LS cruise timing

[Lshungy]

Evening all , does anyone have experience with LS1 Gen3 cruise ignition timing numbers ? Engine is currently running fantastic at all rpm’s and load points but after having a quick look at the basic timing tables at low load cruise rpm’s they seem very short to me . Most around 30 deg . I’ve heard the LS base does not need a lot of advance which is fine at peak horsepower but do the old school rules not apply at cruise loads/ rpm’s ???
I’m used to seeing mid 40’s of timing to help with economy ( which I’m also chasing) and to help keep engine temps down ( which I’m also chasing too )
This setup is in a large 4wd , big tyres kind of deal if it matters .
Cheers Carl

[07GTS]

usually in the 30-40 deg for cruise, depends on the vehicle and rpm, ive seen some in the mid 40's but not sure if they were set knowing its better or just thinking its better

[Geoff2]

Are they not known for a very efficient chamber design? If so, that means less timing under all conditions.

[blown265]

The following quote from RW Tech in a similar recent thread summarises the overall timing approach well.

Quote
"Right, exactly. A street car with distributor ignition should NEVER run with no vacuum advance, locked centrifugal advance, etc.

All the time I see EFI cal files created by "tuners" that don't have nearly enough spark at low load, sometimes they have same spark at low load as they have at high/full load regions in the map.

Tuning at WOT is the easy part that pretty much anyone can do. It's a LOT more difficult to get a good cold start because you only get 1 of those over a 8-12 hour period, and it's also harder to get cruising load areas dialed in because it requires quite a bit of driving at various loads to get it right."
End quote.

Specifically, for an engine with a management system controlling fuel and spark tables, the ability to have the correct amount of spark lead at idle and cruise becomes adjustable to a much finer degree.

I do question why many of the LS based maps Ive seen have only 30ish degrees at cruise? Does anyone have an LS map with 40+ ? Not saying they dont exist, I just havent seen one, and I know the OP would be very interested in seeing one too.

Regards
Paulie

[07GTS]

factory is in the 25-35 deg range for cruise, what id usually recommend (not sure if works in this situation ) is to use the cluster instant fuel usage calculation with cruise control and drive same road same way ect to get the most repeatable tests and adjust timing, this way using the instant usage u can see the overall torque gain/loss as if timing improves torque it will use less throttle and the instant usage improves a smidge and opposite happens if u have too much timing or too less, ive even used the injector timing to the same affect if u have a camshaft with decent overlap to help economy

[07GTS]

the 5.3 LS1 seems to be a little higher



the LS1



the Australian GTS LS1 is a bit different to the rest

[Lshungy]

Geoff2 as far as I’m aware the LS base is quite an efficient design over the previous sbc gen 1 ‘s . I was also of the belief that any engine design / brand that was more efficient required less timing not more ??
07GTS thanks for the spark tables , this engine is an Aus spec not sure how much it differs but it appears to have quite a few more degrees at light loads and in higher in the rpm’s . Unfortunately I do not have instant fuel consumption readouts as this is a conversion into an older 4wd so it may take some time to average out fuel figures and or use throttle/ map inputs to see changes .
I think I might also have to bite the bullet and buy some software and a laptop and have a look in real time .
Cheers Carl

[rebelrouser]

just to ask, is this computer still capable of pulling timing out with the detonation sensors? You can advance it all you want, but the real timing engine sees is dependent on what the detonation sensors are sensing and telling the computer to retard.

[07GTS]

there is knock sensors so it will be safe, best to not rely on knock sensors tho and timing should be more so always in the safe range and the sensors only remove timing for the odd occasion where something isnt right

[RW TECH]

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

[3pedals]

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

[Tuner]

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.

[Lshungy]

Thanks to all who replied and confirming also that higher ignition advance can be used in later model designed engines for better economy in light load conditions.
Now to do a bit of research on the popular LS tuning platforms
Cheers Carl .

[Mat-it]

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?

[3pedals]

That's impossible to predict. Way to many variables. But the difference is very noticeable to me