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Miata stops making boost around 5000rpm

Old 07-13-2018, 02:50 PM
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Default Miata stops making boost around 5000rpm

So i've randomly encountered a strange issue that i need some help identifying. So the car ( 1.8 turbo with mspnp2, stock engine) pulls hard up to around 5000 or so RPM and just loses all boost pressure, it makes a very quiet sound similar to compressor surge. Im not running a BOV at the moment but i wasn't having the issue before i put on a boost controller. I've tried running with wastegate pressure and get the same noise. Any ideas would be greatly appreciated, thanks!
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Old 07-13-2018, 02:57 PM
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overboost protection
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Old 07-13-2018, 03:05 PM
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Originally Posted by 18psi View Post
overboost protection
Overboost protection feels like an instant cut whereas now it feels like the turbo just dies and doesn't make any boost. I'm going to try and get a good datalog of the problem and maybe a video if possible.
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Old 07-13-2018, 03:13 PM
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clogged cat, boost leak, etc etc etc
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Old 07-13-2018, 03:14 PM
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billion things it could be, without datalog/details we're gonna get nowhere
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Old 07-13-2018, 04:07 PM
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Ok so i did a few pulls and got it to happen once in this log, it happened right after the first mark i placed. The car has no cats, 3in exhaust, no boost leaks. I'll be installing a BOV when it arrives to see if that could be the difference but i don't think it's the cause.
Attached Files
File Type: msl
2018-03-20_20.16.18.msl (3.44 MB, 5 views)
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Old 07-13-2018, 04:41 PM
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Originally Posted by Carrera95 View Post
Ok so i did a few pulls and got it to happen once in this log, it happened right after the first mark i placed. The car has no cats, 3in exhaust, no boost leaks. I'll be installing a BOV when it arrives to see if that could be the difference but i don't think it's the cause.
This log is just idle
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Old 07-13-2018, 08:25 PM
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My bad, mixed up the right file.
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2018-07-13_14.12.49.msl (1.69 MB, 6 views)
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Old 07-13-2018, 08:33 PM
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Ok I think i figured it out. My o2 sensor died yesterday so i replaced it with a new one and my afrs must have been messed up. Going over that log looks like I'm lean in boost so I'm going to make some changes and hopefully it'll be good.
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Old 07-13-2018, 11:59 PM
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Originally Posted by Carrera95 View Post
Ok I think i figured it out. My o2 sensor died yesterday so i replaced it with a new one and my afrs must have been messed up. Going over that log looks like I'm lean in boost so I'm going to make some changes and hopefully it'll be good.
u got other issues. Dead o2 sensor won't cause a lean condition at WOT with a ms2. Your fuel is already mapped out. So if it was fine before it will stay fine with a dead o2 sensor. You technically can remove the wideband all together once the car is mapped and it will run just fine under WOT.

what turbo/Wastegate setup so you have? Maybe Wastegate blowing wide open under high rpm boost?

Last edited by borka; 07-14-2018 at 01:33 AM.
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Old 07-14-2018, 05:09 PM
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Ok so i made a couple changes and i'm still getting the same issue. I have a great datalog of the issue occuring twice. I tried stayed on the throttle so you can see boost falling off and the car just loses power. I really have no idea what it could be because its not making any crazy noises, it just stops making boost. Turbo is a china t28 with ebay wastegate. Could my turbo be shot?
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Old 07-14-2018, 05:11 PM
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Forgot the datalog
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2018-07-14_15_modified.msl (1.67 MB, 6 views)
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