im ready for a smaller pulley than s2, but i've heard stories about crappy a/f ratio's and alot of knock. WTF is knock?
thanks

 

the easiest way to explain engine knock is that the gas is being ignited before it's fully in the cylindar... basically the injector feeds the gas, and at a set time, the spark plug ignites it so that the cylanders move, thus making power... when you're getting knock, the gas is being ignited before it's fully in the cylander.

 

thanks man. especially for making it so simple.. i appreciate it

 

Oh boy - you better get the flame suit out LOL!

Knock is detonation - when the fuel combusts during the compression cycle instead of at the optimal position of the piston (top dead).

Some small amounts of knock occur from time to time in all cars, but on F/I cars it is more common because of the increased air and fuel being compressed in the combustion chamber.

If you want to go smaller then the S2 pulley I wouldn't go lower then the 2.9 pulley unless you want to upgrade your injectors to 60#. Also when you start going smaller then 2.7 it is a good idea to look into ways to get the IAT2 temps down as well.

 

no flame suit, it was a legit question.

you're welcome.

 

Colder spark plugs and higher octane are your friend.

Those are the 2 quick and easy ways to reduce/remove knock.

beyond that, tuning will take care of it. but it will cost more, and be more of a hassle (the other 2 are also not going to affect warranty like tuning "might")

 

Knock is actually caused from pre-ignition. Pre-ignition is defined as a normal combustion process starting before the ignition spark fires. This is usually caused by a local hot spot raising the mixture temperature above its auto ignition point. Higher octane fuel lowers the auto ignition point. The engines dynamic compression (determined by timing and static compression ratio), the cylinder head and piston crown design, the atomization of fuel, the IAT, and the cylinder head temperature all affect the auto-ignition point of the fuel. As combustion has started before it was intended to, peak cylinder pressure occurs too early in the cycle. This leads to excessive pressures and temperatures, while the piston is still in an upwards motion with cylinder volume decreasing rather than increasing. Pre-ignition can cause piston and spark plug electrode damage.

The engines knonk sensor will detect pre-ignition, sending a signal to the ECM which will retard the timing, reducing the engine's dynamic compression enough to eliminate pre-ignition. If this did not occur, you may experience detonation.

Detonation is defined as a form of combustion which involves too rapid a rate of energy release which produces excessive pressues and temperatures in the combustion chambers. The fuel literally explodes in the cylinder. Detonation can hole a piston or destroy other engine parts in short order. Detonation is knock taken to the extreme. It is very bad.

 

While some of these explanations are good, they're not very thorough. Rather than try to explain it myself (or "Copy/Paste" pretending I did), I'll just give you this link.

http://www.misterfixit.com/deton.htm

 

simple as it can get

Knock = Boom

 

not true.

in fact if you threw a knock sensor on alot of cars on the road today you would find a little bit.

ALOT of knock....without a PCM to retard timing to avoid detonation = boom.

and sushi, doesnt higher octane INCREASE the flash point of the fuel so that "hotspots" generally arent hot enough to cause pre-ignition?

 

That's something people misunderstand about octane.

For a while people were led to believe that higher octane fuel actually burned slower. LOL

Anyway, here's a pretty good explanation of what higher octanes do.
http://en.wikipedia.org/wiki/Octane_rating

 

I have an 06 ss/sc stage 2 and installed the GM Stage 3 Pulley on Sunday night. It makes a small, but noticeable difference. 16.5 lbs of boost now. Have had zero issues since the install. Do not go smaller than that without a custom tune and upgraded injectors. The GM stage 3 pulley is that smallest one that you can safely run without any other supporting modifications.

 

Yes. Higher octane increases the flash point but reduces the ignition point.

It's the same thing, just said another way. The flash point is the point where with enough compression (temperature and fuel density) and heat, the fuel spontaneously combusts. ie pre-ignition. But lowering the ignition point means that the fuel is harder to ignite ie. higher octane or longer chain hydrocarbons.

 

Knock = uncontrolled rapid fuel burn

Kock effects= high pressures/temperatures = broken parts

 

knock=poop

 

knock > me

 

i havent gotten knock WOT which is good but i do get a little sometimes when i start in 1st gear.

 

an aeroforce interceptor gauge will read that and a wideband gauge would be a good combo.

 

i know what knock retard is, but on the interceptor ive seen it read 32 knock retard before...is that normal or is my car about to blow

 

your knock sensor wont read over 14.62* kr. (whether you really are getting 14.62* or 32* of kr.. it will read 14.62* max


you probably read .32*

 

every car will knock. stock, modded. knock is not always a bad thing. it lets you know how close to the edge you are running.

you can not 100% sure fire get rid of it all. too many variables in it

 

i highly doubt you saw 14* or 32* and had your engine survive. i read that 8* of KR is the most our ecu can correct for. after that it will become fatal detonation.

come to think about it, you were probly reading the ignition timing when you saw 32*

 

oh really?

I cracked the rear head on my Grand Prix (common for 1997 Grand Prix's) and it read 14.62* at part throttle... and 9* at WOT.



No knock is good... it isnt JUST a warning telling you your engine doesnt like it... When you get knock, YOUR ENGINE IS telling you it is HURTING. Unless of course it is false knock, Downpipe hitting something... vibrations vibrating the kr sensor. However, the MORE modded you are.. the more knock will affect you.


Knock is Knock, however, it is much much worse to have 4* knock with a 2.5" pulley, rather than having 4* knock with a 3.3" pulley.

 

not always the case.

running 11.0 a/f and 14 degrees of timing is doing more damage to the motor then something that is runnin 18 degree's of timing, and 1-2 kr*

ALL MOTORS KNOCK, they do it at idle, they do it cruizing, they do it wide open. it's going to happen. you can not tune for every single weather condition known to man.