Crunching Numbers... - Fuel Economy, Hypermiling, EcoModding News and Forum

jdwave · 08-01-2008, 01:33 AM

I'm going to be given

an 05 Civic LX in a week, and was wondering if anyone was willing to help me figure some numbers out..

I already drive extra-conservatively, use P&G and EOC.

Unfortunately, I've never calculated my economy since I shared the vehicle with my mother in the past, and she drove it like a go-kart.

I'm guessing I get about 35-38 MPG city, does that sound about right?

Now, I was recently looking at a thread for my same car w/a grill block.

If he gets 46mpg highway w/only a grill block, what do ya'll think I would be getting in the city with a grill block, header, intake, exhaust, and springs?

I'm trying to figure out how long it will take for the mods to pay for themselves.

I did a little bit of calculating with 35mpg as my starting point, and 45mpg after the mods.

The mods would pay for themselves after about 3.5 years, but that thread I read leads me to believe I can get better than 45mpg city (with mods and driving techniques).

I'm just looking for guestimates, throw some numbers at me

Thanks
-Josh

Bakerboy · 08-01-2008, 05:56 AM

I doubt just those mods will get you 10 mpg, especially city driving. The aero mods really shine when the speeds increase.

bikin' Ed · 08-01-2008, 08:12 AM

Headers, intake and grille block are all Highway type mods. Though they may help slightly around town. The best city mods seem to be IMHO weight loss and driving style.

MetroMPG · 08-01-2008, 12:33 PM

Agreed so far. The mods aren't worth 10 mpg alone in the city. Driving style is, though. A rough guesstimate: count on maybe 5% higher MPG. Also, I've yet to see any good documentation of intake/header/exhaust improving fuel economy at "normal" speeds.

mush3gan · 08-01-2008, 12:34 PM

Quote:

I'm guessing I get about 35-38 MPG city, does that sound about right?

you can't really just assume what your MPG is right now...

you really have to calculate it..everyone's driving style is different, even for the same car

azraelswrd · 08-01-2008, 06:54 PM

Yeah, be meticulous with how much gas you're putting in the tank and how many miles were carried on that amount of gas. After a few tanks you'll get a good idea of where you stand in FE.

To facilitate driving style improvement, a way to monitor your MPG usage is highly recommended. Waiting for a tank to be refilled doesn't help one fine tune driving at any time before that. A scangauge or something similar will help in this (assuming it's for your 2005 car).

At less than highway speeds, weight and tires are the biggest factors to consider as they will have the biggest FE impact moreso than aero.

TIRES
> pump tires up (some go as high as sidewall max, but I just went to 40psi because its TOO bumpy any higher... it's a Scion... you feel everything on that stock suspension!!!)
> consider Low Rolling Resistance tires

DRIVING
> choose your routes carefully to minimize stop-go, idling and congestion
> read over the 100+ tips if not done so already. (100+ hypermiling / ecodriving tips to increase gas mileage - EcoModder.com)

WEIGHT
> lose weight (the less your engine has to lug around, the easier it will be on the guzzling)

With all of that, I bet you'll eek out at least a 5mpg jump, especially with changing your driving habits. The nut behind the wheel is the most significant and easiest thing to mod by far.

A grill block has another benefit besides aero and that is if properly designed can facilitate faster warming of the engine to its optimal thermal levels. But don't expect the world in MPG from just a grill block. From my own tests, a full block gave me a boost in MPG from 3 to 5 (!!!) but the overheating was not worth it so I opted for a mix (full upper, half lower) which is a gain of 1 to 1.6mpg. But I won't make any conclusions until I get my tank refilled and my SG recalibrated on another tank (just to be sure) and of course do more testing in more diverse conditions.