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

[Burban22]

Anyone know what the difference is between these two generations?
What was changed on the later versions to increase +10hp and +5tq. Intake? Cam? Just the tune?
I have an 03 Burban early build with 8th digit T = LM7 so I got the 285hp LM7. I did get it blackbear tuned which definitely woke it up.

2000 - 2003
285 hp@ 5200 rpm
325 tq @ 4000 rpm

2004 - 2006
295 hp @ 5200 rpm
330 tq @ 4000 rpm

 

[Marky Dissod]

Besides switching from a mechanical fan attached the crank, to a pair of detached electrical fans?

 

[Fless]

2004s still came with a fan clutch. Electric fans didn't come in the Hoes until 2005.

 

[Burban22]

Yea I still have mechanical fan which I don’t mind having.

In addition to Blackbear tune I also replaced the stock muffler with a magnaflow 12588 which is nearly a direct swap (needs to be welded). Also added a AFE 54-74101 intake.

I’ve done the easy bolt-ons and will prob stop there for now.

Wondering if anyone knows where the 10hp gain came from in 2004.

 

[Burban22]

Muffler and intake pics attached

 

[Burban22]

2004+ 10hp gain due to flex fuel capable?

 

[Fless]

The LM7 isn't Flex Fuel, is it?

 

[Burban22]

Correct LM7 isn’t flex fuel compatible and that’s the main difference between LM7 and L59 according to multiple posts.

• They are 99% the same. I realized this past weekend that I've had an L59 the whole time I thought it was an LM7. Only differences are more injector flow (33 lb/hr vs 22.5-28, depending on the year iirc), different fuel injector connectors (EV6, I believe, vs minitimer), and a few differences in the ECU. Depending on the year, it got a sensor to detect the ethanol content of the fuel, and also depending on the year, it kept return rails longer than the non-flex fuel motors did.
  
  Besides that, it is literally the exact same motor.

L59 Vs. LM7 Engine : What’re the Differences? | Rx Mechanic

Distinguishing two engines having similar physical looks from the same manufacturer can be tricky. In this L59 Vs. LM7 debate, get both engines reviewed.

rxmechanic.com

The factory L59 injectors were rated at 33-36 lbs. and support about 435 hp at the wheels. Note the 2001-04 return style fuel system cam with 33lb injectors running at 50 psi, while the 2005-07 engines were returnless and had 36.6lb @ 58psi injectors. The easy way to know which you have is the 2002-04 rails were plastic and the 2005-07 rails were stainless.

L59 5.3L Engine Upgrade Guide: Expert Advice for L59 Mods to Maximize Performance

[Editor’s Note: This L59 engine upgrade guide is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at …

www.onallcylinders.com

 

[Burban22]

But different injectors shouldn’t account for the 10hp difference unless L59 was tested while using e85 but I’d think that would be more than +10hp difference.

 

[Fless]

Correct LM7 isn’t flex fuel compatible and that’s the main difference between LM7 and L59 according to multiple posts.

• They are 99% the same. I realized this past weekend that I've had an L59 the whole time I thought it was an LM7. Only differences are more injector flow (33 lb/hr vs 22.5-28, depending on the year iirc), different fuel injector connectors (EV6, I believe, vs minitimer), and a few differences in the ECU. Depending on the year, it got a sensor to detect the ethanol content of the fuel, and also depending on the year, it kept return rails longer than the non-flex fuel motors did.
  
  Besides that, it is literally the exact same motor.

L59 Vs. LM7 Engine : What’re the Differences? | Rx Mechanic

Distinguishing two engines having similar physical looks from the same manufacturer can be tricky. In this L59 Vs. LM7 debate, get both engines reviewed.

rxmechanic.com

The fuel pumps are also different, gas vs FF. FF has slightly less pressure but more flow, IIRC.

 

[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)