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Old 06-20-2000, 06:41 PM   #1
Scooby Specialist
Member#: 386
Join Date: Oct 1999
Chapter/Region: SCIC
Location: Upstairs in the bedroom
1999 Impreza RS-S
Rally Blue & Supercharged

Talking Gas mileage with supercharger!! 305 miles to a tank of gas.

I filled my 99 RS with 91 super unleaded to check my mileage. Mostly city driving with the A/C on. About 30% freeway. I got 305 miles to the tank. I pretty jazzed about it. EVERYONE told me that superchargers are parasites and suck horsepower out of an engine. Obviously not. If such were true, I should have received worse mileage. So, what are you turbo guys getting???????
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Old 06-20-2000, 06:56 PM   #2
Tim Prudence
Scooby Specialist
Member#: 216
Join Date: Aug 1999
Location: san diego, ca USA

Usually about 240 miles. Not that good. Only 5.5 psi non-intercooled.

But then again, I never got 300 miles out of a tank even before the charger went on...

[This message has been edited by Tim Prudence (edited June 20, 2000).]
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Old 06-20-2000, 06:58 PM   #3
Scooby Newbie
Member#: 134
Join Date: Aug 1999
Location: Washington, DC, USA

um, hehe, my understanding of superchargers is that they DO increase parasitic drag on the engine, but the increase is negligible compared to the power gained... and obviously, if you're applying less throttle (and getting comparable power at lower RPM's) you'll get better gas mileage (assuming you're not racing that is

[This message has been edited by KooshDogg (edited June 20, 2000).]
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Old 06-20-2000, 07:01 PM   #4

Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
16 WRX (white)
04 FXT (red)


I dunno... I've never gotten better then 240/tank on my N/A Impreza around town.

I think it's time for a tune up/ECU reset.
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Old 06-20-2000, 09:17 PM   #5
ImprezaRS dot com
over boosted again
Member#: 1458
Join Date: May 2000
Chapter/Region: RMIC
Location: Colorado Springs CO USA
2017 WRX Limited
2015 Forester XT, Tribeca


My mileage is improving over time, as the ECU relearns my airflow with new intake.

In the past 4 weeks since I installed my new design and reset the ECU, I have seen city mileage go from 18 or 19mpg back up to the 23mpg I was getting when I bought my RS! I get over 28mpg at 75mph on the highway.

I also see much less soot sticking to my rear bumper near the tailpipes of the Stromung on my MY00.

Larry "my $0.02 worth has nothing to do with SC mileage" Ganz
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Old 06-20-2000, 11:36 PM   #6
Scooby Newbie
Member#: 642
Join Date: Dec 1999
Location: AUSTIN, TX
Thumbs up

You sure they didn't stick a bigger gas tank in there with the S/C J/K that's really great mileage.
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Old 06-21-2000, 12:44 AM   #7
Scooby Specialist
Member#: 607
Join Date: Dec 1999
Location: SF Bay Area, CA

SCs are indeed parastic. But in the case of sc kits with bypasses, they are only parasitic when they are "engaged" (i.e. under moderate to high load). With a 230hp twin screw autorotor'd system, you're probably loosing 20 or so hp in parasitic losses. But under low load/cruise conditions, power loss and reductions in fuel economy should be insignificant.

As for fuel economy, my turbo car averages between 20-30mpg, depending on driving conditions. This means, with a 12 gallon fill up, a tank will give me between 240 and 360 miles.

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Old 06-21-2000, 01:25 AM   #8
Scooby Newbie
Member#: 917
Join Date: Feb 2000

I remember in an article in Autoweek, a couple years back, in which TRD claimed that their super charger for the 4runner actually increases mpg by 1. This was due to the increase in torque at the lower rpm.

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Old 06-21-2000, 02:45 AM   #9
Scooby Specialist
Member#: 1657
Join Date: Jun 2000
Chapter/Region: BAIC
Location: Kingstowne, Va. USA
2k RSish


Ok, well I only have two mods done to my Impreza... Yoko A520's (SCCA Solo II Street Tire) and my lead (or worse) foot... I have yet to get better than 22 mpg, and that was without ac on the way to San Francisco for a day...

Maybe the latter mod is just too much...

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Old 06-21-2000, 07:56 AM   #10
Scooby Specialist
Member#: 158
Join Date: Aug 1999
Chapter/Region: NESIC
Location: CT
2011 STi
PBP 1999 2.5RS RBP


My turbo kit increased my MPG. Before the Turbo my best was 30mpg. After the turbo, on the way to Carlisle PA, I got 415miles on 12.5g! That comes out to a bit over 32mpg. On the highway we were seeing upwards of 36mpg. Of course when I really get on it I can almost watch the gauge go down. But, with the turbo I have never had less than 23mpg. But right now I just want my car back

Minnam Stage [email protected]
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Old 06-21-2000, 08:27 AM   #11
Scooby Newbie
Member#: 143
Join Date: Aug 1999
Location: Kanata, ON, Canada
1999 Impreza 2.5RS
Supercharged - and STOLEN


On my way to Rimmer I was averaging 27mpg. On my way back - 25mpg. I had been driving fast both ways - up to 90mph frequently.

Ed. [Eaton blower @ 7lbs-boost]
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Old 06-21-2000, 10:30 AM   #12
Scooby Newbie
Member#: 1516
Join Date: May 2000
Location: Sacramento, CA, USA
1999 Impreza 2.5RS


I've got a 99RS with only a K&N drop in, gasket for second air box, and the silencer removed and after 21k miles I still get the same 26mpg I got when I bought it. I do about 1/2 city 1/2 highway and I've never seen more than 2mpg either way. I'm just hoping I can use the AFC I'm getting to put back the miles taken by the new JC Sports intake I'm getting.

Oh yeah, I got worse mileage when I used Chevron 92 octane gas than my normal Chevron 87. Try it out. The engine seems to run better too.

[This message has been edited by frog (edited June 21, 2000).]
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Old 06-21-2000, 10:41 AM   #13
Scooby Newbie
Member#: 1122
Join Date: Mar 2000
Chapter/Region: NWIC
Location: Nampa, Idaho - USA
2000 2.5RS NA
Blueridge Dirty

Thumbs down

I only get about 300 to the tank
But I drag the $hit out of my car. I race from every light I stop at. I do about 30% highway, the rest city. My average city speed is 50. I can't help it ... the car does that or I have an anchor tied to my foot. I'm running Bridgestone RE730, Weapon*R Intake and Unorthodox Pulley. Just my 2 cents...

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Old 06-21-2000, 11:07 AM   #14
Warden of NASIOC Timeout
Super Moderator
Member#: 592
Join Date: Dec 1999
Chapter/Region: TXIC
Location: P-Ville, Texas
'11 X5 xDrive35i
'09 135i 6MT/'15 GTI 6MT


Right now I'm running SFC (Sans-Fuel Computer) and getting the Apex'i S-AFC installed Friday, so I'm only running 4psi right now and getting ~250 miles to a tank full of 93. Hopefully the S-AFC will help with that...and we're gonna add more boost at Performance Subaru.

When I was running the Hyper-R with 7psi of boost, I made it from New Orleans to Houston on one tank (350 miles!) - this while playing with a Mustang GT 5.0 on I-10 for a bit.

Prior to forced induction, my best was 372 miles to the tank with one passenger and the car full of luggage and stuff on a drive up to Canada.
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Old 06-22-2000, 01:31 AM   #15
Tim K.
Scooby Specialist
Member#: 214
Join Date: Aug 1999
Location: Sumter, SC
2014 Massey Ferguson


My car is bone stock and driven on the freeway or open road most of the time. I generally get about 275 miles per fill-up (about 13.5~14 gallons per fill-up). When my wife drives my car, she stretches the mileage out to 27~28 mpg.

Please do not infer my gas mileage is a reflection of how fast I drive. It is well known that my car cannot exceed the 70 mph speed limit. I swear!
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Old 06-22-2000, 01:39 AM   #16
Matt Monson
Scooby Guru
Member#: 832
Join Date: Jan 2000
Chapter/Region: RMIC
Location: Teh Ghetto Garage, CO
99 2.5RS, '85 911
'73 914 and 2012 BRZ


I have a NA MY00 and thought I was getting bac mileage getting 24mpg hwy and 20 city. I guess I should be one happy camper.
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