Boost drop / Help

[Shainal1]

I have a 2006 Subaru Legacy GT. When I first purchased the car last year it was running 15psi boost and then after a few days it went down to 9-10. After resetting the ECU it was running 15psi again however after a day it went back down to 9-10psi again. For a few months boost always changed where some days it would go back up to 15psi but majority of the time it would just run 9-10psi.*

 

I had my car remapped this week and for 2 days it was boosting at 15psi again however today the same issue happened where the boost dropped back down to 9-10 even after the remap. There are no check engine lights.

 

Everything is factory apart from a catback exhaust however the issue was there before I purchased the exhaust. Always runs on 98 octane. There are no signs of any cracks in the lines. I have also cleaned out the MAF sensor however issue still persists.

 

Has anyone else had this issue and how did you resolve it?

 

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[Andy_Mac]

Where about are you located? It’ll be a bit of a stab in the dark fix without some logging.

 

There is a feature called IAM which is ideally at 1.0 but drops when considerable knock is detected. Once this drops below 0.5ish it disables boost control so will run only wastegate pressure which may be what you're seeing.

Can't think of anything else right now that might cause it without giving a fault code. It going back to normal after a ECU reset is something a drop in IAM would cause as it defaults to 0.5, for most, once reset until a full pull or a few mins of driving is done then raises up. 

 

Who did the remap?

[Shainal1]

Where about are you located? It’ll be a bit of a stab in the dark fix without some logging.
 
There is a feature called IAM which is ideally at 1.0 but drops when considerable knock is detected. Once this drops below 0.5ish it disables boost control so will run only wastegate pressure which may be what you're seeing.
Can't think of anything else right now that might cause it without giving a fault code. It going back to normal after a ECU reset is something a drop in IAM would cause as it defaults to 0.5, for most, once reset until a full pull or a few mins of driving is done then raises up. 
 
Who did the remap?

I am located In Auckland New Zealand. Thanks for the help I'll have a look into it. If it is knocking then is there a way to fix it? I got the remap done by https://www.autoupgrades.co.nz .
The weird thing is that this exact issue was happening for a long time even before the remap was done

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[Andy_Mac]

A good tuner will have noticed the issue and been able to pinpoint it. 

Did you mention the issue to them? 

It seems pretty unlikely that they wouldn't have noticed and resolved it knocking like crazy but you never know with some of these none specialised tuners.

Any typical mechanical issue wouldn't disappear when the ECU was reset.

 

Your best bet is to go back to them and say what the hell, why wasn't this discussed or resolved with the tune. 

If that doesn't work out you’ll need to find someone in Auckland who can do some logging for you to test a few things out or hit up one of the Auckland shops that are Subaru experts such as @Subirex Automotive or Possumborne 

[Boxer4turbro]

Could be a stuffed waste gate spring. Possibly needs loosening and then tightening at the desired pressure. The spring inside might be buggered. I bet an electronic controller will fix this. If you've had a remap then the only reason boost will drop or fall will be a mechanical issue unless you have a split in a vacuum hose running towards the boost sensor. 

[Andy_Mac]

Anything mechanical or split hose related wouldn't return to normal after an ECU reset which is why a learned ECU reduction seems more likely

[Gripless]

What @Andy_Mac said ecu reset suggest electrical could be faulty sensor or wiring where reset enables it in ecu again or resets error count.

you need to log data to see what the difference is.

 

also check before you start engine the check light comes on then goes out. I've had a car where the charge light bulb died so it had faults but I had not idea