Boost drop as revs increase to red line

[richiekuk]

After fitting a B200ft (8 PSI) actuator to my B230FK with an MBC.

I bought an NXS MBC, and installing it all was easy.

I now boost to 12PSI happily. But as its an auto and as it holds gears with the throttle pressed. Once I go over 4K rpm the boost starts to drop off, to about 9-10 PSI.

Any ideas how to keep 12 PSI till redline?

[Forrest]

Personally, I am not into performance modding so you'll probably get better replies from others who are.

Assuming you have done a proper stage 0 service, the limiting factor is likely to be fuel or air.

Your B230FK probably has an over-boost function built into its ECU. If it detects too much air for a given engine RPM then it will cut the fuel. This is more like a sudden loss of power rather than gradually hitting a limit.

If the loss of boost is more gradual then something is probably restricting air flow. What sort of condition is the turbo inlet hose in? If it's too soft it might be collapsing under certain conditions and restricting air flow.

I think it's also possible to hit a condition where you're passing so much air over the AMM that it cannot draw enough power. This is unlikely at relatively low levels of boost, but you could try carefully cleaning the AMM if you haven't already to restore its performance.

Good luck!

[baggy798]

Putting some washers behind where the actuator mounts is the only thing you can do. It's either a tired actuator or the wastegate hole is worn a bit, probably a bit of both.

[SalvadorP]

Originally Posted by baggy798

Putting some washers behind where the actuator mounts is the only thing you can do. It's either a tired actuator or the wastegate hole is worn a bit, probably a bit of both.

Your car is looking great on that picture. Too bad it can't go over road bumps! jk
Where did you take that pic? The background and lighting reminds of an old horror movie set, like Nightmare on Helm Street or Texas Chainsaw Massacre.

[richiekuk]

Originally Posted by baggy798

Putting some washers behind where the actuator mounts is the only thing you can do. It's either a tired actuator or the wastegate hole is worn a bit, probably a bit of both.

Will this not cause a big spike?

I thought people pre tensioned the actuator to avoid this?

[360beast]

Originally Posted by SalvadorP

Your car is looking great on that picture. Too bad it can't go over road bumps! jk
Where did you take that pic? The background and lighting reminds of an old horror movie set, like Nightmare on Helm Street or Texas Chainsaw Massacre.

I think it's the AI generated images of Volvo's

https://www.instagram.com/volvoai?igsh=Y2sybWR1ZDNrMWdo

[richiekuk]

Originally Posted by baggy798

Putting some washers behind where the actuator mounts is the only thing you can do. It's either a tired actuator or the wastegate hole is worn a bit, probably a bit of both.

How don’t do this.
I’ve searched but not sure where to put the washers.
I feel people misname actuators and waste gates.

Some pictures would be great
Cheers

[richiekuk]

Originally Posted by baggy798

Putting some washers behind where the actuator mounts is the only thing you can do. It's either a tired actuator or the wastegate hole is worn a bit, probably a bit of both.

I tried some washers between the turbo and the actuator mounting plate. So effectively shortening the rod. This made no difference whatsoever.
I still get a 15PSI spike then 12psi until about 4k rpm then it drops slowly back to about 8PSI.

If it was manual I'd change gear sooner, but its auto and wants to hold the revs indefinitely

[SalvadorP]

Originally Posted by 360beast

I think it's the AI generated images of Volvo's

https://www.instagram.com/volvoai?igsh=Y2sybWR1ZDNrMWdo

I will never again believe anything baggy says ever.
As a Texan genius once said: "Fool me once shame on you. Fool me twice... you can't fool me again."

[baggy798]

Originally Posted by richiekuk

I tried some washers between the turbo and the actuator mounting plate. So effectively shortening the rod. This made no difference whatsoever.
I still get a 15PSI spike then 12psi until about 4k rpm then it drops slowly back to about 8PSI.

If it was manual I'd change gear sooner, but its auto and wants to hold the revs indefinitely

Putting a couple of washers shouldn't cause a spike if had got weaker, but seeing as it made no difference there's really only two alternatives - big boost leak or wastegate hole/puck worn due to use.

My car is the same, even with a stronger BSR actuator and MBC. It spikes to about 14 just like yours but drops to 12/13 to redline. If I adjust the actuator rod for more preload or try and add more boost via the MBC, it just results in a bigger spike.

The turbo is capable of 15 psi (right on the surge line at 6000 rpm), and other people have run that.

SalvadorP suffered the most extreme case of this with the worn wastegate, his car couldn't produce any more than about 1 psi!