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PCM and Technical Tuning PCM and High end tuning discussion here.

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  Topic Review (Newest First)
01-28-2013 03:24 PM
kingnutin It stands for knock, retard. Fun with commas...
01-27-2013 01:17 PM
jonkamholtz LOL I had the same problem
01-26-2013 07:25 PM
auntjemima Ill read it but I know what a knock sensor does. Thanks for the abbrev meaning though!
01-26-2013 06:39 PM
Ejbiers
Quote:
Originally Posted by Ejbiers View Post
Engine knock, also known as "ping", spark knock, or detonation, is a phenomenon that occurs inside the combustion chambers when a portion of the air/fuel mix is ignited under extreme heat and pressure, burning more rapidly than it should for creating optimum power on the piston's downstroke. The result is a harsh detonation as the air/fuel mix explodes, colliding violently with parts of the engine such as the head, piston, cylinder walls, etc., as well as the original portion of the air/fuel mix that was ignited by the spark plug.

Knock can occur at different intensities depending on conditions inside the combustion chambers. It can be caused by various things, including low octane fuel, lean air/fuel mixture, higher boost (smaller SC pulleys), increased engine load, and restricted engine air flow, and all of these things may act to influence each other. Perhaps the two greatest direct causes of knock are: A) excess heat and B) a lean air/fuel condition. Warmer outside air temperatures, "hot" air intake designs, higher engine/transmission temps, incorrect spark plugs, and simply racing the engine at high RPMs can also contribute to heat build-up and knock.

KR stands for knock retard. Knock retard is the PCM's response to detected knock, which results in retarding of ignition timing. KR can be measured using an OBDII scan device. KR is measured in degrees depending on its level of intensity. The more knock that is detected, the greater the response by the PCM in dealing with it. As timing is pulled, power output is reduced. For obvious reasons, zero degrees KR is optimal, but this is not always realistic due to the nature of the engine's operation. Because our cars are supercharged, the effective compression inside the cylinders is much higher than with normally aspirated engines under increased throttle, thus we are prone to knock much more than NA engines when under loads. In fact, it is normal for a SC 3800 V6 to be on the verge of knocking during WOT (wide open throttle), or under heavy load conditions, such as pulling up a grade in overdrive. In order to take advantage of the extra air from forced induction (supercharging), knock is a sort of necessary evil, but you don't want very much. Ideally, you want to get the most power possible before engine knock ensues.

Even a stock vehicle can exhibit knock during WOT at times. If your engine is knocking slightly, say 1-3 degrees, you probably won't notice it, because the PCM uses microphones to listen for these sounds and then takes quick action to correct with KR. A small amount of power will be lost, but it is very small, probably in the area of 5 hp. Higher levels of KR above 4 or 5 deg may require extra response from the PCM to control the knock. When this happens, the engine could lose a noticeable amount of power, and a "ping" sound may actually be audible is extreme cases. When you use premium fuel, cooler plugs, a colder thermostat, or a cold air intake (CAI), you may notice restoration of lost power due to the reduction of existing engine knock (the only way to verify is to monitor KR using a scan tool).

Modifying the engine to run at higher levels of boost (swapping to smaller SC pulleys) can yield considerably more power output, but requires added effort to keep knock and KR under control. Running extra boost will increase heat and test the PCM's ability to deliver the needed fuel. Further lowering intake temps (IC), maximizing engine air flow (rockers, cam, exhaust), and tuning the PCM's fuel curves (PowrTuner) are just a few ways to help keep knock levels in check.
Read that. That will tell you what kr or knock retard is all about
Basically when you engine knocks or pings the knock sensor picks it up and it retards the timing which lowers your horse power. It does this to prevent your engine from blowing apart.
01-26-2013 03:17 PM
auntjemima Ejb, what the hell does KR stand for? I feel retarded every time I read it and don't understand it.
01-26-2013 02:14 PM
Ejbiers Go to your user control panel (user cp)
Then on the right go to edit avatar
And upload whatever pic you want and save it
01-26-2013 02:08 PM
jonkamholtz hey i am trying to get my car pic from my garge gallery to that place on my thread that says no avatar. how do i do that?
01-26-2013 01:28 PM
Ejbiers I hear you man just dont want you to ruin your motor
And from the sound of it i dont think that guy gave you that much info
Especially If he didnt even mention kr which is a problem in stock 3.8s/c cars

In the end he is trying to sell you something and talk up their products. If he didnt do that he wouldnt have a job. Just because he works for gm doesn't mean anything most gm techs i talk to are idiots and are trained to read a book and even suck at that
01-26-2013 01:10 PM
jonkamholtz Thanx for all that info.I Am trying not to go into this acting or sounding like I know what I Am doing when i dont .with that said I have been a tech for most of my adult life with no experience innperformance,you could say a glorafied parts changer ,i am able to pick up on this fairly easy thanx again for your patience and all the info.I also just had a great talk with the tech from 3800 performance who I also discovered works for GM and drives and races a sc3800 . So between him and this forume I think I have a pretty safe gameplan and I have certainly gained a bunch of useful knowledge
01-26-2013 12:10 PM
Ejbiers The ubend is in the down pipe where the o2 sensor goes.
The cat is also on the downpipe
Just replacing the cat will not fix the ubend issue
01-26-2013 12:06 PM
Ejbiers Engine knock, also known as "ping", spark knock, or detonation, is a phenomenon that occurs inside the combustion chambers when a portion of the air/fuel mix is ignited under extreme heat and pressure, burning more rapidly than it should for creating optimum power on the piston's downstroke. The result is a harsh detonation as the air/fuel mix explodes, colliding violently with parts of the engine such as the head, piston, cylinder walls, etc., as well as the original portion of the air/fuel mix that was ignited by the spark plug.

Knock can occur at different intensities depending on conditions inside the combustion chambers. It can be caused by various things, including low octane fuel, lean air/fuel mixture, higher boost (smaller SC pulleys), increased engine load, and restricted engine air flow, and all of these things may act to influence each other. Perhaps the two greatest direct causes of knock are: A) excess heat and B) a lean air/fuel condition. Warmer outside air temperatures, "hot" air intake designs, higher engine/transmission temps, incorrect spark plugs, and simply racing the engine at high RPMs can also contribute to heat build-up and knock.

KR stands for knock retard. Knock retard is the PCM's response to detected knock, which results in retarding of ignition timing. KR can be measured using an OBDII scan device. KR is measured in degrees depending on its level of intensity. The more knock that is detected, the greater the response by the PCM in dealing with it. As timing is pulled, power output is reduced. For obvious reasons, zero degrees KR is optimal, but this is not always realistic due to the nature of the engine's operation. Because our cars are supercharged, the effective compression inside the cylinders is much higher than with normally aspirated engines under increased throttle, thus we are prone to knock much more than NA engines when under loads. In fact, it is normal for a SC 3800 V6 to be on the verge of knocking during WOT (wide open throttle), or under heavy load conditions, such as pulling up a grade in overdrive. In order to take advantage of the extra air from forced induction (supercharging), knock is a sort of necessary evil, but you don't want very much. Ideally, you want to get the most power possible before engine knock ensues.

Even a stock vehicle can exhibit knock during WOT at times. If your engine is knocking slightly, say 1-3 degrees, you probably won't notice it, because the PCM uses microphones to listen for these sounds and then takes quick action to correct with KR. A small amount of power will be lost, but it is very small, probably in the area of 5 hp. Higher levels of KR above 4 or 5 deg may require extra response from the PCM to control the knock. When this happens, the engine could lose a noticeable amount of power, and a "ping" sound may actually be audible is extreme cases. When you use premium fuel, cooler plugs, a colder thermostat, or a cold air intake (CAI), you may notice restoration of lost power due to the reduction of existing engine knock (the only way to verify is to monitor KR using a scan tool).

Modifying the engine to run at higher levels of boost (swapping to smaller SC pulleys) can yield considerably more power output, but requires added effort to keep knock and KR under control. Running extra boost will increase heat and test the PCM's ability to deliver the needed fuel. Further lowering intake temps (IC), maximizing engine air flow (rockers, cam, exhaust), and tuning the PCM's fuel curves (PowrTuner) are just a few ways to help keep knock levels in check.
01-26-2013 11:48 AM
jonkamholtz I will. What I Android saying is that it looks like from that pic you sent that replaceing the cat with a strait pipe will delete the ubend andthe pcm was programed with arear o2 embalater. Are you sayin you don't think this will work.also what is KR?
01-26-2013 11:29 AM
Ejbiers The ubend delete isnt expensive and your gonna get a ton of kr without deleting it.
Its up to you but id delete the ubend before i dropped the pulley
01-26-2013 11:19 AM
jonkamholtz I planned on doing a comlete exaust in about a month.if install two high flow mufflers and put a strait pipe inplace of thecat do you think that I will be fine for now I have the tstat andwill grab the plugs. I HAVE received the pullys but the rest is still comeing Ups hoopefuly Monday.
01-25-2013 08:07 PM
Ejbiers Then grab
1 maybe 2 range colder plugs
180 degree tstat
ubend delete at least (headers and catback will also help greatly and is safer)
and then drop your pulley
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