87 octane '06 Sonata

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)

 

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

 

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

 

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

 

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

 

--
Rob

Florida here, summer all the time.

 

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

 

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

 

[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

 

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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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

 

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

 

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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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

 

[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

 

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

 

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

 

[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

 

OK, so you made up the above statement. I just wanted to confirm that.

Matt

 

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.