Need a little advice 06 WRX - Subaru WRX Forum
 
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post #1 of 12 Old 02-16-2011, 09:45 PM Thread Starter
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Need a little advice 06 WRX

I bought my 06 WRX a few months ago, so I'm a bit of a newb. My problem is poor gas mileage, I'm getting around 10-15 mpg tops. I haven't done much to the car, it came with a couple mods:
perrin short ram intake (not sure if it's really perrin - just a short hose with the MAF and a filter on the end - maybe 16-20 inches in total length)
perrin main pulley
STI Intercooler
All of these mods came with the car except the intercooler, and I've been getting this mileage since the day I bought it. I've put in brand new plugs (NGK iridiums - best ones I could find at the ZONE) and a new air filter. This got me a couple more MPG's. From what I've read I know messing with the intake under 350-400HP is not ideal and can make it run a little rough. If this is the case then should I just buy a stock air box setup? Is there a tried and tested intake that doesn't give you the poor results I could get? Please let me know what you guys think because I'm scratchin my head over here on this one. I don't want to start modding it until I figure this out because something is definitely isn't right.
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post #2 of 12 Old 02-16-2011, 10:21 PM
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How does it run under boost? Still rough? This time of year is when people really start getting problems with injectors. While you had the spark plugs out, did you compression test the cylinders? Some of what you're describing is eerily similar to my car as it has bad ringlands on cylinder #4. My car actually had weird performance at around 2500-3000 RPM. Why the larger intercooler with the stock turbo? You may need to tune for that, but I'm not positive that would make all that much of a difference with that intercooler. I wouldn't blame it too much on the intake just yet, but the Cobb and SPT intakes are good choices if you want to replace it with something other than factory original.

A quick and easy way to check the ringlands (which are a common failure point on 2.5L motors) is to open the oil filler neck when the car is already warmed up. If it's puffing smoke out the neck, it's likely that your ringlands are bad. I don't mean to make you freak out. . . I just wish I had known early on how serious my problem really was. I bought spark plugs, had the BCS replaced, took it to the dealer a few times, and got nothing for all the hard work, except time without the car.

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post #3 of 12 Old 02-17-2011, 12:41 AM
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First off you don't need a tune for a larger tmic. And the intake shouldn't effect gas mileage noticeably. Remember that it is winter and the winter gas mix reduces gas mileage. I would try a good SeaFoam treatment. Go back to the ZONE. SeaFoam in the gas tank, oil, and throttle body should help your car run better and improve gas mileage.

Mike
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post #4 of 12 Old 02-17-2011, 06:38 AM
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+1 on the seafoam. Just not in the TB.... Ingest it through the BPV.

Paul
2002 WRX Sold
2007 WRX Sold
2007 STi totaled
2007 Foz XT sold
2007 MS3
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post #5 of 12 Old 02-17-2011, 06:40 AM Thread Starter
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It runs great under boost. It runs great all the time. I haven't had any issues of any kind. The car does have a super small vibration from time to time when it idles and it is fully warmed up. It is such a small little vibration that only people who work on cars have noticed it. Other than that it runs great, so from what I've read about messing with the intakes that they can sometimes make the car run a little rough I thought that it might be the problem. I know I should get better mileage in the spring/summer but I didn't think I would lose 10mpg in the winter. I'm getting about 125 miles to 3/4 tank (10 gal), should it be that bad now? I will try the sea foam stuff today to see what happens. Thanks
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post #6 of 12 Old 02-17-2011, 08:23 AM
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Originally Posted by littlec5103 View Post
It runs great under boost. It runs great all the time. I haven't had any issues of any kind. The car does have a super small vibration from time to time when it idles and it is fully warmed up. It is such a small little vibration that only people who work on cars have noticed it. Other than that it runs great, so from what I've read about messing with the intakes that they can sometimes make the car run a little rough I thought that it might be the problem. I know I should get better mileage in the spring/summer but I didn't think I would lose 10mpg in the winter. I'm getting about 125 miles to 3/4 tank (10 gal), should it be that bad now? I will try the sea foam stuff today to see what happens. Thanks
+1 on the seafoam, but also the intake may be causing turbulence on your MAF which could be creating issues. If it doesn't read correctly the ECU may be trying very hard to compensate for unstable readings.

"Dustin"
- 08' WRX Premium - SOLD
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post #7 of 12 Old 02-17-2011, 08:30 AM
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Just my .02 but when I first got the car i purchased a spt intake/heatshield (this was before I really planned on modding it). When I finally got it tuned by jorge he said that the car DOES need to be tuned for any intake as there is a poss of a lean condition resulting from any aftermarket intake. He would not even do a baseline with the intake installed. Backing up a little, when I first put the intake on (long before the tune)....I NOTICED a performance loss. I couldn't believe it. I boxed it and put the stock intake back on until a couple days before my tune. Now im glad I did. You may want to either get a tune or put the stock airbox back on if you have it. You may even have a tune on the car you dont know about! Perhaps one designed for a larger turbo and the turbo was put back to stock? The STI intercooler would make me suspicious. You could also check to see if your fuel pump/injectors are stock. Hope you get it sorted out!

Jason
2007 WRX sedan
Cobb Stage 2-protuned by P&L
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post #8 of 12 Old 02-17-2011, 08:28 PM Thread Starter
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+1 on the seafoam, but also the intake may be causing turbulence on your MAF which could be creating issues. If it doesn't read correctly the ECU may be trying very hard to compensate for unstable readings.
This is exactly what I was thinking is going on, but I wanted to hear what input you guys had first. The MAF is right after the air filter followed by a 10 inch hose which goes to the intake. I think I should get a stock unit back on it....but now I need one. I bought the car this way with no stock parts. Does anyone know where I can find the entire stock unit besides Subaru? They want way too much money, so I'd like to find someone with one they don't need anymore. Any tips on that?? If anyone has their entire stock air box set up please let me know and throw out a price! Thanks again everyone for the input!!
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post #9 of 12 Old 02-18-2011, 08:24 AM
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Originally Posted by littlec5103 View Post
This is exactly what I was thinking is going on, but I wanted to hear what input you guys had first. The MAF is right after the air filter followed by a 10 inch hose which goes to the intake. I think I should get a stock unit back on it....but now I need one. I bought the car this way with no stock parts. Does anyone know where I can find the entire stock unit besides Subaru? They want way too much money, so I'd like to find someone with one they don't need anymore. Any tips on that?? If anyone has their entire stock air box set up please let me know and throw out a price! Thanks again everyone for the input!!
Yeah, as for the MAF being directly behind the filter is something that is creating bad turbulence. If you notice on the stock unit the MAF is placed a little further back, which allows the air to smooth out before it takes a reading.

As for finding a stock box I am sure someone has one laying around. Good luck in your searches?

How much was Subaru asking?

"Dustin"
- 08' WRX Premium - SOLD
- 08' Yamaha R1 - Top Speed seen is 204 - SOLD
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post #10 of 12 Old 02-18-2011, 08:54 AM
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If you are still looking for the stock airbox, PM me. I should still have mine laying around somewhere.

Joshua
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX
Cobbtuning.com"
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post #11 of 12 Old 02-18-2011, 09:20 AM
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I can do the box and the hose from the box to the turbo inlet for $50 shipped. OR those pieces plus the air diverter for $70 shipped. PM me if you are interested.

Paul
2002 WRX Sold
2007 WRX Sold
2007 STi totaled
2007 Foz XT sold
2007 MS3
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post #12 of 12 Old 03-03-2011, 09:15 PM Thread Starter
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**Update** I got a stock airbox, so we will see what happens on this tank of gas. Its been a couple days already but I will know more after the weekend. If this doesn't fix it I might start checking some O2 sensors or the maf itself.
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