Difference between 2000-2003 and 2004 - 2006 +10hp 5.3 LM7 L59

[Mudsport96]

The LM7/L59 engines are physically identical from 2000-2006. The 1999 Lm7 had a slightly different cam that you probably wouldn't notice a power difference with 115.5 lsa vs the later 114.
As stated above, injectors and rails are different for the flex engines. Hell the base tunes are identical. Only when the ecu sees extra ethanol does it "switch over" to the flex tune.
The extra 10 hp is a combination of the e fan additions and electric throttle. The later P59 computer in the 03 and later units had way more computing power so more performance could be had.

 

[Burban22]

So my 03 suburban could be 295 hp instead of 285hp if I change from mechanical fan to electric? Attached pic of computer. It has the large blue and green connectors.

I just put in the flex fuel pump with the square connector instead of the original non flex pump with the flat 4 connector. I did this because the fuel sender is “robust” on the flex pump (different design) which is why I changed my pump the fuel sender was worn out and was having some occasional long cranks.



Non flex fuel pump
Carter P75023M Fuel Pump Module Assembly https://a.co/d/ee5sMJG

ACDelco GM Original Equipment MU1738 Fuel Pump and Level Sensor Module with Seal and Float https://a.co/d/doP5oCN

Flex fuel pump with robust fuel level sender
Carter Fuel Systems P74905M Fuel Pump Module Assembly https://a.co/d/aPdv0Xb

ACDelco Gold MU2295 Fuel Pump and Level Sensor Module https://a.co/d/gvb0tyG

 

[Mudsport96]

So my 03 suburban could be 295 hp instead of 285hp if I change from mechanical fan to electric? Attached pic of computer. It has the large blue and green connectors.

That is the p59 computer so yes it can be setup for e fans

Watch this video for how much power the accessories eat. The fan is on this dyno is worth like 7 hp and he explains why it probably eats more.

5.3 dyno test of accessories

 

[Stonefort]

I thought I read the main difference for the power was that the LM7 did not have a separate high and low octane table in the tuning. The L59's high octane table had more aggressive timing......and that is where the power increase is from. But only if it determined you put premium in it (it determines this by not hearing any knock while trying to run the most timing it can get away with)