Multiple tunes for power vs. mpg?

[worldtransfreight]

I'll be using my L86/8l90 for commercial use. Is asking my tuner for a loaded/unladen tune a silly question?

The idea is I turn my phone into a Hotspot to communicate with HPtuners and switch to a more mpg friendly tune program on my laptop. One tuner said that I would basicly have to retune every time.

I know gas engines aren't as flexible as diesel on fuel maps, but there has to be some variables right?

[GHuggins]

You can pretty much tune for both in one tune - you just can't necessarily tune for higher octane fuels without using an E85 trigger somehow to switch timing tables. I'm actually in the middle of tuning one right now that has a cam, running on 91 and has an E85 conversion and is used for highway a lot on top of being used for towing a goose neck loaded trailer behind a 1500 truck. Actually another member on here I think his is doing good and almost wrapped up for the moment anyway until he gets into his transmission... Still fine tuning his TM and timing.

Now with that being said, unless your engine is stock don't plan on a tune that in depth being done overnight. I'm roughly 50 revisions in fine tuning his timing, vvt, tm, DI fueling (that alone requires a lot of playing around with when a cam is involved), E85 multipliers - both for regular fueling and SD fueling (yes there are 2 just for this that require dialing in), open loop tables / modifiers, MAF / VVE tables, and so on and so on. Basically getting into an OE level tune. Lots of fine tuning and testing. With his stage 2 cam, he's getting around 20/21 mpg unloaded, 18/19 with empty trailer and I think 12/14 with loaded trailer on pump. Empty truck he's getting 15/16 on 60% ethanol. I'm happy with that. On a stock 6.2 running 93 the best I've ever gotten with one of my tunes was 25/27 empty truck on highway. All of these should be 4wd trucks used for work too.

SO, basically - yes it's possible to have everything in one tune. You just have to get a good tuner... My personal daily work truck is more or less an overgrown bread truck. 6l ls under the hood coupled to a 5 sp allison going through a low geared rear end. Runs all day in stop and go traffic - in and out of wot constantly all day long all whilst toting around 17 to 20000 lbs Tuned by me - burns half the fuel it did when I got it, but it was WAY detuned to "safely" handle the load of the cargo and 4500 chassi freightliner truck... It's biggest problem are brakes :/

[worldtransfreight]

Thankyou for your thorough input. A couple more questions. I think I will be 11k empty, 21k-ish loaded. I know the 8l90 isn't necessarily made for this, but seems to be a pretty stout trans. What axle ratio would you recommend (31"tires)? Should I just start planning on finding another transmission solution? I would love to try the new 10l1000, but I dont think there's a converter yet for gas. Someone who has had both 10 speeds apart told me the 10l90 and the 10l1000 are pretty much the same, just ones bigger.

[5FDP]

I'd think 4.10's at a minimum or even 4.56's. The 3/4 and 1 ton gas trucks with a 6 speed run 4.10's I believe and 3.42's is pretty much all the half tons can get on the max tow package. But those trucks are more geared towards fuel mileage with the 8 speeds.

[GHuggins]

I assume this is a 2500 or 3500 to be moving around that sort of weight on a daily basis? If that's the case then hold and shift pressures can be adjusted via torque modeling adjustments, but honestly the best way I've found 8 speeds to hold up to power is to kill all torque management and then spend 2 to 3 days dialing in individual shift cells - extremely time consuming and requires the tuner to be in the driver's seat with the vehicle pretty much loaded how it will be... I would probably even lean towards putting lower gears in it, if you really want it to hold up, but then your sacrificing mpg or possibly not if you can drive it around loaded with light throttle - good thing about 5th gens is that they can be leaned up a little by changing a few settings for light throttle input.

[Dominatorstang]

Talking MPG I figure you want to save at the pump and since these engines are built for 91 octane then E85 makes good sense to save fuel cost to me. It also shows to gain power and run cooler. Not great to fuel up more often because of it but hey. Then like Ghuggins mentioned about having a tuning that does well at getting MPG and power can help greatly. I trust Ghuggins for that type of tuning too.