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Old 02-04-2013, 08:06 AM   #1
bluemk3
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Default wastegage duty cycle high. boost wobbles help

So after a street tune I've got a 3 port tuned and peak boost is around 19 lbs out of td04. It wobbles back and forth a few lbs in higher gears. My duty cycle is higher than most cars at around 70% my tuner says he's having trouble getting it to be solid boost up high. Am i looking to lower my duty cycle... He seems to want to raise it... But i think that's the opposite way to go. Any help
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Old 02-04-2013, 08:56 AM   #2
bjohnson_55
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It's wobbling because the turbo dynamics are too aggressive. It's overshooting target boost, over compensates, so it goes under target, then over compensates, goes above target, etc.
You're going to hit slightly higher boost in higher gears. As long as you're hitting target with close to zero turbo dynamics in 3-4 then wastegate duty needs to stay the same. Turbo dynamics are too aggressive.
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Old 02-04-2013, 12:34 PM   #3
bluemk3
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Thanks. What's the best way to resolve it...
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Old 02-04-2013, 05:09 PM   #4
jthatch12
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Originally Posted by bluemk3 View Post
Thanks. What's the best way to resolve it...
Lower turbo dynamics. If you're open source I can send you a copy of my map. We have a similar setup
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Old 02-04-2013, 08:48 PM   #5
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Originally Posted by jthatch12 View Post

Lower turbo dynamics. If you're open source I can send you a copy of my map. We have a similar setup
That would be great. I'm open three inch all the way back spt intake. Big top mount. 19#... Up pipe... Think it could help...? What would it do to the rest if my tune?
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Old 02-04-2013, 09:03 PM   #6
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Quote:
Originally Posted by bluemk3 View Post
That would be great. I'm open three inch all the way back spt intake. Big top mount. 19#... Up pipe... Think it could help...? What would it do to the rest if my tune?
Listen to your tuner. Lower TD effectively lowers the computer's ability to adjust boost. Listen to your tuner, not the interwebs.
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Old 02-04-2013, 09:03 PM   #7
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Quote:
Originally Posted by bluemk3 View Post

That would be great. I'm open three inch all the way back spt intake. Big top mount. 19#... Up pipe... Think it could help...? What would it do to the rest if my tune?
I have the same setup minus the spt intake. I'm running stock intake. It'll give you a real solid tune. I'm making over 250 whp at ~19.5 psi
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Old 02-04-2013, 09:32 PM   #8
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Originally Posted by BlazeRex View Post
Listen to your tuner. Lower TD effectively lowers the computer's ability to adjust boost. Listen to your tuner, not the interwebs.
I think i need a new one... Mine had gotten me to have shaky boost and ran out of ideas.
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Old 04-01-2013, 02:43 PM   #9
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Quote:
Originally Posted by jthatch12 View Post

Lower turbo dynamics. If you're open source I can send you a copy of my map. We have a similar setup
Hey bud, I've been watching this thread and am having the exact same problem. Would you be willing to extend me the same offer of a copy of your map? BTW, I'm stg 2 w/ 3" TBE, up pipe, big tmic, 3 port, K&N panel filter.

Last edited by scoobydo2.0; 04-01-2013 at 04:56 PM.
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Old 04-03-2013, 01:42 AM   #10
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Reduce TD continuous table. If you never reduced it from stock, start out by multiplying by about 0.6. Then if it still oscillates, multiply all cells by 0.9 again and again until it's stable. This will mean you have to have your target boost setup for your boost ramp, or you'll have an overboost spike, as it will be slower to clamp down on boost as it spools up.

Oscillation means that it's overadjusting and never able to settle down to target, so you need to reduce how much it adjusts.
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Old 04-03-2013, 08:23 AM   #11
Black94Snake
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I find it funny how everyone is recommending changing the TD parameters to fix boost oscillation. Every car I've done has been stabilized by adjusting the wgdc tables. If you command too high of a wgdc, you'll overboost.
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Old 04-03-2013, 10:13 PM   #12
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Boost control via WGDC in the EJ205 ROM leads to good boost in one gear and messed up boost in every other. Or good boost control at one ambient temperature and different when the weather changes.

WGDC that's good in 4th will result in abysmally low boost in 2nd and 3rd. WGDC that's good in 3rd will result in boost spikes in 4th and 5th.

People are recommending tuning TD, because that's how you do it right. Once you get target boost and TD right, then WGDC max and initial is used to keep from having an overboost spike when you slam the throttle at 5000 RPM... something well over the boost threshold RPM. Tuning the whole boost curve by WGDC will result in slow spool, or significantly varying boost in different gears.

You can half-ass it in the ROMs that have per-gear compensations and be okay, but the EJ205 ROM doesn't have the WGDC control to do it.
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Old 04-06-2013, 11:54 PM   #13
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Quote:
Originally Posted by Black94Snake View Post
I find it funny how everyone is recommending changing the TD parameters to fix boost oscillation. Every car I've done has been stabilized by adjusting the wgdc tables. If you command too high of a wgdc, you'll overboost.
You have a point. However, in my experiences, this was always due to it being a sudden onset of colder weather, esp in the morning commute. I got better results in the winter by just adjusting the WGDC table, however, when warmer months came, i found it to be underboosting again, having to make changes to the WGDC table. I guess it can be a double edged sword depending where you live. Best compromise in my opinion is a slight change to the TD table and a slight tweak of the WGDC table, to help bring it to a happy medium.
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