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Cosworth YB - Base Timing + Trigger Voltage Questions

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Hi All,


Hope you are well.

Hope someone can help me out here.

I am trying to set up the base timing on my Cosworth YB 4 cylinder engine.

Question 1 :

I have successfully established the Trigger offset number via a timing light to be 285 @ Reference TDC 0

When i click on the "Trigger Calibration" menu my timing is set correctly, as soon as i close this menu to down timing moves 50/60 degrees retarded, If i open up the trigger menu the timing returns to the correct number. When i enter the value "285" i HAVE pressed enter and seen the box turn blue. I believe this value is correctly stored in the ECU, i have also saved the config via F4.

Why does the timing shift when the box is closed, is this due to the "Trigger Arming Threshold" menu not being fully calibrated?Can any one advise?


Question 2:

I am running a 36 tooth trigger wheel, i believe this is configured correctly in the ecu as it runs smoothly at idle. I have a cam sensor mounted in the rocker cover and gapped correctly.

Please see attached screen shots from the trigger scope.

My question is, why am I seeing +12v signal from the crank sensor, i assumed it was a 5v output? Can anyone comment here? 

Can someone kindly look at the trigger scope output and comment.


Many Thanks




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Moved to G4+ forum.

Question 1.  When the "set base timing" screen is open the ignition advance is locked to whatever value you have in the top field, when you close that screen then the ignition advance returns the the value commanded by you ignition table + all the other trims.  So if you see a big jump when you close that screen then it suggests you have much different timing commanded than what was is the lock field.  You can see the final value that the ecu is commanding by looking at the "ign angle" runtime.

Question 2.  You have "VR" sensors, their voltage output is relative to two main factors - "air gap" and the speed of the tooth moving past the sensor.  So, output varies greatly with RPM.  Often <1V during cranking, and on some engines you see >80V at high RPM.

Also - Very important - your CAM sensor is wired backwards, you need to swap the +/- wires.  Crank is correct.

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I have corrected the cam signal, see attachment below, will play with cam timing once my lambda sensor issue is fixed (separate topic). As the car is running too rich.

Thank you

Cam sensor corrected.jpg

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