Mercedes M276.820 3.0 Turbo - Bosch 200BAR Piezo GDI voltage and current waveform

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Mercedes M276.820 3.0 Turbo - Bosch 200BAR Piezo GDI voltage and current waveform

Post by S-Prihadi »


This is the engine: M276 DE30LA as its full name.
Found on W212 E400 and S-Class of the same era and also W205 C43, C400 and C450 in increased HP.
The GDI system is very similar to the M157 AMG. ... -intro.pdf

I have trouble getting a clean signal from this injector if any other channels on my 4425A is being used for voltage. The floating ground voltage of 30V limit of 4425A seems to not able to handle this piezo well.

Since I am a newbie scope user.....
Reading MB document on M157 engine, I freaked out and dare use two channels to scope this 2 wire piezo injector 2 wires. So I connect Channel A positive to the Pin 1 ( Inj.High ) of this injector and Channel A ground to Pin 2 ( Inj.Low ) of this injector, as seen on the wiring diagram attached.

If only injector on Channel A and a clamp for Channel B, it is fine. Add COP 5V trigger voltage on Channel C with its ground to car chassis, the capture goes bad.
I am attaching : "M276.820 Piezo Injector with 5V COP trigger voltage.psdata"
and "M278.820 Piezo Injector Voltage and current only.psdata"

So I was not happy with the limitation, and I got myself a low cost differential probe from MigSic.
The DP750-100, as reviewed here :

With a DIFF probe is where things get interesting.
I can see the voltage drop before current change direction.
Current up is piezo consuming power as a consumer, current down is piezo acting like a capacitor
or mini generator. That is what I think I am seeing :mrgreen: , experts please chime in.

Injector Wiring Diag and scope measuring points.JPG
M278.820 - Piezo Voltage using DIFF probe and Current data.psdata
(1 MiB) Downloaded 195 times
Comparison - DIIF probe 50X and normal one. Engine temperature of captures are not the same.JPG
M278.820 Piezo Injector Voltage and current only.psdata
(1.03 MiB) Downloaded 184 times
M276.820 Piezo Injector with 5V COP trigger voltage.psdata
(1.73 MiB) Downloaded 187 times

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