Supercharger gas milage...

I know, I know another gas milage thread but this is a bit differant as I am not really complaining or asking any questions. I am just telling you all what I found.
I knew going in that switching to a DC from an AC, lifting, and bigger tires would negativly affect my gas milage. I also knew that going with a CAI, super charger, and cat back exhaust would also negativly affect my milage. What I didnt expect was what I recently found out about driving with the super charger.

I just recently got my scan gauge and calibrated it for my truck and tires. Right now my scan gauge speed and GPS speed are spot on with each other and my scan gauge is getting smarter about my driving every fill up.

I thought that by driving around with my truck around in 6th gear as much as possible was the best thing for improved gas milage. WRONG!!! According to my scan gauge over the past 2 week, I have found that because of the supercharger by keeping it in 6th gear, the engine has to work harder because its not on the boost much at all. Even on the freeway this seems to be true (at least up to 65-70mph, then I am just screwed either way).

What I found was that by keeping it at around 1800-2300 rpm's and an even throttle (not really accelerating or decelerating) on level ground my scan gauge reads 9999 a lot of the time. This is something that it never did if I was putting around in 6th gear. I found this out at the end of my last tank and have been experimenting during this tank. My gas milage on this tank has been 17+ on this tank so far and thats almost all around town driving this time. I can only attribute this to be that is about where the S/C really starts to make its power so its easier for the engine to maintain that speed/RPM.

I also found that because of the super charger, it appears to give me better gas milage if I accelerate quickly to my target speed and then set the RPMs/gear to where it needs to be. I a bunch of experimenting with slowly accelerating slowly, in a higher gear, etc and the finding show that its better to get up to speed quicker if you have the S/C. Not sure if this is true of the automatic but it seems to be on my 6spd.

I am hoping that with the change to summer gas, my new found driving style, and the engine lossening up (its only got 7500 miles) I will be able to greatly increase my milage.

Currently I get about 12.5-15mpg according to my distance traveled(odometer)x1.07(size differance of my current tires)/gallons put in my tank. I also use milage meter for my blackberry to record it all. I get about 240 miles per tank right now (thats after the tire size adjustment). I am hoping to improve that greatly with this current driving style. I never really even broke 300 miles with my 6spd AC before either and that had 50,000+ miles and I did many cross US trips with it. I live in the Portland, Or area so my roads are pretty hilly, alot of ups and downs so I will never get the milage of the guys who live in the the "flat" states.

Just my observations of gas milage and engine performance with the super charged 4.0.

 

Well in that case I didnt see shit for a differance in milage then.

And I am sure differant places change gas at differant times. Especially since as of Feb 02 it was still in the low 30 and snowing where I live so...

 

for the best results in mileage, set your fuel cutoff settings on the scanguage as low as possible to keep the scanguage from displaying 9999mpg, because that doesnt get recorded. you always want to show a real mpg reading

 

OK, how/where do I set that, I am going to look in the manual as well but if you can point me in the right direction as well.

 

X2. It seems weird that while cruising you could get a fuel cut-off. Navigate through your setup and you'll find a way to change the % throttle to obtain the fuel cut-off. Get it lower.

 

Ok, I just read through the manual and didnt find anything on setting throttle % or fuel cutoff... I will read it again and see if I can find something.

 

Still couldnt find anything on it, so will try looking through the actual scan gauge and see what I find.

 

I bet that if you would re-gear you would gain some MPG's. I see that you are running 285/75/16's. I am in the same MPG range you have. I do not have a supercharger but I have a ARB bumper and winch with 285-75-16's and my mileage is about 14-17 mixed driving. I can really tell a difference in power switching from stock 265-70's to 285-75's. I am thinking about re-gearing.

 

I doubt I will re-gear. Only going up to 33"s really dosent warrent re-gearing it and any power I lost going with the larger tires I easily gained by adding the supercharger and other go fast items. About the only thing I will do is eventually put an ARB locker in the rear since I have a TRD Sport I dont have a locker or A-trac so a full on locker is in the works. I probably wont go with armored bumpers either, most likely get the whinch that fits in the front/rear mounts.

On a side note, after a little exploring I did find the cutoff threashold on my scangauge. I changed the setting so I get a larger milage span reading but I still do get the 9999 mpg reading quite often. And J1999T, the 9999 reading does add to my average MPG reading. I thought it did so I did some tests and when I am getting the 9999 reading my mpg reading my mpg average goes up.

I am really hoping to get an average of about 17mpg this tank. I did see an average of 19mpg for a short trip I took earlier.

 

I jsut filled up and got an average of 15.5 mpg. I am happy with that. A good portion of that was on the freeway doing 70mph in a very hilly area so that greatly reduced my milage. Unfortunatly if I dont do 70+ I will get smashed by the local log trucks and semi drivers. Plus add in a couple high speed runs at full throttle and thats where i get the 15.5. Not to bad considering how my truck is setup.

I seem to get much better milage in town. I would be interested to see what I get in town for a full tank. I would guess 17+ around town.

 

So I am finding out now with the supercharger I can get 21-24mpg around town but on the freeway down here in Arizona I get 12-14mpg because everywhere out side of the citiesthe speed limit is 75mph and that KILLS my milage. If I spend most of my time around town I get great milage, driving out of town kills me.

I am really tempted to to someday in the future have my 6th gear repalced with a real true overdrive gear. Maybe something that drops the RPMs to 1500 at 75 or something like that.

Anyone else done this? Regearing wont work as I dont want to change all of my power band, just 6th gear and is not really necissary.

 

Yea, it wasnt something I was going to do in the near future. Maybe if/when I have tranny issues and I need to drop it out or when I switch to a FJ manual transfer case then I would do it, but for now its fine. Just thinking and sharing my observations.

 

Great info, I'm looking into the SC and the info given is pretty helpful to know what I might be getting into. Thanks

 

UPDATE UPDATE UPDATE...

OK, it seems that my gas milage was being killed by my BESTOP soft topper. I am seeing milage of easily 20+ mpg on the freeways going up over the mountains and 22+ on flat ground at 65 mph.

If you go and look at my milage on fuelly my last 6 fill ups got better and better as I was going through the mountains. I am seeing awesome milage as of lately and I just recently installed the URD 2.8" pulley and that seriously woke the engine up. I am about to leave on another 1700 mile road trip so we will see what kind of milage I get on this one.

 

With my supercharger on the freeway at speed limit (75mph) going from elko to Salt Lake I get 22.8 mpg and city is 17 mpg if I stay out of boost...weird how your city is better....i guess different driving habits

 

You'll love it if you get SC....I dont drag race or have a SC to act like a sports car...I have it for the torque and its nice to have the power when you need it

 

I am finding that I get the good in town milage down in Tucson, mainly because of how I drive it down there (6th gear, putting around at 35). Up here in Washington I am seeing the same that you are 17-18mpg in town.

Your an auto so its to be expected to see a little better milage out of yours than mine due to the gear ratios. I am interested to see what I get now with this under drive pulley on, it really woke the truck up. You can feel a substantial power increase and the truck just all around feels happier.

 

I really want a SC! Hard to justify it right now though. How much did you guys pay for yours if you dont mind me asking? Best i have found from looking around the forums is i think 3700 with the fit kit. Sound about right?

 

I raped the dealership something fierce for my truck. I got mine as a package deal of truck, supercharger, CAI, & cat back exhaust, tax, title, licensing, and install total out the door for 31,500. I walked in telling them what I wanted, what accessories, what color, and I didnt care about thier kids, wife, paycheck, anything. This is what I am paying now lets make a deal. I am kinda an asshole like that.

The catch on why the dealership did it for so low, I told them I would let them finance me at WHATEVER interest rate they wanted. They came back with a 11.99% interest rate for 72 months. I just smiled and said yea, sure I can do that.

Then when the first payment came due I walked in wrote a check for payment in full and the guys looked at me with a serious WTF face. They gave up profit on the front side expecting to make a ton off me on the back side... The sales manager and salesman wont even look at me when I walk in, I just smile and they look away.

But yea, 3700 is about the best you will find. Dont forget to add in the install kit $300-500.

 

Wish I was able to pull something like that off