Chevy Impala SS Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
31 Posts
Discussion Starter #1
I bought and installed an LT4 chip for my '96 Impala SS. the last 2 digits on the chip are *****81. The original chip # ends in *****71. I bought an additional ECM, (just in case my original unit fails) from Flagship One, and the number on that chip ends with *****91. The the LT4 chip is needed to filter the noise from the headers and 6:1 roller rockers installed on new 383 stroker I built. The original chip picked up the noise from the knock sensors and retarded timing that prevented RPM above 3500. At present. the knock sensors are "OFF", after a dyno tune and RPM power curve is restored, impressive. I am in the process of getting it re-tuned to engage the knock sensors, after changing the old ones for new Corvette sensors, and the # 81 chip. My question is:
What is the difference in chips Between the original # 71 chip that was in my car vs the # 91 chip that was installed in the extra ECM I bought ? Any electrical engineers out there who can answer ? Does the #91 chip filter header/ roller rocker noise like the # 81 Corvette chip?
 

·
Registered
Joined
·
1,874 Posts
LT1 family Knock Modules
16188709 OBD1 B-L99
16188309 OBD1 B-LT1
16177700 OBD1 F-LT1
16177690 OBD1 Y-LT1

16214691 OBD2 B-L99
16214671 OBD2 B-LT1
16214661 OBD2 F-LT1
(don't know if OBD2 F- & Y- LT1 shared the same Knock Module?)
16214681 OBD2 Y-LT4

Sorry, not an electrical engineer.
The LT4 knock module is a 'fix' for an LT1 knock module's erroneous oversensitivity.
IF you install a noisier timing chain, roller rockers, and/or a noisier exhaust system, your older knock module MAY or may NOT mistake the awesome acoustics with knock noises and retard timing, negating the gains that should have been released.
IF your mere LT1 knock module mistakes any of your upgrades for knock noise, THEN - and only then - do you need an LT4 knock module.
 

·
Premium Member
Joined
·
5,220 Posts
Below is the where, not the effect.
Not sure of the sensitivity of the 96 L99 module but wouldn't think it would be notably less sensitive if at all than a lT1

16177700​
1994-1995
F-Body 5.7L​
1​
CONFIRMED
16188309​
1994-1995
B-Body 5.7L​
2​
CONFIRMED
16188709​
1994-1995
B-Body 4.3L​
2​
CONFIRMED
16177690​
1994-1995
LT1-Corvette​
2 ??​
CONFIRMED
16214661​
1996-1997
F-Body 5.7L​
1​
CONFIRMED
16214681​
1996
LT4 Corvette​
2 ??​
CONFIRMED
16214671​
1996
5.7L B-Body​
2​
CONFIRMED
16214691​
1996
4.3L B-Body​
2​
 

·
Registered
Joined
·
31 Posts
Discussion Starter #4
Thanks Markey and 95wagon ! I installed the Corvette chip in my original ECM. It's ready for a final DYNO and see if I can run with the knock sensors turned "ON".
I'll keep both the xxx71 and xxx91 chips, for "spares", and have the spare ECM with the original chip, 16214671. I'll have a tune on that with the knock sensors 'OFF", in case my original ECM with the Covette chip, xxx81 burns out.
Anyone interested in a 4.3 B-Body ECM chip ?? ( My attempt at some humor !)
Thanks again!!
scottdog
Morro Bay. CA
 

·
Premium Member
Joined
·
5,220 Posts
Not that you need it but depending what Flagship charged you, you might want to touch base and say " Hey A%%$%^&ole, give me the Knock module for the PCM you sold me".
 

·
Registered
Joined
·
1,874 Posts
Thanks Marky and 95wagon!
Installed the LT4 knock module in my original PCM. It's ready for a final DYNO and see if I can run with the knock sensors turned on.
The answer is already yes you can (unless something else is wrong?).
I'll keep both the B-LT1 and B-L99 knock modules, for "spares", and have the spare PCM with the B-LT1 knock module.
I'll have a tune on that with the knock sensors 'OFF", in case my original PCM with the LT4 knock module burns out.
Thanks again!!
If the original
PCM
with the
LT4 knock module
burns out, you should definitely try transferring the
LT4 knock module

to the spare
PCM.
 

·
Registered
Joined
·
31 Posts
Discussion Starter #7
Dyno tuning with LT-4 knock sensor chip "ON", revs right up! Had the dyno tuner "flash the spare PCM, I'll just switch the chip, if any problems with original PCM.
Happy with all the modifications, ready for auto cross!
 
1 - 7 of 7 Posts
Top