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Old 06-12-2015, 11:48 AM   #9 (permalink)
Fat Charlie
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Join Date: May 2011
Location: Route 16
Posts: 3,423

Al the Third, year four - '13 Honda Fit Base
Team Honda
90 day: 42.9 mpg (US)
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You've been told before that:

1. High speeds in something with the aerodynamics of a Fit are bad for fuel economy.
2. An automatic transmission is not the best for fuel economy.
3. Using A/C is bad for fuel economy.
4. Loading bunches of weight in an underpowered car is bad for fuel economy.
5. Extreme stop and go, like in a paper route, is bad for fuel economy.

It's also been mentioned that a Civic with a manual is a very different animal than a Fit with an automatic and that bolt-on combustion efficiency tricks aren't going to improve highway mpg on an underpowered brick shaped car.

Coming here is your best first move because how you use the car is the single most important factor in how much gas you burn.

Getting good instrumentation like a ScanGauge or an UltraGauge is the first modification of any kind that you should make- you understand the importance of proper testing, and no test means anything without good data. Refusing to get real time mpg and gph along with real time trip mpg is deliberately deciding not to actually test things. They'll also show you how wasteful (or not) every single action you take is.

Once you figure out how the Fit is happiest being driven, worry about changing how it burns the gas. The most rewarding step will probably be in the ECU. That's really using the same principle as adjusting your driving style first- instead of trying to change combustion itself, change the way you use the power that you get from the combustion.

You can change the aero, but you're basically stuck with its size and shape. A tranny swap may be possible but probably isn't practical or desirable, and same goes for an engine swap, only more so. Modifying things inside your engine just doesn't make sense, especially on a daily driver. Playing with the ECU is the only place I can think of seeing a practical benefit from modifying the engine without a nicely staffed and equipped lab with a machine shop and a test track.

While you're waiting for your SG or UG to come in the mail, click on the Garage link at the top of this page. Search for Honda Fits, and you'll see what people here are getting. Then look at how & where they use the cars and how they've modified them to get those numbers.

Combustion physics in cars aren't the most efficient, but the're the least rewarding area to look for higher mileage. There's enough low hanging fruit on the Fit to feed a small town for a year, so looking at that one apple way up at the top of the tree isn't a very efficient way to... improve efficiency.

Originally Posted by sheepdog44 View Post
Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

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