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chris24z
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Last seen: 1 year 2 months ago
Joined: 04/23/2018 - 14:18
VVC/Intake Cams not advancing

Hello, I'm having issues with the intake cams not advancing. I did some logging to check it out, but I don't know the criteria/requirements for the ecu to allow advancement; so I'm not sure if it's a mechanical or wiring issue.

AEM_SB
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Last seen: 2 days 16 hours ago
Joined: 06/07/2014 - 14:29
The software should include

The software should include different base calibrations for the VQ35 engines, some had 4 variable camshafts (intake and exhaust) while others only had variable intake cams. Please be sure you've loaded the correct calibration for the engine you have. There is an option named 'VVC Minimum Coolant Temperature', it has been a few years but I think this was added specifically due to Nissan VQ actuators not working well at cold temperatures.

 

The ECU changes the variable cam position by sending various duty cycles to the VVC actuators; duty cycle will change depending on the commanded VVC target and the measured camshaft angle. Start by watching the channels VVC1A_Cam_Timing and VVC1B_Cam_Timing, which should be included in the VVC page of the layout; those channels display the measured camshaft position in degrees. Measured position should be near zero when the VVC actuator is unplugged or when the ECU is not sending it a duty cycle. To watch the ECU move the cams, the simplest method is to change the target position using the VVC1_Target [deg] table. If that doesn't result in movement, it's also possible to manually edit the values in the LS3_Duty tables and/or LS5_Duty tables, this will bypass all the ECU's variable cam functions and manually change the duty cycle sent to the VVC actuators. Most actuators should change cam position when their duty cycle is above 40-60%, assuming there is sufficient oil pressure and all the other mechanical parts of the VVC system are working properly.

Two of the VQ35 engine's cam actuators are purely electromechanical (no oil pressure required), unfortunately I don't remember if that was the intake or exhaust actuators. The ECU sends a similar duty cycle signal for both type of actuators.

 

There are also some failsafes that can allow the ECU to disable the VVC outputs if the measured cam position is outside the expected normal range. Default expected range is between -5 degrees and +45 degrees for the intake cams. Feel free to post a log here, we can help look through the data.

 

Hope that helps,

SB