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Old 02-14-2017, 11:35 AM   #1
Imported209
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Default Odd issue with heavy boost oscillating under heavy load.

First off I have a 2002 wrx with a hybrid 2.5 block, blouch 18g turbo, 1000cc DW injectors, newish walbro 255 fuel pump, halman pro MBC, perrin short ram intake and turbo inlet, and Grimspeed metal intercooler hoses for a Sti intercooler. I also have a act lightweight flywheel and stage 2 clutch. All this stuff is decenlty new and all went in with the engine build done by a reputable shop. its tuned for about 20 psi. pretty sure i got everything thats important lol.


Issue I have been having is when boosting under full or 3/4 throttle the car makes boost awesome to about 10-15 psi. then it just falls flat on its face and the boost starts to stumble pretty hard, jumping from 10-15 psi. drives around just fine in the city with the AFR's staying pretty solid.

This whole issue started with me replacing the BPV to turbo inlet hose due to it leaking where it connects to the turbo inlet. drove home great from the garage then next day i fire it up and it starts this.

after fixing one leak that had symptoms no where near this, could I have made another appear? dose this still sound like a boost leak? i'm lost now lol after taking apart the all the silicon hoses and replacing the bad ate up ones with hard pipes and new silicon im somewhat lost. I plan to get a boost leak test done at a shop as my smoke tester literally can only do 5 psi.

any ideas and tips are appreciated!


-Gus
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Last edited by Imported209; 02-14-2017 at 11:40 AM. Reason: new information
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Old 02-14-2017, 11:42 AM   #2
oaklandish_WRX
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still the stock tune? Was there any reason you did the MBC? Cattted DP?
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Old 02-14-2017, 11:47 AM   #3
Imported209
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lol no, its tuned by Mach V in VA. really great shop. catless all the way, and I did the MBC because I personally hate tuning a 3 port and love that I am able to "adjust" a few psi if i want to. I do have tuning experience my self so this isn't a issue for me to monitor and adjust a few things.
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Old 02-14-2017, 11:48 AM   #4
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Quote:
Originally Posted by Imported209 View Post
First off I have a 2002 wrx with a hybrid 2.5 block, blouch 18g turbo, 1000cc DW injectors, newish walbro 255 fuel pump, halman pro MBC, perrin short ram intake and turbo inlet, and Grimspeed metal intercooler hoses for a Sti intercooler. I also have a act lightweight flywheel and stage 2 clutch. All this stuff is decenlty new and all went in with the engine build done by a reputable shop. its tuned for about 20 psi. pretty sure i got everything thats important lol.


Issue I have been having is when boosting under full or 3/4 throttle the car makes boost awesome to about 10-15 psi. then it just falls flat on its face and the boost starts to stumble pretty hard, jumping from 10-15 psi. drives around just fine in the city with the AFR's staying pretty solid.

This whole issue started with me replacing the BPV to turbo inlet hose due to it leaking where it connects to the turbo inlet. drove home great from the garage then next day i fire it up and it starts this.

after fixing one leak that had symptoms no where near this, could I have made another appear? dose this still sound like a boost leak? i'm lost now lol after taking apart the all the silicon hoses and replacing the bad ate up ones with hard pipes and new silicon im somewhat lost. I plan to get a boost leak test done at a shop as my smoke tester literally can only do 5 psi.

any ideas and tips are appreciated!


-Gus
Boost Leak
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Old 02-14-2017, 11:51 AM   #5
Imported209
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Thanks boss! just wanted a confirmation. I guess ill have to wait for the test to be done XD in the mean time should I be looking at anything specific?
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Old 02-14-2017, 11:55 AM   #6
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that's pretty strange to get oscillation with an MBC. you disconnected the stock EBCS, right?
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Old 02-14-2017, 12:00 PM   #7
Imported209
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Yes I did. just left in the connector so it doesn't throw a code. its hooked up right as per the instructions.
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Old 02-14-2017, 12:03 PM   #8
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I also contacted Mach V tuning ( very good shop in my area) the other day and they think its a boost leak too. This will be the first spot I look is the turbo inlet and all the lines for it.
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Old 02-14-2017, 12:20 PM   #9
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do you have an adjustable compressor to test the MBC? that's a pretty big boost leak, should be able to find something that big by inspection
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Old 02-14-2017, 12:28 PM   #10
Imported209
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what do you mena by adjustable compressor? I do have a air compressor that is adjustable but its at the wifes parents like and 1 hour away.
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Old 02-14-2017, 02:51 PM   #11
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What is your AFR in boost under WOT?
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Old 02-14-2017, 07:40 PM   #12
Imported209
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I would have to check, i try not to go WOT atm. my map says 10.5 but if i remember right im at about 10.5-11
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Old 02-15-2017, 05:16 PM   #13
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just checked my AFR after fixing a leak on the intake to turbo inlet. the afr's are at 12.0! the car is running "more smooth" so im fairly possitive after feedback that there is 1 more solid leak somewhere in the turbo inlet. i cant see any obvious leaks so ima keep hunting. but the major oscilation is still there, just not as bad. so im also thinking there is one after the turbo and before the throttle body. I did have 1 nut on the back side of the intercooler not want to go back in right (threads are done, gonna have to re thread).
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Old 02-16-2017, 10:04 AM   #14
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12:1 under full boost is kind of on the lean side. do you have a wide band or is that the stock afr sensor? could be a leak in the intake housing allowing unmetered air in causing it go lean... however an intake leak won't cause your boost issue, that issue will lie post turbo. keep looking...
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Old 02-16-2017, 06:24 PM   #15
Imported209
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yeah I have a wideband. After further inspection today I did notice some of the intercooler y pipe and BPV to intercooler bolts are lose and probably caused it.I did fix the BPV bolt thread but wasnt able to get the y pipe on the back(need to drill it out and helicoil it). also a while back I did have to JB weld a hole in the intercooler so im just gonna go back over that with some more jb weld or actually weld the aluminum. If im lucky Ill be able to boost leak test it at the garage I go to. at this point im looking at that intercooler for the issue.


My issue seems post turbo and namely at this intercooler. will post back monday.
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Old 02-21-2017, 09:05 AM   #16
Imported209
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Alright, Took it to the garage I work at alot and we fixed the boost leak. long story short the JB weld I had used 5 years ago finally took a **** and we just re JB welded it, fixed the thread with a helicoil and we went for a drive. ran a whole lot better but still had the problem.

So the best worst idea one of us had was to literally drive the crap out of it. and we did. we re created this issue prob 7 times before we got the missfire code. Cylinder number 3 missfire. swapped coils 1 and 3 and verified that it is the coil that was on number 3 is bad. pretty sure issue solved. Thanks guys!
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Old 02-21-2017, 07:52 PM   #17
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Problem solved. Coil pack was bad and I replaced it. no more issues. you could clearly see the white spark marks where it arced in the coil pack boot.
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Old 02-21-2017, 07:56 PM   #18
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barvo
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