any answer about knock

[TFI-J]

hi guys

i m wondering what is knock and what does it do or effect
please give me some tips about it!!!

 

[pooya]

Knock is pre-detonation.
It is when the fuel/air inside your cylinder ignites in the wrong area/ wrong time.

It is ok if it happens very little, but a lot of knock will destroy your engine.
The main leader of knock, is warm air. The cooler the air that comes in, the less likely it is to get knock.
Also, lower octane gas is prone to get more knock then higher octane gas. That is why people put in race gas when they raise the boost really high.
Also, your 2g. will not detect knock with a logger...you have to see if you ecu pulls timing, in order to see if you are getting knock. I believe our ecu pulls timing with every 7 counts of knock. So if your ecu is pulling timing, you need to tune better, or get better gas, or colder/denser air.
The ecu knows your car is knocking with a little microphone that determins which tick is knock, and what isn't.
Someone please give me rep. point for this...


EDIT: 7 counts of knock seems kinda high to me....maybe it was first 7, then after that it's every 3? I'm going to have to double check on that.

 

[luvmygst]

Knock is pre-detonation.
It is when the fuel/air inside your cylinder ignites in the wrong area/ wrong time.

It is ok if it happens very little, but a lot of knock will destroy your engine.
The main leader of knock, is warm air. The cooler the air that comes in, the less likely it is to get knock.
Also, lower octane gas is prone to get more knock then higher octane gas. That is why people put in race gas when they raise the boost really high.
Also, your 2g. will not detect knock with a logger...you have to see if you ecu pulls timing, in order to see if you are getting knock. I believe our ecu pulls timing with every 7 counts of knock. So if your ecu is pulling timing, you need to tune better, or get better gas, or colder/denser air.
The ecu knows your car is knocking with a little microphone that determins which tick is knock, and what isn't.
Someone please give me rep. point for this...

Kinda

I have never heard of pre-detonation, I have heard of pre-ignition, and detonation, but they are not the same thing.
Detonation
Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.
Pre-ignition
Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. The two are completely different and abnormal phenomenon.

I pulled that from a web page because its is easier than typing .

Another thing is hot air into the motor can cause knock, but cold air into the intake can cause knock also, because the air is more dense, causing a lean mixure. KNock is bad but pre-ignition is worse. Try this page for a more detailed explanation. Its like 8 pages long. http://www.streetrodstuff.com/Articles/Engine/Detonation/

 

[TFI-J]

thanks guy
i read a fourm saying that by useing water injection will get ride of knock
is that ture ,if not how do i try to get rid of or at lease control it!!!

 

[pooya]

thanks guy
i read a fourm saying that by useing water injection will get ride of knock
is that ture ,if not how do i try to get rid of or at lease control it!!!

Water injection, alky injection, nitrous, higher octane gas, or bigger intercooler.

 

[luvmygst]

Water injection, alky injection, nitrous, higher octane gas, or bigger intercooler.

Nitrous wont help. Water/alky injection reduces knock by reducing the temp in the combustion chamber. You can do a number of things to help, reduce timing, increase octane, reduce the air temp entering the motor( a bigger ic) to name a few. Are you having a problem with knock or are you just wondering?

 

[pooya]

Nitrous wont help. Water/alky injection reduces knock by reducing the temp in the combustion chamber. You can do a number of things to help, reduce timing, increase octane, reduce the air temp entering the motor( a bigger ic) to name a few. Are you having a problem with knock or are you just wondering?

Wouldn't nitrous cool the income air, which would reduce knock?

 

[TFI-J]

no
i m just wonderring because i like to learn more about it !!

well pretty soon a will be geting my fmic and water injection kit so im guessing i'll be all set rite!!!

and what does knock can do to you car will it make different with the way it run!!!

 

[pooya]

no
i m just wonderring because i like to learn more about it !!

well pretty soon a will be geting my fmic and water injection kit so im guessing i'll be all set rite!!!

FMIC and water injection should be enough for whatever setup you end up choosing.

and what does knock can do to you car will it make different with the way it run!!!

I have no idea what you just said, but im guessing you're asking what knock does to your car.

A lot of knock can destroy your engine, thats about it.
Avoid it at all costs.

 

[Masochist]

Wouldn't nitrous cool the income air, which would reduce knock?

Nitrous increases combustion chamber pressure. When you significantly increase the cylinder pressure in the engine, it also increases the engine's tendancy to detonate. That is why proper use of nitrous requires timing adjustments and fuel delivery adjustments when in use.

 

[luvmygst]

Wouldn't nitrous cool the income air, which would reduce knock?

If you spray just N2O into a motor, when it gets into the cylinder it breaks down into 2 parts nitrogen, 1 part oxygen, creating a really lean condition. Even a properly setup N2O kit is not a way to control knock its a way to make more power.

 

[pooya]

If you spray just N2O into a motor, when it gets into the cylinder it breaks down into 2 parts nitrogen, 1 part oxygen, creating a really lean condition. Even a properly setup N2O kit is not a way to control knock its a way to make more power.

What about an N-Tercooler kit?
That would work, right?

 

[girlieracr4g63]

You can also see knock because of something as simple as a bad motor mount etc.


Wendy

 

[luvmygst]

What about an N-Tercooler kit?
That would work, right?

THat would cool the air entering the motor, yes. But its still not a good way to control knock. What happens when the bottle is empty? Back to the same old problem. I think we are getting off the thread topic though.

 

[luvmygst]

You can also see knock because of something as simple as a bad motor mount etc.


Wendy

IM not saying your worng but how could that cause knock? Or are you just saying it could cause knock to show up when logging?

 

[girlieracr4g63]

Well as odd as it sounds the vibration can cause the engine to retard timing. I had a halfshaft vibrate, and caused this to happen a couple of years ago.


Wendy