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Grant Baker

Subaru Knock settings

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Hi Guys.

Just about to install a P+P G4+ WRX 5/6 to a 2000 Subaru Impreza UK Turbo WRX.

Has anybody got any example knock settings for the stock knock sensor?

Specifically the Knock Frequency, Gain Channel etc?

Thanks in advance.

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Hi Grant, I don't have any experience with knock control on this engine myself, however our documentation says that a 6 kHz narrowband filter is the one to use up to until the version 7 WRX.

For most vehicles a gain of 1 or 2 works well.

Scott

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Grant I have a lot of experience with this particular engine. You will want to use 6 kHz as mentioned. In some cases 7 kHz. But you will get the level of feedback needed with a gain of 1. Adjusting per cylinder is needed as well. These engines tend to produce more noise on certain cylinders then others due to design and Knock sensor placement. So monitor this and adjust the cylinder gain accordingly. A typical threshold is set to somewhere around 570 for knock level. You will want to monitor this and adjust to your needs. Each engine differs with internals, fuel, and amount of ignition timing applied. 

Good luck and stay safe.

- Rich RDE

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Thank you Rich.

The Gain of 1 - is this in the Main settings you mean?

IE:

Knock Mode - Internal

Freq Channel - 6khz

Gain Channel - 1

Clear I-Trim

etc etc?

I found that with the recommended setting of 100 in the Gain channel that the noise was way too much and just revving the car at standstill produced a knock level of 700-800!!

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Any more to this? also having the exact same issue..

 

Used some of the settings mentioned in this post but it still counts knock when maybe cruising at 2500rpm, seems to definately hear bumps too. V1/2WRX stock knock sensor however.

 

 

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Hi Sancho,

If you are hearing knock and the ECU is confirming it then you likely need to reduce your ignition timing in your main ignition table in the areas where knock is occurring. You should be able to look at the 'Knk Ign Trim' tables and see where the knock is occurring.

Scott

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pretty sure it's because I've got knock threshold set to 0 lol :blink:

I really need some knock detection equipment, have been given some ideas of retarding the ignition table, log the knock noise, and going from there to establish a "base" knock noise reading, obviously not as good and as accurate as actual knock listening. 

 

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Hi Grant, I don't have any experience with knock control on this engine myself, however our documentation says that a 6 kHz narrowband filter is the one to use up to until the version 7 WRX.

For most vehicles a gain of 1 or 2 works well.

Scott

Dear Scott

 

Im working on a Forester EJ255 with bore size 99.50 mm, I read from the post above 6 khz narrow band Knock sensor for the EJ20 92 mm is a good choice, so considering that EJ255 has a bigger size, the same frecuency apply??? higher or lower would be a better fit, (considering everything else the same)?

The sensor is exactly the same, but considering that bore oversize, with way should I go?

Another idea, please confirm is it has sense..... Run 4000 rpm and change frequency so see if we get higher "counts" near any frequency range???? And then use the range that picket up higher values?

 

Regards

Alex Maroto

 

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Hi Alex,

The calculation to help determine the correct filter is:

Knock Resonant Frequency (Khz) = 1800/(3.14 * piston diameter in mm)

For you this is:

Knock Resonant Frequency (Khz) = 1800/(3.14 * 99.5)

Knock Resonant Frequency (Khz) = 5.76 kHz.

The closest frequency filter to this is 6 kHz, so I recommend trying this.

You could setup the knock control with a filter of 6 kHz, run a PCLog to check what the noise level is like over a range of engine speeds and loads. Then set the filter to something like 10 kHz and record another PCLog. You can then look at the 'Knk Level Cyl X' parameters to confirm that there is more engine noise present with the 6 kHz filter.

Scott.

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now I think I'm getting it figured out. So i set the frequency to 13Khz and a gain of 7. I've been running this map without knock control for a year on E85. I'm still learning alot so any feedback is much appreciated. Also the reason I didn't think it was working before was because with a gain of 1 it wasn't picking up anything. 

So do I need to setup the individual cylinder gains for #3 and #4 cylinder to bring them more inline with the rest.

image.thumb.png.254661008b202bd7adafbeb363b3c573.png

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The spike on Cyl 4 happens after you lift off so I wouldnt be worried about that too much (probably clutch/driveline backlash), you can use the TP delta lockout to ignore that.

I would probably bump the threshold up a little above 5000RPM or reduce the gain as that just looks like normal noise to me rather than knock.

 

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