[f575gtc]

man I am goinh to MISS the 28-33mpg average in my current car

[PaulVincent]

Driving techniques that brought mileage in the 31-37 mpg on my MS3 have not helped much at all on the STi. On the MS3 I received app. 24 mpg as it was being broken in. Then it was 28 mpg for several thousand and once fully broken in using all my fuel saving techniques, the 31-37 mpg was where I stayed. The 37 was hyper-miling on the Interstate, but I would get at least 31 on state rural road (eight stops in 30 miles, with about 7-8 of those miles in town). I cannot begin to get those results on the STi regardless of what I do. Please realize that other than mileage, I prefer the STi in every way. It is two rungs up on the ladder.

[BAD STI]

Originally Posted by MRstink

I thought when your under boost, your motor is acquiring it's extra displacement through the wasted energy or exhaust, which means the power of a v8 with the low rotational friction of a 4 banger.

so how does using lower gears to stay out of boost give you better gas mileage, to do a hill your going to need a certain amount of power, and when a turbo is supplying the extra power instead of rpm, wouldn't that make it have less friction loss.

The more boost the more fuel that is injected. That Is why its good to stay out of boost if you are trying to save gas. However I don't belive that its better to drive in a lower gear because it doesnt boost as soon. If Im careful I can avoid boost in all my gears. If I do need to accelerate in say 5th or 6th the boost is negligable.

[ptgreg]

Are there any mods that I can do that boost HP plus mpg? I know I am asking for alot. I do appreciate all the response thanks again.

[BAD STI]

Originally Posted by ptgreg

Are there any mods that I can do that boost HP plus mpg? I know I am asking for alot. I do appreciate all the response thanks again.

Probably a stage 2 protune if you tell your tuner that you want better fuel economy.

[PaulVincent]

So I've decided to try driving in S or S#, and the first results have been good (only 20 miles worth) as I've averaged 16.8 in town (just computer figures not measured fuel added from same pump). Now I'm going to try strictly S# (last two days had a majority but not all in S#). But why would S or S# (especially in town) yield better mpg figures than I? Note that this is about 2 mpg better than I.

[gjtracer]

^ because instead of giving it more gas to bring the car to the speed (in I) you need it to, you are using more boost instead of gas (in S or S#)

[MRstink]

I know that, but think about this, it takes X amount of thermal energy to maintain or accelerate your car.

running higher rpm induced more friction on the motor, more surface area the pistons and everything move against. a turbo doesn't take much from the motor to be spun.

if your running at low rpm with boost vs. higher rpm without it, the amount of power going to the wheels is the same, but it takes more thermal energy (gas) to arrive at it when ran at higher rpm.

6 liter vette gets 27 something mpg because it uses LOW rpm and has the displacement to lug it.

a turbo increase the amount of displacement your motor has on demand, with less friction that adding more or larger pistons/stroke.

*try this! put your car into neutral, give the motor a tiny bit of gas, it will settle at an rpm (lets just say 3000). give it a little bit more gas and now it's settling at a higher rpm (lets say 5000). the amount of gas your giving it at that moment, is how much fuel you waste not moving, just running the motor at that rpm. so if a turbo is ran off of wasted energy, your saving that gas

just because you inject more fuel under boost rpm vs rpm, your still injecting less fuel than if you were trying to accelerate or maintain speed using low rpm and the turbo to make up the torque difference between revs

Originally Posted by BAD STI

The more boost the more fuel that is injected. That Is why its good to stay out of boost if you are trying to save gas. However I don't belive that its better to drive in a lower gear because it doesnt boost as soon. If Im careful I can avoid boost in all my gears. If I do need to accelerate in say 5th or 6th the boost is negligable.

[jjs1313]

i have noticed a serious increase in mpg by shifting at 2k and just using the I setting, i try to make it fun by watching my slow fuel consumption driving techniques have seen an aroung town increase to 27 mpg consistently,

[Miss2.5RS]

Originally Posted by jjs1313

i have noticed a serious increase in mpg by shifting at 2k and just using the I setting, i try to make it fun by watching my slow fuel consumption driving techniques have seen an aroung town increase to 27 mpg consistently,

Shifting at 2k?! Not good...

Congrats on getting 27mpg in your car, I have fun in my car, personally!