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Variable Cam Control Tuning: PID Calibration

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PID Calibration

02.51

00:00 - The next step of the process is only relevant to continuously variable cam control systems so if you're tuning a switched cam engine, you can jump ahead to the next step.
00:10 For continuously variable cam control systems however, this step will be the most critical of the entire process and it's essential that you spend the time here to gain good control or the rest of the tuning process will be flawed at best.
00:24 Before completing this process, I suggest you review the PID tuning module in the body of the course as this is what we'll be doing.
00:32 Every ECU has a slightly different process and different parameters available here but we'll cover the generic steps here and then get a little bit more application specific inside of the worked examples.
00:44 The first aspect to deal with here is to set a base duty or feed forward value for each of the cams that you're controlling.
00:52 The process of doing this is to disable the cam control or alternatively set the PID gains to 0 and then slowly increase the cam actuator duty cycle from 0 in 1% increments while monitoring the cam position in the software.
01:06 This should be done with the engine and oil at normal operating temperatures and you should be doing this at around 3000 RPM to ensure realistic oil pressure.
01:16 What you're looking for is the duty cycle when the cam first begins to move.
01:20 Be aware that as soon as the cam does start moving, it's just going to keep going and this will more than likely cause the engine to run pretty badly but don't stress, there's no risk of doing any damage here.
01:32 Once you've found the base duty value for one cam you can repeat this for any additional cams.
01:38 It is important to test each cam actuator as they almost certainly will have slightly different base duty cycle values.
01:45 Now we can start optimising the PID values.
01:48 Many aftermarket ECU manufacturers will provide pre set base PID values for the common engines that they support where the ECU manufacturer has developed these PID values in house and proven that they work well.
02:01 While generally I'm cautious about using base values that someone else has developed, in my own experience, across a wide range of different ECU platforms and engines, I've found that this does typically provide a good starting point.
02:15 Even so, I'd still recommend actually testing the response to ensure that it's working well and you may fine benefit in tweaking these base gain values a little if required.
02:26 The process for actually tuning PID gains on a cam control system is quite easy compared to many close loop control systems and you can refer back to the practical skills module that covers this process for more detail.