Knocklink, detonation and boost questions...
06 April 2003, 11:09 PM
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I understand that the knocklink will indicate when the engine is experiencing detonation.
I lit up the amber lights in second gear over the weekend, probably as I over revved the engine, also did it again when I missed a gear change. That was the only times.
Is this an incorrect reading caused by an over-stressed engine.
The car never lights up when coming on full boost in fourth or fifth.
My car is a STI Series 2, running on Optimax and millers. After fitting a boost gauage, the boost seems to peak at 20 PSI, isn't that a bit high, I would have thought I would get fuel cut off by then?
What is detonation, and how does bad fuel cause it? I thought detonation was the fuel igniting before TDC...
I lit up the amber lights in second gear over the weekend, probably as I over revved the engine, also did it again when I missed a gear change. That was the only times.
Is this an incorrect reading caused by an over-stressed engine.
The car never lights up when coming on full boost in fourth or fifth.
My car is a STI Series 2, running on Optimax and millers. After fitting a boost gauage, the boost seems to peak at 20 PSI, isn't that a bit high, I would have thought I would get fuel cut off by then?
What is detonation, and how does bad fuel cause it? I thought detonation was the fuel igniting before TDC...
07 April 2003, 12:48 AM
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Could well be a one-off event.
IMHO "The Knocklink" is a relatively simplistic circuit - it uses a simple wideband passive filter - thus any very loud noise - outside the generic knock frequency of 1-12khz or the specific resonant knock frequency of subaru imprezas 6-7k could trigger it.
With regard to your boost - I am surprised it can run that high - the standard MAP Sensor cannot handle it - I wouldn't be surprised if you found that you had a fuel cut "Remover" fitted - either that or a very good ECU & Map Sensor Upgrade - personally I think the former is more likely.
As to what detontion is I hope this helps:
Happy to help,
Chris
IMHO "The Knocklink" is a relatively simplistic circuit - it uses a simple wideband passive filter - thus any very loud noise - outside the generic knock frequency of 1-12khz or the specific resonant knock frequency of subaru imprezas 6-7k could trigger it.
With regard to your boost - I am surprised it can run that high - the standard MAP Sensor cannot handle it - I wouldn't be surprised if you found that you had a fuel cut "Remover" fitted - either that or a very good ECU & Map Sensor Upgrade - personally I think the former is more likely.
As to what detontion is I hope this helps:
“Detonation”, also known as “Knock” – “Pre-Ignition” – “Pinking” – is an abnormal combustion event in the engine, identifiable by its characteristic sound.
Engine detonation occurs when the air/fuel mix ignites within the combustion chamber in an uncontrolled manner, instead of by the progressive action of a moving flame front. Detonation produces sharp pressure pulses, if allowed to go on for more than a few seconds, these very sudden pressure changes within the cylinder can damage the engine. In a worse case scenario, pistons, rings and even the head itself can suffer major damage.
Note also that the higher the specific power output of the engine (i.e. hp per litre), the greater the likelihood of damage if detonation occurs.
Engine detonation occurs when the air/fuel mix ignites within the combustion chamber in an uncontrolled manner, instead of by the progressive action of a moving flame front. Detonation produces sharp pressure pulses, if allowed to go on for more than a few seconds, these very sudden pressure changes within the cylinder can damage the engine. In a worse case scenario, pistons, rings and even the head itself can suffer major damage.
Note also that the higher the specific power output of the engine (i.e. hp per litre), the greater the likelihood of damage if detonation occurs.
Chris
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