Ok I have been reading over and over these chip wars thread and so on. SO my ? aer if I can get a striaght answer.
1. What is a ping/detination?
2. What is a Audible Ping?
3. Why dose the truck ping?
4. Why dose it Ping AUDIBLY?
5. This can not abovisly be good so what is it exactly doing to the motor?

Thanks

 

WEll thats some good info to know, anyone want to share with the class.

 

Detonation, or ping, is caused when the air-fuel mixture burns prematurely in the cylinder.

On the compression stroke, the spark plug fires just before the piston gets to the top of its travel (or top dead center). How far before top dead center the plug fires is determined by the timing.

If the fuel/air charge burns too rapidly, or if the timing is too advanced, the power of the charge is exterted on the piston before it starts its power stroke. This is detonation.

It is rough on the pistons and connecting rods, because it applys a downforce when the piston is still moving up.

That is why higher octane gas is needed for engines with more advanced timing, Higher octane gas burns -more slowly- than lower octane gasoline.

If the engine pings even w/ high octane gas, you have to retard the timing to compensate.

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Regards,
Gordon

'99 Red Lightning

 

Ok this is just my opinion:

1. What is a Ping/Detonation?
Knock/Ping/Detonation occurs when the combustion starts in a mass of the air/fuel mixture before the flame front reaches that mass of the air/fuel mixture. Keep in mind that I did not say ignition, because there is a time delay between ignition and combustion, this time delay is called ignition delay. Also note that the ECC or distributor (We) has control of the ignition (Spark) not the combustion. Many things can contribute to this; I will cover most in question 3.

2. What is Audible Ping?
I would describe Audible Ping as detonation that the human ear is able to hear. With the advent of Knock sensors, in most cases Audible Ping is nearly unheard of. It is not uncommon for to have inaudible Detonation/Ping in an engine, which is taken care of by your knock sensors, they alert the ECC of the situation and the ECC pulls enough timing and/or add enough fuel to calm the detonation.

3. Why does the Truck Ping?
A Ping/detonation can be cause by a lot of factors the main ones are:
Fuels anti-knock index
Charge Temperature (Temp of the air/fuel mixture)
Charge Density
Charge Pressure
Turbulence
Swirl (Swirl of Air Fuel mixture)
Presence of inert gases
Air / Fuel Ratio
Presence of “hot spots”

Now you are likely wondering why I have not mention Spark advance?
Because Spark Advance doesn’t cause Ping.
What, how can you say that?
Lets go back to ignition delay concept and spark advance. I defined the ignition delay as the amount of time it took from ignition to combustion, right? Well that ignition delay can be translated to angles of crank position at a certain speed (RPM). Knowing this we could ignite (with a spark plug) the Air/Fuel mixture such that its combustion pressure in the cylinder and hence the piston would be a smooth and have its peak at TDC of the combustion stroke. Spark advance is the firing of the spark plug before TDC in terms of crank angle. If we set our spark advance more than our ignition delay, you will experience detonation. This happens because the flame front as it travels, it will increase cylinder temperature and pressure and hence will increase the temperature and pressure of unburned gases above Self-ignition temperature, and the gases will burn be the flame front reaches them.. To avoid Knock, it must insured that the flame front travels through and burns all gases (unburned fuel/air) that have been raised to or above self-ignition temperatures, before they Self ignite or predetonation. Recall my claim that we did not have control of the combustion, but we did of the ignition. This control is spark advance.
In all likelihood, if you’ve read this far, you will be interested in how Air/Fuel and Octane fit in?
Well when you go to a higher air/fuel ratio (less fuel, called lean it out) you can achieve a higher flame front speed and temperature. From this rapid temperature change a very rapid pressure change will occur. This rapid temperature and pressure change will push the end gases above self-ignition temp before the flame front can reach the end gases, resulting in knock. As you know Octane refers to the knock resistively of a fuel, the higher the octane the more knock resistively. We loosely defined Knock as preignition or self-ignition, so we can say that octane is the resistively of a fuel to preignite. An increase in this resistively allows you to increase end gas temperature and pressure while not preigniting, equaling more power.

4. Why does it ping audibly?
I believe it pings audibly because enough energy is being released to produce enough “noise” for you to here it. A “light” knock would most likely not be heard. A “heavy” knock would likely be heard. If you hear it Knocking, assume you have a heavy knock and seek help ASAP.

5. This cannot obviously be good so what is it exactly doing to the motor?
The “knock” is generating High-pressure pulses that can damage engine components. These many include, but are not limited to Head Gaskets, Pistons, connecting rods and cranks. Additional when this knock is present with a vehicle running “too lean” the combinations of these high-pressure pulses and the elevated temperatures can more easily push holes thru pistons, often refered to as melting pistons.

This is a work inprogress, so I will/should update and add more detai to it when I'm not Insomniac man, and have fresh eyes and a head.
Steven

P.S. Bad dog gave a Pretty good Description.

 

Thanks for bring me to school on the subject. Good job

 

SilverBullet, I have noticed over time that Board members have commented that the Lightnings run on the rich side fuel-wise. I was wondering if you knew this was true? And, if so, why would this specified? To compensate for the supercharger? I would assume that running rich would not help gas mileage.

By the way, I like your explanation. I think I might have actually understood some of it.

 

Actually,i thought Bad dog was alot easier to understand.BUT!!<If I ever want a REAL sophisticated explanation of detonation,I will definatly call silver bullet! LOLGood job to the both of ya

 

Actually my explanation was wrong, in that I neglected the part about pre-combustion caused by pressure and heat, as well as the spark. That's the same phenomenon that causes dieseling after you shut a car off.

Between Silver Bullet and me, we could come up with something that was both readable AND technically correct.