Boost fluctuation: Boost control settings vs EBC vs bad turbo
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- Posts: 16
- Joined: Tue Jul 23, 2019 2:48 pm
Boost fluctuation: Boost control settings vs EBC vs bad turbo
First time uploading attachments here so hope they work. Basically here is my issue I am having.
So every time I hit the duty cycle that's set in my boost control table the boost drops down, then hits the quick spool setting then boosts back up only to drop the boost back down again. Checked for boost leaks and as far as I can tell all couplers are good, bov is good, wastegates are not loose. I am having some intermittent vtec issues that I am chasing but don't think I am coming in and out of vtec. The only two other things I can think of is head lift or turbo is going bad. I think I cooked this one to be honest as the blades are starting to ever so slightly rub on the compressor housing and have very little shaft play. But it doenst smoke or make and funny squealing. I think head lift because the overflow was full..... but no bubbles in the rad when the car is idling. That's all I can really think of so if anyone has had this issue or can ask some questions that I have not thought about yet please feel free to comment. Here is a picture of a datalog of the exact issue Im having.
So every time I hit the duty cycle that's set in my boost control table the boost drops down, then hits the quick spool setting then boosts back up only to drop the boost back down again. Checked for boost leaks and as far as I can tell all couplers are good, bov is good, wastegates are not loose. I am having some intermittent vtec issues that I am chasing but don't think I am coming in and out of vtec. The only two other things I can think of is head lift or turbo is going bad. I think I cooked this one to be honest as the blades are starting to ever so slightly rub on the compressor housing and have very little shaft play. But it doenst smoke or make and funny squealing. I think head lift because the overflow was full..... but no bubbles in the rad when the car is idling. That's all I can really think of so if anyone has had this issue or can ask some questions that I have not thought about yet please feel free to comment. Here is a picture of a datalog of the exact issue Im having.
- Attachments
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- travis tune 1.2.skl
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- Boost issue.jpg (338.74 KiB) Viewed 1915 times
Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
Post the actual datalog instead of just a picture so we can see all parameters.
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
Ok. I logged the issue 4 times so I am unsure if this one will match the picture but the issue is there for you to see. This is the third log of the oscillation. Is there anything mechanically that could be causing this such as a BOV or leaking Wastegate diaphram?
- Attachments
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- boost issue 3.s3d
- (73.02 KiB) Downloaded 108 times
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
Try changing the quick spool to something closer to 1100 mbar
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
That would be 15-16PSI, that would be more than I am commanding in the actual boost table. Would that keep it from dropping after hitting my target duty %? And is that just a band aid covering up whats causing the boost to drop?
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
Do I possibly have too much gate? I have dual 44's with 3lbs spings. My power goals are around 550-650 using a Borg Warner s300sx turbo. So my thought is not enough back pressure, gates open and let too much exhaust gas out making the turbo spool drop then try to rise back up again and this process repeats.
Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
You currently have the quickspool set near 1400mbar.
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
Ill have to look at that when I get home, currently at work. The last time I looked I believe I set it up to 6 or 8 PSI then it goes to my duty cycle on the boost map. If quick spool was set at 20psi, wouldnt it kick back on immediately if it dropped below the 47% duty? In that first pictures you can see it drops to 6psi before quick spool kicks back on. Unless I am over looking something.
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
When I got home last night I opened up calibration and my quick spool is set at 7psi which would convert into only 482.6 mBar. Unsure why you're seeing 1400mBar. I have asked around on other forums about this issues and some have suggested that I have too much gate. I am running dual 44's using a T4 BW s300sx turbo on a 83mm B18b sleeved block, using a 4 port EBC to control the boost. Ive heard 4 ports can be a bit touchy and I could possibly mess around with the Hz levels to slow down the sampling rate, I am currently at 72 Hz IIRC. Their thought was that when the gates do open they let out a lot of exhaust pressure which then drop the turbo spool down and then the turbo is playing catch up with my table and quick spool settings. Which, when looking at the log posted above, does make some sense to me that this could be happening. I have a 44mm block off flange coming so I can test this theory. I also am thinking of down-sizing my turbo coming from a .92 AR to a .70 and t3 turbo vs the t4 I currently have. Any thoughts?
Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
If you look at the activation pressure setting of 1082 in mbar, and then look at the quick spool settings, you have it set to 1495mbar. In PSI you should have this set to something closer to 1 or 2 psi or about 1100mbar.
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Re: Boost fluctuation: Boost control settings vs EBC vs bad turbo
So I changed a couple things since I was having the boost oscillating issue. I went ahead and blocked off one of the gates. The thought behind doing this was too little back pressure my turbo to loose spool really quick due to 88mm's of gate letting too much exhaust gas out at once. And second I bought a t3 style turbo. This didnt really have much to do with the situation beside I thought I might have cooked my borg warner. The boost issue has resolved, I can hit 10 psi and hold steady throughout the RPM range. Too much gate was this issue IMO. Activation pressure was left at 1psi and quick spool set to 6 psi.