What is engine knock (or ping)?
Discussion
its the explosion happening before the piston gets to the top of travel, so the explosion hits the top fighting the travel of the piston before assisting its travel down the bore.
this creats a pink (sounds like a spanner loose in the cylinder...a rattle)
>> Edited by Guillotine on Tuesday 15th February 19:37
this creats a pink (sounds like a spanner loose in the cylinder...a rattle)
>> Edited by Guillotine on Tuesday 15th February 19:37
Engine knock is when 2 flame fronts start at opposite sides of the cylinder. When the 2 shock waves hit each other you get Knock (detonation or pre-ignition). Most modern vehicles have knock sensors to automatically retard the timing through the P.C.M when this occurs. Ping is a lesser version of knock.
And a "knock" can be caused by worn internal engine parts usaully crank or connecting rod bearings.
Trooper2
And a "knock" can be caused by worn internal engine parts usaully crank or connecting rod bearings.
Trooper2
Knock/detonation/pinking are different terms for the same thing, which is an explosion inside the combustion chamber rather than a smooth progressive combustion. It sounds just like somebody hitting the side of your engine with a hammer. It's very destructive and can cause the piston to break up. There are various potential causes but the most likely are the fuel octane rating too low, mixture too lean, excessive ignition advance, compression ratio to high, hot spots inside the combustion chamber or air intake temperature too high. Usually it's a combination of factors rather than any one thing. High performance engines are usually close to detonation under some conditions, and it only takes a little change to make the engine knock. So for example it might do it on a particularly hot day, or when you use cheap low octane fuel.
The term 'knock' is also used to describe mechnical noise from worn bearings.
The term 'knock' is also used to describe mechnical noise from worn bearings.
Perhaps too technical, but anyway:
There is low and high speed pinking (knocking in tech-term). Low speed knock can be heared as a loose spanner under the bonnet. And can be provoked/tested by high gear, low revs and full throttle. High speed knock cannot be heard (due to engine/wind/other noise), and will cause major damage in no time, but is very rare. Both are caused by not even/proper detonation in the cilinder (incorrect fire-front) as stated before, due to low octane/high compression, etc.. Ok, will stop now.
Rob
There is low and high speed pinking (knocking in tech-term). Low speed knock can be heared as a loose spanner under the bonnet. And can be provoked/tested by high gear, low revs and full throttle. High speed knock cannot be heard (due to engine/wind/other noise), and will cause major damage in no time, but is very rare. Both are caused by not even/proper detonation in the cilinder (incorrect fire-front) as stated before, due to low octane/high compression, etc.. Ok, will stop now.
Rob
Perhaps too technical, but anyway:
There is low and high speed pinking (knocking in tech-term). Low speed knock can be heared as a loose spanner under the bonnet. And can be provoked/tested by high gear, low revs and full throttle. High speed knock cannot be heard (due to engine/wind/other noise), and will cause major damage in no time, but is very rare. Both are caused by not even/proper detonation in the cilinder (incorrect fire-front) as stated before, due to low octane/high compression, etc.. Ok, will stop now.
Rob
There is low and high speed pinking (knocking in tech-term). Low speed knock can be heared as a loose spanner under the bonnet. And can be provoked/tested by high gear, low revs and full throttle. High speed knock cannot be heard (due to engine/wind/other noise), and will cause major damage in no time, but is very rare. Both are caused by not even/proper detonation in the cilinder (incorrect fire-front) as stated before, due to low octane/high compression, etc.. Ok, will stop now.
Rob
The only thing you need to know is that knock, ping, pinking (call it what you will) is very very bad which means very very expensive. As soon as you get the slightest hint that your large capacity high power engine is doing any of these things you need to get a proper fix. The symptoms don't sound like much but the long term (not that long!) impact can be devastating to both engine and wallet. If possible, retard the timing temporarily until you can get everything properly set up. Better a bit of excess fuel consumption and power loss than a full engine rebuild.
Hire cars can be prone to ping when you give them a good thrashing but if the ping becomes a rattle it's time to lift off!
On my rv8 it used to sound like rustling leaves down the headers. The only time I ever got knock was taking a 90 degree corner at about 20 mph in 4th or 5th. I heard a man in the sump with a sledgehammer bashing the sides of the block. I could almost count the strokes!
Pre-ignition (pinking) can lead to detonation (knock) if unchecked.
Boosted.
On my rv8 it used to sound like rustling leaves down the headers. The only time I ever got knock was taking a 90 degree corner at about 20 mph in 4th or 5th. I heard a man in the sump with a sledgehammer bashing the sides of the block. I could almost count the strokes!
Pre-ignition (pinking) can lead to detonation (knock) if unchecked.
Boosted.
Koncking and Pinking are detonation of unburt fuel/fuel leftovers that do not have enough of an octane rating to remain intact under compression, after the spark and combustion has occurred. Some engine actually run with slight detonation. It is indicated by a spike in the chamber pressure after combustion. An engine can run for quite a while with mild detonation. But it is anbnoying. Indications are pitted pistons and scuffed edges. Evenbtually this can lead to possible cracked/broken rings.
What people get it confused with is preigniton. This is very bad and where the fuel ignites, before the spark. If this occurs then the engine will probably only last a few miles. May bad things can happen with this such as cracked heads, damaged pistons etc.
What people get it confused with is preigniton. This is very bad and where the fuel ignites, before the spark. If this occurs then the engine will probably only last a few miles. May bad things can happen with this such as cracked heads, damaged pistons etc.
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