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05-11-2010, 09:06 PM | #1 |
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Member#: 84482
Join Date: Apr 2005
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Tri-State
Location: PA / Element Tuning
Vehicle:2005 STI.UR gt4088r E85 pro comp sti |
Boost dropping after full boost is reached
Ok everyone, this boost issue has been a work in progress, so I will fill you in and hope someone can help
Brand new Boost control is a eboost2, turbo is gt40r with twin 38mm wastegates with 17psi springs The issue started before the new boost controller so I know it is not the boost control, something is causing this. What is happening is full boost is dialed in but right after full boost it is dropping down to 17psi then back up to 19, then levels out. I have not been able to have any luck getting it to hold boost. I ran just the one wastegate port and it was even worse lowest boost was 14psi, so I have both nipples of the wastegates tied into the eboost2 and it is the best since having the eboost2 in. Things I know New solenoid, plumbed correctly, rpm correction already dialed in(obviously not helping), eboost2 boost settings correct for those that know...sp45 wg10 (really low gain to not cause a boost spike), sensitivity 15 to cause steady boost Major issue/things i am not sure about I don’t know if a small boost leak could cause this type of problem, there isn’t a large leak because there are not other signs..idle, hydra, tune, boost control other than dip is steady. Most reading I have done on the issue causes 1. full boost is not obtainable or 2. boost tapers to redline, not really my situation. Next step is to create a boost leak tester, but anyone have any other ideas because i am not sold on the boost leak cause Code:
rpm boost 4150 19.03 4200 20.26 4250 20.88 4300 22.1 4300 22.1 4400 22.1 4400 21.49 4550 20.88 4500 19.65 4600 19.03 4650 19.03 4700 17.81 4750 17.81 4750 17.81 4850 17.19 4900 17.81 4900 17.81 4950 19.03 5000 19.03 5000 19.03 5050 19.65 5150 19.65 5200 19.65 5250 19.65 5250 19.65 5350 19.65 5400 19.65 5400 19.65 5500 19.65 5500 19.03 5550 19.65 5600 19.65 5650 19.03 5700 19.65 5750 19.65 5800 19.65 5800 19.65 5900 19.65 5900 19.65 5950 19.65 6000 19.65
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05-11-2010, 10:48 PM | #2 |
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your waste gate is to small it cant get the extra gases out fast i enough so you get boost creep and than it starts flowing out and regulates it salfe
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05-12-2010, 02:31 AM | #3 |
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I have no idea what's up with your boost controller.
If you were using the stock ECU I'd say add more WGDC in the area where boost is low. But damn... 20psi at 4200 from a GT40. I should have gone twinscroll. |
05-12-2010, 07:36 AM | #4 | ||
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Quote:
Quote:
yeah I hear ya wgdc, spool is pretty nice for a large turbo. I have the boost correction where it is supposed to raise boost after a certain rpm. Nothing seems to do the trick. I did forget to mention it seems like this problem was getting worse and worse with the drop off after 22psi until I used both tial wg nipples and that stopped it from dropping to 14psi |
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05-12-2010, 10:11 AM | #5 |
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An issue with the boost solenoid perhaps?
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05-12-2010, 10:32 AM | #6 |
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i thought the same thing, but this is a brand new solenoid we are dealing with...i am leaning towards something mechanical, it happens right after full boost even if it is a high rpm pull where full boost it 6000rpms vs a 2500rpm 4th gear pull
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05-13-2010, 06:21 PM | #7 |
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anyone with any other ideas?
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05-13-2010, 08:20 PM | #8 |
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Pretty sure this is what is happening:
1 - your WG spring is too small (or just not tight enough) to hold over 17 psi consistently. Thus, under constant above 17psi presurre, it is blowing open. Try tightening it. 2 - By looking at your boost pattern, you are over boosting since you are probably running 100% WDC to get to your peak but then it's not holding b/c the spring itself is then popping open. 3 - Solve this with a stronger/tighter spring and then you want to tune your WDC from really high (80-100%) when building boost to a more reasonable level (under 80%) once you've flatlined your boost. It should almost look like a cross over with the WDC dropping right before you can get to peak boost. EG: rpm boost WDC 3800 9.5 100 3850 10 100 3900 12 100 3950 14 95 4000 17 92.5 4050 18 90 4100 18.5 87.5 4150 19.03 85 4200 20.26 82.5 4250 20.88 80 4300 22.1 80 4300 22.1 80 4400 22.1 80 4400 22.1 81 Continues with 22 psi but maybe some tweakes +/-10 WDC depending on how your engine/head breathes with your cam setup and all... good luck Last edited by Fongers; 05-13-2010 at 08:26 PM. |
05-14-2010, 10:29 AM | #9 | |
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Quote:
Code:
(rpm) tps (psi) wastegate PID (%) 3000 102 1.84 0 3050 102 2.46 0 3050 102 2.46 73.6 3100 102 2.46 74 3100 102 2.46 74 3150 102 3.07 74 3100 102 3.07 73.2 3150 102 3.07 74.4 3200 102 3.07 73.2 3200 102 3.68 73.6 3200 102 3.68 73.2 3250 102 4.3 73.6 3250 102 4.3 73.6 3300 102 4.91 73.6 3300 102 4.91 73.2 3350 102 5.53 72.8 3350 102 5.53 73.2 3400 102 5.53 73.2 3400 102 5.53 72.8 3450 102 6.14 73.2 3450 102 6.75 72.8 3500 102 6.75 72.8 3500 102 7.37 72.4 3550 102 7.98 71.6 3550 102 7.98 71.2 3600 102 8.6 71.6 3600 102 8.6 71.6 3700 102 9.21 71.2 3750 102 9.82 70.4 3750 102 10.44 70 3800 102 11.05 69.6 3800 102 11.67 69.2 3850 102 12.28 68.8 3900 102 13.51 68.4 3950 102 14.12 67.6 3950 102 14.74 66.8 4000 102 15.96 66.4 4050 102 17.19 64.8 4100 102 17.81 64.4 4150 102 19.03 63.6 4200 102 20.26 62.8 4250 102 20.88 62 4300 102 22.1 61.6 4300 102 22.1 60.8 4400 102 22.1 60.8 4400 102 21.49 61.2 4550 102 20.88 61.6 4500 102 19.65 62.8 4600 102 19.03 63.2 4650 102 19.03 64 4700 102 17.81 64.8 4750 102 17.81 65.2 4750 102 17.81 65.6 4850 102 17.19 65.6 4900 102 17.81 65.2 4900 102 17.81 64.8 4950 102 19.03 64.8 5000 102 19.03 64.4 5000 102 19.03 63.6 5050 102 19.65 64 5150 102 19.65 64 5200 102 19.65 64 5250 102 19.65 64 5250 102 19.65 64 5350 102 19.65 64 5400 102 19.65 64 5400 102 19.65 64 5500 102 19.65 64 5500 102 19.03 64 Last edited by blowbyu24; 05-14-2010 at 10:45 AM. |
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05-14-2010, 12:43 PM | #10 |
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The fact your map is setup right tells me that if nothing changed, then it really is the wg not staying closed... try tightening the springs a notch or two and see how that serves you. Remember, these things are operating at 500F+ so they do eventually wear out a bit.
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05-14-2010, 08:34 PM | #11 |
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Boost dropping after full boost is reached
I don't have twin scroll but I had issues with the bpv leaking under boost I would change the spring or try to shim it more. Just my thought
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05-15-2010, 04:51 PM | #12 |
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Well my bud and I did a boost leak test and found two leaks. One the nipple back under the throttle on the drivers side of the intake mani, it had a gash in it and my air temp sensor on my fmic piping was leaking. Buttoned them up and lowered the sensitivity on the eboost2 now it hits 22 and stays stready now. I sure had odd symtoms of a boost leak. Thansk everyone for ther input
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05-16-2010, 06:35 PM | #13 |
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For future readers :
Don't know what your setup is but this is how it should be : You must use a 3 port solenoid. It will have 2 outputs. One is open at 0% WDC while the other is open at 100% WDC. The output that is open at 100% WDC goes to the top port on both wastegates. The output that is open at 0% WDC goes to the side port on both wastegates. So at 100% WDC you are sending maximum pressure to the top ports of the wastegates which along with the spring pressure is resisting exhaust gas back pressure. If exhaust gas back pressure is still over powering this setup, you need to increase the spring force in the wastegates. Or increase flow through the turbine by increasing nozzle area or changing turbine wheel specs. |
05-17-2010, 01:34 PM | #14 |
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Glad you were able to figure it out about the leak! I had the something similar happen to me and it turned out to be my WG even though I was searching for a leak for months... 2 ways to skin a cat!
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