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'85 2.3-16 '99 C280 '11 GLK350
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Why are knock sensors needed when the engine
is run on premium gas ?

Think about it.
Fuel contamination
High temperatures and low humidity
Unusual engine stresses, including towing uphill at, or above, max capacity

I'm sure others will think about it some more than me. :)
 

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2013 C250
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7,273 Posts
And in emergency situation where only regular is available, the car will run okay without damage. I prefer having the knock sensors as standard.
 

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As both posters above, but mainly because makers know that "premium" can vary from brand to brand,(even station to station) and certainly country to country
 

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1999 ML320
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Discussion Starter #5 (Edited)
Fuel contamination
High temperatures and low humidity
Unusual engine stresses, including towing uphill at, or above, max capacity

I'm sure others will think about it some more than me. :)
I would consider high temp and low humidity
as normal driving conditions in many parts
of the world.
Towing uphill even at max load should not cause
knocking since that is within the performance
specifications described in the manual.
These by themselves do not explain why knock
sensors are necessary.

Bad gas will give an engine fits but surely, if it is bad
enough, just having knock sensors can't save the
engine from being damaged.
 

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2004 W220 (S430) ; 2001 R129 (SL500) Sport
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I guess my question is why you care. Knock sensors are non-intrusive and don't cost any fuel or performance economy. Whatever their marginal cost may add to the price of a new car is negligible. That said, IF you need them they are there and can save you expensive engine damage. Do you want the ones on your car removed? Your question is puzzling.
 

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222.132 & 221.122 & 213.050 & 906.633
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I guess my question is why you care. Knock sensors are non-intrusive and don't cost any fuel or performance economy. Whatever their marginal cost may add to the price of a new car is negligible. That said, IF you need them they are there and can save you expensive engine damage. Do you want the ones on your car removed? Your question is puzzling.
The point from previous posts already was not only to protect the engine from bad fuel but you could not reach the engine economy and power even for a very accurately known and constant quality fuel. Since conditions still vary, engine load varies etc, one would lose economy and power if the engine was not able to adapt with the aid of knock-sensors (and other means).
 

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1999 ML320
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Discussion Starter #8
The point from previous posts already was not only to protect the engine from bad fuel but you could not reach the engine economy and power even for a very accurately known and constant quality fuel. Since conditions still vary, engine load varies etc, one would lose economy and power if the engine was not able to adapt with the aid of knock-sensors (and other means).
This is along the lines of what I am thinking.
The sensors are needed during the normal operation of the vehicle within the intended
performance envelope. Without the sensors, even with known and accurate fuel, the
vehicle will not perform according to design. In other words, the vehicle can exhibit
knocking in normal operation if there are no knock sensors.

The bad gas benefit is incidental to this. I have a hard time believing
MB will install knock sensors if the only benefit is the ability to run on bad gas once
in a while. Besides , doesn't bad gas void the warranty ?
 

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2004 W220 (S430) ; 2001 R129 (SL500) Sport
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I suppose I misinterpreted your original post. What I got was "If you're using premium fuel anyway, why do you need knock sensors?" I know just like most folks that knock sensors do more than adjust the spark timing to the octane in the fuel, but my question grew out of the way I read your post. I inferred you thought they might be compromising engine performance for the sake of protecting us from the consequences of using fuel we shouldn't or that they were just unnecessary. That's the problem with not being able to hear inflection and see non-verbals to complete a message. You were asking a question for which you already had the answer, right?
 

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'85 2.3-16 '99 C280 '11 GLK350
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Clearly, in milfun's world, everything and everyone is perfect; all owners test their gasoline before pumping it into their cars; they all know the exact performance, towing and operating specfications of their vehicles and never, ever, exceed them; they never operate their vehicles in unsual environmental situations, such as high, dry heat. milfun's world is quite a nice place, no?

Luckily for the rest of us, Mercedes engineers engines, cars, trucks, and commercial vehicles for "the real world" and for real drivers.
 

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2005 Black E55
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13 Posts
Clearly, in milfun's world, everything and everyone is perfect; all owners test their gasoline before pumping it into their cars; they all know the exact performance, towing and operating specfications of their vehicles and never, ever, exceed them; they never operate their vehicles in unsual environmental situations, such as high, dry heat. milfun's world is quite a nice place, no?
.
do bad fuel injectors lean out cylinders in milfuns world?
 

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1999 ML320
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Discussion Starter #15
Clearly, in milfun's world, everything and everyone is perfect; all owners test their gasoline before pumping it into their cars; they all know the exact performance, towing and operating specfications of their vehicles and never, ever, exceed them; they never operate their vehicles in unsual environmental situations, such as high, dry heat. milfun's world is quite a nice place, no?

Luckily for the rest of us, Mercedes engineers engines, cars, trucks, and commercial vehicles for "the real world" and for real drivers.
Yes, this exactly confirms my point which is ...
The engine will NOT perform to spec without knock sensors.

MTI, there is a spec, you know. Put it another way, unless one lives in Antartica , MB has tested the engine under the conditions at your place. Put it yet another way
not to belabor the point but to get it across to some, NONE of the conditions you
mention above constitute abnormal driving conditions.
 

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The engine will NOT perform to spec without knock sensors.

what does that even mean? if i unplug a knock sensor the car wont run?

what is 'to spec'? hp wise?

and besides.. i thought you wanted NO knock sensors.
 

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1999 ML320
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Discussion Starter #18
No, because parameters "outside of spec" do not exist in milfun's world, only the real world.
This is a question for those of you who are in the industry. What's the development
history behind knock sensors ?
Wasn't it developed to squeeze more performance from engines rather than
allow engines to operate "in the real world" (as MTI would say) ?

On another note, I have no idea what MTI means by "real world". However if MTI lives
in another world, then I would understand perfectly.
 

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Why are knock sensors needed when the engine
is run on premium gas ?

Think about it.
Whenever you're about to post something like this, ask yourself if you're an engineer.

Ask your engineer friends if they build stuff with things tacked on that aren't necessary.

Lots of people that can't afford things or can't understand things resort to cynicism when it comes to whether something is "needed." Happens a lot in Chevy/Ford crowds, I imagine.

Do you suppose the "bean counters" made them put it on? How about the "lawyers?" "Marketing?"

Let's see, who else are we cynical toward?

How many other times are you the only person out of the world's billions in population that sees things clearly?

Give me a break.
 

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1999 ML320
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Discussion Starter #20 (Edited)
No need to be defensive, lkchris.

I asked simple questions. If and when you can contribute to the answers, I am all ears.

Why are knock sensors needed when the engine is run on
premium gas ?
What's the development history behind knock sensors ?

Whenever you're about to post something like this, ask yourself if you're an engineer.

Ask your engineer friends if they build stuff with things tacked on that aren't necessary.

Lots of people that can't afford things or can't understand things resort to cynicism when it comes to whether something is "needed." Happens a lot in Chevy/Ford crowds, I imagine.

Do you suppose the "bean counters" made them put it on? How about the "lawyers?" "Marketing?"

Let's see, who else are we cynical toward?

How many other times are you the only person out of the world's billions in population that sees things clearly?

Give me a break.
 
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