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rnagy86
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« on: April 12, 2016, 05:50:52 AM »
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Hi I've this issue with a car that has a sudden boost loss and some fluttering in MAF voltage a bit higher up the rev range. This only happens in 4 and up gears. It's a 2.7T with k04 hybrids. I have no idea what's causing this so I am putting it up here maybe someone will have a glory idea. Thanks  |
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spacey3
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« Reply #1 on: April 12, 2016, 06:34:30 AM »
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Flutter >5k looks like surge to me, not sure on the boost drop earlier though
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rnagy86
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« Reply #2 on: April 12, 2016, 07:46:48 AM »
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Flutter >5k looks like surge to me, not sure on the boost drop earlier though
I noticed in that log that the flutter starts at camshaft changeover. |
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rnagy86
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« Reply #3 on: April 14, 2016, 08:47:50 AM »
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I did another log today, it's really bad, and I can't find any hardware fault. I'd really appreciate a glory idea  |
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rnagy86
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« Reply #4 on: April 14, 2016, 09:09:23 AM »
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And as a reference here is a 3rd gear pull as well which does not show
this symptom.
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spacey3
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« Reply #5 on: April 15, 2016, 02:54:51 AM »
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Just lay off the boost a couple of psi in the problem area... Apart from that, bigger/laggier turbo (or large turbine housing) so you don't hit the surge point  |
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rnagy86
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« Reply #6 on: April 15, 2016, 05:40:13 AM »
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Just lay off the boost a couple of psi in the problem area... Apart from that, bigger/laggier turbo (or large turbine housing) so you don't hit the surge point Well the turbos have no problem making that boost in 2nd and 3rd gear around 4k, so I don't see why they can't do it in 4+ gears. For the fluttering, sure i will decrease boost but the low rpm range sudden 0.5 bar boost loss is what bothers me really. |
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spacey3
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« Reply #7 on: April 15, 2016, 06:15:07 AM »
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You make boost earlier in the higher gears with more load, thus you're making just a little too much too early.
Think of it as an issue with the turbos being too efficient at low rpm. The engine simply can't consume the airflow (for a multitude of reasons).
Could have a dabble with the gear based boost and slightly lower it in the affected rpm's in the higher gears?
Just some ideas...
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rnagy86
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« Reply #8 on: April 15, 2016, 07:54:22 AM »
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You make boost earlier in the higher gears with more load, thus you're making just a little too much too early.
Think of it as an issue with the turbos being too efficient at low rpm. The engine simply can't consume the airflow (for a multitude of reasons).
Could have a dabble with the gear based boost and slightly lower it in the affected rpm's in the higher gears?
Just some ideas...
I understand what you are saying, I just never did saw such low rpm surging, and to be honest I don't know how it looks like on the logs, and I can't hear anything weird in the car either. It's weird though the engine has all the bells and whistles with ported heads and all and the turbos are not that big, anyway I did what you suggested and attached a log, now i guess i need some more duty cycle up top to bring boost back up. Thanks |
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spacey3
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« Reply #9 on: April 15, 2016, 04:09:52 PM »
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When I came across surge I found it would cause the boost drop when it occurred heavily, but just slight chuffing (sometimes not audible on the road) can be read with those wobbles on the maf. If you're right on the edge of surge, maybe the weather has made it worse/noticeable now? Good luck |
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rnagy86
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« Reply #10 on: May 13, 2016, 08:30:14 AM »
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I think it's fairly obvious now...  https://www.youtube.com/watch?v=Hl2f808QvEkI am really disappointed in all this now. It would be nice to figure out what's the restriction at this point. Time for bigger cams?   |
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« Last Edit: May 13, 2016, 09:15:37 AM by rnagy86 »
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rnagy86
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« Reply #11 on: May 17, 2016, 03:48:51 AM »
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Measured exhaust back pressure today before the turbo in the exhaust manifold, and it peaks at 2.5bar and stays there while the boost pressure is at 1.6 bar and it still surges at 1.6 bar, which is nothing.  |
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nyet
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« Reply #12 on: May 17, 2016, 09:30:14 AM »
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Disable vvt?
Odd that it is happening near the crossover point.
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rnagy86
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« Reply #13 on: May 17, 2016, 09:53:30 AM »
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Disable vvt?
Odd that it is happening near the crossover point.
Yes I did that today already, no change at all. Moving the switchover point to 6k did not change a thing either. |
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nyet
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« Reply #14 on: May 17, 2016, 10:13:02 AM »
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Hmm. In one of your logs, your battery voltage seems super low... 13.3 v... maybe alternator/battery/electrical?
Bad things seems to coincide with crossing 13.5 volts
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