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Excessive fuel consumption

Old 07-23-2016, 12:01 AM
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Excessive fuel consumption

My car stats:
2007 WRX with a TBE

So just like most subie owners I occasionally gun, but drive fairly conservatively on a daily basis. I drive a total of about 54 miles round trip to work and back. I thought my car might be consuming too much fuel, so I decided to fill up and watch the gauge. So on Wed this week I filled up my tank all the way. Today it's down to just about a 1/4 tank. So from wed till today I drove 162 miles, started with a full tank, and now down to a 1/4. That's absurd!! Any ideas what could be causing this? Something very similar happened to me back in 2011. I took it to the dealer, and Subaru said one of my injectors was leaking. They replaced all 4 and it ran fine.
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Old 07-23-2016, 08:16 AM
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Wow. I would kill to get 154 per half tank. I average 124 per half tank! Course this is thanks to driving in commute traffic.
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Old 07-23-2016, 10:03 AM
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Well I used to be able to drive almost two weeks on a full tank, and now I used 3/4 in 3 days. Think maybe the addition of the DP might have something to do with it?
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Old 07-23-2016, 11:14 AM
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Haha, ummmmm yes.

Maybe give us a timeline of what mods you did and you MPGs from those times? Also, did you get tuned for your DP? Those play a big difference. Also how heavy your foot is.

When I went to stage 2, DP and tune, I actually crept up in MPGs. Andddddd then I decided that enjoying the POWAH was moar fun. Just gotta pay to play.

Many years later (read wear and tear) on the power train, multiple mods later and a commute that is typically below 50mph on highway...I'm down to ~17mpg on avg tank. Back in the good Ol days I was getting ~150-160 on a half tank...right after the changes.

assuming you've been doing regular maintenance on your engine, answer the above questions and you'll get better feedback from the community.

Last edited by CHESTON; 07-23-2016 at 11:17 AM.
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Old 07-23-2016, 11:59 AM
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I had a cat-back for a while, and it ran fine. About 2 months ago I added the DP. No tune because I didn't know you had to tune something like that. My foot was heavy at first cuz the extra power was fun, but then cooled down. I've been doing regular maintenance too.
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Old 07-23-2016, 12:53 PM
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Hmm. Hope no damage to your motor. When you change DP, that's a significant change to the engine flow. Get tuned ASAP To avoid potential damage to your engine.
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Old 07-23-2016, 12:56 PM
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Or I can just go back to stock DP. I know you need a tune for extra air/fuel but this is just exhaust flow. Pardon my ignorance, but how can It damage the motor if the exhaust just flows more freely?
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Old 07-23-2016, 02:03 PM
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Well the turbo and stock DP affect the air/fuel parameters that your OEM ECU is dealing with.

Afternarket DP causes your turbo to increase its flow characteristics, as the OEM cat is a notable restriction. Your computer doesn't know how to / have enough data tables to properly handle the added flow in some instances (especially WOT/full load scenarios).

Therefore best to get tuned. A Cat-back exhaust doesn't change the flow characteristics beyond what OEM ECU can handle as the OEM cat is still present. But once you go DP (aka Turbo-back exhaust), it's a whole 'nother ballgame.
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Old 07-23-2016, 06:49 PM
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Ok that makes sense. Thanks a lot for your help
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Old 02-28-2018, 10:20 AM
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From the dead! I use to be able to get 320 miles on a full tank. Now I get 150-175 miles on my built block driving easy.
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