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Old 02-25-2023, 09:16 PM   #1 (permalink)
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Join Date: Feb 2023
Location: Los Angeles
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Civic - '06 Honda Civic
90 day: 35.03 mpg (US)
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Long Time Lurker: Dual Purpose Civic

Hi all,

I've come across this forum quite a few times within the past, just by Googling different ways to improve efficiency and performance. I finally decided to register, so here's my 2006 Civic EX manual which I've had for over 4 years or so. I'm hoping to get some feedback on further improvements I can make to both the car and driving techniques. I primarily bought the Civic because of my love for Hondas, and knew it would be a comfortable, cheap, and reliable commuter car, that's still fun to occasionally drive in the canyon roads. The car was originally bone stock with about 160k miles, and I've slowly added some parts throughout my ownership.

I never really started to log MPGs until the last 14k miles as you can see, but it would easily do low 30s with combined city/highway driving in stock form. My drives changed quite a bit throughout my ownership..there were times I had long commutes, other times I would have to drive to job sites with heavy tools and equipment. As such, I wouldn't say the past MPG history reflects the potential efficiency of the car.

I was initially going to make full wheel covers until I read the Chalmers study that was posted by a few members, and watching Julian Edgar's aero vids. I instead made outer wheel covers and intend to also add the rears once the rain clears up. Prior to the wheel covers (not yet tested), I was able to hit 39.6 MPG without advanced hypermiling techniques. This was mostly highway, cruising around 65 or slower, with about 20% of the trip in stop and go traffic. 5th gear is a bit short; the car does 65mph at or slightly below 3k RPM iirc. Peak torque 128 lb-ft @ 4,300 rpm. Curb weight 2,767 lbs. I'd estimate that the vehicle dropped a bit in weight after swapping out suspension, wheels/tires, and spare tire.

My goal is to see what MPG is realistically achievable, both city and highway driving, without any extreme hypermiling techniques and/or major body modifications. The car now has about 207k on the clock, and I'd like the engine to last as long as possible, so no partial grill block off, etc.

Here's what I have so far:

Aero:
-3/4 covered flat underbody (ends before rear axle; Civic Hybrid sedan front under panel and both Left and Right side under panels)
-HFP front lip and side skirts
-SI rear spoiler
-Outer wheel covers to be installed and tested
-Either DIY smooth block off front fog light inserts or install brake ducting

Suspension/Alignment:
-Moderate drop on Tein FlexZ with .25" front rake, no preload, -2.5 Front Camber, -1 Rear Camber, 0 toe all around
-Rear camber arms

Wheels/Tires/Brakes:
-Aluminum lug nuts
-17x7.5 +48 Enkei RPF1s (15.25 lbs) with 225/45/17 Continental Sport Contact5 (21 lbs) at 40 PSI for commuting. High offset accounts for the front wheels tucking in considerably to the wheel wells for better aero; tires provide a great balance between grip and low rolling resistance.
-Centric rotors with Stoptech Sport/Hawk HP+ pads. Was considering upgrading to larger TSX rotors and calipers, but there would be a huge weight penalty here, especially for an already underpowered car.
-DIY wheel covers

Engine:
-UltraGauge (for some reason, ~3 months ago, the DTE (distance to empty) calculation went way off and calibrating doesn't seem to work. It reads ~2 miles even after complete fill up. No idea what's causing that...)
-Typhoon SRI
-Muffler

Weight Reduction:
-Spare tire and tools removed
-Air intake plastic jug delete

Current thoughts:
I'd like to further improve the vehicle without spending too much more, nor compromising on practicality and comfort (ie. removal of door panels, speakers, etc.). Considering adding an additional STI 1" lip underneath, but it extends forward and will have some gaps in between the current lip since it's not made for this front lip. The other option would be '09+ facelift front end with HFP lip, as this would supposedly hang slightly lower than the current pre-facelift. It seems like the factory side mirrors could be vastly improved upon compared to other designs, but there aren't any aftermarket side mirror options that look great and are reasonably priced. Would love to hear your thoughts, comments and suggestions!

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