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Old 08-20-2007, 02:16 PM   #1
Ryeeno
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Default Power Issue in 5th - Comes in Waves

Went for a big highway cruise for the first time since Catback and protune (AP) and had this issue.

On the first big uphill section in 5th gear, power dropped way off around 3300 RPMs. On a mild grade the power would come on in waves from 3300 RPM on. Hard to describe. Not a jerky motion but more like a regular, oscillating wave. I tested 4th and 3rd and there was maybe a slightly similar feeling but it was really noticeable in 5th. The more throttle, the more noticeable the waves. WOT would barely lift the RPMs on any level of grade in 5th.

Any ideas?

Stage 2 2002 WRX.
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Old 08-20-2007, 02:20 PM   #2
thummel26
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gotta be the tune....catback itself wont have anything to do with it.
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Old 08-20-2007, 02:30 PM   #3
Master2192
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Do you have a boost gauge? It sounds like a boost waver, either caused by the tune or changing elevation.
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Old 08-20-2007, 02:54 PM   #4
Ryeeno
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I have a boost gauge but it's sitting in the box right now waiting to be installed.

My first thought was boost leak. The RPM spot where it kicked in was right at the usual point where the turbo would kick in. The tune was a few weeks ago and I hadn't noticed anything until that point. Seemed to happen pretty abruptly - like all of a sudden something felt off. Pain in the ass.
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Old 08-20-2007, 03:14 PM   #5
mpggomd
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sounds like your boost is waving up and down...are you using the stock controller??
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Old 08-20-2007, 03:41 PM   #6
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Sounds exactly like boost oscillation. Seen lots of people posting about this problem lately, very strange. I had the same thing. I took my boost solenoid off, took it apart and cleaned it with brake cleaner, the problem has never returned.

Boost would oscillate from 17psi to like 12psi, back and forth. Very annoying.
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Old 08-20-2007, 03:46 PM   #7
Ryeeno
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Quote:
Originally Posted by mpggomd View Post
sounds like your boost is waving up and down...are you using the stock controller??
Yes, stock controller.
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Old 08-20-2007, 05:33 PM   #8
ikhan1999
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nice thread... i'm having a similar issue (feels like power comes on in waves). I'll keep an eye on this thread.
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Old 08-20-2007, 06:50 PM   #9
Ryeeno
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I'm curious about other possible fixes. Also curious about why it's so noticable in 5th, but not other gears.
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Old 08-20-2007, 07:13 PM   #10
Frizondizog
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I had the same issue a long time ago, I had a boost gauge tho, Boost was just going back and forth due to a broken vacumn line
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Old 08-20-2007, 07:20 PM   #11
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Quote:
Originally Posted by Ryeeno View Post
I'm curious about other possible fixes. Also curious about why it's so noticable in 5th, but not other gears.
probably because in the higher gears, the engine load is greater = more boost required
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Old 08-30-2007, 03:43 PM   #12
passion4JC
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Someone solve this boost oscillation problem please! I've been having that too...
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Old 08-30-2007, 04:05 PM   #13
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Boost oscilating issues. Maybe I should right a faq on how to program the boost control system so these tuners can read it and not have this issue. I would gladly fix your map for free but if its a protune its locked and I cant open it. If they will convert to street tuner I would be happy to adjust it for you. I used to have these issues myself. It always shows up in taller gears. The lower the RPM and the load the more pronounced.

Clark
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Old 08-30-2007, 05:00 PM   #14
WRXShawn
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I used to have that with an early version of the OTS Cobb stg2 map but with a later version it went away. I had the stock BCS at the time.
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Old 08-31-2007, 12:32 AM   #15
passion4JC
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Quote:
Originally Posted by AZScoobie View Post
Boost oscilating issues. Maybe I should right a faq on how to program the boost control system so these tuners can read it and not have this issue. I would gladly fix your map for free but if its a protune its locked and I cant open it. If they will convert to street tuner I would be happy to adjust it for you. I used to have these issues myself. It always shows up in taller gears. The lower the RPM and the load the more pronounced.

Clark
FAQ would be nice.

I forgot to tell you earlier Clark that I'm running a TDC e-tune. Just re-flashed the Cobb Stg2 OTS and the oscillation was even worse.
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Old 08-31-2007, 01:49 AM   #16
AZScoobie
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Who wants a fee tune via email? I will remap the car with Cobb or open source and you try it and then you can provide feedback... If you have a protune now it must be converted to street tuner format so I can access it. If your tuner wont do that you are out of luck. Email me your file and I will get on it.

CLark
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Old 08-31-2007, 07:08 AM   #17
passion4JC
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me, me, me...i'll try it...
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Old 09-06-2007, 01:41 PM   #18
passion4JC
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update...sent my Cobb map to AZScoobie...waiting for the retune...will post feedback...
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Old 09-06-2007, 04:07 PM   #19
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ahh.. I remember this issue... My tuner cured it by changing the pill in the vacuum line and a bit of retuning...
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Old 09-06-2007, 08:10 PM   #20
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You want to see some real boost oscillation, have your big IC crack the nipple off your wastegate! My boost was going from 12 to 20+, very disturbing.
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Old 09-07-2007, 12:06 AM   #21
scraggy
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Quote:
Originally Posted by AZScoobie View Post
Who wants a fee tune via email? I will remap the car with Cobb or open source and you try it and then you can provide feedback... If you have a protune now it must be converted to street tuner format so I can access it. If your tuner wont do that you are out of luck. Email me your file and I will get on it.

CLark

Any utec love?
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Old 09-07-2007, 10:58 AM   #22
94'325is
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Have you guys tried cleaning your stock BCS? My 03' was doing the exact same thing and I took it off and cleaned it and now I hold 17 psi in all gears. It takes only a few minutes to clean and it makes a huge difference.
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Old 09-07-2007, 01:32 PM   #23
passion4JC
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Cleaned the BCS several times. Also cleaned the MAF sensor several times too. Checked all vacuum lines, even cleaned them to make sure...and it is still doing it.
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Old 10-29-2007, 07:36 PM   #24
Ryeeno
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Bump this up. Did the email tune work out? Mine is still doing it. Boost goes from 14 - 9 - 14 - 9 in 5th. Flashed back to Cobb Stage 2 93 OTS Map and it's even worse (shows up in 4th).

Tuner says it mechanical and mechanic says it's the tune.
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Old 10-29-2007, 08:17 PM   #25
Haelan
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There are many causes for boost oscillations. One thing to check before you start ripping stuff apart...

Do a log on your intake manifold pressure vs. the wastegate duty cycle %. I had a problem overboosting causing an oscillation-type effect (waves of power). If you look below at the bottom you'll see a high duty cycle (70%), it gets to 14.22 PSI, and the ECU says "Oh ****..." and lowers the wastegate duty cycle, but it still climbs another 1.3 PSI before finally settling down.

The problem was MUCH more pronounced in the higher gears. According to my boost gauge my pressure looked spot on, but my ECU is clearly seeing higher pressures than I want it to with a stock map.

What fixed mine: loosening the wastegate arm. You'll lose that immediate power surge in lower gears that feels nice coming off a stop, but you'll have steady boost in higher gears--no more rollercoaster. If anyone reading knows about PID loops, that is essentially what the ECU software is doing to control the boost pressure. The mechanical wastegate arm would apply to the PID Smax and Smin threshold. Depending on how the arm is adjusted creates a 'minimum' boost pressure (mechanical boost)--with all the gains set to 0. The tighter you have that set the more likely your PID loop will overshoot (under-damped). Loosening it too much and you'll be taking forever to build boost and may not hit it at all (over-damped). Having the boost shoot up to the correct PSI as quickly as possible without ringing out is critically damped.

You can fix it with a custom tune to modify your boost map or wastegate duty cycles, and provide a nice stabile boost curve that will be much better than the conservative stock settings.

Just know that blindly tightening your wastegate arm does have consequences and the ECU will not always be able to regulate the BCS to keep boost pressure below it's maximum threshold.

Primary Wastegate Duty Cycle (%) Manifold Relative Pressure (psi)

72.16 11.61
72.16 13.2
70.98 14.22
59.61 15.67
47.45 15.38
41.96 13.78
44.71 12.48
47.06 12.77
47.84 13.35
47.84 13.93
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