Ok so everybody and their mother knows that a stock evo tapers down, as you get closer to redline, is it because of the bleed off with the boost control solenoid?
So would like a UNOS forged MBC solve that?

Or can you remove it with ECU flash? And exactly what on ECU Flash is associated with it? and a general explination on the variables and how to remove taper would be cool? i searched, but still didnt get it?

I know with VE you always get taper as the heads will flow more at a higher rpm, but people mentioned having solid boost all the way to redline?

 

There's harware limitations everywhere. Once the pressure coming from the turbo manifold gets high enough it's going to start opening the wastegate. So 1.) the OEM Boost Control Solenoid (BCS) can't physically vent off enough boost. 2.) The vacumn/boost lines have a limit to the amount of airflow they feed to BCS, so once it bottlenecks inside the hose itself and at the BCS it's going to start using that excess pressure to open the wastegate.

Hence why WORKS removes the little brass restrictor from the vent hose coming off of the BCS and they install it in the boost hose coming off of the turbo manifold that feeds the BCS.

This allows them to lower the pressure comming from the turbo manifold and allows the BCS to vent more freely. However... this is a quick fix, one you can get away with if only running 20-22 psi. The draw back is that when the BCS directs the presure back to the wastegate so as to vent off, the wastegate is now getting less pressure acting on it and therefore 1.) doesn't open as fast and 2.) doesn't open as much. So the turbo stays spooled up a little longer than normal after it's supposed to be venting... no biggie kind of acts like anti-lag...hehe. Plus... if your Blow Off Valve starts to vent off due to more boost than it can handle it will cause some taper too.

My next opinion is probably more true.

I think it varies per car.


Mine boosts to 21 almost 22 PSIg @ 4,000 feet above sea level and will hold that boost till it's programmed taper which I set to start at 6500.

 

how do you program taper? what variables are involved as far as ECU Flash goes?

 

A Combination of Boost limit, Boost desired Engine Load, and Wastegate Duty Cycle. You can up the Boost Cut Delay Timer too.

some more options would be to change out the hoses,Boost Control Solenoid and the external wastgate spring.