explain pinging

[NOZILR]

could some 1 explain what pinging is and what to look out for

[DoughBoy]

Pre- Ignition. When your air/fuel mixture ignites before the spark goes off.

[DoughBoy]

Heh copied from http://www.allfordmustangs.com/Detailed/60.shtml

KNOCK, DETONATION OR PING

This is an intense pressure wave within the cylinder created when a LEAN mix of air and fuel ignites before the spark is delivered.The fuel/air mixture goes off by itself a micro second before the spark plug fires, at that time you have two intense high pressure waves clapping together and that energy wave hitting each other is the sound you hear. The sound you hear is from the actual vibration of the cylinder wall

Under normal circumstances, when the fuel-air mixture in the engine burns, it does so in a controlled manner, releasing the energy that produces the force that drives the pistons. Now, if you think about it, it might seem that the correct time for the spark plug to ignite the mix would be when the piston reaches the top of its stroke. Then, as the mix burns and energy is released, the energy pushes the piston down. The problem is that it takes a certain amount of time for the mix to burn. If you wait until the top of the stroke to ignite it, the bulk of the energy will be applied to the piston only during the latter part of its downward movement.

In order to get the maximum use out of the combustion energy, the mix is ignited while the piston is still moving up. This is called "advance". As the engine speed increases, fuel has less time to burn and advance is increased accordingly. Ignition advance is controlled by the engine management computer. It varies in response to a host of other conditions but the base advance curve is a function of engine speed.

Now we have a new problem. As the mix is ignited earlier, it is not compressed as much and has a tendency to burn at an uncontrolled extremely high rate (it basically explodes). This is called "detonation". When this happens, all the energy in the fuel is released almost instantly. The resulting shock wave slams into the piston which is forced through it by the inertia of the engine and the combustion in other cylinders . The resulting stress on the engine is enormous.

Detonation can be caused by several things not just a lean condition or bad choice of fuel octane: Too much compression and too much timing can also be to blame.

The most common way to describe the sound of detonation is: "like shaking a can full of marbles", but the BEST way to verify the existence of detonation is by reading the sparkplug's. If the plugs are very white, show a very eroded electrode and signs of metal deposits, then you have DETONATION.

The Cure: Less timing and/or higher octane gas and/or colder plugs.

Higher octane gas is a good safety measure. Is the $.10 per gallon worth that extra risk? Another myth about octane is that higher octane produces more power, wrong. Higher octane fuel is less volatile, less explosive, less prone to detonation.

A more 'volatile' fuel actually produces more energy per unit volume.You just have to watch out for detonation more. That's why higher compression engines use higher octane fuel, higher compression ratio (and higher altitude, lower air pressure) increases the tendency for detonation. Run super unleaded, but don't expect to gain power from the more expensive fuel. You CAN get more power, but it's from running more compression and spark advance.

PRE-IGNITION

This is premature ignition before the spark plug fires, usually caused by something glowing inside the cylinder such as carbon deposits or too hot a sparkplug tip. Do not confuse this with detonation. It is not the same.

Usually pre-ignition occurs when there are lots of "red hot" carbon deposits and unburned fuel in the combustion chambers.

If you turn of the ignition and your stang wants to keep on running, then you have pre-ignition.

The Cure: Eliminate carbon deposits and/or colder plugs, check fuel system.

[Steve]

Pinging, or detonation, is when the air fuel mix spontaneously explodes before the flame front started by the spark plug.

Several things can cause pinging, lean air/fuel mixtures, too much timing, excessive heat (eg, raised inlet temperatures from poor intercooling or hot days), poor fuel supply.....

You can hear pinging, but in general if you want to avoid it, make sure you use good fuel, dont use excessive boost or boost hard on hot days, or if you have been sitting in traffic for a while (heat soak in intercooler), dont overload the car in too high a gear (eg, going up hill in too low a gear), get your plugs changed regularly, and change your fuel filter when it is scheduled, dont advance the intitial (base) timing. and lastly, get your car on a dyno, just to do a power run and check the air/fuel ratios.

Remeber, the more mods you do, the more you need to be aware of the potential for detonation - just keep the tune conservative, ie dont try and wring every last pony out of your car, and drive sensibly and you 'shouldnt' have any problems

[EnricoPalazzo]

Ive just re installed my stock ecu from an aftermarket ecu, and under WOT, im sometimes gettin a rattling sound coming from the left side of the engine ..(if looking from the front of the car). This rattling is quite loud and has me thinking its detonation for some reason. Would this be happenin with a stock ecu? I will check the plugs for lean conditions aswell as check base timing as it may be advance to much.

[Steve]

rattling? injectors?

[R31Nismoid]

it could be a loose exhaust or something?

strut tops... do you have aftermarket ones?

[EnricoPalazzo]

Yeh i do. I will check, but yeh its a loud rattling sound, im not sure what pinging sounds like thou. It only happens sometimes, and only at WOT. if i accelerate at 70% it doesnt do it. On the plus side the car is running nicely on the stock ECU finally. No boost cuts so far.

[R31Nismoid]

If you've got aftermarket tops then it's just them.

Mine do it, becuase when you replace the stock items (with lots of rubber around them)

Aftermarket ones dont have any rubber at all and make heaps of noise.

My rears are make more noise than my fronts though.

[EnricoPalazzo]

Hmm why is it only doin this now. I dont think it would be the struts then.....

I wish i could properly explain the sound. Ill have to check under the bonnet tomorrow to see if anythin is loose.