Knock sensing flags

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UNISA JECS
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Knock sensing flags

Post by UNISA JECS » Mon Jul 28, 2008 7:51 am

I wanna see how many members that tune there own ECU's (Calum/Nistune etc) have to say about the subject, do any of you disable your knock sensing flags or modify them?

I ask this because after doing soem datalogging its quite easy to see that sometimes the ECU well retard timing sometimes (I really doubt that im am truely knocking) as low as 8* a WOT and soemtimes not as much or none at all within side the flaged portions, once out of this flaged portion timing continues as prescribed on the map.

I'd also like to point out that I do have knock sesning enabled..duh.

I also looked at factory turbo'd timing maps in reguards to there flaged portions vs there NA counter parts and the SR20DET only flags knock up to 3200rpm whereas the NA SR20DE flags up to 4850rpm.

The NA KA24DE (like theres a turbo one from the factory lol) flags knock up to 4800rpm.

Im starting to think maybe there is just more noise on a turbocharged vehicle with regaurd to monitoring knock successfully hence the lack of upper rpm knock sensing of the SR20DET and VG30DETT.
Screen shots:
S13 KA24DE
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S13 SR20DE
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S13 SR20DET
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Z32 VG30DE
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Z32 VG30DETT
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GZ@hybridka
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Re: Knock sensing flags

Post by GZ@hybridka » Mon Jul 28, 2008 12:16 pm

UNISA JECS wrote:
Im starting to think maybe there is just more noise on a turbocharged vehicle with regaurd to monitoring knock successfully hence the lack of upper rpm knock sensing of the SR20DET and VG30DETT.
Sounds like a plausible interpretation, I have a few patent references on the knock system, ill try dig them up and see if they shed any light.
Last edited by GZ@hybridka on Mon Jul 28, 2008 4:21 pm, edited 1 time in total.


PL
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Post by PL » Mon Jul 28, 2008 4:44 pm

This is a very interesting subject. Unfortunately the knock strategies seem to vary from engine to engine so each must be asessed individually.

I mainly play with SR's and the S13 DETs seem to be quite well behaved. I've always left knock sensing active. It's tempting to turn knock sensing on further up the RPM range so that it actually provides some sort of protection - instead of shutting its eyes as soon as boost comes up! But I've never had the time to give it a good try. It would certainly appear that they've disabled knock sensing at higher RPM due to mechanical noise causing false triggering.

Awhile ago I did an S15 and it was jumping to the knock maps all the time! And it was only running stock boost! Most annoying - and a real trap when tuning.

PL

UNISA JECS
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Post by UNISA JECS » Mon Jul 28, 2008 5:38 pm

Also I forgot to state that all 5 of the above mentioned engines use the same exact knock sensors. As a matter of fact plenty more do as well, these are USDM Nissan FAST screen shots but also the JDM Nissans use the same sensors I just haven't posted the JDM FAST screen shots:

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Matt
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Post by Matt » Mon Jul 28, 2008 7:26 pm

Just so you guys know... there is an auto knock map update feature now inside Nistune on the grid view windows for fuel/timing

If ticked it will update your knock map whilst you update the main map. (Do a knock copy first to set the initial values)

Sometimes people like to have the same contents on both maps so it isnt pulling timing whilst in the middle of tuning because it started running values in the knock maps

Those patents make for good bedtime reading, plenty in there. I'm interested how the SR20 knock detection works since I've not had any luck getting knocking reporting on the bench for these ECUs

Matt
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Post by Matt » Mon Jul 28, 2008 7:29 pm

Just so you guys know... there is an auto knock map update feature now inside Nistune on the grid view windows for fuel/timing

If ticked it will update your knock map whilst you update the main map. (Do a knock copy first to set the initial values)

Sometimes people like to have the same contents on both maps so it isnt pulling timing whilst in the middle of tuning because it started running values in the knock maps

Those patents make for good bedtime reading, plenty in there. I'm interested how the SR20 knock detection works since I've not had any luck getting knocking reporting on the bench for these ECUs

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