a guy i was talking to said that if you run a turbo on low levels of boost, you'll get better gas mileage than without a turbo. is there any turth to this? i'd love to get a turbo in my truck*, but with gas prices the way they are, i just can't see losing gas mileage. however, if i could get better gas mileage, and then if i wanted to, flick a switch and run high levels of boost (saw something about a turbo that lets a hemi deliever 500 rear wheel horse power on the forum the other day) when i want, that would be great. does anyone know anything about any of this? thanks.


*actually a power wagon i'm planning on getting, not my dakota

 

any time you add more air, you have to add more fuel to achieve the 14:1 air to fuel ratio. so even at low levels of boost you need to add more fuel to keep things in check.

more power, YES. better mileage, NO.

 

that's what i thought, this guy thinks he is a know it all, but i figured i'd ask just to make sure. thanks man.

 

Just because you have a turbo on your truck doesn't mean you "boost" everywhere you go. I only boost when I intend to. When you boost, no you won't get better gas mileage cuz you'll need to put extra gas in there. But most of the time, you're in vaccum while you drive. If you're in vacuum, you're not boosting.

Now, turbos WILL increase mpg because they really assist the air flow into the engine. Your engine doesn't have to work to "suck" in air. In most cases, folks generally pick up mpg with turbo's. For example, me adding 4.56's lost mpg on the interstate and the turbo put me back to where I was prior. We're talking like 1mpg though...maybe 1.5. Don't get a turbo to hope you get better gas mileage. The side note for that is when you floor it, you get MUCH worse mpg than you were w/o it. A bad tune with f/i won't give you better mpg either. Another example, last year I used my smt6 with a 9th injector and factory 1 bar map sensor. When I put in my 47# injectors and 2 bar map with the awesome tune that's out now, I have now CONSISTENTLY gotten .5 mpg better. I've driven for 6 weeks now with the new tune and with city only driving, it's been .5 better. Even with the winter gas so it might do even better come Spring. So the tune will also dictate what you get. Putting a turbo on a car doesn't mean you're gonna see increases. Confused? LOL.

The STS system is on sale through kenihemi for $3600. An smt6 piggyback unit, 8 new injectors, 2 bar map sensor and tune(s) is $1000. Boost controller and meth injection would put you at $5000. ALL of your factory injectors are replaced. No auxilary injector crap is needed anymore. And the new tune eliminates ALL part throttle boost issues we had last year.

The base turbo that comes with the kit will spool enough for 450 to 500hp. It'll spool 30psi if need be but when you calculate engine CI, hp levels, airflow and boost, you're limited to about 500rwhp with that turbo. On the hemi, that's about 12psi I'm guessing. And you probably would want to safeguard your engine a little before doing that on a regular basis.

I run 3.5 psi in low boost so I don't thrash the engine everytime I turn around. Plus it's easier driving around through traffic when I decide to put the pedal to the floor.

 

is it a good or bad idea to run superchips with the STS turbo? and is it possible with the smt6 tune?

 

You can run the 87 program with the turbo and smt6 so that you can use the Superchips features. If you went to the track and ran some 115 gas and had meth and i/c, you MIGHT could get away with the perf tune. I have to retard timing as it is w/o the programmer. Adding superchips in there will just increase timing that much more and cause you to have to pull that much more out.