can rise or sink when temperature increases or decrease.
In that case, we know have 2 well know types of thermistor: Positive Coefficient(POT) and Negative Coefficient Thermistor.
POT: Material resistance is proportional to rise of temperature & vice versa.
NOT: Material resistance is inversely proportional to rise of temperature & vice versa.
Because resistance change means voltage drop and available voltage in a fixed reference voltage circuit can be affected as well. Hence this opens up for some type of configuration of thermistor circuit. But generally, all these configurations are again, basically application of voltage divider law.
When searching for thermistor coefficients, there are 2: temperature/resistance and voltage output/resistance. In a circuit, voltage output can either be available voltage or voltage drop, as the two complement but in the same time contradict each other, therefore its definition should depend on situation.
For example:
In reality, the temperature and resistance are not always proportional.
Coolant temperature sensor can usually be found as a plug on the side of the cylinder head, where a hole on the head is. There is 2 wires leading away one is a signal wire(red) the other one must be ground. The 5V feed is ECU internal. This makes testing the ECT simple, just by back probing the signal wire and ground the multimeter, start the engine and the temperature will change in accordance with specification, if not, you know what to do. Simplicity in design and function doesn't mean it's not important to check the ECT when the engine is starting cold or idling warm. Because, the signal makes the ECU "thinks" of how the engine is warm or cold. If the engine is warm and the ECT reads cold, the ECU will make the mixture rich and retard the spark timing, making a warm idle for your car, for example. This of course leads to bad CO and severe fuel consumption.
As you notice, after a while, the car's fan turns on as it reaches a certain level of temperature, blowing all the really hot air in your face. That is certainly for "cooling the coolant". Because the engine temperature and the coolant's temperature balance out, the coolant can't really cool the engine so good anymore. Hence the fan will turn on to blow air temperature in-through the radiator to balance out the coolant's temperature. This whole function is packed into what we call a thermal fan switch. Sometime it is ECU controlled, most of the time it senses temperature by itself, which I think is more reliable because when other thermistor fails it will fail this thermal fan switch from the ECU.
Thermal fan switch is kind of "backwards". The input is a mechanical change, and output is an electrical trigger. All it does is when temperature reaches a level which will eventually close the circuit of the fan's motor to battery. When the coolant decrease back to the ideal temperature, the temperature sensed @ the coolant switch material makes the contact retracted, or opened, in a few second the fan will turn off.
Checking this switch is simple, heat it up and check for continuity, or available voltage.
Saturday, September 24, 2011
Testing MAP sensor
We can't be talking about Mass air flow without taking Manifold Absolute Pressure into account.
Why is it called "absolute pressure"? Well I guess it is because the intake air pressure in the manifold is essential as how much power we will get when the intake valve is opened. In other words, it is the pressure that is untouched by the atmosphere (only through the throttle body) that is ready in the intake manifold to be vacuumed in.
Air, gas - in general, has three main physical properties that we are all common about: Volume, Temperature, Pressure - and they are the 3 musketeers who can't exist without others. When pressure increases the volume will be squeezed smaller; when temperature rises the gas will likely to expand, and when trapped in a confined space, the expanding gas will build up pressure - those are undeniable gas/air properties and based on this we must have a MAP sensor inside our intake manifold.
Basically, the MAP sensor does the same thing as a MAF sensor - measuring how much air coming in. You might thing the MAP is so much different from a Hot-wire MAF because it measures the volume of incoming air, and MAP is measuring pressure, how? The ECU can't feel the pressure, it's micro-processor is just a 1 dimensional being, the only thing that makes sense to it is "0" and "1". But, because we use the event of massive volume of air coming in or increased air pressure is in the manifold that we turn them to affect our sensors to create electrical signals, the ECU will now receive something different that it can process on. And, think about this: both MAP and MAF give the same type of analog, voltage signal to the ECU, the only difference is the way they operate.
The MAP sensor utilizes a semi-conductor material (it can be silicon) which will become pressurized under high pressure and will start conducting electricity. Using a 5V Reference from the ECU, the Voltage output fed to the ECU will change after the ability to conduct of the material, and it depends on the pressure it gets.
(autoshop101.com)
So basically this is similar to a rheostat configuration, and a Vc in, Voltage signal as a divider's output, and an earth.
How do we test a MAP sensor? Aftermarket MAP sensor means the ECU is modified, hence we won't be able to find it inside the intake manifold as we usually do. But normally, there are 2 methods that we can use to test the MAP is Off-car and On-car.
On-car test is simple: find the MAP, identify the wires(Vc; PIM; E2) and then back probe. As the ignition is turned on not the engine, we will be able to retrieve the MAP's maximum reading. This is because 1 bar of atmosphere is able to get inside the manifold through by pass air control, without encountering any vacuum being created because the intake valves are not moving, the cylinders are not moving at all.
Other than that, try turn on the engine and the PIM reading will eventually drop down to minimum readings for idling. This is because maximum vacuum is created by the cylinders hence the absolute pressure inside the manifold is minimum. There are still atmospheric pressure blown in but not enough for the vacuum.
As we open more throttle, more pressure hovers inside the manifold and if we maintain this pressure level we can still have maximum pressure applied to the MAP sensor.
Off-car is even simpler with the vacuum tube removed. Therefore the reading on the MAP is always maximum 1atm anyway. So if we block the hose by a vacuum tube and apply vacuum to it, we can see the voltage reading decreases, just like closing the throttle and let the engine idle.
So overall, MAP sensor and MAF sensor can be either alternatives or complements, depends on the configuration of the engine. They both measure air by sending voltage signal telling the ECU of how much air coming in, just different by the way they utilize which properties of air.
In which case, MAF & MAP sensor is no more useful when it comes into forced-induction engine, where air intake pressure and volume exceed way beyond what of a naturally-aspirated induction. A MAP sensor will change its way into a boost sensor or pressure gauge, measuring pressure which is much higher than atmospheric, and minimum pressure exceeds higher vacuum level. At that point, idling and wide open throttle needs to be monitored more powerfully differently.
Why is it called "absolute pressure"? Well I guess it is because the intake air pressure in the manifold is essential as how much power we will get when the intake valve is opened. In other words, it is the pressure that is untouched by the atmosphere (only through the throttle body) that is ready in the intake manifold to be vacuumed in.
Air, gas - in general, has three main physical properties that we are all common about: Volume, Temperature, Pressure - and they are the 3 musketeers who can't exist without others. When pressure increases the volume will be squeezed smaller; when temperature rises the gas will likely to expand, and when trapped in a confined space, the expanding gas will build up pressure - those are undeniable gas/air properties and based on this we must have a MAP sensor inside our intake manifold.
Basically, the MAP sensor does the same thing as a MAF sensor - measuring how much air coming in. You might thing the MAP is so much different from a Hot-wire MAF because it measures the volume of incoming air, and MAP is measuring pressure, how? The ECU can't feel the pressure, it's micro-processor is just a 1 dimensional being, the only thing that makes sense to it is "0" and "1". But, because we use the event of massive volume of air coming in or increased air pressure is in the manifold that we turn them to affect our sensors to create electrical signals, the ECU will now receive something different that it can process on. And, think about this: both MAP and MAF give the same type of analog, voltage signal to the ECU, the only difference is the way they operate.
The MAP sensor utilizes a semi-conductor material (it can be silicon) which will become pressurized under high pressure and will start conducting electricity. Using a 5V Reference from the ECU, the Voltage output fed to the ECU will change after the ability to conduct of the material, and it depends on the pressure it gets.
So basically this is similar to a rheostat configuration, and a Vc in, Voltage signal as a divider's output, and an earth.
How do we test a MAP sensor? Aftermarket MAP sensor means the ECU is modified, hence we won't be able to find it inside the intake manifold as we usually do. But normally, there are 2 methods that we can use to test the MAP is Off-car and On-car.
On-car test is simple: find the MAP, identify the wires(Vc; PIM; E2) and then back probe. As the ignition is turned on not the engine, we will be able to retrieve the MAP's maximum reading. This is because 1 bar of atmosphere is able to get inside the manifold through by pass air control, without encountering any vacuum being created because the intake valves are not moving, the cylinders are not moving at all.
Other than that, try turn on the engine and the PIM reading will eventually drop down to minimum readings for idling. This is because maximum vacuum is created by the cylinders hence the absolute pressure inside the manifold is minimum. There are still atmospheric pressure blown in but not enough for the vacuum.
As we open more throttle, more pressure hovers inside the manifold and if we maintain this pressure level we can still have maximum pressure applied to the MAP sensor.
Off-car is even simpler with the vacuum tube removed. Therefore the reading on the MAP is always maximum 1atm anyway. So if we block the hose by a vacuum tube and apply vacuum to it, we can see the voltage reading decreases, just like closing the throttle and let the engine idle.
So overall, MAP sensor and MAF sensor can be either alternatives or complements, depends on the configuration of the engine. They both measure air by sending voltage signal telling the ECU of how much air coming in, just different by the way they utilize which properties of air.
In which case, MAF & MAP sensor is no more useful when it comes into forced-induction engine, where air intake pressure and volume exceed way beyond what of a naturally-aspirated induction. A MAP sensor will change its way into a boost sensor or pressure gauge, measuring pressure which is much higher than atmospheric, and minimum pressure exceeds higher vacuum level. At that point, idling and wide open throttle needs to be monitored more powerfully differently.
Thursday, September 22, 2011
TPS testing
In engine operations, there are 3 main phases: Off, Idle, Throttle. The throttle butterfly is an inevitable component that decides anywhere the engine is between Idle and Full-open throttle, and that control is mainly in the hand of the driver, and partially the ECU.
Electronic engine management has become so importantly accurate, therefore the ECU knowing exactly how wide-open the throttle butterfly does is a MUST, so it can manage the Rest of the subsystem to operate in the satisfaction of this throttle position.
There are 2 main sides of the throttle body: Mechanical and Electrical.
The mechanical part is usually a coiled/spring butterfly vane that is always coiled to be at closed position, and linked to the gas pedal. The throttle is inside the throttle body and is mounted right before all the intake valves of the cylinder head - for best accuracy and air efficiency.
Beside the throttle butterfly, when idling @ closed position, there needs to be an auxiliary air passage called by-pass air, this will be addressed in bi-pass air control system.
There are 2-types of electrical insides the throttle position sensors, based on what type of ECU-feeding signals they give: analog and digital, hence hereby we have Linear(analog) TPS and Switch-type TPS(digital)
In linear: The electrical part consists of where the mechanism of the butterfly is linked to the variable resistor part of the position sensor circuitry. The variable resistor works on the same principal as the Vane type Mass airflow meter, as a voltage divider where the output signal that simulates the throttle position feeding to the ECU is variable along the side of the rheostat.
Here is an example:
(autoshop101.com - Toyota)
In expansion, there are many others modification can be done to the TPS circuit. For example, because @ Idle, the engine needs minimum fuel, therefore a fuel-cut switch can be integrated with the wider slider of the rheostat when it is at closed position so it pushes the fuel switch open - similar to the fuel switch of the vane airflow meter. From this, We can see that the Mass airflow meter and the throttle position sensor are kind of alternatively functional, since the kind of signal when mass air flows through the sensor as well as the signal when the throttle is open are proportionally, and sequentially related. In other word, the ECU can't receive a 4.5V signal of mass air without 4.5V signal from the wide opened TPS, and even if, this has got to be faulty.
Testing an analog TPS:
We can see that this potentiometer is capable of delivering variable signals. As we move the slider at any various position, we get different voltage output signal from VTA. For all the test procedure to be successful, it is important that we determine the location of the potentiometer on the throttle body - in this case it is the black box on the left of the throttle body as in the pictures. After obtaining the part numbers and determining the TPS type, we have to get the correct wiring diagram to show us what the 4 pins with wires coming out are. This is a fairly simple circuitry to we can generally break them down as this standard wiring diagram, though different manufacturer have different layouts.
The diagram shows the fuel cut-off switch for IDLE position as the Slider closes it will push the IDL1 terminal closes, this should be an alternative or complement to the fuel pump switch.
Similar principal to the Vane MAF meter, we can also have a resistor check. As we put the Ohms meter between Vc and E2 and move the slider, we will experience a constant resistance, because we check the circuit from Vc, through the whole rheostat NOT the VTA terminal.
Between VTA and E2, we can see that the resistance changes decreasingly from large, as we open the slider. This means that the resistance is largest @ closed position so we get minimum voltage signal, and smallest @ wide open so we can have large (not exceed 5V) voltage signal. Remember this rheostat and VTA is just like a voltage divider, and resistance is inversely proportional to Output voltage signal. Therefore this explains the result obtained:
For the IDLE switch, @ closed position we will have continuity between VTA and IDL1, as we slightly move the slider away that connection disappears.
Switch type signal:
There are several reasons for the Throttle Position Switch to be developed along side as a complement for the analog signal, and yet they are quite important. The IDLE fuel cut-off switch control mentioned above on the analog TPS is an important part of Switching TPS function as a whole, and yet it is one of the reasons. What about @ full throttle? What would we want the engine to run? We want full-power, and yet all the fuel pump switch is on, ignition timing is advanced and injector frequency get higher - another reason for this switch type. Those 2 are the main visible reason. But the truth is in order for the ECU to recognize clearly and reliably fuel cut off control and ignition timing corrections, the feed should be the solid and reliable digital signal, not the precise varying analog signal.
Here is a casual layout for any switch typre TPS:
Electronic engine management has become so importantly accurate, therefore the ECU knowing exactly how wide-open the throttle butterfly does is a MUST, so it can manage the Rest of the subsystem to operate in the satisfaction of this throttle position.
There are 2 main sides of the throttle body: Mechanical and Electrical.
The mechanical part is usually a coiled/spring butterfly vane that is always coiled to be at closed position, and linked to the gas pedal. The throttle is inside the throttle body and is mounted right before all the intake valves of the cylinder head - for best accuracy and air efficiency.
Beside the throttle butterfly, when idling @ closed position, there needs to be an auxiliary air passage called by-pass air, this will be addressed in bi-pass air control system.
There are 2-types of electrical insides the throttle position sensors, based on what type of ECU-feeding signals they give: analog and digital, hence hereby we have Linear(analog) TPS and Switch-type TPS(digital)
In linear: The electrical part consists of where the mechanism of the butterfly is linked to the variable resistor part of the position sensor circuitry. The variable resistor works on the same principal as the Vane type Mass airflow meter, as a voltage divider where the output signal that simulates the throttle position feeding to the ECU is variable along the side of the rheostat.
Here is an example:
In expansion, there are many others modification can be done to the TPS circuit. For example, because @ Idle, the engine needs minimum fuel, therefore a fuel-cut switch can be integrated with the wider slider of the rheostat when it is at closed position so it pushes the fuel switch open - similar to the fuel switch of the vane airflow meter. From this, We can see that the Mass airflow meter and the throttle position sensor are kind of alternatively functional, since the kind of signal when mass air flows through the sensor as well as the signal when the throttle is open are proportionally, and sequentially related. In other word, the ECU can't receive a 4.5V signal of mass air without 4.5V signal from the wide opened TPS, and even if, this has got to be faulty.
Testing an analog TPS:
We can see that this potentiometer is capable of delivering variable signals. As we move the slider at any various position, we get different voltage output signal from VTA. For all the test procedure to be successful, it is important that we determine the location of the potentiometer on the throttle body - in this case it is the black box on the left of the throttle body as in the pictures. After obtaining the part numbers and determining the TPS type, we have to get the correct wiring diagram to show us what the 4 pins with wires coming out are. This is a fairly simple circuitry to we can generally break them down as this standard wiring diagram, though different manufacturer have different layouts.
Similar principal to the Vane MAF meter, we can also have a resistor check. As we put the Ohms meter between Vc and E2 and move the slider, we will experience a constant resistance, because we check the circuit from Vc, through the whole rheostat NOT the VTA terminal.
Between VTA and E2, we can see that the resistance changes decreasingly from large, as we open the slider. This means that the resistance is largest @ closed position so we get minimum voltage signal, and smallest @ wide open so we can have large (not exceed 5V) voltage signal. Remember this rheostat and VTA is just like a voltage divider, and resistance is inversely proportional to Output voltage signal. Therefore this explains the result obtained:
For the IDLE switch, @ closed position we will have continuity between VTA and IDL1, as we slightly move the slider away that connection disappears.
Switch type signal:
Here is a casual layout for any switch typre TPS:
The output signal doesn't care how many degree the throttle is at, it only cares when the slider is in a certain range where either the IDLE switch or the PSW switch is STILL in contact, in this case 0-1.5 degree and 70-wide open, anywhere in between neither the IDLE fuel cut off nor the Full throttle fuel pump is activated.
Therefore, continuity check is the only thing that maters since there are normally only 3-4 pins coming out and we know is PSW, Common(E), IDLE and maybe a 5V Vc feed.
What happen when the slider is @:
IDLE: this is where we do nothing to the slider, it's already @ IDLE position. So 5V from ECU is grounded, therefore all the voltage drop will be across a resistor inside, hence we will have near zero volt coming out. There is continuity and the resistance over this is readable(1k Ohms)
Anywhere in between: We tilt the slider, and our V meter reads "5V", @ both PSW and IDLE we get 5V signal this means the 5V circuit is not completed, the resistor will not consume any of the available voltage hence we have 5V out of the pins.
PSW: similar to IDLE when the slide is in range.
For the record, position sensor is the biggest and most important "Commander" for the ECU while it's acting like a CEO. Position sensors represents the driver's demand of operating modes/loads for the engine, so it is very important that the ECU receive both analog and digital signals.
Wednesday, September 7, 2011
Testing Vane Airflow Sensor
This is the component normally mounted between the throttle body and the end of the intake manifold passages. It's purpose is to have a configuration where we can set a sensor up that will react with what's happening through the whole air intake tube to feed the ECU with important information about how to run the engine.
No argument, ECU is a computer, so the signal that this particular type of MASS AIRFLOW SENSOR or ANY type of M.A.F give has to be in Voltage signal. It's called VANE or FLAP MAS because the basic concept is: aerodynamic/mechanical reactions of the flap/vane according to how big the flow of air is, will be turned into voltage signal feeding to the ECU by a mechanical link between flap movement and a variable resistor in series with the line where Vsignal is coming out. So if we have a variable resistor, in a configuration where voltage divider applies, it will control the outcome voltage, not necessarily Ohm's Law this time!
There is a small circuit inside this little device, well every sensor needs their cute little circuitry obviously. In this particular Vane MAFS, you will see there are 7 electrical pins coming out of the plug of where the square little black plastic box sealed on the flap body. Those 7 pins represent the relationship of this circuit with "the rest of the car's circuit". Well of course in this case "the rest" is referred to ECU because this sensor seems to be simple enough that it only needs to answer to the ECU.
So this circuit is not complete, but it will run by itself like any other circuit if we just supply a little bit of voltage through the right pin. And NOT every part of any of these circuitry that appears inside the little box.
There are 3 main parts represented by those 7 pins: The thermistor circuit; The Main vane voltage output signal circuit, and the Fuel pump switch circuit. Yet they seem physically connected but their operations in terms of circuitry are separate.
The thermistor circuit, convenient to locate close to the signal output circuit, because when we built a sensor to measure how big the volume of air flowing through per second, we thing why not include air temperature measurement too: Temperature-Volume-Pressure are inseparable when talking about air/gas.
So in the wiring diagram, we can see that this circuit only needs an Earth for itself (E2), and everything comes out is temperature, because there is another sub-materialized circuitry inside the little nob that sticks out inside the air passage as well. Temperature will have geometric and volumetric effects on the material, and hence turn into a mechanical effect- and finally electrical signal is outcome.
Forget the fuel pump switch and the T.H.A, the Mass air flow signal is Vs; Vb; Vc; E2. Where Vs is supply of 12V, Vc is input signal from ECU of 3-5V; and Vs is output signal that will NEVER/SHOULDN'T be greater than the ECU's input signal. But like I said, this circuit can run fine with only 5V to Vc. We can see that 5V from Vc can easily make it to earth, with a variable resistor in it's way which will act like 2 resistors with it's adjustable needle pointing out for the signal output. Which acts kind of like a voltage divider circuit with 2 resistors and an output leads away between those 2 resistors (Vs).
This variable resistor is configured to be Maximum at Vane CLOSED position, so when Vc of 5V comes through the rheostat to Vs we will have minimum signal, because most of the voltage drop is for the BIG selected resistant part on the rheostat, only a little comes out for example 1.26V.
As the vane opens wider(got pushed in by more air) the rheostat becomes smaller, hence Vs leads a bigger output signal, just like how a voltage divider works as we change the value of its resistors. And of course, we can't have a voltage divider where all the supply comes out the output terminal while none goes to the following resistor to earth, that would make NO SENSE of a voltage divider anymore. That's the reason why the signal must not be or be bigger than the ECU input. But, when you have Vb hooked with the 12V+ battery, 5.08V(actual @ max open position) might as well be what you have.
Current is not a concern in this type of circuit, where only Voltage and Resistance matter. So we can test the operation of this VANE MAFS by 2 ways through resistance meter check and available voltage check.
Put the black lead on the E2, @ Vs varied between 80-900 Ohms in total and this is fairly between specification. This only tells me that the rheostat is in the voltage divider range in order to have a desired voltage signal. E2-Vb & E2-Vc both possess the same amount of resistance ,this tells me that the maximum resistance of the rheostat and the Vb resistor are similar.
It behave seemingly like exponential. But as Ohm's law applies: V=IxR, this relationship should be linear and directly proportional because vane angle represents proportions of the rheostat being selected.
Fuel pump switch: a smart mechanical link between the rheostat's needle @ zero angle position and the fuel pump switch.
Disadvantages:
There are several types of air flow device besides this vane they are Hotwire Mass air flow sensor, Karman Vortex air flow sensor. And the most common is hotwire mass airflow sensor. The reason this Vane device is not called "sensor" because it is actually a meter, which convert analog mechanical movement into electrical signal. Other sensors convert heat energy into voltage signal, or photographic changes into voltage signal, which are more likely to be called "sensor" than "meter".
The Vane type mass airflow meter consists of a moving mechanical flap, hence the weight and recoil force of the spring setup exert on the flap can restrict the flow of air, hence restrict performance.
In consistent and frequent operation of the intake air, a complex of mechanical components will eventually worn out, and dirt deposits on components. Which may lead to hard starting when the engine needs the vane to actually opens up a little bit when throttle is not depressed.
Beside, the spring composition can be out of service too, which will terminate all the voltage output function of this vane type mass airflow meter.
Comparing to the Hotwire, the vane MAF takes more room and weights much more heavier than a tube of plastic with some wire in it, hence replacing a vane with a hotwire is a much better choice. In fact, most cars use hotwire MAF sensor.
-Large & heavy
-Performance restricting=> lessen fuel economy
-Not as reliable as the hotwire MAFS
-Not as accurate as the hotwire MAFS
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