I am gradually warming to the idea of the SAFCII knock function.
The manual says it picks up some but not all dangerous knock. That being said I am finding it is pretty capable and thought I would share this experience from when my car was running lean ( approx 16.33afr at 2800 ) and I had a little play.
Idle @900-1000 rpm - I heard audible knock due to engine being a bit old and when I tune out the engine noise the safcII knock level goes down. 15 down to 9 approx.
Sustained knock ( preignition ) @2500rpm 50 approx. - The other day I went up a medium incline after being in traffic with hot idle. Put my foot down firmly going up hill suddenly the engine stopped momenterily Safcii showed wide knock. I was in line trace mode instead of the usual spike it showed a square box at 20 to 50 high which was broad enough on the time scale to stop the engine. I think I had put a lot of fuel in so when it ignited it was over a longer time period.
Lift off knock
Boosting up a steep hill lift of throttle after 10 secs boost around 5-10 psi just after lift off.
Knock reading spikes to 24 at 2560 rpm. Normally on this hill I show 0 knock at any boost.
The car was slowing and did not seem to stumble.
Knock at speed ( 100-110 kph)
Intermittant knock occuring here 44@2560 in OD up hill accelerating with no noticable engine stumble.
Knock pulled timing
Boosting up steep hill 5psi approx 2nd gear 33@2695 35@2800 car noticibly sluggish.
Zero knock on steep hill
End afr testing.
Adjusted fueling to from 16.33 to 13.61 afr approx @ 2800 rpm which is still a little lean as recommended is 12.4 afr for boost.
For reference Safc base setting info -
This knock Ive found was with base setting of 150 at 20degC 98ron fuel FMI - Testing done around 15C ambient except for idle. Manual ECU auto gearbox.
Conclusion:
Different screen settings are needed to show different knock conditions.
Using the knock screen setting and digital rpm monitor that remembers the max knock value is good so you dont have to watch all the time and this seems to be the most sensitive. I find some times the trace will change and the digital will show same sometimes the reverse will happen so they seem to be doing different jobs.
From forums -
The temperature at which you set the safcII can effect knock levels and therefore the base setting.
( Not letting the safcii unit get hot is also essential )
Forums say apexi says below 60 knock is OK
Some forums say below 50 Is OK
My experience showed if you have a problem like heat from a lean engine causing pre ignition you can noticably stall with around 50 knock when accelerating up hill.
44 knock at speed did not seem to be a problem , I recall seeing 95 flash at speed with no noticable issue.
Using the max value and the trace value together can help to see when revs drop if there is major knock involved. Above I have tested lean at low and medium revs but I am not so keen to do this at higher revs so I hope that helps and would be interested in others experiences with knock.
The manual says it picks up some but not all dangerous knock. That being said I am finding it is pretty capable and thought I would share this experience from when my car was running lean ( approx 16.33afr at 2800 ) and I had a little play.
Idle @900-1000 rpm - I heard audible knock due to engine being a bit old and when I tune out the engine noise the safcII knock level goes down. 15 down to 9 approx.
Sustained knock ( preignition ) @2500rpm 50 approx. - The other day I went up a medium incline after being in traffic with hot idle. Put my foot down firmly going up hill suddenly the engine stopped momenterily Safcii showed wide knock. I was in line trace mode instead of the usual spike it showed a square box at 20 to 50 high which was broad enough on the time scale to stop the engine. I think I had put a lot of fuel in so when it ignited it was over a longer time period.
Lift off knock
Boosting up a steep hill lift of throttle after 10 secs boost around 5-10 psi just after lift off.
Knock reading spikes to 24 at 2560 rpm. Normally on this hill I show 0 knock at any boost.
The car was slowing and did not seem to stumble.
Knock at speed ( 100-110 kph)
Intermittant knock occuring here 44@2560 in OD up hill accelerating with no noticable engine stumble.
Knock pulled timing
Boosting up steep hill 5psi approx 2nd gear 33@2695 35@2800 car noticibly sluggish.
Zero knock on steep hill
End afr testing.
Adjusted fueling to from 16.33 to 13.61 afr approx @ 2800 rpm which is still a little lean as recommended is 12.4 afr for boost.
For reference Safc base setting info -
This knock Ive found was with base setting of 150 at 20degC 98ron fuel FMI - Testing done around 15C ambient except for idle. Manual ECU auto gearbox.
Conclusion:
Different screen settings are needed to show different knock conditions.
Using the knock screen setting and digital rpm monitor that remembers the max knock value is good so you dont have to watch all the time and this seems to be the most sensitive. I find some times the trace will change and the digital will show same sometimes the reverse will happen so they seem to be doing different jobs.
From forums -
The temperature at which you set the safcII can effect knock levels and therefore the base setting.
( Not letting the safcii unit get hot is also essential )
Forums say apexi says below 60 knock is OK
Some forums say below 50 Is OK
My experience showed if you have a problem like heat from a lean engine causing pre ignition you can noticably stall with around 50 knock when accelerating up hill.
44 knock at speed did not seem to be a problem , I recall seeing 95 flash at speed with no noticable issue.
Using the max value and the trace value together can help to see when revs drop if there is major knock involved. Above I have tested lean at low and medium revs but I am not so keen to do this at higher revs so I hope that helps and would be interested in others experiences with knock.
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