Got a little problem that I can not figure out, need a little help. Thanks in advance.

My car is loosing boost in the top rpms like really bad. Around 6000 rpms my boost is falling from 1.3 too .05 (bar), and there is a Whssssss sound like the Bvo is opening up. This is happening in every gear 1-4. I turned down the boost too 1.0 and it is still dropping off, with the same sound.

This is what I have done so far as test to try to correct the problem.
I replaced all Three hose on the BOV. I traded out the Forge BOV with the stock BOV and a Greddy BOV. I took the splash guard off and checked and tighten all the IC hoses. I traded out the MBC with another MBC. I traded out the Air Filter, even took out the Air Filter for testing purposes. On the manifold I took the vacuum hoses off and plugged them. Replaced the waste gate.

I am very lost and out of things to try.
thanks

My mods if you need too know is as follows:

Works 93 octane flash Ecu ,Ultimate 3" Turbo exhaust /3" Cat,MBC,Clutch line,Greddy boost gauge, Crank pulley,K&N Filter,Forge Bov

 

I see the logic in what you have attempted to change. The forge BOV has several springs from the factory. I am running the weakest spring (Green) with no problem of the valve opening up. It sounds as if the BOV is not your problem.

I am running a Forge DV, Greddy EBC, 3'' catback, and intake. I have not had a psi fall of problem. If I did, the EBC can adjust to this. The MBC is more difficult to get precise.

If you are confident none of the IC hose are leaking, then that is not a problem. They could have a cut of some type that only opens under pressure. A small slip of a flat head screwdriver would do that in a heartbeat. I don't know if slit would be large enough to let out that kind of pressure though.

I assume you put a correct working wastegate on the car, so that can't be the problem.

That leaves the MBC and maybe the works reflash. I would speak with them about the potential problems a MBC would cause with the air/fuel, ECU, timing, and knock controll etc......of their reflash. I am not sure if you should run a MBC with their programing. Maybe you can.

Sorry I could not be of more help, just trying to give you ideas.

 

I have spoke with Works, they said there re-flash would not cause this problem.
I have turned down the boost too 1.0 = (14.5 boost) this is even lower then factor, and still the Whssss. and lost in boost.

Something else I tried was to take it up to 6 k when I hear the Whssss. sound let off the accelerator then right back on the gas. I get the same sound again and boost will not go past .05-.06.

Note the Whssss . sound only happens onces in each gear and the boost never returns to normal unless RPMS falls below 6 k.

 

So even if your not at wide open throttle and only pushing say .50 bar when you hit 6,000 rpm it blows off???

I would send the ecu back to be reflased to stock and see if that cures it.

Thats jacked up, maybee replace the waste gate actuator before you send of the ecu.

 

He may be on to something. The wastegate could be getting a signal to release or it may be malfunctioning. The only thing I am familar with is the vacum line hooked in from the EBC. I assume you have the MBC hooked into the Actuator and the wastegate? The MBC could be fine. How long is your vacum lines to your actuator and wastegate? You indicated earlier that you think vacum pressure is ok. Is that still your thought? Have you tested it?

I assume you can tell the differense between wastegate release and BOV release. I myself would not know the difference. If you can that may pinpoint the problem more.

 

The MBC is hooked to the actuator and wastegate. I did change too another MBC for testing purpose and got the same result. The vacum lines are a little longer then stock. I took the vacum lines off the manifold and plugged them up did some more testing and had the same sound and fall off in boost.


Let me throw this in also, I had the car placed on a Dynojet too try to located the problem. While on the Dyno the car pulled PERFIT, WTF. SO I took the car off the Dyno and did some road testing and the same problem occured, like ok, back to the Dyno to find out what it is. I got the car back on the Dyno and (NOTHING) again it ran perfit. Man, This Sucks..

Thanks again for all the help ..

 

i had the same problem with my evo. it was a loose clamp on the piping, it sounded like the exact same thing. i also got a new bov to see if that was the problem and it was not. Just trying to help!

 

The dyno thing is intresting.
When you are on the dyno the hood is open and on the road it is closed, yes?
I know my upper IC hose touches the hood some when it is closed. This may be a long shot but when the engine rocks under power and the hose hits the hood maybe it is causing a leak.
There has to be a reason why it doesn't do it with the car on the dyno. IF it does it all the time otherwise then it pretty much rules out bad parts like the MBC and the BOV.
You could try popping the hood to the secondary latch and carefully driving it to see if it still leaks off the boost or not. This would increase the clearance of that upper hose.

 

Thanks Timzcat,
I took you’re advised and popped the hood to the secondary latch and did a run like that through 1st and 2nd gear. The car ran great. I did more then 20 pulls with the hood down and up, each time the car ran great with the hood up and with the hood down it ran like ****.
Well I did some more testing. The first thing I did was take the hose between the turbo and the air box and checked for anything that would not allow air to flow. I put everything back on and did some more testing and the same thing happen. GRRR
Well I took the air scoop off and ran with just the top and the air filter in place, the car ran great. It seems to just be running out of air on the top end.

So after testing many theories and items, I decided to leave off the scoop and just run with the top of the air box and the air filter.
This will work till I can get a stand alone ECU.

Note: I took my car out to where the kids run and its marked off for quarter mile runs. My car ran 111 mph. MBC set at 1.4 bar.

Thanks again Timzcat you got me going in the right direction.

 

is this that problem that if the scoop is not properly secured it will flop up against the hood and block air flow? i thought someone else had a problem that sounds similar to this one.

 

You know Bs.. I don't have the pins in to hold the scoop down. I will install the pins and c if that works.
Thxs still learning

 

hopefully that works for you!

 

Actually this reminded me of something that happened recently.. did you tap into the BOV line for your boost gauge? I was playing "midnight club" (if you know what I mean) and I noticed my car was unusually slow.. Discovered that the vacuum line split in the Tconnector.. What was happening was (with the stock BOV) that the pressure from the BOOST (positive pressure as opposed to vacuum) was keeping the blowoff valve closed.. without that added help, the BOV would open under spring pressure under boost and leak (Down to around 14.5psi)

Keep that in mind when your troubleshooting...

Oh, in my case there was a telltale noise that sounded like Curly (from the three stooges going Woob-woob-woob) kinda like the honking noise those loud blowoff valves make when their setup incorrectly.

 

Isn't it amazing what you can figure out if you just keep asking questions. Life is a trip.

 

Oh well, ignore my input unless you like humorous car stories.. looks like you caught the problem I didn't see the more recent posts..