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tweedo

Legacy Boost Issues

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Hey all,

I've searched far and wide to find an answer for this with no luck so here goes.

Over the last few weeks my Legacy,
('04 Twinscroll Manual) has been showing an increase in boost on the gauge when usually it would be showing little to none.
At a guess it is reading 3-5psi higher than usual.
This is happening under very low throttle input (15-20%) and very little load.
It seems to be normal at higher throttle inputs, although, I have been rather nervous to give it the jandal so am unsure exactly how it's performing at full throttle.

I have been taking the odd Learning View reading over the time of noticing it and have also noticed that there is some higher knock readings (-2.10/2.45) creeping in too, mostly in the 1.15-1.49 g/rev ranges and at 2700-4299 RPM.

I have the ability to log to try and figure out what may be going on but am unsure of what exactly I would need to be logging.

If someone could point me in the right direction for a start, that would be much appreciated.
Cheers!

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Posted (edited)

Have you inspected your turbo inlet pipe/hose?

 

I had similar problems, i'd reach boost super quick on partial throttle. 

 

Replacing the terribly worn and torn turbo inlet fixed this issue for me. Also greatly reducing the number of knocks. 

 

My IAM hasn't dropped from 1.000 since

Edited by romeyromes
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What are the figures for the fueling correction in LV (the row at the top)?

That's normally a good way to tell if there is a leak somewhere.

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Thanks to you both for the speedy replies guys. 

I haven't checked out the inlet as of yet but will try and do that this coming weekend. 

Am I needing to take the intercooler off to get a good look at that, do you think? 

Even with that bit of knock showing, my IAM has never dropped below 1.000 though. 

 

The Fuel Correction side of things hasn't really strayed outside of +/-2% in any of the ranges either. 

There was a +5 in the 1st and +4 in the 2nd range at different times over the last couple of weeks but it has since gone back to being relatively normal I would say so no real signs of a leak anywhere. 

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Normally a torn pipe or vac line that has slipped off would lead to a sizable change in that fuel trim table which it obviously hasn't...

 

You haven't changed anything or given it any kind of service out of the ordinary?

 

Post up a log of cruising and WOT if you can with it including:

 

RPM

AFR

BOOST

BOOST TARGET

COOLANT TEMP

FKC

FLKC

FUEL CORRECT %

FUEL LEARN %

IAM

INJECTOR DUTY %

LOAD G/REV

MAF G/S

THROTTLE %

WGDC %

 

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Hey Andy, 

 

Nothing out of the ordinary of late. 

Only thing I have done is after the fact which was to clean the EBCS and the MAF. 

 

I will try and get these logged tomorrow after work and report back. 

 

Cheers! 

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Posted (edited)

Evening Folks, 

 

Finally got around to logging some data.

Here go the results.

 

If any of the smart cookies out there want to have a look and potentially give me some insight into what may be going that would be awesome. 

Thanks to @Andy_Mac for your help as per usual 👍 

 

https://drive.google.com/file/d/1iD42yVoBhM2F4D43Iei13572tx5iddGW/view?usp=drivesdk

https://drive.google.com/file/d/1ndKBlh2ct5kn43js4lqULKZFRyEOsC6R/view?usp=drivesdk

 

 

 

 

Edited by tweedo

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Hey guys, 

 

Just a wee follow up on this issue. 

I had the car in at Subaru the other day for a recall and got them to check over it while it was there. 

They discovered that the vacuum line to the BCS was cracking so I will go ahead and replace this. 

 

 

Would someone be so kind to point me in the right direction for doing this... where to get vac line from, easiest method of removal and replacement etc. 

 

Thinking I will replace the MAF sensor at the same time.

I got a price for one from Subaru the other day... lucky I wasn't sitting down or I would've fallen off my chair. $387+gst! 

So, advice on the best place to source these would be great too.

 

Cheers, 

             Graham. 

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12 minutes ago, tweedo said:

Hey guys, 

 

Just a wee follow up on this issue. 

I had the car in at Subaru the other day for a recall and got them to check over it while it was there. 

They discovered that the vacuum line to the BCS was cracking so I will go ahead and replace this. 

 

 

Would someone be so kind to point me in the right direction for doing this... where to get vac line from, easiest method of removal and replacement etc. 

 

Thinking I will replace the MAF sensor at the same time.

I got a price for one from Subaru the other day... lucky I wasn't sitting down or I would've fallen off my chair. $387+gst! 

So, advice on the best place to source these would be great too.

 

Cheers, 

             Graham. 

I have got a brand new maf sensor. PM me

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Hey all,

 

I thought I would try once more to get a solution to doing this before I just go ahead and book it in somewhere to be done. 

 

I've been wanting to change this vacuum line as I'm sure that's where the issue stems from but can't for the life of me figure out how to go about it.... it is so tight in there especially the turbo end of the line it seems like so much has to come out just to get at it which, for me, seems like quite a daunting task. 

 

So, if any of the Gen 4 owners or gurus out there could give me any guidance at all it would be greatly appreciated. 

Cheers!

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I've done it a few times but have yet to find an easy way.

It really is hit or miss getting the right angle to slip the new line onto the nipple on the underside. A few different length and angle long nose pliers will make it a bit less daunting. It's even more of a pain with a top mount intercooler. I'd definitely be removing that. 

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Cheers for the reply @Andy_Mac.

At least I now know that it is doable without tearing everything out! 

 

I went ahead and removed the I/C this arvo as suggested, not sure if it gets me any further ahead or not haha. 

Will have to purchase an array of long nose pliers to try and get in there.

 

I did notice with the intercooler off now that the turbo inlet pipe may be starting the fray and perish too so may be worth doing it all at the same time (making the vacuum line much easier too). There was also quite a bit of grimey oil residue around the turbo end of the inlet too, not sure where exactly it is coming from though. Anything to look out for/worry about? 

 

Anyway, could somebody be so kind to point me in the direction of a suitable replacement, OEM or aftermarket please. As long as it was a direct fit.

Cheers! 

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I did it by hand without any pliers but it is a pig to do and it's all by feel.

 

Oil round the inlet will mean it isn't sealing anymore so needs replacement.

 

I like the Kobe inlet pipe I have. Considerably cheaper than most brands for a silicone inlet.

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Awesome, cheers Andy. 

Where did you happen to source this from? A quick Google search provides nothing locally. 

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5 minutes ago, tweedo said:

Awesome, cheers Andy. 

Where did you happen to source this from? A quick Google search provides nothing locally. 

IDK about the same brand but the silicone inlets are available for certain models on Trademe, Moonlight Racing NZ or potentially boost performance NZ

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