87 octane '06 Sonata

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I have noticed a slight valve chatter with regular gas. It goes away with mid-level grade gas. Anyone else notice this. '06 Sonata LX (V6)

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Rob



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Rob wrote:

I don't think fuel octane can have any bearing on the valve train. What you are hearing typically is detonation, commonly called "pinging." Typically, this will increase with more throttle at a given speed or at lower RPMs (lugging).

I have the 4 cylinder engine, but I have not noticed any problem as yet on standard 87 octane. Have you tried a different brand of fuel? I've found that not all brands are equal with regard to resistance to detonation.

Matt

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I stick to "name brand" stations. (BP, Chevron and sometimes Racetrack) They all ping with 87 octane. Runs great on 89. No big deal its just Hyundai says 87.

Rob

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Rob wrote:

Well, it does cost several cents more per gallon so it may be a big deal over time. I specifically asked the salesman about this before buying my I4 Sonata and he said 87 was fine. So far, he has been right, however, pinging typically occurs during warmer weather and it hasn't been above 45 since I bought mine. July and August will be the test for me.

Matt

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I think you guys need to move to the Midwest (NOT necessarily into a big city like Chicago, either).

In the Midwest, because of ethanol subsidies, 89 fuel is actually cheaper than 87, especially in states like Iowa and Illinois. I run all my vehicles on 89 out here. When I drive outside the midwest, they all run on 87 just fine.

In the Midwest, no dealer would be allowed to treat their customers the way some of you are treated at some of your dealerships. Since even Toyota and Honda still fight for recognition in these parts, you can be sure that customers for nameplates like Hyundai and Kia are going to be treated like kings and queens. Indeed, we would make sure these people would not even eat if they didn't (and some have not).

On the subject, a little light pinging apparently is not bad for a vehicle, and General Motors even claims it is preferable, giving you the "greatest efficiency" for your fuel. Heavy, consistent pinging, especially under acceleration IS a concern.

Of even greater concern would be that, in my experience, these things tend to get worse in time. Indeed, some vehicles that ran just fine on 87 when they were new, ended up having to run on straight premium in the last years before I junked them (yes, I kept them tuned and in good, running order).

This is something to be watched carefully through the years.

Tom Wenndt

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Rev. Tom Wenndt wrote:

Where does GM say that? I think that is just an excuse for poor engine design and management. I've never read any legimate source that said detonation is good for an engine. And most engine makers go to great lengths to prevent it.

I'm not saying it causes instant death as it seldom does, but heavy pinging under a heavy load can trash your pistons in short order.

Matt

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I will do one better than that. I am still looking for when Consumer Reports last did a report on gasoline. But whenever that was, even they also said, "Don't worry about some occasional light pinging - DO worry about consistent, heavy pinging, especially under acceleration."

I'm with you. I don't like it even a little bit, and when I hear even a single ping or two (and I know that this is what I am hearing), I go to a higher octane fuel. And as I also mentioned, I would expect the problem only to get worse through time.

Agree with another writer - the problem seemed to be less in the Winter then in the Summer in the vehicles where I had this problem (none recently).

Tom Wenndt

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Rob
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[original post is likely clipped to save bandwidth]

Octane increasing additives are used EXPLICITLY to reduce pinging or premature detonation. That is actually the only value with higher octane fuels since they have lower energy content than low octane fuels.

Higher octane fuel may allow particular engines that need them perform better thus offsetting the lower energy content for those engines.

gerry

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gerry wrote:

True, but what is your point? This has nothing to do with the VALVE train, which was my point.

And there is no such thing is premature detonation. There is preignition and there is detonation, there isn't premature detonation. All detonation is undesirable, no matter when it occurs.

True. Most modern engines have knock sensors to detect detonation. When this is detected the engine control computer will typically retard the timing until the pinging stops. This will reduce the performance of the engine. If higher octane fuel prevents this, then it can increase the performance of such an engine.

But this still has nothing to do with the valve train. :-)

Matt

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[original post is likely clipped to save bandwidth]

Seems we just are playing with words here ;) An internal combustion engine detonates it's charge. It is fairly violent compared to igniting a gas burner in a furnace, thus "detonation" is a reasonable word for "ignition" in this context.Whichever word you prefer, I believe we can agree "initiation of combustion" and it's timing, speed of progression and cause is what matters.

If the valves "chatter" with lower octane fuel as indicated in the original post but do not with higher octane fuel, it has something to do with the charge igniting before it should or the flame (blast) front traveling too fast. Delay in ignition or speed of the flame front is the only thing higher octane fuel changes.

gerry

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gerry wrote:

No, an internal combustion engine ignites its charge and burns it. Yes, it burns very fast, but it is a burn, not an explosion, which is what detonation is. Detonation and combustion aren't the same thing with respect to an IC engine.

My point is that either the valves weren't chattering and the OP was hearing detonation, or the valves are making noise and something is wrong other than octane. The two simply aren't related. The valves are closed against their seats when the combustion (or detonation) occurs.

Matt

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Here is a nice tutorial on the subject:

http://www.streetrodstuff.com/Articles/Engine/Detonation /

As you can see, detonation is not a reasonable word for ignition.

Matt

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[original post is likely clipped to save bandwidth]

Look up " detonate" in a good dictionary and you will find it is not as defined as used in the above reference! It is not "spontaneous combustion"!

An example is

http://www.yourdictionary.com/ahd/d/d0172500.html

"To explode or cause to explode."

http://en.wikipedia.org/wiki/Detonate

states

"involves a shock wave and a reaction zone behind it"

Indeed one detonates a thermo nuclear weapon and that sure is not spontaneous combustion as defined in the reference you choose ;)

This is just to point out that different groups use different jargon. Thus I indicated not to worry too much about folks using different wording. I concede I use the words in more general engineering context, not automotive jargon.

In context of this discussion and using your choice of wording, octane affects both "pre-ignition" and "detonation", inhibiting both.

gerry

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gerry wrote:

Detonation used in the automotive sense isn't all that different. The spontaneous combustion is in effect an explosion. That is what makes all of the noise. It is the shock wave hitting the cylinder walls, piston and head that makes the racket.

It makes sense to use automotive jargon when talking about an internal combustion engine, which was the topic at hand.

Octane inhibits detonation, but has almost no affect on pre-ignition. Pre-ignition typically occurs from hot spots in the combustion chamber. Octane slows down the burn rate and lessens the chance of spontaneous combustion, but it doesn't prevent hot spots and it doesn't prevent ignition so it has littly if any affect on pre-ignition.

Matt

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[original post is likely clipped to save bandwidth]

This is intended as an interesting dialog and learning exercise, not an argument!

Since Octane rating explicitly affects the fuel's flash temperature, it certainly affects how hot a hot spot must be to cause a problem and does affect pre-ignition significantly.

An interesting site that discusses octane and pre-ignition explicitly is

http://www.eric-gorr.com/techarticles/Fuel_Basics.htm

"As you may have guessed from the earlier discussion of octane numbers, high octane fuels have a considerably higher auto ignition temperature to keep these pre-flame reactions from causing sudden uncontrolled pressure rises. If the charge burns fast enough or the fuel is resistant enough to auto ignition (high octane) then all is well and the pressure rise isn't too extreme." ... "We defined pre-ignition previously as the starting of the burning process by a source other than the plug"

gerry

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gerry wrote:

Octane affects the auto-ignition temperature and the burn rate. Pre-ignition is NOT auto ignition, that is the entire point. It is simply ignition from a point source other than the spark plug. Keep looking, maybe you can find a source that supports your assertion that octane has a significant affect on pre-ignition, but I doubt it.

If it had a substantial affect on pre-ignition, it would also have a substantial affect on regular ignition by the spark plug, and suppressing such ignition in a spark ignition engine wouldn't be a very good thing. :-)

Matt

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[original post is likely clipped to save bandwidth]

I just posted that if you actually chose to read it. It appears you are not interested in any discussion that doesn't meet your pre-conceived ideas.

Not at all, a spark temperature (from a spark plug) is commonly 60,000 Kelvin!!!! So dramatically far above the flash point of any useful fuel air mixture the affect on spark induced ignition is thus nil.

gerry

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[original post is likely clipped to save bandwidth]

"It's a commonly held misconception that higher Octane fuel slows down the flame speed"

from http://www.eric-gorr.com/techarticles/Fuel_Basics.htm

gerry

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[original post is likely clipped to save bandwidth]

Read the reference you posted

http://www.streetrodstuff.com/Articles/Engine/Detonation/Page_2.php

According to that, "detonation"

"can actually cause fracture of valves-intake or exhaust"

The resonance can cause the valves to unseat briefly and force them closed with force.

gerry

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