Knock Control
Knock Control
Can someone explain the knock control strategy of S6? I believe it basically retards the ignition and CEL on. What is the maximum value that we can regard as knock with 92 mm pistons?
Re: Knock Control
The golden question, you'll need a dyno and some careful testing to make sure that the S6 is not only identifying real knock when it matters, but also not mis-identifying other engine noises as knock and roasting your exhaust valves unnecessarily. It took me about 2hrs solid dyno running to get the detection adequately set and tested on the Lotus we built.
Re: Knock Control
Pat is very experienced on EJ series engines so he may have some inputs.
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pat
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Re: Knock Control
The S6 knock detection is ratiometric, ie what is the current spectral energy compared to the average. There is no "normal" value as such, but you can run the engine with retarded timing to ensure there is definitely no knock, then you will see what is normal for your engine. The will give you a baseline, and will represent roughly what knockBase you should end up with. Then, you can ramp in the timing until you get trace knock, compare these values with those that are the baseline to setup the Event Detection Level (which is normally set at about 1.5*knockBase, ie if the background level is 30 then the ECU will look up the threshold at a knockBase of 30, will find that any value 45 or greater is a knock, so if you get one reading of 47 it will be detected as knock, whereas 35 would not. Of course this is just a "get you going" set of values, and you'll need to check with your own engine, you may find that with a knockBase of 30 piston and valve noise could give spikes of 50 which are not knock, or you may find that even 40 is slight knock.
You need to set your knock filter frequency to 6.12kHz for 92mm pistons, that seems to be the best match. You will probably find that cylinder 2 and 4 will generate phantom knock before others do, so it's not unusual to see higher event detection levels on 2 and 4... if it is real knock then you can put in a per cylinder ignition correction, and perhaps also a little fuel, just remember to set the per cylinder correction enable threshold lower than 100% throttle under Breakpoints and Thresholds, otherwise they won't get applied!
Hope this helps,
Pat.
You need to set your knock filter frequency to 6.12kHz for 92mm pistons, that seems to be the best match. You will probably find that cylinder 2 and 4 will generate phantom knock before others do, so it's not unusual to see higher event detection levels on 2 and 4... if it is real knock then you can put in a per cylinder ignition correction, and perhaps also a little fuel, just remember to set the per cylinder correction enable threshold lower than 100% throttle under Breakpoints and Thresholds, otherwise they won't get applied!
Hope this helps,
Pat.