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GT86 Cam Position flutter

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ecu: motec m150

engine: stock FA20 with Harrop Supercharger

Just wondering if anyone has come across an issue like this with VVT motors and in particular the GT86. During ramp runs and sometimes during idle the cam position will start oscillating and behaving erratically. I have left the default VVT settings alone in the motec and have only tried increasing the "smoothing". I have included screenshots.

Any Ideas?

P.S. This same exact issue presented itself on the previous engine/engine harness. So it is not engine/engine harness specific. Battery voltage is consistent at 14V and all grounds in engine bay checked and verified to be visually good.

Attached Files

First, the non-ECU related possible issues: Are you using the factory recommended oil viscosity? Particularly since this is worse with one cam -- Any chance there is a mechanical problem with a timing chain (or belt) tensioner? Have you tried replacing the VVT solenoid (or can they be swapped to see if the problems follows the solenoid).

Does this only occur when the oil is hot (or cold) or when the oil pressure is low (or high)?

Now for ECU config issues:

What are the VVT settings for the PID? What does the VVT duty cycle look like when this is occurring? What is the Feed Forward value when this is happening? My Mazda CAM control is amazing with the Motec M1.

When I see large overshoots and oscillating, I often try increasing the Derivative gain (if that doesn't help, then I will lower the Proportional Gain).

Hi Kevin,

As David has said, have you changed the oil viscosity from the standard that Toyota recommends? I have found with these engines (I look after the Toyota 86 Race series cars) that they are very susceptible to variations between oils, and even the same weight, but a different brand, can cause the cams to exhibit strange behaviours.

With the M1 side of things, the base values in the Cam setup are just that, base values that allow for the engine to be run and driven onto a dyno to be tuned. Each Cam needs to be tuned, starting with the Position Offset parameter, then the Feed Forward table (all PID disabled by setting the values to 0) and finally the PID.

@BlackRex and @David Ferguson,

Thank you for your replies! I really appreciate it!

Mechanically there is nothing that is the same on this engine vs the previous engine. The whole engine and its sensors, cam solenoids, and wiring harness were removed and replaced. The oil being used is not oem spec as the engine is tracked quite heavily in the heat so it is using slightly thicker oil MOTUL 300V 5w30 which hasn't been a problem for the car since 2013 while using the stock ECU.

As for the PID params David was asking for here they are for the exhaust cams (screenshot attached).

Attached Files

Inlet cam logging from my car.

Attached Files

Thanks @BlackRex, your log looks very different than mine:

Attached Files

I'm running Motul 300v 0W-40 in our car and the cam control is absolutely fine. I know that I did need to spend some time initially with the offset and feed forward values compared to the base map but even then our control was pretty close straight out of the box. I don't know if it will be helpful but in my current calibration I have a proportional gain of 1500%/1000 deg and a derivative gain of 60% per 1000 deg. I'm also using a smoothing value of 30%

From your log it looks like the derivative component is what is driving the large oscillations in your output duty so it may be worth reducing this gain and testing.

The last 86 that I did has different DC, offset, and smooth numbers for each of the cams.

Ex1 53.5 0.0 20

Ex2 40 -2.0 20

In1 49 1.7 30

In2 47 1.5 10

I did have the same PID values for all of the cams,

P = 900

I = 2500

D = 60

The Min/Max DC numbers for the actuators is;

Ex = 40/90

In = 30/90

Frequency 300Hz, Ref Voltage 12V

It appears the PID settings that BlackRex has listed above are the default values from the latest package. The ones I'm using I believe are the default values from the original package. I've tuned 86's using both packages with no issues with the cam control which makes me wonder if there's something mechanical going on that's affecting the ability of the ECU to control the cam position accurately.

I agree with BlackRex that the feed forward and offset need to be adjusted for each cam individually. I've generally found that I've ended up with the same smoothing on both intake cams and then the same value for both exhaust.

There have been some changes with the engines through the 4 years of the Mk1 Toyota 86 that may effect the operation and tuning parameters of the cam control system, with the 2017 on engine being different again. The vehicle that I did the last Package on was a new 2016 car, and whilst the numbers from the original package did a pretty good job on controlling the cams, the updated settings made it better.

@Andre, we have done a complete engine swap (including the engine harness and all engine sensors, cam actuators, cam control solenoids etc). If something is wrong, it must be electronic as the cam position oscillations have persisted even after this swap. Only thing left to swap out is the body wiring harness and then if that fails throw the whole car in the dumpster. ;)

I am trying to see if the motec cam settings can be tweaked to get an acceptable level of control before I junk the car... haha

Did you finally solve this problem?

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