What is KR???
#2
Senior Member
Posts like a Turbo
Join Date: Jun 2004
Posts: 287
Likes: 0
Received 0 Likes
on
0 Posts
KR stands for Knock Retard. What it means is when the computer senses a predetonation of the combustion mixture BEFORE the spark plug fires, it will pull the timing by 'retarding' it to prevent it on the next fire. That way the plug fires before the detonation would occur on it'* own.
This is usually caused by heat or a hotspot in the cylinder causing the combustion to go off before the spark plug sets it off.
Timing advance is when the plug fires before the piston reaches TDC *top dead center* on it'* stroke. By doing this, maximum power can be achieved so that the flame wave hits the piston JUST after TDC so it'* down stroke is more powerful.
The more timing that is retarded by knock, the less power you make, hence the reason why you never want to have it, even in my case 3 degrees of retard can cause a good amount of loss in power.
Cold air intakes help as the air coming in is cooler and doesn't get as hot as it reaches the cylinder. The air coming out of the blower after compression usually hits near 200+degrees in temperature. A thermostat helps by lowering the temperature of the block, helping to prevent detonation via heat.
Hope this makes SOME kind of sense
This is usually caused by heat or a hotspot in the cylinder causing the combustion to go off before the spark plug sets it off.
Timing advance is when the plug fires before the piston reaches TDC *top dead center* on it'* stroke. By doing this, maximum power can be achieved so that the flame wave hits the piston JUST after TDC so it'* down stroke is more powerful.
The more timing that is retarded by knock, the less power you make, hence the reason why you never want to have it, even in my case 3 degrees of retard can cause a good amount of loss in power.
Cold air intakes help as the air coming in is cooler and doesn't get as hot as it reaches the cylinder. The air coming out of the blower after compression usually hits near 200+degrees in temperature. A thermostat helps by lowering the temperature of the block, helping to prevent detonation via heat.
Hope this makes SOME kind of sense
#8
Senior Member
True Car Nut
Originally Posted by Logan
Sorry about my questions
So would 1 degree of KR have the cylinder fire 1 degree after the piston reaches TDC?
So would 1 degree of KR have the cylinder fire 1 degree after the piston reaches TDC?
#9
Senior Member
True Car Nut
Join Date: Jan 2003
Location: Bloomington-Normal, IL 1997 SE
Posts: 3,734
Likes: 0
Received 0 Likes
on
0 Posts
KR isnt really a problem on NA motors, but on the SCed ones the pressurized air/fuel mix might explode before it gets to TDC, which would propel the piston backwards and really screw up the engine if it happened enough.
#10
Senior Member
True Car Nut
Join Date: Jul 2003
Location: Westerville, Ohio 2000 Black SSEi
Posts: 6,127
Likes: 0
Received 1 Like
on
1 Post
Knock is when detonation in the cylinder occurs from two sides of the fuel charge. One from the spark plug the other from a hotspot somewhere in the chamber. When the 2 flame fronts collide it causes a pinging or knock. This is what the knock sensors listen for.