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Old 06-26-2004, 01:35 PM   #1
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Default What is KR???

Ive heard this a lot lately, what exactly does this mean?
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Old 06-26-2004, 01:57 PM   #2
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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
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Old 06-26-2004, 03:48 PM   #3
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OHHHHhhhh. Yep i understand, thanks for clearing that up
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Old 06-26-2004, 05:35 PM   #4
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I thought KR referred to the sign on my bathroom door
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Old 06-26-2004, 09:45 PM   #5
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one degree of KR=~2-3 HP loss.
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Old 06-26-2004, 10:33 PM   #6
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knock is indeed retarded
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Old 06-27-2004, 09:45 PM   #7
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Sorry about my questions

So would 1 degree of KR have the cylinder fire 1 degree after the piston reaches TDC?
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Old 06-27-2004, 10:47 PM   #8
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Quote:
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?
The timing is pulled accross the board on all cylinders. The kr system is actually good for the motor or else would cause some serious damage. With that said you can disable it for a short run for lets a day at the drags but will throw a code. Some guys have put in a switch for a bypass while racing. The better policy is trying to manage the kr and mod without increasing kr.
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Old 06-27-2004, 11:43 PM   #9
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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.
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Old 06-28-2004, 12:10 AM   #10
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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.
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