Weird boostcontrolling!

[Gustaf]

I just bought an Legacy RS fitted with some kind of bleedvalve mounted to some hose under the bonnet, near the right front wheel. I haven't even have time to trace the hose but i thougt i'd ask first.

The boostlevels are quite weird! If i really put the gas fully the boost peaks quite fast to 0.9bar but directly drops to 0.7-0.75 and keeps there thru the revs. Is the bleedvalve bleeding at all? Shouldn't the boost remain at 0.9bar. (3inch system from turbo and back + sport airfilter) Or is it the MBC that pulls it down to 0.7bar?

But then when i use the car "normaly" and press the gas say 75% the boost goes up to 0.5 and then slowly reaches 0.7 if i push it a little more. But the boost feels quite unwillingly above 0.5bar.

I have a Apexi AVC-D (non closed loop) MBC in another car. Is it worth to install in the Legacy? Even if i dont plan to boost more than 0.9 bar, but will i get rid of the weird boostlevels.


KINDLY REGARDS /Gustaf, Sweden

[Legacy777]

Yeah I'd say it has something to do with that connection/bleedvalve. However I couldn't specifically say what though.

[Gustaf]

How should the bleedvalve or in the future the solenoidvalve from the AVC-D be connected? If I install the AVC-D how do I bypass the stock management???

[Legacy777]

I'm really not sure to tell you the truth. I think dave might have had an avc or something to control boost.

Any one have any suggestions.

[StartRestart]

The boostlevels are quite weird! If i really put the gas fully the boost peaks quite fast to 0.9bar but directly drops to 0.7-0.75 and keeps there thru the revs. Is the bleedvalve bleeding at all? Shouldn't the boost remain at 0.9bar. (3inch system from turbo and back + sport airfilter) Or is it the MBC that pulls it down to 0.7bar?

But then when i use the car "normaly" and press the gas say 75% the boost goes up to 0.5 and then slowly reaches 0.7 if i push it a little more. But the boost feels quite unwillingly above 0.5bar.

I have a Apexi AVC-D (non closed loop) MBC in another car. Is it worth to install in the Legacy? Even if i dont plan to boost more than 0.9 bar, but will i get rid of the weird boostlevels.

KINDLY REGARDS /Gustaf, Sweden

It's b/c your car is spiking really bad. Bleeder style MBC are accurate, but tend to spike a lot. It sounds like it's set at 0.7bar, and will spike to 0.9. Actually if you put that EBC in, you might still have spiking problems. The electronics can't react as fast as a really nice Ball&Spring MBC ( in most cases). Try out hallman's MBC, or make one by doing some research

Legacy's turbos are small and spool quick, you'll notice some spiking on hard shifts too- i don't know much about any new EBC though, so wait for more info on those.

[Gustaf]

I've hade both manual end electronic boost controllers on other turbocars without problems. I REMOVED the bleedvalve yesterday and just connected the 2 lines with a small pipe. The result was, kind of no difference at all! The car boosts away to 1bar when i push full throttle and then rapidly descends to 0.69-0.7 in every gear. This is the only legacy RS i have driven so I don't now how a stock, standard rs should boost. Does it hold 0.7 constant or ????

But someone has to now how to connect boostcontrollers!? And if you use 3rd party boostcontrollers, how do you disable the stock boostcontrolling.

[Project_Legacy]

But someone has to now how to connect boostcontrollers!? And if you use 3rd party boostcontrollers, how do you disable the stock boostcontrolling.

yea i have to ask the same thing. i just bought an MBC and the instructions say that i have to disable the stock Boost Control (wastegate solenoid). do i just connect the vacuum line inlet of the wastegate solenoid straight into the MBC bypassing it that way? sounds like it to me but i dont wanna blow anything up. what do you guys say?

[Project_Legacy]

nothing huh??

[vrg3]

http://www.graphics.cornell.edu/~v/vacuum/

Unplug hose L from the boost control solenoid. Connect it to your boost controller's inlet. Place a cap on the exposed fitting of the solenoid.

Unplug hose K from the boost control solenoid. Connect it to your boost controller's outlet. Place a cap on the exposed fitting of the solenoid.

Alternatively, just remove hoses L, M, and K (and the union fitting) entirely. Cap off the side fittings on the boost control solenoid. Use 1/4" vacuum hose to connect the inlet of your boost controller to the compressor outlet, and the outlet of your boost controller to the wastegate actuator.

[Project_Legacy]

hmm seems like i got it right the first time! thanks for the reassurance.

do i absolutely have to place a cap on the wastegate solenoid fittings?

also, stupid question but... do i unplug the wastegate solenoid harness??

thanks vrg3.

[vrg3]

If you think you may ever want to use the solenoid again, you may as well protect its innards with a 10-cent vacuum cap. Maybe spray a little WD-40 in there before as well.

Yes, leave it plugged in.

[Project_Legacy]

well the solenoid was faulty anyway. so i dont really care about it. thanks for the help though. very useful.