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GravelRash

AIM being pulled during normal driving

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Hi,

Recently I've been observing that my AIM is being pulled during normal driving. Last night I was doing a regular drive and it's one that I know will cause my IAM to drop. Here's the ECUTEK / Datazap logs of the drive.

I was in traffic, driving up a fairly steep hill. AIM was pulled from 1 down to 53 before slowly coming back upwards. The logs don't record this, but eventually the car will return the AIM to 1.

My concern is this is happening quite a bit although not as low as 0.5 usually.

I would like to understand what's occurring, any potential for engine damage, and ultimately how to fix this.

https://datazap.me/u/xhf6z8vrcl08/aim-being-pulled-during-normal-driving?log=0&data=4-12

Car is obviously modified and only runs Shell vPower 99 E5. The last 4 fillups have been from different Shell garages around the country. Unless Shell has a nation wide fuel problem, I don't think it's the fuel.

Any observations are welcome.

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Scoobypedia discusses the Subaru knock mitigation algorithm in excruciating detail: http://scoobypedia.co.uk/index.php/Knowledge/SubaruKnockControlStrategyExplained

The implication of your chart (very helpful apart from the axis autoscaling being useless sometimes) is that there are 4 knock events during your drive, possibly corresponding the some abrupt changes in throttle, although without particular pattern. The knock strategy does what it does around these events, but the response is hard to predict due to the complexity of the response.

I can't say whether knock events are common or uncommon having not been able to log this myself.

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Gosh, that description really gives a feel for the complexity of a modern ECU's knock control.

However, doesn't the D4S with dual injectors use Toyota's ECU programming, rather than Subaru's?  Dual injection is bound to complicate knock control even further.

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The data includes a D4S trace, but I don't know what it means, and it seems to be more than just on-off. Probably versions of Both, A, B, none. I know that dual injection systems ideally vary their duty dependent on economy versus power goals, but I don't know if the GT86 system is that sophisticated.

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13 hours ago, MartinT said:

However, doesn't the D4S with dual injectors use Toyota's ECU programming, rather than Subaru's?  

Denso ECU, similar to those in Subaru's.

10 hours ago, nerdstrike said:

The data includes a D4S trace, but I don't know what it means, and it seems to be more than just on-off. Probably versions of Both, A, B, none. I know that dual injection systems ideally vary their duty dependent on economy versus power goals, but I don't know if the GT86 system is that sophisticated.

D4S is indeed just an indicator of PI/DI/Both.

Loads of people in the US get really shitty over IAM changes. Some will occur unless mapped conservatively, this engine is high compression and the setup is known to be overly sensitive. High gear loading can do it as well. Dropping to 0.5 isn't ideal though, especially if you're on V-Power.

I take it that as you're running EcuTek you're tuned as well. There is a lot of knock correction going on. Look at the ign correction - fine parameter, any time it's negative it's pulling timing, any time it's positive it's trying to restore the IAM. That's FLKC. FBKC is Knock Correction

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To bring some closure to this thread.

The car has spent some time with the tuners. I don't know exactly what they changed in the tune other than some fine-tuning but over the last few days I've been doing my usual driving and the IAM value isn't being pulled as often and when it is pulled it's not being pulled as much.

The engine itself is in good working order and apparently there's no indication of knock actually occurring. The current thinking is that the sensors are hearing phantom knock, probably caused by the semi-solid engine mounts.

Unrelated to the knock investigation I also had the car raised up 1cm due to it ground-striking on uneven ground. This ride height increase has made the car ride smoother which I think could also be helping with any phantom knock signals.

Next steps will be to investigate putting some dampening material on the knock sensors and surrounding areas to further reduce any phantom knock signals.

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1 minute ago, Mike said:

How have you been logging the IAM?

The car is ecutek tuned and I've got the dongle and app on my phone, with a custom dashboard setup.

The AIM is under 'Advanced Ignition' IIRC when setting up the widget.

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