Re: [ST] General thoughts on ping

[John Ulizzi <jaulizzi@xxxxxxxxxxxxx>]

Carbon build up? In one of your motors ? Yea ,
right...

:-)

--- Jonathan West <triumphnutter@xxxxxxxxx> wrote:

> So, I don't know who originally posted the original
> "ping" thread but here's my
> thoughts on it.  Sorry it's late, I'm just getting
> caught up from the holiday
> weekend.
> 
> Ping=pinking=kock and ping=detonation.  It's all the
> same thing.  It can be
> catastrophic to an engine if ignored.  It can warp
> pistons, damage valves,
> destroy rings... any number of really bad things. 
> It literally hammers the
> combustion chamber when it happens.  It is nothing
> more than part of the
> fuel/air mixture exploding prematurely due to a
> number of different causes. 
> Essentially, the fuel air mixture is ignited by the
> spark, and the resultant
> flame travel and gas expansion compresses the rest
> of the mixture to the point
> that it detonates prematurely before the flame
> travel can consume it.  It's
> like two different explosions, and the combination
> of the two is way more than
> the parts were ever meant to handle.  The poor
> timing of the second explosion
> is counterproductive to the mechanical efficiency of
> the power stroke.  It can
> be catastrophic.   
> 
> How do you eliminate it?  There are a number of
> factors that affect it.  
> 1) Detonation thrives in high temperatures.  Try to
> avoid heavy throttle in
> slow moving traffic where the engine temps might be
> higher.  Also, full
> throttle at low rpm increases the combustion chamber
> pressures moreso than full
> throttle at high rpm, so know that you are inviting
> detonation by doing this in
> an engine that is susceptible to it.  
> 2) High Octane fuel helps quell it due to the slower
> burn rate.  The slower
> burn rate helps mimimize the compression of the
> unburnt fuel so it does not
> ignite prematurely.  That's why the best octane fuel
> is the lowest octane you
> can run without detonation.  
> 3) Retard the ignition timing.  Starts the whole
> ignition process later in the
> stroke giving it less chance of detonating due to
> lower compression speed. 
> Obviously you're not gonna change this without a
> tuneboy.
> 4)Reduce compression ratio.  Clean out any carbon
> buildup on the piston or
> chamber that is consequently shrinking your
> combusion chamber volume, and
> thusly raising your compression ratio. 
> 5)Sometimes a colder range spark plug can help...
> all this does is dissipate
> more heat into the head, so depending on the design
> of the combustion chamber
> and how the flame propagation and travel was
> originally designed and
> anticipated, this may or may not help.  In other
> words, you could be putting
> more heat into the wrong place with a colder plug. 
> 
> Incidentally, my 99 ST started doing this same thing
> on 89 ocatane fuel.  I've
> been using 91 or better and have not had any issues.
>  I have to wonder if there
> is substantial carbon build up now with 24k miles. 
> It did not always do it.  I
> would also be inclined to believe that the fuel
> quality is not what it was
> years ago.  
> 
> Anyway, hope this helps whoever was having trouble. 
> 
> 
> Good luck,
> Jonathan West
> 
> 
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