87 octane '06 Sonata

Page 2 of 2  
gerry wrote:


I saw the above statement.

I don't find this statement in the article, even using the search function. Where do you find this?
Matt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[original post is likely clipped to save bandwidth]

The article states resonance and the structure of the engine to vibrating. There is no reason to presume a valve held closed only by spring action stays firmly seated and unaffected by the engine structure vibration.
Something that "can actually cause fracture of valves-intake or exhaust" surely implies severe stress on the valve train. Even if the valves stay closed, a stress severe enough to deform them will be transmitted to the cam assembly which is in positive contact (via hydraulic action).
There may well be a jargon issue as to this being "valve chatter" but the reference clearly states valve involvement.
The below is on page two
" Detonation
Unburned end gas, under increasing pressure and heat (from the normal progressive burning process and hot combustion chamber metals) spontaneously combusts, ignited solely by the intense heat and pressure. The remaining fuel in the end gas simply lacks sufficient octane rating to withstand this combination of heat and pressure.
Detonation causes a very high, very sharp pressure spike in the combustion chamber but it is of a very short duration. If you look at a pressure trace of the combustion chamber process, you would see the normal burn as a normal pressure rise, then all of a sudden you would see a very sharp spike when the detonation occurred. That spike always occurs after the spark plug fires. The sharp spike in pressure creates a force in the combustion chamber. It causes the structure of the engine to ring, or resonate, much as if it were hit by a hammer. Resonance, which is characteristic of combustion detonation, occurs at about 6400 Hertz. So the pinging you hear is actually the structure of the engine reacting to the pressure spikes. This noise of detonation is commonly called spark knock. This noise changes only slightly between iron and aluminum. This noise or vibration is what a knock sensor picks up. The knock sensors are tuned to 6400 hertz and they will pick up that spark knock. Incidentally, the knocking or pinging sound is not the result of "two flame fronts meeting" as is often stated. Although this clash does generate a spike the noise you sense comes from the vibration of the engine structure reacting to the pressure spike. "
... "can actually cause fracture of valves-intake or exhaust"
gerry
--

Personal home page - http://gogood.com

gerry misspelled in my email address to confuse robots
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
gerry wrote:

OK, so you made up the above statement. I just wanted to confirm that.
Matt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Matt Whiting wrote:

I appears so. It's hard to see how a pressure spike in a sealed combustion chamber could cause the valves to open, since they'd be under extremely high pressure holding them closed.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Brian Nystrom wrote:

I won't go so far as to say it is impossible. I have never, however, seen any data to suggest that it occurs. And the valves I've seen that have failed due to detonation, failed due to weakness induced by high temperatures, not pressure or resonance induced forces.
If someone can produce some data that shows this, I'll certainly change my view. However, the poster above was just making stuff up and that won't change my view. :-)
Matt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[original post is likely clipped to save bandwidth] On Sun, 29 Jan 2006 13:47:39 GMT, Brian Nystrom

Not to be argumentative but study the fluid dynamics of detonation in a compressible gas some time. You will find the shock wave often has reaction zone behind it that include negative pressures. The movie "Back draft" demonstrated that several times.
There also is no reason to assume the engine structure vibration from "detonation" only affects the valves of the cylinder currently igniting.
Again, just food for thought. The whole structure vibrates thus it is very difficult to know what components may be affected. How can one preclude the valve train vibrating if the entire engine structure has been shown to vibrate?
I neither claim proof of such nor accept such has been demonstrated to never occur.
gerry
--

Personal home page - http://gogood.com

gerry misspelled in my email address to confuse robots
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[original post is likely clipped to save bandwidth]

Well, I just commented that your statement:
Specifically your statement "But this still has nothing to do with the valve train."
Was contradicted by the references you provided.
gerry
--

Personal home page - http://gogood.com

gerry misspelled in my email address to confuse robots
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
gerry wrote:

I was specifically referring to the "valves chattering" or whatever terminology was first used. I've still seen no evidence that this occurs.
Matt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.