8
Jan

Analyzing Picoscope cylinder pressure graph by USB Autoscope software Part 2


In the previous video, we showed the Px test
performed using the Pico 4225 and the Px35 cylinder pressure transducer included to the
USB Autoscope kit. Those users who have the wps500 pressure transducer
can use it instead of the Px35 transducer. Let’s run a test with this transducer. We will do the Px test on a faulty KIA Sorento
2007 2.4, which engine does not start well and when you press the accelerator pedal,
it stalls; this is the same car that was shown in the previous video. To begin with, we do all the necessary connections. We connect the high-voltage wire of the cylinder
being tested to the spark gap through a special adapter. In place of the spark plug we install the
wps500 pressure transducer together with a PxFlex deep well adapter, connect the signal
cable from the transducer to the input “A” of PicoScope 4225. To obtain a synchronization signal with an
ignition spark, we use a capacitive probe, which we connect to the high-voltage wire
of the diagnosed cylinder. We connect the high-voltage probe to the input
“B” of PicoScope through a special peak detector. It should be noted that all measurements are carried out through the adapters from the USB Autoscope. The Pico software configuration process was
shown in the previous video – for different pressure transducers
it is almost the same. The measurement duration should not exceed
the time of one frame, which for this measurement mode is 50 seconds. We start the engine. Slowly increase engine speed; after a few
seconds the engine stalls. We stop recording signals. The received waveform file must be saved on
your computer; To do this, call the menu “File=>Save As”. Then convert the saved file to the USB Autoscope
file format using the forum http://forum.autoscope.eu/. After opening the received waveform file,
the software automatically detected deviations on the cylinder pressure graph and marked
it in red. Let’s run an automatic signal analysis. To do this, call the menu “Analysis=>Run
Script”. As a result, the USB Oscilloscope program
provided the results of an automatic analysis of the cylinder pressure graph, which indicates
that exhaust gas output is very difficult. Let us compare two Px test results obtained
on the same faulty engine: one was recorded using the Px35 transducer, and another using the wps500 transducer. Here are the results of a test performed using
the Px35 transducer. And here are the results obtained using the
wps500 transducer. As you can see, the results are almost the
same. On this car, the exhaust system was clogged
with small internal parts of collapsed catalyst. After cleaning the exhaust system and replacing
the catalytic converter, the test was performed with the first, and then with the second transducer. Compare the results of the Px script: Here is the result of the analysis of the Px35 transducer signal. And here is the result of the analysis of
the wps500 transducer signal. In both cases, the test showed that the exhaust
system functions normally now. This technique is applicable for all types
of gasoline engines, regardless of the brand of car. The following equipment is recommended for testing: – wps500 pressure transducer (it is required
to replace the original inlet port connector with a modified one manufactured by USB Autoscope) – deep well adapter M14 (M12 or PxFlex depending on the engine); – capacitive probe; – peak detector for the capacitive probe; – high voltage Spark Gap tester. To be continued…

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