The initial ignition timing can be set using T4 for different markets so in the US the startup timing should be spot on unless someone forgot to set it for the correct market?? Once the engine is running I believe the knock sensors take over so keeping the ignition timing rite on detonation but it would have to detect the onset of detonation to retard the timing so I see your thinking
is the KV6 known for failure in the US? They fail here too. Normally HGF but it's often caused by the cooling system loosing coolant so dropping in level which then air locks and cooks the gaskets!!
Hi Nodge!
This is from the LRNA Freelander Technical Training book put out for dealers and techs; "During combustion knock, the frequency of (piezo-electric knock sensor) crystal oscillation increases, which alters the signal output to the ECM. The ECM compares the signal to known signal profiles in it's memory. If the onset of combustion knock is detected, the ECM retards the ignition timing for a number of cycles. When the combustion knock stops, the ignition timing is gradually advanced to the original setting."
And also; "If the knock sensor inputs indicate the onset of combustion knock, the ECM retards the the ignition timing for that particular cylinder by 3 degrees. If the combustion knock indication continues, the ECM further retards the ignition timing in decrements of 3 degrees, for a maximum of 15 degrees from where the onset of combustion knock was first sensed. When the combustion knock indication stops, the ECM restores the original ignition timing in increments of .75 degrees."
A few point related to this that I'm thinking about;
1. The ECM memory 'decides' if it's knock based on past history, either related to initial programming or previous operation.
- there's a lag as the ECM builds memory
- there's a lag as it responds
- the impetus is always to advance timing up to the knock point
2. US models are spec'ed OK by LR at 87 octane in the manual (approx. 91 UK), so;
- I'd assume that this is the initial ECM setting
- spark retards up to 15 degrees, but doesn't have an advance function
- fuel economy and running do actually improve- at least up to
91 US octane (94 UK), leading me to think that operation on 87
is a retarded condition of continually borderline knocking, with the ECM
constantly attempting to advance the timing. Pretty hot running...
...Big troubles with the KV6 here- yes overheating is causitive to complete failure, but the causes for overheating are generally coolant loss due to mechanical failure- liners and gaskets, as well as leaking heater cores brought about by over pressure situations caused by same. I'm thinking that detonation vibration and forces may be the underlying factor linking all of the above. Interesting to speculate on...
In researching other vehicles (to possibly replace the Hippo), I've been genuinely shocked to see how fragile modern engines are- mostly cooling and HGF! Maybe we're pushing them too hard...
(My other 'truck' is an '86 VW Golf NA diesel- no turbos for me
)
Scott
