what i don't like is the fact that we are giving away our country's money to these foreign countries/oil companies. simple and plain.

not here to whine about the prices, but i am here to help people not buy 50-60gallons of "terrorist funds" a year.
on the other side, mods with more power and better fuel econo cannot hurt. or can it?

if the guy wants to know how to improve the fuel economy, who are you to say he is whining? you simple don't have to write to or read this thread. SIMPLE AND PLAIN.

i think and hope we all can get along. we are here on this forum to help people out or tell them about our experience, good or bad. we are not here to talk about people, we are here to talk about our cars.

 

My this thread got interesting!

I take your question seriously. You have a very light car with a very big engine that already gets good fuel economy. However, fuel economy is a measure of performance like any other. If you want to improve it along with power, well splendid!

I have no experience with the LS3 A6, so this may not help. My car is an '05 Z51 manual. I have quite a number of mods including: a 228/232, 600/600, 112 +5 cam, Trickflow 225 heads, Calloway Honker, FAST 90, Dynatech 1 7/8 X 32 headers, Corsa Sports, an underdrive pulley and a tune. The A/F ratio is 12.5 ish. I have also never checked the actual fuel mileage. I have however, checked what instant MPG the DIC indicated on a flat stretch on the freeway at various stages during the mod process, as a set of relative reference points.

Factory stock, at 400 miles, the DIC said 28 in 6th at 77 MPH. Today, the DIC says 32. With a prior tune at 13.0 A/F it said 34. Without the cam and heads but with Crane Gold Race 1.8's, the DIC said 31. All of these readings were in 6th at 77MPH on a flat stretch. I suspect, but don't really know, that these mods made the engine more efficient under that circumstance. The LS2 is a big engine spinning at very low RPM's, in that particular circumstance. It is apparently quite efficient in its stock trim. I suspect, but don't really know, that a similar set of mods (except, of course, the heads) would have a similar impact on your car. It's not so different from mine. Since the engine is bigger, they might produce slightly superior results.

Good luck!

 

My understanding is;

A/F ratios on a Dyno @ WOT (or whatever % of WOT the drive by wire allows) don't compare to A/F ratios at 1600-1700 RPM partial throttle steady cruise. Low RPM steady cruise should be controlled by the O2 sensors, WOT by pre-determined maps.

 

My understanding and yours are the same on this point. My tuner may have changed something else, too, like timimg. His assignment was to cut the power a little bit. I know that is heresy.

Another possibility is that I had the air on, at 32 MPG (for sure) and didn't at 34 MPG (don't recall but the weather was cooler by at least 20 degrees). Ambient temp could account for some difference, as well.

All that aside, the point is that a cam/head package doesn't necessarily cut MPG. In my case, every modded state resulted in better MPG than stock.

 

A/F ratios range from about 14.5-15:1 at cruise to 11:1 under 9psi of boost. That's on a Radix blown 6.0L truck. I would imagine an N/A motor would be similar, maybe not as rich at WOT.

The only way that I could see a forced inducted motor being more effecient is if you downsized it. Fewer cubic inches can be made to run as well or even better if you pressurize it. When you set the cruise, the blower is just along for the ride. Your smaller engine running under vacuum should do better than a large one. The blower's there to grow the engine when you ask it.