FI and Fuel Economy

[Aquaman]

Just wondering how many of you have experienced IMPROVED fuel economy with forced induction.

My experience (daily driving city & highway in a major metro area):

NA: 19-21 mpg
AA stage 2 (gen 2): 21-23 mpg
AA stage 2 (gen 3): 25-27 mpg

E46 M3 SMG (2003)

I keep telling my wife that the supercharger pays for itself!...LOL

[TxZHP04]

How are you determining mpg?

[Aquaman]

On board computer MPG calculator, and also manually by mileage/gallons.

[TxZHP04]

I would expect the OBC to reflect higher mileage as a lot of tuners don't adjust the calculations for the larger injector size (or pulse width, whatever the particular kit happens to change). I don't know whether AA does this or not.

To be perfectly honest though, I'm pretty skeptical of your 25-27 mpg mixed city/hwy unless that's mostly hwy miles and unless you're staying well out of the boost. I mean no offense, it just doesn't sound right.

[ridin325]

I am getting 32mpg after supercharger and I was getting 28 prior to instal. I can acctually tell a difference to.

[Lemonsqr]

FI and fuel economy do not go hand in hand....

[ridin325]

FI and fuel economy do not go hand in hand....

If you drive the hell out of the car all the time then yes. But if you drive it normal it will increase due to less use of the throttle, aka easier/faster to get up to speed and easier to maintain speed.

[Aquaman]

I hear you, man...I was quite surprised with this as well - until i did the calculation myself. Also, driving the same distance to and from work, my refueling intervals have also lengthened.

To be honest, during DD, my rpm hardly ever goes above 4500 (averaging in the 3000's). Tracking or any hard driving will push the mpg to 13-16.

No false claims, just wondering if others are experiencing the same...


I would expect the OBC to reflect higher mileage as a lot of tuners don't adjust the calculations for the larger injector size (or pulse width, whatever the particular kit happens to change). I don't know whether AA does this or not.

To be perfectly honest though, I'm pretty skeptical of your 25-27 mpg mixed city/hwy unless that's mostly hwy miles and unless you're staying well out of the boost. I mean no offense, it just doesn't sound right.

[Aquaman]

I agree, with an SC, there is always a certain amount of boost...maybe in minimal boost scenarios, engine efficiency is improved?

If you drive the hell out of the car all the time then yes. But if you drive it normal it will increase due to less use of the throttle, aka easier/faster to get up to speed and easier to maintain speed.

[mcr_driver]

used to get 23-25 after my supercharger i'm getting 26-27 easily i could get more if i wasn't enjoying it soo much :4ngie:

[mikem7709]

I never did any manual calculations before the charger but have done since and my OBC always reads about 20% lower consumption than its actually doing. Ie. OBC reads 24 mpg and I`ve actually done 18-19 mpg.

But who cares. If I go easy I can get 250-300 miles on a tank or if I`m having fun I can empty in under 150 miles. :P

[sheefo2k]

I get worest gas mileage now but thats because I keep smiling when i hammer it lol so to me thats better

[zracer196]

WOW...My computer says that is roughly what I am getting...Did not take me long to see I was NOT.

I found out that with the larger injectors that are run (my kit is an AA as well), that the computer is OFF and can not be changed easily...AA does NOT recalibrate them.

I drive mine pretty easy and see no where near that. Maybe 20 mpg if I am lucky.

[njoni007]

I always measured how far does one tank take me and average them..I usually get 50km more or less (with driving habits...aggressive or easy) because even before SC the meter never did measure correctly (10-15% off).

However, if I drive hard I get the same amount of km if I was driving hard without SC, and if I drive easy I get well over 500 km with one tank. With the new LSD installed I have got even better economy, and it went 520km with spirited driving (hitting the RPM limit at least once a trip).

So I can say that I have gotten an improved gas economy with SC.

[Aquaman]

Thanks for the input guys...

Maybe someone can help me think through this:

Larger injectors --> more fuel delivery, no recal on OBC configs (set to smaller injectors and less fuel delivery). So with no recal on the computer (it is still processing for OEM hardware), wouldn't it give an an artificially LOWER fuel economy reading (rather than a falsely elevated one)?

Or would it be the reverse?

[BimmerDude18]

Thanks for the input guys...

Maybe someone can help me think through this:

Larger injectors --> more fuel delivery, no recal on OBC configs (set to smaller injectors and less fuel delivery). So with no recal on the computer (it is still processing for OEM hardware), wouldn't it give an an artificially LOWER fuel economy reading (rather than a falsely elevated one)?

Or would it be the reverse?

Its the reverse. The pulse widths are smaller with larger injectors so the computer sees less fuel delivery.

[redronin]

you guys have some rediculous numbers

i went from 19 to 22 and i was eccstatic (sp?)

[ridin325]

you guys have some rediculous numbers

i went from 19 to 22 and i was eccstatic (sp?)

lol, do you do alot of traffic driving

[redronin]

lol, do you do alot of traffic driving

yes unfortunately, or not, depending how you look at it. i live 4 miles from my parents, and 1 mile from my university. less than 3 from anything else in my town, so i havent done any highway driving on the car since i was a freshman about 4 years ago :)

[ridin325]

Thats still a good average for all street and I am sure you get on it every now and then.

[redronin]

Thats still a good average for all street and I am sure you get on it every now and then.

yeah.

wait did you say every corner?

yeah!

[ridin325]

Nice that is def why but you are enjoying it and that is all that matters

[Aquaman]

Its the reverse. The pulse widths are smaller with larger injectors so the computer sees less fuel delivery.

BD,

Why would the pulse widths be of smaller (shorter intervals)? Wouldn't that counter, or at the very least, minimize the benefits of going with a larger injector?

I mean, why go with a larger injector and then limit the output? Why not just stay with stock injectors and increase the pulse widths?

[BimmerDude18]

BD,

Why would the pulse widths be of smaller (shorter intervals)? Wouldn't that counter, or at the very least, minimize the benefits of going with a larger injector?

I mean, why go with a larger injector and then limit the output? Why not just stay with stock injectors and increase the pulse widths?

The factory injectors max out under high boost (near redline). But around town where you don't get much boost the demand aren't much higher than without a SC. So you have an injector that flows fuel twice as fast, you have to leave it open about half as long.

At redline you are getting close to maxxing it out though.