I just replaced an LT1 knock module in a 95 F-body LT1 with an LT4 knock module in an attempt to reduce my false spark knock (still get the same 10 deg KR with 93 octane or 103 race unleaded with either module).

However after making the switch to the LT4 the scanner showed no EGR %. Prior to that it would run 0% during off throttle or full throttle and 99% at part throttle.

Any ever see this or know what it is?

Should I keep the LT4 module in? My next step was to get a pcmforless tune and desensitize the kR since I know at least part of it is false.

 

Generally, EGR is only activated when engine operating conditions would promote high combustion chamber temperatures. Most typical condition is lugging the engine at low RPM in O/D. You see a variable duty cycle on the EGR during those conditions. I get a lot of scan logs to reveiw for people, and I don't recall any that have almost continuous 100% DC on the EGR. Is that what you are saying you were getting before.... 99% EGR almost all the time, between off-idle and 3,500rpm (stock programming does not activate EGR above 3,500rpm)?

EGR lowers the combustion chamber temperatures, to reduce the formation of NOx (emissions issue). It would seem logical to activate it when the engine is experiencing operating conditions that promote knock. But it shouldn't be activating at WOT or above 3,500rpm.

 

Yes, you are correct. Previously I was getting EGR during the times you describe. During light throttle but not at high rpm or WOT. Typically when EGR kicks in it is generally 99% duty cycle.

After the change to the LT4 KM. I am not showing any EGR at any time even after driving for 20 minutes.