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Old 03-21-2014, 02:20 PM   #1 (permalink)
jedi_sol
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Join Date: Mar 2009
Location: Tustin, CA
Posts: 929

2013 STi *SOLD* - '13 Subaru Impreza WRX STi
Subaru
Sports Cars
Team Turbocharged!
90 day: 26.59 mpg (US)

1996 Geo Metro *RETIRED from Ecomodding* - '96 Geo Metro Base
90 day: 58.68 mpg (US)
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Squeezing extra MPG out of P&G (EOC WHILE KEEPING THE CAR ON??)

Ever since I took my car into the dealership to service, I disconnected my kill switch, so I have just been doing regular ENGINE ON P&G this whole week. I noticed something interesting.

This might not apply to all cars, but on my 2013 Subaru WRX Sti, I notice then when I shift to neutral to ENGINE ON coasting, my ScangaugeII indicates 9999mpg for a half second when rpms reach approx. 900rpm.
Does this mean my injectors are actually turning off for that half second around 900rpm? I busted out my Torque App and drove to my regular “testing grounds” to verify.

Testing grounds – 1 mile stretch of road with a slight incline, late at night, in a business park so no traffic to disturb

I setup the Torque App to read FUEL USAGE to the 1000th decimal point, because I know fuel usage for 1 mile neutral coast would be minimal, but this is simply for testing purposes.

I drove up to 40mph, shifted to neutral to initiate coasting , set the app to start reading fuel usage until a pre designated ending point. I did bi directional runs

Straight engine on coasting
.018
.015
.016
.015
AVERAGE - .016 fuel used

Engine on coasting, blipping the throttle to allow rpms to sweep 1000rpms down to 900rpms
.014
.014
.014
.014
AVERAGE - .014 fuel used

Straight engine on coasting
.015
.015
AVERAGE - .015 fuel used

Total fuel used with STRAIGHT ENGINE ON COASTING IN NEUTRAL - .0156
Total fuel used with ENGINE ONE COASTING IN NEUTRAL WHILE BLIPPING THE THROTTLE – .014

That’s a potential extra 10.26% savings in fuel WHILE USING A FUEL SAVING TECHNIQUE!

I’m thinking of the potential benefits for ecomodders
1) Achieve “simulated” EOC while keeping the engine on means you keep power steering on, you keep full braking power, you keep your ac running.
2) Less wear on clutch on transmission if you no longer need to bump start

On this morning’s commute to work, there is a long downhill I normally coast in neutral, typically scangauge II reads 150-200mpg during the whole coast down, I blipped the throttle more rapidly to stay in the 900rpm sweet spot and my scangauge II indicated 9999mpg on the whole way down.

I’ll do more testing and post up my Torque App readings later!

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See the rest of the Sti project log:
http://ecomodder.com/forum/showthrea...log-26612.html
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The Following 5 Users Say Thank You to jedi_sol For This Useful Post:
California98Civic (03-22-2014), Joggernot (03-22-2014), mikeyjd (03-21-2014), sarguy01 (03-25-2014), WilliamYH09 (03-26-2014)