Jump to content

v5 Impreza G4+ PnP Knock Control


Chris R
 Share

Recommended Posts

Hi, I'm struggling with setting up knock control on an the above.

I read the below from an old forum post but it doesn't make sense to me.

The version 5 may be wasted spark but it's sequential injection. It has a cam sensor and I'm pretty sure is capable of 720 sync. 

Why then can it seemingly not do individual cylinder knock control?

On my logs the background noise on cyl 1&2 are identical as are cyl3&4 but I can't figure out why?

While I can adjust gain settings for background noise from front of engine to closely match the rear two cyls up to 4500rpm, after that the traces diverge then re-converge toward the red line. No gain setting seem to see the two pairs of cylinders recording same background noise levels. I have confirmed with det cans it's not knocking.

I'm more used to dealing with individual cylinder thresholds so you don't need to worry so much about individual cylinder gain. 

image.thumb.png.bc5cb4be64dc9905c91123dee24c3257.png

Link to comment
Share on other sites

It was just the way the firmware in G4+ was written, the knock window was based on the ignition event.  So if you have a distributor with only one ignition drive used for all cylinders, then you can only monitor knock as a single group and if knock is detected you can only apply retard to all cylinders.  Similarly with wasted spark you have the same ignition event on a pair of cylinders, so you can only monitor knock on those cylinders as a group and you can only retard the cylinders as a pair.  

Link to comment
Share on other sites

Thanks for that.

So should I set Cyl 2 Allocation to Cyl 1 ITrim Table and Cly 4 Allocation to Cyl 3 ITrim Table? Or is it OK to leave each respective allocation?

Also I'm struggling a bit to know whether I should be using centre frequency (6.2kHz) or second harmonic with the standard knock sensor on a 1999 WRX?

I *think* (but haven't checked) the 1998+ sensor is 2 wire. Does this mean it's wide band?

The problem I see with this is presumably cyl3&4 gain controls don't work independently? If cyl3 is overall quieter (being it's the other side of the block from the sensor) than cyl4 then the margin to threshold will be greater on cyl3? 

Lastly, should this statement concern me?

image.thumb.png.04bead08a03dcf7d61543aa55a543215.png

Link to comment
Share on other sites

9 hours ago, Chris R said:

So should I set Cyl 2 Allocation to Cyl 1 ITrim Table and Cly 4 Allocation to Cyl 3 ITrim Table?

Yes.

 

9 hours ago, Chris R said:

Also I'm struggling a bit to know whether I should be using centre frequency (6.2kHz) or second harmonic with the standard knock sensor on a 1999 WRX?

On our EJ207 8KHz works the best.  I havent and personal experience with the earlier ones.  

 

9 hours ago, Chris R said:

I *think* (but haven't checked) the 1998+ sensor is 2 wire. Does this mean it's wide band?

There are exceptions but 2 wire japanese knock sensors are generally wideband.  

 

9 hours ago, Chris R said:

The problem I see with this is presumably cyl3&4 gain controls don't work independently? If cyl3 is overall quieter (being it's the other side of the block from the sensor) than cyl4 then the margin to threshold will be greater on cyl3? 

Possibly, I havent heard of anyone having issues getting acceptable knock control on the early WRX's though.  

 

10 hours ago, Chris R said:

Lastly, should this statement concern me?

Not if you have a G4+. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...