LT-4 knock module
11-23-2005, 01:54 PM
#1
Melting Slicks
Thread Starter
LT-4 knock module
How do you know if you need the knock module? I put headers on my LT-1 car so it's obviously a little louder but how do I know if it is sending false knock to the ECM and retarding the timing? Is there an easy way to tell?
The car doesn't exhibit any overt signs that the timing is being changed. Just a little bit of a burp backfire on part throttle shifts occaisionally is the only difference with the headers. Otherwise feels nice and strong.
The car doesn't exhibit any overt signs that the timing is being changed. Just a little bit of a burp backfire on part throttle shifts occaisionally is the only difference with the headers. Otherwise feels nice and strong.
11-23-2005, 02:56 PM
#2
Racer
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You will have to run some kind of data logger connected to your car while running to see if any knock is being picked up and the timing retarded. A speed shop equiped with the right software could do this or there are various software makers out there that make software to interface with your computer. Some allow you to make changes(the expensive ones) and some just show you what the car is doing and do not allow any changes.
11-23-2005, 10:14 PM
#3
Melting Slicks
Headers alone probably don't warrant an upgrade to the LT4 knock module. GM used it mainly for the extra valvetrain noise generated by the roller rockers.
11-24-2005, 09:09 PM
#5
Safety Car
Can someone explain what the LT4 knock module does? I searched awhile back and found several threads but nothing that really tells it's purpose or how it works.
Does it simply desensitize the ECM to knock picked up by the knock sensors? Is there a reason to upgrade an older LT1 car (which has 1.6 RR, headers, and a timing problem) to the LT4 system, and what does that entail?
Does it simply desensitize the ECM to knock picked up by the knock sensors? Is there a reason to upgrade an older LT1 car (which has 1.6 RR, headers, and a timing problem) to the LT4 system, and what does that entail?
11-24-2005, 09:49 PM
#6
Le Mans Master
Originally Posted by ScaryFast
Can someone explain what the LT4 knock module does? I searched awhile back and found several threads but nothing that really tells it's purpose or how it works.
Does it simply desensitize the ECM to knock picked up by the knock sensors? Is there a reason to upgrade an older LT1 car (which has 1.6 RR, headers, and a timing problem) to the LT4 system, and what does that entail?
Does it simply desensitize the ECM to knock picked up by the knock sensors? Is there a reason to upgrade an older LT1 car (which has 1.6 RR, headers, and a timing problem) to the LT4 system, and what does that entail?
11-24-2005, 10:02 PM
#7
Drifting
[QUOTE=ScaryFast]Can someone explain what the LT4 knock module does? I searched awhile back and found several threads but nothing that really tells it's purpose or how it works.
Does it simply desensitize the ECM to knock picked up by the knock sensors? Is there a reason to upgrade an older LT1 car (which has 1.6 RR, headers, and a timing problem) to the LT4 system, and what does that entail?[/QUU
Under ideal conditions the burning fuel in a combustion chamber propogates as an even wavefront from the spark plug to the face of the piston, pushing the piston down. Knock occurs when the fuel begins to self ignite at other places in the combustion chamber, creating secondary wavefronts that collide with the primary coming from the spark plug. This creates instantaneous high pressure spikes in the combustion chamber resulting in audible noise and mechanical vibration. In the extreme condition the piston, connecting rod, crank and other rotating parts begin to self destruct from these vibrations.
The knock module is designed to recognize these vibrations and retard the timing to stop the pre-ignition (knock) condition. I am not sure about this but I believe when GM put in the roller cam and rockers in the 96 LT4s they found that the mechanical harmonics of the valve train sometimes fooled the knock module into thinking their was combustion chamber knock. They cteated an LT4 knock module that fixed this problem. They were able to discriminate the difference between spark knock and valvetrain noise, and revised the firmware in the knock module.
I had a 95 LT1 that I upgraded to roller rockers and LT4 valve springs. I installed the LT4 knock module at the same time. I do not know if it made any difference since I did not take a baseline timing scan before nor a post installation scan later. The module was $35 so I figured why not.
The module fits into the ECM mounted over the battery on the drivers side. It is easy to change. Disconnect the three ECM connectos, pull out the ECM, open it up and you will see the knock module.
Does it simply desensitize the ECM to knock picked up by the knock sensors? Is there a reason to upgrade an older LT1 car (which has 1.6 RR, headers, and a timing problem) to the LT4 system, and what does that entail?[/QUU
Under ideal conditions the burning fuel in a combustion chamber propogates as an even wavefront from the spark plug to the face of the piston, pushing the piston down. Knock occurs when the fuel begins to self ignite at other places in the combustion chamber, creating secondary wavefronts that collide with the primary coming from the spark plug. This creates instantaneous high pressure spikes in the combustion chamber resulting in audible noise and mechanical vibration. In the extreme condition the piston, connecting rod, crank and other rotating parts begin to self destruct from these vibrations.
The knock module is designed to recognize these vibrations and retard the timing to stop the pre-ignition (knock) condition. I am not sure about this but I believe when GM put in the roller cam and rockers in the 96 LT4s they found that the mechanical harmonics of the valve train sometimes fooled the knock module into thinking their was combustion chamber knock. They cteated an LT4 knock module that fixed this problem. They were able to discriminate the difference between spark knock and valvetrain noise, and revised the firmware in the knock module.
I had a 95 LT1 that I upgraded to roller rockers and LT4 valve springs. I installed the LT4 knock module at the same time. I do not know if it made any difference since I did not take a baseline timing scan before nor a post installation scan later. The module was $35 so I figured why not.
The module fits into the ECM mounted over the battery on the drivers side. It is easy to change. Disconnect the three ECM connectos, pull out the ECM, open it up and you will see the knock module.
11-24-2005, 10:55 PM
#8
Safety Car
Originally Posted by NEVERL8
The module fits into the ECM mounted over the battery on the drivers side. It is easy to change. Disconnect the three ECM connectos, pull out the ECM, open it up and you will see the knock module.
Actually, I don't think it would actually help as I have real knock, not false knock from the rockers.
jwt - sorry, I didn't mean to hijack your post. Did you check your timing with some datalogging software?
