Custom Trigger shape Bosch Quickstart spinning backwards

[DrahtFahrzeugHammer]

Hi everyone,

I need some help with my Volvo 850 project. As i mentioned in the project thread already, i have an issue with the camshaft trigger wheel. It is the trigger shape of bosch quickstart, but it is spinning backwards, which means that spark is not working propperly and i probbably won't get VVT to work like that.

The crank has a 60-2 trigger shape on the flywheel with a VR sensor

I am running a proteus board with STM32F4 chip and a hall effect sensor. Here is a Snapshot of the engine sniffer. Same as on the build thread:

image.png

and here an image of the trigger wheel:

Triggerrad_Nockenwelle.jpg

It spins counterclockwise as seen from viewing position in the image

If you need any more information i would be glad to provide it

[AndreyB]

Is there a chance of you making conclusions too quickly? Please confirm that you have tried both "falling" and "rising" mode.

[DrahtFahrzeugHammer]

So the rotation direction doesn't matter for the trigger shape? Bosch Quickstart is not symetrical.

I'll try falling edge later today

[DrahtFahrzeugHammer]

Earlier this evening i tested the falling edge setting and it did infact fix the ignition firing every crank rotation:

OOOOOOOHHHH i get it now. The bosch quick start trigger shape is in fact symetrical. But when the signal is inverted. That is why changing from falling to rising edge fixes it.

Might be useful to add that information to the trigger documentation for Quickstart. That would have helped me. I would add that if it is ok. Just have to get logged into github somehow

Falling edge:

2025-09-25_18_54_56_362rpm_0_maf_0.0.png

Rising edge:

2025-09-25_18_56_10_720rpm_0_maf_0.0.png

[DrahtFahrzeugHammer]

Here is proof:
I modeled the inverted shape in FreeCAD:

image.png

Then i filipped it 180° and turned it 140°

image.png

and it fits perfectly

[AndreyB]

https://github.com/rusefi/rusefi_documentation/blob/master/HOWTO-contribute-to-documentation.md