Engine Pinging (Manual)

  • Thread starter fyfee
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fyfee

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Now, when I drive my grandpa's 2003 Holden Astra Convertible, I like to be in the right gear in all situations...pretty obviously. The engine never makes a 'ping' noise when I drive. Ever

However, when my grandpa drives, around corners he tends to be in the wrong gear...3rd gear at about 20km/h. Clearly it's the wrong gear for that speed, but everytime that happens, the engine pings.

I believed that it had something to do with the transmission because of when it happens. I asked a mechanic I know about it and he said the engine pings because it's firing too early i.e before TDC.

Is this right? I trust him to know because well, he's a mechanic, but I wondered if thats the exact reason it 'pings'?
 
fyfee
Now, when I drive my grandpa's 2003 Holden Astra Convertible, I like to be in the right gear in all situations...pretty obviously. The engine never makes a 'ping' noise when I drive. Ever

However, when my grandpa drives, around corners he tends to be in the wrong gear...3rd gear at about 20km/h. Clearly it's the wrong gear for that speed, but everytime that happens, the engine pings.

I believed that it had something to do with the transmission because of when it happens. I asked a mechanic I know about it and he said the engine pings because it's firing too early i.e before TDC.

Is this right? I trust him to know because well, he's a mechanic, but I wondered if thats the exact reason it 'pings'?
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The engine is tuned correctly and is normal, ignition will pretty much always fire BTDC (and adjust itself depending on engine speed/load and pinging) and even at idle speeds the ignition is already well BTDC. When your grandpa puts his foot down to gain speed in the wrong gear he is loading up the engine heavily at low engine speed, the ignition will start to advance (fire even earlier) for faster engine speeds as it should, this load and ignition advance increases combustion temperatures causing the ping, but is normal as the engine is not tuned to run in that manner (ECU ignition profile/cam profile etc).

The fact is the engine is not tuned for low RPM loads like that. That sort of driving should be avoided but I wouldn't worry about it too much unless it is often and excessive, then you should have a word to your grandpa.
 
He can use higher octane gas, which does not ignite as easily, to help lessen the preignition. However, this is treating the symptom, not the cause. As mentioned in the first reply, the real issue is loading the engine heavily at low RPM. Without the shorter ratio of a lower gear, the engine is really lugging to climb up the power curve in a higher gear.
 

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