Welcome to the North American Subaru Impreza Owners Club Tuesday September 2, 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 > Factory 2.0L Turbo Powertrain

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 09-26-2012, 05:30 PM   #1
low_&_loud
Scooby Newbie
 
Member#: 203168
Join Date: Feb 2009
Chapter/Region: NESIC
Location: 617/978
Vehicle:
e30 daily drifter
18G WRX 335whp (sold)

Question 18G Choppy Boost in 5th Gear

Hey guys -
I've had an 18g with supporting mods (below) on my car for about 4 months now, originally with a grimmspeed EBCS, but it was creating wavy boost (overshooting then undershooting target boost and oscillating a bit up top), and I was having some boost creep pretty bad in 4th/5th. I went to a grimmspeed MBC per my tuners recommendation and really love the slightly quicker spool/ rock solid boost, except now especially with it getting cooler out, when I roll into the throttle in 5th, the boost comes on then starts to get choppy. It is a quick ch-ch-ch-ch-ch sound, but it is under throttle which from my understanding is not compressor surge, please correct me if Im wrong.

The weird part is sometimes it gets to the point the car feels like its bucking a bit but I always let off the gas as soon as I start hearing this, Ive only figured that out by staying on the gas long enough to see if it goes away and almost never does once it starts (unless I pedal it a bit). This leads me to believe it is some kind of surge, but thats where Im confused. Ive read the FAQ and understand what WG flutter is but this seems kind of extreme. It doesnt do it if I shift into 5th and Im already ripping on it, and it doesnt do it in any other gear... Only if I roll into most or full throttle from a relatively low RPM (as in passing someone on the highway) does it happen.

The tuner's suggestions was to tighten the wastegate actuator arm, which I am going to try, but I wanted to get a few more opinions here before I start to play around with it...Any ideas on whats going on here/how to fix it?

Thanks!

Relevent Mods:
18G
Grimmspeed MBC
STi Uppipe
Cobb Catted DP, Catback
Perrin Inlet
DW 750 Injectors
TGVs deleted
STi TMIC
Walbro 255
NGK BR6 plugs
KSTech Short Ram Intake
* Registered users of the site do not see these ads.
low_&_loud is offline   Reply With Quote
Old 09-26-2012, 07:08 PM   #2
wrxlaunch
Scooby Specialist
 
Member#: 181298
Join Date: May 2008
Chapter/Region: MAIC
Location: MD
Vehicle:
99 SF

Default

Are you sure its not wastegate opening and closing; regulating boost? Is it Overboosting in 4th or 5th? If so turn boost down til it holds rock solid at tuned level.
wrxlaunch is offline   Reply With Quote
Old 09-26-2012, 07:10 PM   #3
WRick
Scooby Newbie
 
Member#: 86107
Join Date: Apr 2005
Chapter/Region: E. Canada
Location: 10% REAL FRUIT JUICE
Default

Quote:
Originally Posted by low_&_loud View Post
Hey guys -
I've had an 18g with supporting mods (below) on my car for about 4 months now, originally with a grimmspeed EBCS, but it was creating wavy boost (overshooting then undershooting target boost and oscillating a bit up top), and I was having some boost creep pretty bad in 4th/5th. I went to a grimmspeed MBC per my tuners recommendation and really love the slightly quicker spool/ rock solid boost, except now especially with it getting cooler out, when I roll into the throttle in 5th, the boost comes on then starts to get choppy. It is a quick ch-ch-ch-ch-ch sound, but it is under throttle which from my understanding is not compressor surge, please correct me if Im wrong.

The weird part is sometimes it gets to the point the car feels like its bucking a bit but I always let off the gas as soon as I start hearing this, Ive only figured that out by staying on the gas long enough to see if it goes away and almost never does once it starts (unless I pedal it a bit). This leads me to believe it is some kind of surge, but thats where Im confused. Ive read the FAQ and understand what WG flutter is but this seems kind of extreme. It doesnt do it if I shift into 5th and Im already ripping on it, and it doesnt do it in any other gear... Only if I roll into most or full throttle from a relatively low RPM (as in passing someone on the highway) does it happen.

The tuner's suggestions was to tighten the wastegate actuator arm, which I am going to try, but I wanted to get a few more opinions here before I start to play around with it...Any ideas on whats going on here/how to fix it?

Thanks!

Relevent Mods:
18G
Grimmspeed MBC
STi Uppipe
Cobb Catted DP, Catback
Perrin Inlet
DW 750 Injectors
TGVs deleted
STi TMIC
Walbro 255
NGK BR6 plugs
KSTech Short Ram Intake

wastegate opening and closing rapidly.

the grimmspeed EBCS was not the one overboosting, the guy who dialed the tune is.
WRick is offline   Reply With Quote
Old 09-27-2012, 10:09 AM   #4
low_&_loud
Scooby Newbie
 
Member#: 203168
Join Date: Feb 2009
Chapter/Region: NESIC
Location: 617/978
Vehicle:
e30 daily drifter
18G WRX 335whp (sold)

Default

Im pretty sure thats exactly what the problem is, is the wastegate chattering open and closed, not operating normally though (its a distinct oscillating sound like its just flapping open and closed and gets increasingly louder as you stay on the gas). This phenomenon starts around 10-15psi though, it isnt at target boost trying to regulate it. It holds 19psi dead nuts on everywhere else though, doesnt overboost anywhere with the current setup.

And yes I agree that it wasnt the EBCS's "fault," but when it comes down to it the tuner had originally recommended just going with an MBC on the 2.0L, I chose the EBCS because I had heard so many good things about it, but in the end I probably should have just taken his advice (for my setup, Im not saying this is what everyone needs to do). It definitely hits harder with the MBC so Im not complaining. Im not looking to point the blame in this thread or make any suggestion about the EBCS's performance, I just want to sort out this issue. For whatever reason it just wasnt working out on my car when I had it. In the grand scheme of things I am very happy with the car, it just has this weird little issue.

So maybe his advice on tightening the WG actuator would hold it shut "harder" and prevent the WG from opening and closing like that in 5th. I guess Ill have to try it...just wanted some opinions.

Thanks
low_&_loud is offline   Reply With Quote
Old 09-27-2012, 10:59 AM   #5
lukeskywrx
Scooby Specialist
 
Member#: 59837
Join Date: Apr 2004
Chapter/Region: SWIC
Location: Arizona
Vehicle:
2004 Spec-C Type RA
What MAF? -Speed Density!

Default

Don't boost hard in 5th unless you are shifting there from the top of 4th, problem solved.

to get peak boost in lower gears you have to run high WGDC, in high gears that causes the oscillations as the car overshoots and tried to correct. If you want perfect boost in 5th you may have to give up a little spool in the lower gears.
lukeskywrx is offline   Reply With Quote
Old 09-27-2012, 11:50 AM   #6
JdMS13
Scooby Specialist
 
Member#: 207299
Join Date: Apr 2009
Chapter/Region: MAIC
Location: Downingtown, PA
Vehicle:
2002 Outofcommission
Subaru..rght?

Default

Run a MBC and the grimmspeed EBCS in series. Works perfectly from what I've been told. See this http://forums.nasioc.com/forums/showthread.php?t=602674
JdMS13 is offline   Reply With Quote
Old 09-28-2012, 01:51 PM   #7
shamrock 05
Scooby Guru
 
Member#: 120057
Join Date: Jul 2006
Chapter/Region: MWSOC
Location: *outskirts of motor city*
Vehicle:
2004 "Bugeye" WRX
WRB

Default

Quote:
Originally Posted by lukeskywrx View Post
Don't boost hard in 5th unless you are shifting there from the top of 4th, problem solved.to get peak boost in lower gears you have to run high WGDC, in high gears that causes the oscillations as the car overshoots and tried to correct. If you want perfect boost in 5th you may have to give up a little spool in the lower gears.
I have heard the above statement of not going WOT in 5th gear many times.....but I would think that the tuner could fix this and lower the boost. My car was doing this as well on the td04 stg 2 tune and I have a GS 3port....so I had him lower the boost by a few psi and its gone. HOWEVER, I dont go wot in 5th, if im on the highway and wanna get moving.... I downshift and rev match into 4th and get on it.......thats just me though.
shamrock 05 is offline   Reply With Quote
Old 09-28-2012, 03:44 PM   #8
low_&_loud
Scooby Newbie
 
Member#: 203168
Join Date: Feb 2009
Chapter/Region: NESIC
Location: 617/978
Vehicle:
e30 daily drifter
18G WRX 335whp (sold)

Default

I'm not going to sacrifice boost in other gears just to fix this, so I guess I'll leave it as is, I wasn't sure if this was something that could be fixed independently somehow. I considered running the hybrid EBCS/MBC setup, and maybe I will in the future but for now I'm done spending money on parts and dyno sessions I think.

Is this oscillating phenomenon actually harmful to the turbo like compressor surge? Or is it just annoying and hinders performance in 5th a little?
low_&_loud is offline   Reply With Quote
Old 09-28-2012, 10:29 PM   #9
lukeskywrx
Scooby Specialist
 
Member#: 59837
Join Date: Apr 2004
Chapter/Region: SWIC
Location: Arizona
Vehicle:
2004 Spec-C Type RA
What MAF? -Speed Density!

Default

If you are not seriously overboosting it is just annoying, no damage done.

You can sometimes get rid of it by tweaking turbo dynamics
lukeskywrx is offline   Reply With Quote
Old 09-28-2012, 11:07 PM   #10
Unabomber
Big Ron
Moderator
 
Member#: 18062
Join Date: Apr 2002
Chapter/Region: MAIC
Location: I can save you a ton of cash
Vehicle:
on car parts so PM
me b4 j00 buy

Default

Remember: The nights are getting cooler. This causes overboost in many, many cars, ESPECIALLY in 4th/5th gear. You should NOT be hammering your car in 5th gear EVER. It's an overdrive gear for MPG only. Stop nailing it in 5th before you shatter that gear.
Unabomber is offline   Reply With Quote
Old 09-29-2012, 01:27 PM   #11
lukeskywrx
Scooby Specialist
 
Member#: 59837
Join Date: Apr 2004
Chapter/Region: SWIC
Location: Arizona
Vehicle:
2004 Spec-C Type RA
What MAF? -Speed Density!

Default

We had a local guy (idiot) do a long 6th gear pull from 40-140+ MPH and he melted down a piston even with e85. I would worry about this more than a broken gear, but hey its your car....

lukeskywrx is offline   Reply With Quote
Old 09-29-2012, 02:21 PM   #12
WrxWrb
Scooby Newbie
 
Member#: 287477
Join Date: Jul 2011
Chapter/Region: Tri-State
Location: 607
Vehicle:
02 Wrx Wagon WRB
EVO III 16g=Fun

Default

Hey I'm having the same issue you describe on my car. Took a video of it this morning. Still haven't figured out what the issue is.

WrxWrb is offline   Reply With Quote
Old 10-01-2012, 10:36 AM   #13
low_&_loud
Scooby Newbie
 
Member#: 203168
Join Date: Feb 2009
Chapter/Region: NESIC
Location: 617/978
Vehicle:
e30 daily drifter
18G WRX 335whp (sold)

Default

Quote:
Originally Posted by Unabomber View Post
Remember: The nights are getting cooler. This causes overboost in many, many cars, ESPECIALLY in 4th/5th gear. You should NOT be hammering your car in 5th gear EVER. It's an overdrive gear for MPG only. Stop nailing it in 5th before you shatter that gear.
Thanks for the input but I think you missed what my problem is here. The issue isnt overboosting, since Ive gone to an MBC it hasnt overboosted at all (confirmed w/boost gauge that has memory setting). I will adjust the MBC as needed with temperature decrease in any case. Ive never in my life heard of anyone shattering 5th gear but Ill keep that in mind...

This issue occurs anywhere from 1/4 throttle or higher in 5th gear, depending on the RPMs I am trying to accelerate from. If I need to accelerate hard enough that Id floor it in 5th Id just downshift, I'm definitely not just matting it and waiting for it to spool up and pulling from 50mph or less to 100+, this is just a little nuance that's annoying driving on the highway if you just want to get around someone and give it some gas. I drive ~40 mi of highway daily so I'm just trying to make the car a little more friendly for it (if possible). I also know its modified/turbo swapped and isn't going to drive like a stock WRX which is fine. I'm an engineer and for better or for worse try to keep improving the way car drives, thats all.


Quote:
Originally Posted by WrxWrb View Post
Hey I'm having the same issue you describe on my car. Took a video of it this morning. Still haven't figured out what the issue is.

http://www.youtube.com/watch?v=8YhRfOi6AtM
This is similar but mine is definitely a higher frequency. Ill try to take a video as well when I can, probably should have done it to begin with. Mine is also occurring with no change in throttle position, i.e. if I'm barely on the gas cruising in 5th, and ease into 1/4-1/2 throttle and stay there, it'll build boost and begin to accelerate then start the chatter after a few seconds. Yours seems to be when you accelerate then back off the throttle a bit?

Last edited by low_&_loud; 10-01-2012 at 10:46 AM.
low_&_loud is offline   Reply With Quote
Old 10-01-2012, 11:28 AM   #14
djuhnk
Scooby Newbie
 
Member#: 331392
Join Date: Sep 2012
Vehicle:
2002 WRX
Black

Default

Have you tried tightening the actuator a few turns? I have the same grimmspeed ebcs problem with wavy boost. Very annoying when you spend that and end up with wavy boost. I guess internal wastegating is just inferior
djuhnk is offline   Reply With Quote
Old 10-01-2012, 12:01 PM   #15
WrxWrb
Scooby Newbie
 
Member#: 287477
Join Date: Jul 2011
Chapter/Region: Tri-State
Location: 607
Vehicle:
02 Wrx Wagon WRB
EVO III 16g=Fun

Default

Quote:
Originally Posted by low_&_loud View Post
This is similar but mine is definitely a higher frequency. Ill try to take a video as well when I can, probably should have done it to begin with. Mine is also occurring with no change in throttle position, i.e. if I'm barely on the gas cruising in 5th, and ease into 1/4-1/2 throttle and stay there, it'll build boost and begin to accelerate then start the chatter after a few seconds. Yours seems to be when you accelerate then back off the throttle a bit?
mine will sometimes do it when i back off the throttle. Sometimes when driving up hills though I can be holding it perfectly steady and then all of a sudden boost drops off completly and the whole car will shake.
My tuner thinks that my bpv might be faulty causing the fluctuations.
WrxWrb is offline   Reply With Quote
Old 10-01-2012, 05:37 PM   #16
CHEWY911
Scooby Newbie
 
Member#: 179450
Join Date: May 2008
Location: Minnesota
Vehicle:
2004 WRX
Silver

Default

I had the same problem with my 18G. You're getting compressor surge. Basically you're falling out of the effeciency island on the compressor map for that turbo. An 18G is a pretty quick spooling turbo especially under heavy load in 5th gear and your getting high pressure and low flow event. Like others have mentioned you might have to lower waste duty cycle if you can't tune it out in the turbo dynamics table.



Quote:
Originally Posted by low_&_loud View Post
Thanks for the input but I think you missed what my problem is here. The issue isnt overboosting, since Ive gone to an MBC it hasnt overboosted at all (confirmed w/boost gauge that has memory setting). I will adjust the MBC as needed with temperature decrease in any case. Ive never in my life heard of anyone shattering 5th gear but Ill keep that in mind...

This issue occurs anywhere from 1/4 throttle or higher in 5th gear, depending on the RPMs I am trying to accelerate from. If I need to accelerate hard enough that Id floor it in 5th Id just downshift, I'm definitely not just matting it and waiting for it to spool up and pulling from 50mph or less to 100+, this is just a little nuance that's annoying driving on the highway if you just want to get around someone and give it some gas. I drive ~40 mi of highway daily so I'm just trying to make the car a little more friendly for it (if possible). I also know its modified/turbo swapped and isn't going to drive like a stock WRX which is fine. I'm an engineer and for better or for worse try to keep improving the way car drives, thats all.




This is similar but mine is definitely a higher frequency. Ill try to take a video as well when I can, probably should have done it to begin with. Mine is also occurring with no change in throttle position, i.e. if I'm barely on the gas cruising in 5th, and ease into 1/4-1/2 throttle and stay there, it'll build boost and begin to accelerate then start the chatter after a few seconds. Yours seems to be when you accelerate then back off the throttle a bit?
CHEWY911 is offline   Reply With Quote
Old 10-18-2012, 12:44 PM   #17
WrxWrb
Scooby Newbie
 
Member#: 287477
Join Date: Jul 2011
Chapter/Region: Tri-State
Location: 607
Vehicle:
02 Wrx Wagon WRB
EVO III 16g=Fun

Default

Anything ever get resolved with this ?
WrxWrb 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 12:30 AM.


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.