Wierd Boost problem...please help.

[MBGSTI]

Whats up guys...
I'm a LONGGGGGGG time DSM owner...i've owned 4 AWD talons..and 1 galant vr-4 in the past 7 years...and i kinda of feel a little dumb being that i just found this site...

I'm helpin a friend out with his 95 talon...@ my shop..I needed to get some input.

Car: 1995 eagle talon AWD 5 speed
Mods:
BR 2.5 down pipe with a cat
Apex N1 exhuast
Hallman MBC
Greddy BOV with intake bypass
K&N intake system
RRE upper intercooler pipe kit
Small 16G upgrade with BR changeover kit
Fuel pump upgraded

Problem:
The turbo is VERY laggy...
@ 3500 it produces 5# of boost..
@ 4000rpm 9#'s
@ 5000rpm 13#'s
@ 6000rpm 16#'s
@ 7000rpm 20+ #'s or fuel cut

I have tried palying with the MBC and have swapped out another known good MBC, and the problem continues...very laggy, and as i play with the MBC settings the only thing that changes is the is the amount of boost that comes up @ the 3500 RPM level, which goes up or down as i adjust the controller..
No matter what the MBC is set @, the turbo gains boost REAL SLOW.

The car has a cat and a smaller 2 1/2" downpipe.

When i unplug the wastegate vacuum line, the hit the gas, the turbo has NO problem hittin 20+ psi @ 3500rpm...i have to let off before fuel cut/blown motor time.

The cars owner already tried replacing the actuator...
I have driven cars with boost creep, but this car can't hardly make any boost, then when it does it seems as if it can't limit/regulate it...

I have checked the MBC vacuum lines, and its installed correctly.

Thanks in advance.

Mark

 

[MBGSTI]

I just noticed...i posted in the wrong area, can a Mod. move this over for me, thanks...

 

[1993eclipseGS]

Is the wastegate flapper stuck open? Did you try to use a different wastegate? Are there any blown out gaskets around the turbo area or loose bolts(exhast manifold/o2 housing)?

 

[danielbui]

what o2 housing are you using? is it stock or aftermarket? if its stock have you ported it? if not ported that could be the reason for the creep as in the weak link in the chain. as for your lag make sure there are no leaks in the turbo to were boost can escape. next check for boost leaks then if all else fails remove turbo and check the turbo for failure. to control my creep i removed the vaccum line from the boost control solenoid to my wastegate and T-ed into my BOV vaccum line. it held @ 10psi for normal driving but still creeped/20+ psi/fuel cut if i raced. i just ported my o2 housing ALOT.......stress the word ALOT.

 

[MBGSTI]

Is the wastegate flapper stuck open? Did you try to use a different wastegate? Are there any blown out gaskets around the turbo area or loose bolts(exhast manifold/o2 housing)?

I don't think its stuck open, when i removed the line from the MBC to wastegate actuator and went for a quick spin the car, it had no problem hittin 20+ psi with very little lag.
The guy has already replaced the actuator, so i assume its good, and to some exent the car does regulate boost., if the diaphram was bad, the car would have the problem of overboost all the time.
No blown out gaskets,...i may have to remove the turbo and everything to get a good look..?
Thats a bummer,
Not as much as a bummer as the blown motor on my STI :laugh: :thumbdown , i would rather have smaller problems like this..Thats why i always have my trusty DSM.

 

[MBGSTI]

what o2 housing are you using? is it stock or aftermarket? if its stock have you ported it? if not ported that could be the reason for the creep as in the weak link in the chain. as for your lag make sure there are no leaks in the turbo to were boost can escape. next check for boost leaks then if all else fails remove turbo and check the turbo for failure. to control my creep i removed the vaccum line from the boost control solenoid to my wastegate and T-ed into my BOV vaccum line. it held @ 10psi for normal driving but still creeped/20+ psi/fuel cut if i raced. i just ported my o2 housing ALOT.......stress the word ALOT.

No boost leaks, but u brought up a few other things to look into
thanks

 

[danielbui]

also i ported the wastegate port as well

 

[gsxtacy]

I don't know so I am gonna ask. Is the wastegate sourced to a good MAP source? Back when I sourced the wastegate/MBC to the compressor housing I had erratic boost.

Try sourcing the BOV, MBC, wastegate DIRECTLY from the manifold. The line that used to source the BOV alone.

Like I said I am not seeing the car so I don't know.

Another thing that causes slow spool is exhaust leaks, but you said with the wastegate closed 20 psi is not a problem.

Hope you figure it out

gsxtacy

 

[danielbui]

on mine it was straight from wastegate to BOV vaccum no other paths taken.

 

[MBGSTI]

The MBC control vacuum line tees in from the BOV vacuum line...coming directly from the intake manifold...
The cars is in cherry shape, no leaks...anywhere..in the exhuast or air intake systems.

At first i thought i might have a bad turbo,but once i pulled off the wastegate vacuum line and the turbo spooled nice and fast to 20+ psi, that kinda made me change my mind.

@ this point i'm leaning towards pullin out and porting the flapper/02 housing.

 

[danielbui]

good to hear progress! as they say HOG IT OUT.

 

[danielbui]

during reassembly install a new wastgate from a vendor it sounds like you have another weak link. the wastegate is not holding boost but is opening early or already open due to small amounts of boost or maybe vaccum. the serious lag is caused by this. when your car generates enough pressure in the manifold it will force air into the biggest opening causing boost creep. this is when you start to feel boost and enter into 20+psi range not at lower ranges because at low boost your power is leaking through the wastegate port. so unplugging the wastgate vacc line released the actuator arm and let you spool like you needed but when it opened boost creep took over and continued to rise. this is just my opinion hopefully it helps.

 

[cbellsondsm]

i agree with danielbui i had a wastgate actuator that was banged up pretty bad and i had......boost but after i replaced it and ported the turbine inlet (little difference) i noticed a whole lot, maybe its a dead sprint or diaphram in the WG actuator that pops open under the slightest booost, after all u said you had good boost, with no MBC so naturally no presssure was sent to the WG actuator just my two cents hope this helps a little

 

[cbellsondsm]

dead spring not dead sprint my fault its kinda late/early