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-   -   Losing boost pressure on occasion (http://legacygt.com/forums/showthread.php?t=201743)

Yfarmeaahka 02-15-2013 03:02 PM

Losing boost pressure on occasion
 
I have looked everywhere for people with similar symptoms and can't seem to find any. I have a 2006 legacy gt with AVO drop in filter and TMIC, sti UP, Cobb DP with cat, borla CBE an its tuned by infamous1.

I noticed awhile back that I was getting a turbo whine that I kinda just assumed was normal. After gettin the car tuned it ran fantastic. About 2-3 months ago I started loosing boost until my car had been ran for a long time (8-10psi). I made me a brilliantly engineered boos leak tester with an empty cup holder style container of dash wipes, a valve stem and transfer case rear output shaft seal for a Nissan Titan.
http://i1286.photobucket.com/albums/...psd79908d0.jpg
http://i1286.photobucket.com/albums/...ps91374a27.jpg

I plugged the exhaust an pumped the system with smoke on a evap leak smoke machine. I found one heck of an UP leak so I replaced that gasket and fixed that. Now I still lose boost but not as often or for as long. I never build boost until my thermostat is fully warm and now someone's it only hits 8-10psi until its been driven a little longer than it being warmed up and before it was almost all the time. Now when it does act up sometimes it will kick in full boost on a test pull to see of its working but it will spike 8-10 and hold until its higher rpm then shoots to 16-17psi and then will be perfectly normal until I shut the car off and let it cool down again.

I have checked for boost leaks doing the smoke thing but if I try to pressurize it more than 4psi there is a valve that makes a noise so I can't hear any leaks over it and I was told that valve is supposed to do that. I was thinking it may be my oem bcs but the fact that its electronic it would either work or not work, no in between but it's also solenoid still and had mechanical moving parts so I don't know. I'm kinda at a loss at the moment.

If anyone has seen this before or has some useful tips please help.

Yfarmeaahka 02-15-2013 03:21 PM

I can do LV and logs if someone thinks that may help.

mwiener2 02-15-2013 03:27 PM

yes

Yfarmeaahka 02-15-2013 08:11 PM

I'm not too sure on how to post a log but here is a LV.
http://i1286.photobucket.com/albums/...ps6aa982e2.jpg

a93x 02-16-2013 01:31 AM

congratulations.

Yfarmeaahka 02-16-2013 01:50 AM

I don't get it.

technicalgarage 02-16-2013 04:00 AM

The 9% on learning D doesn't sit well with me.
Maybe you're running lean under load and knocking enough for the ecu to drop IAM and disable boost control, causing you to run on spring pressure?

Yfarmeaahka 02-16-2013 07:28 AM

I would be very happy if it was just a tune issue. But that kinda makes sense maybe, I got my car tuned before I realized I had an up pipe leak and I know it was there at the time because of the whine from the gasket acting like a reed on a wind instrument. Maybe that made it run a little richer so it got leaned out to compensate and now that its not leaking it is too lean.

Yfarmeaahka 02-16-2013 09:56 AM

could anyone tell me how to post a log file?

mwiener2 02-16-2013 03:14 PM

Quote:

Originally Posted by technicalgarage (Post 4296661)
The 9% on learning D doesn't sit well with me.
Maybe you're running lean under load and knocking enough for the ecu to drop IAM and disable boost control, causing you to run on spring pressure?

except 10% is not that much and IAM isn't dropping. Unless he has 15 miles since the last reset of the ECU.

Yfarmeaahka 02-16-2013 03:52 PM

At the time of the log and LV I just did it was working properly but I'm not exactly sure how much/little driving it takes to change the LV. I'm going to assume it depends on how many miles that have been driven sense the last ecu reset. I did reset it recently but its been atleast 200 miles ago.

iNVAR 02-16-2013 07:03 PM

You have to post a log of when this is occurring. Until you do that, this is just guesswork. And contrary to what mwiener says, adding 9% fuel is not insignificant or something I would just dismiss. It's also unusual that none of your other trims are affected (they look perfectly normal.)

Get a log.

Yfarmeaahka 02-16-2013 08:33 PM

Yeah when I did the last log it was working properly but I'm kinda afraid to drag out the RPM's when it's doing it. It's hard to have a laptop with me at all times because I use my sisters. Hopefully I'll get lucky soon.

I also find it odd it usually only does it when the temperature is could out. Usually happens below 40 but last night was 35 and it was doing fine. I'm also not too familiar with tuning and what not so does that 1.05 on the knock table mean much?

Also I don't know how to post a log.

iNVAR 02-16-2013 08:37 PM

Can't say for sure without a log of the original event that triggered it. It could be false knock, or not.

mwiener2 02-16-2013 09:02 PM

ECU can go +-50%. 10% is pretty small.


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