Guys,

I have an Evo IX stock turbo with a TBE and I just installed a MBC referenced from the intake manifold. My boost is set at 21 psi but it tapers to 18 psi starting from 5000 RPM. I suspect that the tapering is either due to the wastegate spring pressure being too low or the limitations of the turbo itself. However, looking at the compressor map it looks like the turbo shouldnt hit choke flow until 7200 RPM or so.
Can someone confirm my suspicions? Thanks,

-Tim

 

All stock turbo Evo's taper

 

The taper is due to your stock ECU ROM. Have it flashed for 50$ and its gone.

 

regardless of if the ecu is flashed or not, you are still going to see some taper on the stock turbo no matter what members may say. 21psi-18psi is normal

 

Correct me if I'm wrong but a MBC will fix the ecu tapering problem will it not? If this tapering is normal with the stock turbo then will a higher pressure wastegate actuator fix the problem? Or is the turbo housing too restrictive and I'm hitting choke flow?

 

if you get an EBC, you can set an increase correction rate % when boost tapers off.

 

that does not make sense, if he has a mbc the ecu should not be controlling boost anymore (the lines running from the wga, and compressor side of the turbo should not be connected to the solenoid anymore).

Like everyone else said you will not be able to completely get ride of the taper.

 

You're right i didnt see he had a MBC BUT after my flash i have no taper....it SPIKES but no taper.......from 23-24 then holding steady at 21psi. And my gauge is accurate. I dont think EVERYONE's tapers. Maybe people think the spike to the holding psi is a taper.........and maybe it is but i never thought of it like that. I thought members had a hard time getting control of the "spike" as opposed to the "taper"

 

the higher pressure wastegate actuator will fix your tapers issues, just be careful as more boost can break things if not in moderation