2013 Subaru Impreza WRX STi Hatchback EcoMod Thread
 

Hey EM folks - Finally got to a point where I could get the car I've been after for a long time now.

http://i1280.photobucket.com/albums/...psoecaa8dy.jpg
http://i1280.photobucket.com/albums/...psycgy7uvd.jpg
http://i1280.photobucket.com/albums/...pswosc9b1y.jpg
http://i1280.photobucket.com/albums/...psenp0zcvz.jpg

I'll probably be taking it pretty slow with the mods on this car. There is no roof rack and no mudflaps.

Things I know I'll do:

• A more complete rear diffuser that reaches farther under the car than the stock plastic hint of a diffuser
• Take out the Kicker speaker in hatch area added by previous owner - Done; minus 14 lbs
• DCCD testing to see if any setting makes it easier to increase MPG - Doing

Things I'd like to/might do assuming I can make them look "nice" and/or "cool":

• More complete underbody (it's not terrible from the factory to begin with)
• Grill blocks
• Clear covers for the fog light areas to improve flow
• Front lip
• Side skirts
• Small boat tails from rear wheels
• Somehow fill in/cover the wheels in a "stylish" way that fits in with the look of the car
• Flush-er door handles (Lamborghini style?) - definitely outside my current skillset
• Rear bumper corners
• Weight reduction by taking out spare and equipment
• Tire spats
• Side mirrors folded with alternate mirrors added someplace
• Stage 1 Tune

Inspirations:

• jedi_sol, of course: 2013 Subaru Impreza WRX STI - Project Log
• This thread from iwsti: GD: BlueScooby's 06 STI
• Volkswagen XL1

The car came with Michelin Pilot Super Sport 245/40ZR18 tires on it - so LRR isn't really a thing with it right now. For sake of peace of mind and safety, I'll likely stick with sticky tires.

And pulse and glide is very fun in this car, especially in Sport # (sharp) mode. :D

Welcome! Gkad you have seen jedi's STi. I noticed your fuel log does not have your combined average FE rating from EPA. That will be the number the log uses to calc how far above EPA rating you take this car. You might add it. I found it on the EPA site and they say it is 19 mpg combined. That means you are already beating average with a heavy stick at nearly 24. Here is the EPA link: https://www.fueleconomy.gov/feg/Find...n=sbs&id=32534

Totally endorse your take on doing mods for this car. It is too clean to wop with coroplast. Lol. Enjoy your ride. Subscribed to see what happens next.

James

Thanks, James! Just added the combined number.

That first tank was about 60% mostly interstate travel so I won't always be able to beat the EPA number so handily, unfortunately. City driving is definitely going to bring it down, but I'll do my best!

Key-off at any stop that will last longer than 10 seconds or so (poor man's stop/start technology). I have been doing if for years and am still running a 1998 starter motor.

Also, do you use deceleration fuel cut off mode for braking?

[EDIT: AND BUY ONE OF THESE:
http://www.ultra-gauge.com/ultragauge/
IT WILL PAY FOR ITSELF QUICK LIKE

+1

The less time your very thirsty motor is running, the better your economy will be. A kill switch would go a long way in this car.

That, and sticky tires are probably the lowest hanging fruit.

My previous car had large(r) displacement and very short gearing, and for that reason aero mods were practically irrelevant. Engine-off coasting could more than double my economy on some trips.

So far engine on coasting in neutral has been helping quite a bit. I had lots of highway miles on my last two tanks, so I feel like my current average (23.9 mpg, 25.8% above EPA - June 19, 2018) is a bit inflated compared to what I'll get with more tanks for added sample.

Congrats on the higher numbers. Not sure if you are replying to my post or another or none... but DFCO is not engine off coasting, if you are replying to my post. DFCO is engine on, in gear, to slow the car instead of braking. Your computer will automatically shut off the injectors when you take your foot off the gas. ...

Hey James, wasn't replying to anyone in particular - just updating.

I mention engine on coasting because 1, I'm not quite ready to commit to something like a kill switch, and 2, my last car was an automatic so I feel much better about coasting in neutral with this manual car. It's so much nicer and seems to coast easier and farther too.

So these STi's have a cool feature called the DCCD or driver controlled center differential.

http://i1280.photobucket.com/albums/...psx15awk7g.jpg

Through that, we can control the initial limited slip differential torque. The car's quick reference guide says this, "This system adjusts the torque-distribution ratio between the front and rear wheels of the center differential to suit driving and road surface conditions."

The 4 pages in the owner's manual don't mention torque-distribution between front and rear wheels (although it does mention left to right). It's language focuses on how the car responds and what each mode would be best suited to (Auto + or manually increasing the initial LSD torque is for slippery or questionable traction situations and Auto - or manually reducing the initial LSD torque is for high traction conditions).

It does mention that "A higher initial LSD torque setting gives the vehicle greater traction when driving straight ahead but makes cornering more difficult. Remember this when adjusting the initial LSD torque. In general, higher initial LSD torque settings assist driving on slippery roads and lower settings for non-slippery roads. When the vehicle is stuck in snow or mud, setting the initial LSD torque to the maximum [LOCK, if you're familiar with these vehicles] will help to free the vehicle."

My question for you guys would be am I wrong to interpret that I can use this somehow to make the car roll easier aka get better mileage on the highway and/or city? (and being safe about weather and driving conditions and sticking to the Auto and + - when the drive might be questionable)

With a minimal amount of Googling, here's some logic from a 2008 post over on the iwsti.com forum:

Source Post, Source Thread.

I like the simplified logic presented in that post (might be too simplified, and I think it's effective to make the point), but I'm probably biased. However, none of the people that were arguing against being able to influence MPG through using settings on the DCCD ever responded directly after that post beyond one person that was already in the pro-use-dccd-for-better-mpg camp agreeing with it. What do you think?