Posted: 5/25/2026 11:20:07 PM EDT
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Small V8- 5.3 Liter, Gen3 LS, small cam 208in/214ex .550", small- 70mm turbo, 3.73 gears. Discuss strategies to maximize fuel efficiency with converter locked, light acceleration and steady highway cruise. The obvious: maximum ignition timing at low manifold pressure is done. Using HPTuners, I have just started moving around 02 switch points: Bumped ( +30mV) to .481 volts, aiming for about 15.1 AFR at cruise. How lean can I cruise? Other than listen for audible knock, what other signs of TOO LEAN should I watch for ? Power Enrich threshold at 115 kPa, so its pretty easy to stay out of PE. Once into boost curve, I ramp up to +20% fuel and water+methanol begins at 7PSI peak flow 10 Gallons per hour at 12PSI |
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Originally Posted By Positronic: Discuss strategies to maximize fuel efficiency ...... steady highway cruise. If you need 50hp to cruise then the most efficient engine will be a 50hp engine. Running a 500hp engine at 50hp is very inefficient. This is why economy cars have small engines - so they can operate at a higher fraction of their maximum power. Too much timing at light load conditions can cause dangerously high cylinder pressure without producing audible knock. Given the emphasis on fuel economy I would bet that the factory tuning for cruise conditions is close to the maximum MPG you will get. |
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Seeing some pretty encouraging trend: with O2 switching at .481 Volts, the last fuel fills have netted 12 miles per gallon, local short trip commuting-- That is a Huge improvement from the baseline, It had been running in the 10.5 to 10.9 range since turbo install summer 2024. . AFR running in the 14.9 to 15 range cruise. Also, have DFCO enabled, so total fuekl cut after 6 seconds of coasting.. ZERO fuel going downhill also helps a bit with engine braking on long grades. Might next install a relay and in cab toggle switch, so I can keep converter locked in 3rd gear, or even 2nd for towing low speeds on big hills. , , Any other tips from experienced TUNERS are welcom. Thanks |
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Originally Posted By Morgan321: You can't tune away the pumping losses that result from operating a high power engine at very low power settings. EPA Door sticker rating was 17 mpg highway- Hope that is still attainable, a free flowing exhaust, and a nearly free-wheeling turbo impeller shouldn't fuck up to much. Hopeful that I can get close to ECO-Boost economy numbers- but with a more durable, reliable long lived V8 |