LS cruise timing

[RW TECH]

Are there any thoughts on how much this strategy will save? That is if you go from say 30 deg.@14.7 to 40 deg. and a lean burn do you get 1, 2, 5 mpg better?

It will be more than just one or two, more like several. If you have an engine on the dyno and you put it at a low load Cruise RPM area, you will see the torque meter escalate if you begin to increase timing. I personally have seen torque go up all the way up to 60° on Gen 4 LS, but that was with racing fuel and about 11:00 to 1 compression ratio. Mileage may vary but the point is it will be more than just a couple better.

[RW TECH]

While looking at factory tables keep in mind the OEM's have to meet NOX emissions standards............

And to reduce NOX they are required to use richer A/F closer to stoichiometric than you would use for best economy.

I've been using 40+ degrees in the cruise area of every LS combo I've been tuning. All have been on Holley EFI.
They like the low load cruise timing high, just like old school stuff

Same as tuning a carb for best fuel economy, presumably you are using A/F lean as possible which requires more advance.

Absolutely. Folks should not go about believing that the spark and fuel settings in low load operating ranges on an oem application are there only to keep the engine from knocking its brains out.

[Tom Walker]

As far as OEM timing and fuel tables are concerned, priority #1, is meeting the current emission target.
If the current emission target is not met, all the other factors become a mute point, ( economy, driveability, power ,reliability and etc).
All of those factors are very important to the OEM, but 1 is set in stone that has to be met while the others are on the "wish list" of objectives to be persued.
Most of us here, do not have the same goals or constraints as the OEMs, thus our tuning methods and philosophy's take a somewhat different path as has been expressed very well by several posters on this thread.

[Lshungy]

While the topic has slightly shifted to include fueling requirements at cruise this brings me to another question on my mind . Currently as far as I’m aware the current tune cruise mixtures are based around stoich not the typical 16-17 :1 . With the tuner stating that these early LS based engines do not like to be run leaner at cruise , with anything leaner requiring more throttle input and hence more fuel negating the advantages of leaner mixtures .
Does this sound plausible or is it just his personal opinion/ experience??
This also maybe vehicle/ application specific and especially in my case of heavy vehicle / large tyres etc .
Cheers Carl

[07GTS]

heavy vehicle i would think would like stoich fueling to keep best torque, its all based on torque as the vehicle requires a amount of torque just to keep it going at cruise, with the normal variables like ambient temps and wind the same torque needs to be made to hold speed so any way u can make that torque with timing or fuel its just if the engine is doing it more efficiently or not,

the Aus LS1 had a lean cruise and ive noticed it dosnt really do much if anything, personally ive made the best at stoich just with timing and injection timing to suit my camshaft, going leaner as well ive only noticed gains when using e85 but also u have to then be in open loop which isnt the best as u can be dialed in and then be at a constant headwind using more load with a richer afr that the trims would normally keep at stoich for such situations