What Exactly is Knock?

came across this in a book during the week, interesting enough so i said i throw it up

What Exactly is Knock?

The semantics of knock, pre-ignition, or detonation can be argued among automotive engineers, however it is basically an uncontrolled ignition of the air fuel mixture. The uncontrolled part means that it doesn’t occur at the desired time in the combustion cycle. Normally the timing of the ignition is designed to maximize pressure in the cylinder so that it will push the piston down with the most force. Knock can cause high cylinder pressures at times when it actually counteracts the force and also cause shockwaves within the cylinder. It is the shockwave that emits the characteristic "tinkling" sound you often hear when the engine is knocking. In reality by the time you hear knock the chances are that the engine has been knocking for a while. Car manufacturers are continuously researching better ways of detecting knock and in the future we may see more direct methods such as pressure sensors and ionized current measuring however the majority of cars still use an indirect method of detecting knock by listening to the ringing sound of the cylinder using a piezoelectric knock sensor

knock knock whos there ..bye bye pistons

:lol:

Just a Question while we're on the toppic! With the Knock sensor on the Power FC Commander what should the reading be! Mine is around 11 going through the Gears but it red lined the other day for a split second and the reading read in the Thirtys! Can that happen? It's back reading 11 now!

30's is still nothing mental.... I've seen 70 on an Apexi hand controller.

11 is a very acceptable level, and 30 is fine if razzed to death.

[quote author=ericsti link=topic=4150.msg43754#msg43754 date=1193832914]
Just a Question while we're on the toppic! With the Knock sensor on the Power FC Commander what should the reading be! Mine is around 11 going through the Gears but it red lined the other day for a split second and the reading read in the Thirtys! Can that happen? It's back reading 11 now!
[/quote]
Thanks for welcoming me to the site
Heres a good site I found to answer any of those questions in relation to the Apexi Power FC you were afraid to ask... I found it quite helpful

http://paulr33.skylinesaustralia.com/docs/powerfc-faq/powerfc-faq.htm

Eric i asked AndyF the same question and he said
40 was the max he would recommend as a safe level for an everyday
- road car ................So 30 is fine

I've often seen alot higher on mine say with bad fuel , or O2 sensor gone
etc.......

Niall.

Twinnie,
That's a great site.

Thanks
Niall.

[quote author=Niallyboy link=topic=4150.msg43787#msg43787 date=1193849125]
Twinnie,
That's a great site.

Thanks
Niall.
[/quote]
I also have the manual in English at home
It is a good site, basically tells you most of the things you need to know and never knew about Apexi's car brain product Oh and no problem

Thats a great link to the Power FC

Especially the part about "poor mans anti-lag" :lol: :lol: :lol:

thats a great site about the pfc , some really useful stuff there,

Thanks to all that answered my Question! I can drive her now with no worries!