Misfire Counter
Discussion
Hi all,
Currently looking at a 718 GT4 and have had the results of the 111 inspection / overrev report.
There are 0 overrevs however there are two codes noted as:
M530_misfire counter total, cylinder 3: 4018
M550_misfire counter total, cylinder 5: 3522
Car is only a couple of years old and approx 3k miles. Can anybody shed light on the above and whether there is anything else which should be checked here?
Thanks
Currently looking at a 718 GT4 and have had the results of the 111 inspection / overrev report.
There are 0 overrevs however there are two codes noted as:
M530_misfire counter total, cylinder 3: 4018
M550_misfire counter total, cylinder 5: 3522
Car is only a couple of years old and approx 3k miles. Can anybody shed light on the above and whether there is anything else which should be checked here?
Thanks
The misfire counter for each cylinder is a cumulative figure that is added to each time the crankshaft speed drops below an adapted threshold.
The misfire counters need context - unless the car is genuinely 'misfiring' and a check light is on they cannot be used effectively on their own. If the figures are taken in combination with the total runtime of the engine they can be more useful; other factors like mixture adaption and cylinder specific rough-running figures add up to give a clearer picture of engine health.
An engine running at a continuous 3000rpm will see 1500 'ignitions' per cylinder per minute.
An hours worth of driving at the same engine speed, 90000 per cylinder.
A general rule of thumb with mileage/runtime is between 20/25 miles per hour of driving in the UK - so a 3k mile car will likely have been running for around 120-150hrs; potentially 11 million individual ignitions using the above example. 4000 misfires would be a miniscule number in this scenario.
It is not uncommon to see counters in the tens of thousands on perfectly happy engines with 2-3000hrs of runtime on them - the DME effectively micromanages the combustion using its available sensors and actuators and adapts over time. When the monitoring is so precise, it is nigh on impossible to have an engine completely free of misfires.
Worth mentioning, the misfire counters have no bearing on the Over-Rev figures - Over Revs are incidents over the engine speed limit, where the engine is forced over the set limit by selection of an incorrect gear at high speed for example; exclusively on manual transmission cars with regard to Porsche.
The misfire counters need context - unless the car is genuinely 'misfiring' and a check light is on they cannot be used effectively on their own. If the figures are taken in combination with the total runtime of the engine they can be more useful; other factors like mixture adaption and cylinder specific rough-running figures add up to give a clearer picture of engine health.
An engine running at a continuous 3000rpm will see 1500 'ignitions' per cylinder per minute.
An hours worth of driving at the same engine speed, 90000 per cylinder.
A general rule of thumb with mileage/runtime is between 20/25 miles per hour of driving in the UK - so a 3k mile car will likely have been running for around 120-150hrs; potentially 11 million individual ignitions using the above example. 4000 misfires would be a miniscule number in this scenario.
It is not uncommon to see counters in the tens of thousands on perfectly happy engines with 2-3000hrs of runtime on them - the DME effectively micromanages the combustion using its available sensors and actuators and adapts over time. When the monitoring is so precise, it is nigh on impossible to have an engine completely free of misfires.
Worth mentioning, the misfire counters have no bearing on the Over-Rev figures - Over Revs are incidents over the engine speed limit, where the engine is forced over the set limit by selection of an incorrect gear at high speed for example; exclusively on manual transmission cars with regard to Porsche.
Edited by Pope on Wednesday 24th August 23:41
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