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Old 01 Dec 2011, 05:05 AM   #1 (permalink)
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boost problem

HI all

I have a forester xt 04 with tbe, walbro fuel pump, catless up-pipe and td05 18g and has been tuned. When i got car back from tuners it was awesome. Boost was coming on nice in all gears around 3k and by 3.5k it was at full boost (17psi) all the way to redline. Even under light throttle she would be taking off at 3k and boosting nicely. Then after 3 or 4 days i was holding back in traffic in 2nd gear and put my foot down and i didn't feel my boost coming on. Looked at the revs and they where up around 5k. When i took off from a set of lights on wot it boosted fine. I installed a guage to see what was happening. When i'm in 1st, 2nd or third the boost guage doesn't get out of vacuum it rises and falls unless i'm on wot. I can redline without getting any boost at all under moderate throttle. However when i'm cruising in 5th the boost pressure builds and i take my foot off the accelerator the guage will drop to 20 vacuum and if i touch the gas again the guage will jump up to the pressure it was before i took my foot of the gas. So its not building boost pressure in lower gears unless on wot but builds boost ok in higher gears while light on the throttle. I checked all hoses, exhaust, restrictor pill, bpv, fuel filter. Took it back to the tuners and data logged and they couldn't find out what's causing this either. Has this happened to anyone else or does anyone know what might be causing this to happen. Any help would be greatly appreciated.
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Old 01 Dec 2011, 08:16 AM   #2 (permalink)
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Re: boost problem

was it mapped for the mods?
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Old 01 Dec 2011, 09:33 AM   #3 (permalink)
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Re: boost problem

yes it was
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Old 01 Dec 2011, 09:50 AM   #4 (permalink)
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Re: boost problem

If your tuner cant see the fault ur screwed
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Old 01 Dec 2011, 01:04 PM   #5 (permalink)
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Re: boost problem

sound slike it needs a mechinic who knows what there doing to fualt fin don it, basicly go step by step through the engine and try to identify where the issue is.

Where abouts are you?
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Old 15 Dec 2011, 10:05 AM   #6 (permalink)
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Re: boost problem

i did a boost leak test. Found a few small leaks and one on the intake manifold gasket. Replaced the gasket and re-checked for leaks. All good in that department. However the problem still persists. I checked the exhaust for leaks and that came back fine so...
Maybe a wastegate problem its internal 15psi. I cant hear any fluttering just a slight whistle sometimes when it should be building boost but isn't. The whistle sounds a bit like my bpv when i change gears. Bpv is good tho. I've bypassed the bcs still with no luck. Don't think its the clutch it still accelerates fine just doesn't build boost like it should
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Old 16 Dec 2011, 12:54 PM   #7 (permalink)
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Re: boost problem

have you got a rolling road with a decent operator anywhere near?
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