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I just purchased a 2004 Fleetwood bounder 36' motorhome with the 8.1 and Allison 5 speed. The PO had a Banks Power 49558 PowerPack System installed but never updated the tune for it.
What should I look at changing in the tune to help get more MPG and power?
Getting more mpg with a brick that runs a 8.1 is really not going to happen. Maybe if you drive 55-60mph everywhere you'll get okay mileage but I highly doubt you can ever really improve it.
To get the most power from it will require 91-93 octane and doing changes to power enrichment and timing to obtain the most power. The extra cost to run that fuel will not be made up with improved gas mileage so it's a lose/lose situation if you ask me.
You have a lot more air flow now so you need to do your VE and MAF. The motor homes have a tendency to break pistons because PE never kicks in. Your pulling a big hill with tons of weight at 14.6 afr and boom. Get that PE to kick in and shoot for 12.5-12.8. Once you do that you can mess with the timing. Don?t remove burst knock on that either. The PE will make hill pulling a lot better. But gas mileage you might pick up 2mpg with a really good tune. When I went with CAI and mufflers and tune I went from 6 mpg to 9 mpg hauling 12,000 lbs. post your tune file.