Interestingly my VW's used to always pink - and I believed the dealers when they said it was ok - even after replacing knock sensors when I demanded they take action to fix the problem - but ever since I was converted to go Japanese, The Toyota and Honda have never pinked regardless of whether I use V power, Ultimate or a Supermarket petrol.
Come to think of it - even when I needed to change down a cog or two they never actually pinked.
Edited by Pendlebury on 05/10/2008 at 14:59
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Knock sensors are not the most reliable of items-hard to calibrate and can pick up vibrations in the engine from other than the combustion chamber-better to do a good ignition calibration in the first place than rely on the sensor as some manufacturers do.
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My 1.6 Focus used to 'pink' uphill under slight throttle, never did it in reverse though so must have been the gearbox ;)
My 1.8 Almera couldn't be made to pink for all the tea in Tesco's - Jap made in Vikingland (N.E.)
Dog.
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Where a car is built and where the calibration was done bear no relation to each other.
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I don't think cars ping as nearly much as they used to.. say 10 years ago.
My Dad's Fiat Tempra used to pink a lot whilst going up a certain hill near where we live.
Since then he's gone to automatics which hardly pink at all because they change down earlier then manuals.
My Ford Ka used to ping on that same hill, but didn't at all if I used Super Unleaded but did make a roaring sound if i was to push the throttle too much.
I've never heard my MG ZR ping ever!
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Typically, a knock control program will be consistently advancing the ignition beyond its open loop value. The default open loop advance value for a given set of engine operating conditions is always on the safe side, plus another margin of safety.
During driving, the ignition is advanced until the knock sensor detects knock, then, backed off, and then, slowly, advanced again. This process continues all the time.
So, if you've been driving with a light foot, the ignition will be well advanced (this used to be done by the vacuum advance unit on the distributor), and so, when you put your foot down, the engine will pink, just for a second, until the knock control has gone through enough retatd cycles to stop the pinking.
So, while you do hear momentary pinking, I haven't heard prolonged pinking for years.
Knock sensors do have a difficult job to do - Montegos, for example, could run really badly with no power because the knock sensor mistook an exhaust rattle for knocking, and so, retarded the timing fully! I've also come across an engine with worn valve gear being brought into the workshop with the engine management light on, holding knock sensor trouble codes in memory - oddly enough, no number of new knock sensors fitted by previous garages could fix the faults!
Added to the general problem of the ambient acoustic environment, is the problem that the sensors themselves produce only a tiny signal which is easily swamped by electrical interference, which, if it's in the ~4kHz frequency range, where knock is detected, the ECU cannot filter it out.
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What you say is true,if a car is fitted with a knock sensor,but as I said earlier,it can be hard to calibrate them and,as you say,they can be swamped by other vibrations in the engine.Because of these concerns,some vehicles are not fitted with sensors,and in these cases,the ignition calibration would be set to just below BLD(borderline det.) at WOT(or as you say,open loop).
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Fully agree jc2 - the thing I'm surprised about is that we haven't seen more use of the Saab Trionic system, where the spark plug electrodes are used as sensors when the plug isn't firing.
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