Owner of a 2007 Z06 will be doing 2 trips covering about 6,000 miles from east coast to elevations such as Denver and heat as hot as in New Mexico.

Objective is with the price of high octane gas was to custom tune for all those climate and elevation changes, the summer heat but conserve fuel.

All areas of the claibration had to be touched to assure during part throttle and using cruise control engine runs leaner but does not induce knock but assure if getting into Power enrichment that engine would be safe.

First pass of testing with mileage tune was done with weather about 90 degrees. This way if engine does not have a lot of knock then tune would be close.

As results show even with fuel trims about 5% lean to as much as 8% lean and taking engine as high as about 4,800 RPMs there was almost no knock and the little knock there was was less then 2.5 degrees

There is something I don't understand about the relationship fuel trims and mileage.
No matter how lean / richt you set the fuel parameters the oxygen sensors will bring back the engine to run stoichiometric (assuming it's OL). How can you affect mileage with fuel trims?

The only thing I can imagine is that if the fuel trims are positive the engine runs between stoichiometric and slightly lean, and when the fuel trims are negative the engine runs between stoichiometric and slightly rich.
So setting the fual parameters so to have positive fuel trims would save some fuel.

Is there another reason? Can you set a different target for the oxygen sensors? Like 15.5 instead of 14.7?

Stefano

That is why I stated all areas of calibration wre touched as what you mention IF only the fuel injectors were leaned out a lot then the O2s would see that and just command more fuel.

By keeping the STFTs values within it's operating window then LTFTs are low and PCM does not do anything about it but other areas like timing also have to be tuned and as you notice even in the above testrun and engine taken to 4.700 RPMs the engine only produced 250 HP of the 505 the LS7 outputs.

Mmhh... more questions:

Are you saying that the engine IS running leaner than lambda = 1 but because the STFT remain between -1 and +1 LTFT won't change?

Is it possible to tune this way a 98 PCM (like mine) using LS1Edit or is it possible only for newer PCM's and a more powerful software?

Talking to a local car shop that is used to tune European cars they explained that they usually change the lambda target for different areas of the VE table.
What they do is set lambda lower that 1 for fuel economy in low load areas, and they set it up to an AFR of 13.5 for that VE areas used during acceleration (a lower AFR at WOT).
This has nothing to do with PE, it's still in CL.

Many cars over here have a wideband oxigen sensor as stock equipment (Like the Bosch LSU-4): those PCM's don't have a closed loop for lambda = 1 and an open loop with a power enrichment. The lambda value is constantly controlled in every load condition: from idle to WOT.

Can you change the AFR target using the GM narrow band sensors?