Welcome to the North American Subaru Impreza Owners Club Tuesday July 22, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Engine Management & Tuning > Open Source Reflashes

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 09-30-2013, 01:43 PM   #1
Soarer
NASIOC Supporter
 
Member#: 134872
Join Date: Dec 2006
Chapter/Region: Tri-State
Location: Danbury, CT
Vehicle:
98 Legacy GT Wagon
STi Swap

Default Lean part-throttle between 0-10psi at lower RPMs

I recently got my motor together and running well and got it tuned. During daily driving I'm noticing a flat spot when I start transitioning into boost. For example, I'll be cruising along at 40mph in 4th gear on a backroad at about 2800rpm and come to a slight grade, so I'll give it a little bit more gas.... light boost will start to build and I'll notice my AFRs go to around 15.5 and the car will lightly stutter a bit. If I get into the throttle more, it'll build heavier boost and the AFRs will drop into line at about 13-12-11 depending on how much throttle I give it. It's the part-throttle cruising conditions that really annoy me because that's 98% of what the car sees as a daily driver.

Before pestering my tuner about this, I wanted to rule out mechanical issues first. I was wondering if it could be due to a bad MAF, front O2 sensor, MAP sensor, etc, etc... Does anyone have any input on this issue and how to diagnose it? Thanks very much for you any help! I'm great at mechanics but a novice at tuning so forgive me if I sound ignorant. I do have a Tactrix 2.0 and ECU flash and RomRaider software.

Car details: 1998 Legacy GT swapped to EJ257 block, B25 heads, plugged B25 cams, no AVCS, 2002 WRX wiring harness and ECU, SPT intake, Bosch 1000cc injectors, TGV deletes, VF48 turbo, catless 3" exhaust, v7 6sp, STi top mount.
* Registered users of the site do not see these ads.
Soarer is offline   Reply With Quote
Old 10-07-2013, 12:07 AM   #2
Soarer
NASIOC Supporter
 
Member#: 134872
Join Date: Dec 2006
Chapter/Region: Tri-State
Location: Danbury, CT
Vehicle:
98 Legacy GT Wagon
STi Swap

Default

Interesting development... I cleaned my MAF and now it's running waaaay rich. My AFR gauge is going to 10.0 full rich when I get on it... Hmmmmm
Soarer is offline   Reply With Quote
Old 10-14-2013, 11:38 AM   #3
Soarer
NASIOC Supporter
 
Member#: 134872
Join Date: Dec 2006
Chapter/Region: Tri-State
Location: Danbury, CT
Vehicle:
98 Legacy GT Wagon
STi Swap

Default

Anyone got any ideas on this? I was running a bit lean under light boost, then cleaned the MAF and now I'm running way rich under boost. Is this a tuning problem (i.e. the car was tuned with a dirty MAF and the scaling was off to compensate for the MAF being dirty, now it's clean and things are going haywire) or could this be a mechanical problem such as a bad MAP sensor or fouled O2 sensor???

Also, I don't know if this is related or not but I get a small backfire during easy driving conditions when I shift. I've never heard it when I'm getting on the car in heavy boost but when I'm just leisurely driving around under light loads, I'll shift and occasionally hear a "pop" from the motor like unburnt fuel igniting.
Soarer is offline   Reply With Quote
Old 10-15-2013, 08:01 AM   #4
sidewayz
Scooby Specialist
 
Member#: 5810
Join Date: Apr 2001
Chapter/Region: Tri-State
Location: Easton PA
Vehicle:
2001 S366 2.5RS

Default

Did you remove the maf to clean it ?
sidewayz is offline   Reply With Quote
Old 10-15-2013, 09:55 AM   #5
nmlittlebigman
Scooby Specialist
 
Member#: 321409
Join Date: May 2012
Chapter/Region: SWIC
Location: Arrey, NM
Vehicle:
2015 WRX LTD
WRB

Default

Sounds like a post turbo boost leak.
nmlittlebigman is offline   Reply With Quote
Old 11-27-2013, 09:54 PM   #6
BeastianSTI
Scooby Specialist
 
Member#: 310506
Join Date: Feb 2012
Chapter/Region: South East
Location: Florida
Vehicle:
2005 WRX STi
Blown Up Color

Default

If it was a boost leak ( inherently post turbo ), it would run rich under any sort of boost. I would imagine that the tuner would have noticed that his pre defined map for ur intake wasn't taking kindly to your car ( if the maf was a big problem ). Try unplugging the maf and taking it for a cruise. Don't go into heavy boost or anything, but feel out that low throttle boost range. Report back as to whether or not it feels any better.
BeastianSTI is offline   Reply With Quote
Old 11-27-2013, 09:57 PM   #7
BeastianSTI
Scooby Specialist
 
Member#: 310506
Join Date: Feb 2012
Chapter/Region: South East
Location: Florida
Vehicle:
2005 WRX STi
Blown Up Color

Default

I'm thinking you may have either a faulty maf sensor or front a/f sensor.
BeastianSTI is offline   Reply With Quote
Old 12-02-2013, 03:08 PM   #8
BeastianSTI
Scooby Specialist
 
Member#: 310506
Join Date: Feb 2012
Chapter/Region: South East
Location: Florida
Vehicle:
2005 WRX STi
Blown Up Color

Default

Any updates on this mate? For all the other scoobies out there.
BeastianSTI is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 05:19 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.