Boost behaving badly
 

Rexperts.

Have spoken to Joe about this and want a little advise before pulling the cooler off.

After doing a few searches I think its either a split pipe or a faulty BOV.

Just fitted a boost gauge (have checked and its working 100%)

Car is making no vacuum between turbo and throttle body.

Driving normally i start to accelerate boost climbs to 0.4 bar as soon as it reaches 0.4 the boost drops to 0.15 bar. then when i get off the gas (BOV goes off) boost spikes to 0.5 bar.

car has power FC set to about 1.3 bar so its not ECU related.

thanks guys. All help appreciated.

What bov have you got

You are not supposed to have the boost gauge plumbed in between the throttle body and turbo.

It needs to be plumbed into the intake manifold.

There should be no vacuum between the throttle plate and turbo. As under idle air enters the intake manifold through the idle control valve.

When you get off the throttle. the throttle snaps shut and the slight millisecond delay of the BOV opening combined with the inertia of the air still flowing toward throttle body will cause pressure between the throttle body and turbo to rise sharply then drop as the BOV opens fully.

the boost rising to 0.4 and then back down to 0.15 bar under full throttle is unusual though. You probably have a boost leak.


Really though, you should plumb the vacuum line of the gauge to the intake manifold then report back.

[QUOTE=pmh;502537]What bov have you got[/QUOTE]
factory BOV
[QUOTE=Mister Two;502538]You are not supposed to have the boost gauge plumbed in between the throttle body and turbo.

It needs to be plumbed into the intake manifold.

There should be no vacuum between the throttle plate and turbo. As under idle air enters the intake manifold through the idle control valve.

When you get off the throttle. the throttle snaps shut and the slight millisecond delay of the BOV opening combined with the inertia of the air still flowing toward throttle body will cause pressure between the throttle body and turbo to rise sharply then drop as the BOV opens fully.

the boost rising to 0.4 and then back down to 0.15 bar under full throttle is unusual though. You probably have a boost leak.


Really though, you should plumb the vacuum line of the gauge to the intake manifold then report back.[/QUOTE]


Thank you, will change plumbing and report back.

[QUOTE=Mister Two;502538]You are not supposed to have the boost gauge plumbed in between the throttle body and turbo.

[B]it matters not, both areas see virtually the same boost/vac[/B]

It needs to be plumbed into the intake manifold. - [B]yes or before the TB, either is fine[/B]

There should be no vacuum between the throttle plate and turbo. As under idle air enters the intake manifold through the idle control valve.[B]
no, air enters thru the TB/turbo as well - the idle cv supplements this to control idle[/B]

When you get off the throttle. the throttle snaps shut and the slight millisecond delay of the BOV opening combined with the inertia of the air still flowing toward throttle body will cause pressure between the throttle body and turbo to rise sharply then drop as the BOV opens fully.

the boost rising to 0.4 and then back down to 0.15 bar under full throttle is unusual though. You probably have a boost leak.


Really though, you should plumb the vacuum line of the gauge to the intake manifold then report back.[/QUOTE]

so you can run the boost gauge line off the comp housing or wastegate actuator line if you want - because that sees vaccuum as well.

what ebc or mbc are you using?

what is stock wastegate spring boost pressure? cause im guessing that is all you are using to control boost especially if spring pressure is about 0.4bar

[QUOTE=norwest_rumbler;502570]so you can run the boost gauge line off the comp housing or wastegate actuator line if you want - because that sees vaccuum as well.

what ebc or mbc are you using?

what is stock wastegate spring boost pressure? cause im guessing that is all you are using to control boost especially if spring pressure is about 0.4bar[/QUOTE]

He said powerfc to 1.3 bar.

[QUOTE=norwest_rumbler;502570]so you can run the boost gauge line off the comp housing or wastegate actuator line if you want - because that sees vaccuum as well.

what ebc or mbc are you using?

what is stock wastegate spring boost pressure? cause im guessing that is all you are using to control boost especially if spring pressure is about 0.4bar[/QUOTE]


EBC is PFC using factory EBC which is set to 1.3.kg/cm^2 (about 1.3 bar)

turbo is VF23, i dont know alot about the VF series.

i have now changed the location of the boost control feed to the inlet manifold and getting normal operation.

boost is peaking at 0.7 bar.

things to check next?

[QUOTE=magic1;502582]EBC is PFC using factory EBC which is set to 1.3.kg/cm^2 (about 1.3 bar)

turbo is VF23, i dont know alot about the VF series.

i have now changed the location of the boost control feed to the inlet manifold and getting normal operation.

boost is peaking at 0.7 bar.

things to check next?[/QUOTE]

if you find your problem please let me know, my boost peakes at 0.7 bar aswell using power FC, but ive got it set to 1.0 bar on my hand controller.

[QUOTE=magic1;502582]
things to check next?[/QUOTE]
sorry i havent used that type of bc.
sounds like pfc/stock solenoid operation/settings - basically stock solenoid is not bleeding off enough air to raise boost.

I think that if you are using Power Fc to control boost with the stock boost solenoid, you need to have the little brass olive in place to control the flow of air to the solenoid and thus the wastegate actuator.

Feel the vacuum line coming off the little nipple on the compressor housing of the turbo. Squeeze down alone the hose to feel if there is a hard bit. It should be between the nipple outlet and the T piece. If there is none, no matter what setting you use with the Power FC hand controller it will always run wastegate spring pressure.