PTFB/Hesitation/Crap mileage

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kidatari
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PTFB/Hesitation/Crap mileage

Post by kidatari »

Edit: Yes, I saw the sticky, but it didn't really help. Any concrete answers?

Car info-
MY91 Turbo Sedan, Helix DP/Custom 3" catback, Saab IC, Greddy boost gauge.

Recently I've been having a part time full boost issue, combined with hesitation. I get full boost (.7 bar) under partial throttle, and when I'm under boost, I can feel the car hesitating at 2-3 spots through the rev range. My boost gauge (teed off between the compressor and the boost solenoid) needle wavers around a lot, also. I've also been averaging 200mi to 3/4 tank if I'm lucky. I think that part is related to the PTFB issue, being on boost while cruising on the highway.

Something is definately wrong here, but I don't know what could be causing it.

Does anyone have any input on what to look into, or what the problem could be? It's driving me nuts :(
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vrg3
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Post by vrg3 »

What kind of boost control are you using?
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BAC5.2
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Post by BAC5.2 »

Well, I get 200 miles out of a whole tank in the city... if I'm lucky...

Hesitation can be timing retardation. My car did it with the VF11, but it seems to have smoothed out a LOT with the 16G.

I'd first suggest seafoaming, then just do a complete tune up (including a compression test).

I did this on Sunday, and my car feels SO much smoother now.
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kidatari
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Post by kidatari »

I'm using stock boost control.

Could it be knocking (or seeing false knock) and pulling timing? Is that what it's supposed to feel like?
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magnux
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Post by magnux »

Yea, seriously.. I'd be happy if I could get 200 miles to the tank in city driving. *shrug*

Could be injectors. Have you checked your spark plugs?
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vrg3
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Post by vrg3 »

That's weird that you'd get full boost at part throttle.

Have you checked the vacuum lines that have to do with boost control? Maybe they're leaky or maybe the restrictor's missing or something.

Have you changed your air filter recently?
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BAC5.2
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Post by BAC5.2 »

I got mostly full boost at part throttle. Well, I did with the VF11. The most I can get at part throttle with the 16G is about 5psi.
2009 Outback 2.5XT. 5MT. Satin White Pearl.
2009 Impreza 2.5i Premium. Blue.

[quote="scottzg"]...I'm not a fan of the vagina...[/quote][quote="evolutionmovement"]This will all go much easier if people stop doubting me.[/quote]
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kidatari
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Post by kidatari »

I did change my air filter, to a K&N about a month and a half ago. I also did plugs at the same time (NGK V-Powers). I think I'm going to replace all the vacuum lines all around the boost solenoid tonight to see if it does anything.

Is there a restrictor/check valve/etc in any of the vacuum lines dealing with the boost solenoid? I don't see any in the diagram.
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BAC5.2
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Post by BAC5.2 »

It could be "low boost mode" thing that I was experienceing with the stock boost control.

I'd highly suggest switching to a manual boost controller. I got significant driveability improvements when I went to an MBC. Mine is a freak unit from Vikash, and it's super consistent. Spool time is impressive with such a big turbo.
2009 Outback 2.5XT. 5MT. Satin White Pearl.
2009 Impreza 2.5i Premium. Blue.

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vrg3
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Post by vrg3 »

Yes, there's a restrictor in the line going from the solenoid to the intake resonator.

Not that I'm unbiased :), but I suggest using this diagram:

http://www.graphics.cornell.edu/~v/vacuum/
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kidatari
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Post by kidatari »

vrg3 wrote:Yes, there's a restrictor in the line going from the solenoid to the intake resonator.

Not that I'm unbiased :), but I suggest using this diagram:

http://www.graphics.cornell.edu/~v/vacuum/
I have that diagram printed out and it's the front page of my service manual binder 8)

Edit- I'm blind, nevermind.
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