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Old 11-11-2012, 05:39 PM   #1
jsBLwrx
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Default Is this normal? Boost guage needle fluttering on semi hard acceleration

Hi all, newbie here

l have a 2013 opb sedan with 1200 miles on the odo.

Bought the car with seven miles on the odo and had been driven the car under 4k rpm for the break-in period

Today, l've wanted to see how much boost the turbo is generating and did a couple of slightly less than pedal to the floor acceleration on the second gear. This is what I've observed and concerns me:

Between 4500-5200rpm: boost appeared to settle at 10lbs

Then the needle on the boost gauge fluttered wildly between 13-16lbs when the engine rpm was around 552-5800rpm

The car is bone stock and it's a limited pkg that was equipped with the SPT boost gauge, the STS and the SPT axle-backs

So, what gives? Thanks folks
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Old 11-11-2012, 07:16 PM   #2
drewvdw
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Bring it to the dealership. You have a warranty. That seems very strange, I can't think of any other similar issues. You should be producing a fair bit more boost than that.
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Old 11-11-2012, 07:22 PM   #3
jsBLwrx
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Quote:
Originally Posted by drewvdw
Bring it to the dealership. You have a warranty. That seems very strange, I can't think of any other similar issues. You should be producing a fair bit more boost than that.
Thanks. what is the normal boost pressure that i should see when its stock? Thanks again for your assistance
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Old 11-11-2012, 07:28 PM   #4
drewvdw
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That I don't know...Maybe 15psi? Something like that? Maybe someone else can confirm.
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Old 11-11-2012, 07:42 PM   #5
jsBLwrx
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Quote:
Originally Posted by drewvdw
That I don't know...Maybe 15psi? Something like that? Maybe someone else can confirm.
Thanks once again. I will run the car a couple of more times and observe the pressure vs rpm. Lacking any better scientific methods in applying just how much I'm rolling on the gas pedal, I will floor it on the second gear.... Lol.... Thanks
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Old 11-11-2012, 08:52 PM   #6
drewvdw
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Try third or fourth too, you don't need to go through the entire RPM band, just until the boost gauge levels out.
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Old 11-11-2012, 09:18 PM   #7
BKALLDAY
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I have a 2013 sedan too. Boost should not shoot up like that. My boost peaks at about 12 PSI and it should hold while you're still on it. Take it to the dealership.
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Old 11-12-2012, 09:02 AM   #8
jsBLwrx
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Hi all
tested this morning at six o'clock. Did pulls from 3, 4 and 5 with speeds between 40 - 75.

l did not observe the fluttering but the boost consistently spiked to 15lbs and quickly settled between 12-13lbs.

thanks all for your assistance B- )
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Old 11-12-2012, 09:30 AM   #9
jthatch12
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Quote:
Originally Posted by jsBLwrx
Hi all
tested this morning at six o'clock. Did pulls from 3, 4 and 5 with speeds between 40 - 75.

l did not observe the fluttering but the boost consistently spiked to 15lbs and quickly settled between 12-13lbs.

thanks all for your assistance B- )
Do a full 3rd gear pull, from ~2.8k to ~7.
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Old 11-12-2012, 09:41 AM   #10
xluben
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Quote:
Originally Posted by jsBLwrx View Post
l did not observe the fluttering but the boost consistently spiked to 15lbs and quickly settled between 12-13lbs.
^This is normal. The fluttering is not. Target boost just shy of 14psi, but it will taper down at higher RPM's.

Quote:
Originally Posted by jthatch12 View Post
Do a full 3rd gear pull, from ~2.8k to ~7.
This is the best way to check the boost curve. If you don't have any way to do a data log, then you could try a video of the tachometer and boost gauge.

Here is a typical boost curve for a stock car:

http://accessecu.com/dyno/graph.php?...rgb1=000000255
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Old 11-12-2012, 09:44 AM   #11
NoGraffix
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The stock BCS is a bleed type system in form lack of better words just sucks. Also the stock map is less the great. You really shouldb't experience a flutter that distinct though (3psi range), so it might be possible you have a leak somewhere or your wastegate isn't opening smoothly. Do a quick check for any leaks and making sure the actuator arm to the wastegate seems like its operating correctly.
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Old 11-12-2012, 10:12 AM   #12
jthatch12
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I had flutter like the OP when my WGDC wasn't fully dialed in yet. Normally happens when Turbo dynamics is compensating for over boosting. Hence if he's experiencing fluttering for a full pull (near high rpms ) I would safely say the issue is wastegate related. The interesting part is the I'm assuming the car is not tuned yet. So it may be something to talk to Subaru about
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Old 11-12-2012, 12:33 PM   #13
jsBLwrx
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Quote:
Originally Posted by xluben
^This is normal. The fluttering is not. Target boost just shy of 14psi, but it will taper down at higher RPM's.

This is the best way to check the boost curve. If you don't have any way to do a data log, then you could try a video of the tachometer and boost gauge.

Here is a typical boost curve for a stock car:

http://accessecu.com/dyno/graph.php?...rgb1=000000255
Thank you for the advice. I will try this probably early in the morning
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Old 11-12-2012, 01:35 PM   #14
JAMM0N
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Its supposed to flutter from all the shaking it never sits still. @5th gear you should be @ -10. From gear 1-4 itll go up and down even hit 0 pressure.

Youll be getting positive if your really revving it almost 5k rpms w boost shifting really slow meaning 3rd gear to 40mphs and then shifting to 4th then gertting to 60mph where you get the positive boost but it wont hold for long till you have to shift to 5th gear without even getting close to redlining.
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Old 11-12-2012, 03:21 PM   #15
jsBLwrx
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Hi all, thanks for all the help. It would seem all good for now. I will keep a close eye on the gauge for now.

I couldn't replicate the flutter..... l will consult the dealer and also consider going stage ll. There is one dealer that's supposed to be mod friendly

Thanks again everyone
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Old 11-16-2012, 08:14 AM   #16
tunertype
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Quote:
Originally Posted by jthatch12 View Post
I had flutter like the OP when my WGDC wasn't fully dialed in yet. Normally happens when Turbo dynamics is compensating for over boosting. Hence if he's experiencing fluttering for a full pull (near high rpms ) I would safely say the issue is wastegate related. The interesting part is the I'm assuming the car is not tuned yet. So it may be something to talk to Subaru about
He said he'd never taken it above 4k, so the car never had a chance to dial in the TD compensation until he did. that was probably the issue since seems fixed now.

If I'd gotten to test drive it before he bought it. it would have had plenty of chances to learn the TD @ redline.
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Old 11-16-2012, 08:21 AM   #17
scoobay38
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i am having the same problem with my 94 wrx, and my boost gauge rushes down to 16 pounds but doesnt feel like that
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Old 11-16-2012, 09:20 AM   #18
jsBLwrx
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Quote:
Originally Posted by tunertype

He said he'd never taken it above 4k, so the car never had a chance to dial in the TD compensation until he did. that was probably the issue since seems fixed now.

If I'd gotten to test drive it before he bought it. it would have had plenty of chances to learn the TD @ redline.
Hi all. Thanks for the comments. Had a few chance to get into it since my last post, and the boost guage is doing fine

FYI the car is purely stock other than the SPT catback that came with the car

Thanks again.
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