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Старый 29.09.2008, 12:41   #1
1(P@shencia)
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По умолчанию Тест широкополосных лямбда-зондов, AEM, PLX, Innovate, Zeitronix, Fast, etc


Background
The art of tuning an engine is not new, dating back to the birth of the internal combustion engine over 100 years ago. For a generation or two, methods such as vacuum gauges, CO meters, and the black art of reading spark plugs were the main tools in a tuners arsenal. Due to the lack of accuracy of these methods, tuning was nothing more than subjective analysis and best left to the seasoned professional.

Later, as emissions standards tightened and as racing engines started to produce higher and higher outputs, the need to accurately determine air-fuel ratio became increasingly important. Technology improved and wide band air fuel ratio meters with embedded data logging equipment emerged. For many years this technology was out of reach for all but the most well heeled DIY tuner. The cost of accurate reference level wideband air fuel ratio meters was in the several thousand dollar range.

The affordable meters on the market, at the time, used conventional narrow band O2 sensors- the same type of sensors found in most early EFI cars. Such sensors are only accurate around the stoichiometric range, which is an air fuel ratio of 14.7:1. Accuracy in this range is useless for performance tuning where wide-open throttle ratios may drop as low as 11:1, and certainly in the 13:1 range for most naturally-aspirated engines.

The big breakthrough for the performance aftermarket occurred when Bosch made the LSU4 wide band O2 sensor available for a reasonable price, and the aftermarket responded by making affordable wide band air fuel ratio meters using this sensor. This is a boon to the DIY tuner as now there are many wideband air fuel ratio meters available on the market for a reasonable price.

From A to Z, we gathered the most popular digital wideband air-fuel meters for comparison. The brands are AEM, Dynojet, FAST, FJO, Innovate, NGK, PLX, Zeitronix.

Part of our analysis was to assess the ease (or difficulty) in getting each unit installed and operating. Wiring up eight units took some time, but fortunately on an engine dyno we didn't need to concern ourselves with a clean installation.

Not All are Equal
Many questions have arisen since the widespread availability of wideband air-fuel meters.

First, since all of these meters use the same Bosch sensor, and since this sensor is factory calibrated, are they all more or less equal? The answer is no. There is significant difference between the controllers and circuitry used in the various meters. How the sensor's heater is controlled and how the pump current is switched and controlled, for instance, are critical for accurate sensor operation. Other questions also can be posed: Which meter is the best performing one? Which meters have the features I need?

With these question and few subjective answers to be found, we set out to determine which meters were the best. The task was a difficult one but we were determined to find the answers.

Methodology
The plan was to take eight popular units and test them right out of the box using calibrated compressed gas. We'd then run them for an hour on a test engine, with leaded race fuel, to simulate wear on the sensor. Finally we'd test them again with calibrated lab gas. The compressed gas is from Scott Specialty Gasses and formulated to SAE standards for .8 lambda and .895 lambda (11.76 AFR and 13.15 AFR respectively). The gas gives us a control with which we can test each sensor without introducing variability - such as a change in rpm if we were to use the test engine's exhaust gas. To further control the study we used Westech's expensive ECM LambdaPro which read dead-on for both of the gas controls.


(1) Sensors were tested using laboratory gas specifically formulated to yield 11.76 AFR and 13.15 AFR. This way each sensor sees the exact same "exhaust gas", letting us measure the accuracy and responsiveness of each meter.

(2) After testing with lab gas the sensors were run-in for an hour with race fuel, on a test engine (Westech just happened to have a Chevy motor in the dyno room that day.) The run in simulates the wear and tear a sensor goes through with live fuel and heat conditions.

(3) Nine bungs were welded into the exhaust; eight for the sensors under test and one for Westech's own meter. Datalogging was performed during the engine run-in to assess the capabilities of each meter.

(4) A common power and ground supplied each meter to ensure no other variables influenced the testing.

During the dyno testing, we also logged data from all of the units. This gave us a chance to configure each unit's analog outputs, and to compare response time (latency) and accuracy under various loads, sweeps, and conditions. We also verified that the logged data matched the values displayed on the various gauges and displays. All the units shared a common and robust power and ground setup.

The chart on the following page summarizes our findings across four categories. Of particular note was the issue of re-calibration. All of the units certainly rely on the factory calibration of the sensor from Bosch. The manufacturers may even perform some sort of a calibration of the sensor to their units during their assembly process. However, as far as we could tell, only two units appeared to be capable of re-calibration to compensate for sensor wear. The Innovate unit is self calibrating, while the NGK requires the user to turn a knob until the display reads "CAL." Both measure the air-fuel ratio of free air to calibrate the sensor.

This raised the obvious question: If a unit is not capable of calibration, how does the user know when the sensor is going bad? We know from the Bosch data that the sensors themselves change as they age.

As previously discussed, air/fuel data is most useful when correlated with other key parameters like throttle position, manifold absolute pressure, and RPM. And this sort of correlation absolutely requires data logging. So, even though all of these units feature useful real-time displays, the most important parameters are response time and the quality of the logging solution. Response time is critical because it's possible to have accurate data, but, due to high latency/delay, the data is essentially in the wrong column of your fuel map.

Results - At a Glance
Listed below, from A to Z, are the eight meters we tested. All use the Bosch LSU4 wideband oxygen sensor. There was a surprising amount of variation between the various units, in terms of both accuracy and response time. We also rated the ease of use, display, and included software. The participants were AEM, Dynojet, FAST, FJO, Innovate, NGK, PLX, and Zeitronix.

AEM
AEM
The AEM unit was accurate during our tests, but with no real data logging capability, of limited usefulness for actual tuning. It was average for response time.

AFX (NGK)
The NGK unit exhibited low scores for accuracy, and it was missing the required wire for analog output. It does not have data logging capabilities. Considering NGK makes their own wideband sensors, it is a surprise this unit ships with a Bosch sensor.

Dynojet
The Dynojet unit was hard to set up, and the included logging software was very limited. The Dynojet exhibited the slowest response time tested

FASTThe FAST unit had internal datalogging, but no logging analysis software. This made it less useful for real tuning. Setting up the analog outputs was somewhat difficult. Display is nice and intuitive.

FJO
The FJO unit had tricky wiring for the sensor, the controller, and the analog outputs. It was also difficult to setup the analog outputs with the included configuration software. The included logging software was counterintuitive.

Innovate
The Innovate unit was accurate, exhibited the fastest response time, and included very good analysis software. Innovate claims to be the only truly digital unit, and the high accuracy and low latency seem to support their claims. Setup and wiring was complex and somewhat confusing.

PLX
The PLX M300 does not include logging software, and exhibited accuracy at +/1 AFR (the worst tested).

Zeitronix
The Zeitronix exhibited accuracy of +/- .54 AFR, and gradual lean drift under some conditions. The included logging software was relatively difficult and lacked features.

The only regret we have is that we couldn't effectively simulate long-term sensor "aging." Aging is mostly due to oxidation of the sensors internals and fouling of its ceramic elements. Operating conditions and fuel type are big factors in the aging process. Exposure to lead in race gas, metallic elements in octane booster additives, oil or carbon fouling and really high operating temperatures contribute to rapid aging, and a resulting loss of sensor accurancy. Because of aging it is important to have an air fuel ratio meter that can be calibrated. The common type of calibration is called a free air calibration. This is when the meter compares the output of the sensor to what it should be when exposed to a know oxygen content gas, air. If an air fuel ratio meter is lacking the ability to calibrate, the sensor should be replace at regular intervals. The trouble is when should the sensor be replaced? It takes some experience to know when this is appropriate.

We did try to emulate this idea using a variety of old and damaged sensors we had laying around. With one of these sensors, the Innovate XD-16 would show an error code indicating that the sensor was bad. However, when we connected the same damaged sensor to any of the analog gauges they read as much as 3 AFR off. Again, the obvious question is: If your gauge can't tell you when a sensor is bad, how could you ever trust it?


Optimizing Wideband Sensor Usage
Other things to keep in mind to ensure proper sensor function and longevity are exhaust back pressure, rich mixtures, and under/over heating.

A high exhaust backpressure forces more exhaust into the sensors pump cell which can cause an air fuel ratio meter to read richer than what the engines really running. Turbo engines run a relatively high amount of backpressure in the exhaust manifold before the turbine, making them a poor place to locate the sensor.

Missfires due to a malfunctioning or underpowered ignition or an extremely rich mixture can cause false lean readings because unburned liquid fuel in droplets block the small hole leading to the sensors pump cell.

A wideband sensor should not be placed in the exhaust stream and left unheated. The hole to the pump cell can quickly become clogged and contaminated by exhaust byproducts, especially during a start cycle from a cold engine. The sensor can also be damaged by exposing it to temperatures above 700 degrees C, like those typically before the turbine in turbo engines. You never want to place a sensor there anyway due to the aforementioned issues with sensor accuracy and backpressure. Lastly you don't want to place the sensor so far away from the engine that its 10 watt internal heater cannot keep the sensor hot enough.
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Старый 21.11.2012, 21:59   #2
Art-mr2
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...Хотябы выводы в двух словах (по русски)
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Старый 21.11.2012, 22:00   #3
1(P@shencia)
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ну по сводной табличке и так все понятно без слов
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Старый 21.11.2012, 22:00   #4
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иновейт - круто, нжк - гавно?
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Старый 21.11.2012, 22:00   #5
1(P@shencia)
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что-то типа того
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Старый 21.11.2012, 22:00   #6
5(psycho)
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я бы добавил что инновейт не теряет точность при устанвоке близко к мотору ( аем начинает врать безбожно из-за перегревов, которые контроллер не компенсирует ) требует меньше времени на разогрев зонда ( аему требуется время что бы нагреться от выхлопных газов, видимо его родной подогрев использует меньшие токи чем инновейт, ибо сенсоры у них идентичные )

ну а скорость отклика это вообще эталон, + ко всем достоинствам инновейт можно перекалибровать, а это очень важно при работе с высокооктановыми сортами топлива, из-за которых сенсор уходит от зводских калибровок
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Старый 21.11.2012, 22:01   #7
6(advan1)
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А кто че скажет про:
ШЛЗ+ЕГТ Вемс
http://shop.vems.hu/catalog/product_info.p...products_id=101
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Старый 21.11.2012, 22:01   #8
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сам зонд там бошевский хороший, проц слабоватый, а софт как и любой опен сорс нуждается в доработке

короче не парьте мозг и работайте с инновейтом из гражданских устройств он лучший, не гражданские стоят совершенно других денег
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Старый 21.11.2012, 22:01   #9
6(advan1)
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вемс рассматриваю потому, что там сразу два в одном и смесь и темп выхлопа(в цифровом виде), а с инновейтом слишком часто проскальзывают тамы с гемором его работы и установки-калибровки, ни про аем ни про вемс такое неслышал.

п.с. может и на стенде с иновейтом проще, а как в повседневной жизни и если учитывать что это будет работать с ультимейтом, то что предпочтительней?
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