I've been doing a bit of traveling this week and I know I'm not driving that conservatively. My question has more to do with straight highway driving at 70. Was there a loss before and after your supercharger install? I think I'm seeing a little more than I was expecting, but Hwy 90 isn't the best place to establish straight highway mileage. I bit too much stop and go and too many jerks who think they have the right to go as slow as they want in the left lane.

I may need to put it on the interstate. Just wondering what y'all have experienced. I need to get around to installing my exhaust too. Cooler temps can't be that far off.

 

Mine dropped by a few mpg.

This weekend doing 75/80mph I got about 19mpg. When I was n/a YEARS ago, i was getting 21-22mpg.

 

I get best S/C 16mpg, but I am lifted with heavier tires. New, I would see best 18-19mpg N/A. This was with the Roush tune, with how the truck feels and acts, I feel I am going to be a little better.

 

im kinda curious on how the old 97-03s are doing with the L swaps

 

If you guys are getting 19 enjoy while you can. I would say lucky to be 15-17 on highway. Of course this obviously depends on how much boost and tune. And even on the highway I have been know to pass the idiots.

 

I have a centi so no real boost till about 2500 rpm. I cruise at less that 2500 rpm so I only have to contend with the power required to spin the Blower. I may have lost a few mpg but I never bothered to calculate it. The gas gauge does seem to be connected to the boost gauge though.

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at 70mph with the cruise on I get around 17mpg with the Harley truck, the green truck shall we just say "smiles per gallon", with the procharger around 25 mpg in texas with the cruise on and 3.55 gears

 

the more normal you drive the better mpgs will get, i can get 19 at best, i just cant help my self

 

The best I have got was 16 mpg on the interstate. It's a whole different story when I start playing with it around town.

 

my problem is I can't stop playing around, I have had my supercharger in for just over a year and have yet to run thru a tank of gas with me not going into boost at least 4-5 times per trip, and I only live 5 miles from work, no highway, just side roads, and deer.

 

I also live close to work (7 miles to be exact). I get on the highway and off the highway more than anything. Horrible on gas mileage. I average 10-11mpg around town since I am on and off the highway so much.

 

The question had nothing to do with fuel costs, but I knew someone would bring that up. I fully expected a loss in overall mileage. But, all things being equal at highway speeds, the only difference is you're turning over the supercharger with the bypass open. Stoich is stoich in closed loop, so unless there is more power being used to turn the blower, I wouldn't have expected much of a difference in closed loop operation in theory. It's just not so in the real world and I wanted to know other folk's experience to make sure I didn't have a problem.

 

Concur! You get better fuel economy when going from stock to custom tune, but then when you go supercharger you'll be lucky not to go below where you started. My 2003 5.4 initially got 15mpg driving to work, 17freeway. Added eaton and at first 13.5 driving. Then added better tune and I'm back up to 15 to work and 17ish highway. Of course those highway runs where at a posted speed of 70 and as we know with the eaton passing is fun!!!!!! Now when I tow it goes way low, but then I still can pass anything even with a 5500lb.

 

Interesting point about boost bypass, most of Eaton converts run with it INOP. The stock ECM has no provisions, only the HD/L ECM does.

 

Not true. Roush uses the load based signal from the IMRC to operate the bypass solenoid. There are parameters in the PCM for the IMRC and are used to contol the bypass.