I believe it is just a feature of the ECU and how the waste gate actuator is configured. There is a little trick to make the turbo hold more boost by adjusting the waste gate actuator. you do this by taking it off the turbo and turning the "rod" about three times or so. I believe its clockwise. I know of a guy locally that is holding 20 or so pounds of boost by doing this little "trick".

 

Well, when something doesn't seem to fit linear logic, I will definitely raise my hand to ask questions.

In any case, having just given myself a crash course in turbo sizing via online resources, it seems the 16g is just walking too quickly out of its efficiency range at that boost level and rpm.

Here's another nice website that discusses turbo sizing for a 2.0L engine: http://wolfkatz.com/DreamweaverDocs/...on%20Small.pdf

Looks like if you want more boost efficiency in those rpm ranges, you'll need to be 'livin large' = $$$

 

this is the correct one for the TD05HR

 

Also even with MBC it seems to taper...if ECU is not the cause, my suspicion is that the WG spring is not strong enough allowing the flapper to open up.

 

Forgive me if I am wrong but from what I have read, it has to do with the efficiency of the turbo. Stepping to 22psi from 19psi doesn't always produce a corresponding increase in WHP but it definately increases the stress on the engine.

I guess this is one of the areas skilled tuning comes in -- balancing efficiency, power and reliability.

 

What are the X axis units? Is this chart identical to the 10.5t?

 

hate when they cut off parts of documents .... I believe kg/sec for the compressor yes the turbine side would be different

 

But even on this std rotation 16g 20 psi is in the 68% island

 

According to my chart, 22psi boost at 7000rpm requires ~0.28-0.29 kg/sec. This falls outside the turbo's efficiency zone (e.g. <68%), and it gets worse as the rpms increase.

Now I understand.

 

On the EVO 2.0L, 20psi (2.4 bar PR) at 7000rpm requires ~530cfm, which is on the very fringe of the turbo efficiency window.

 

Thanks TedB I have also been wondering the same question and had heard the same conclusion now I am sure.

 

Yes I passed with Stage 1

 

yep Ted B any turbo will reach its point of deminishing returns where it is making pressure by heating air. The net is more pressure but fewer molecules of 02. I believe it's boyle's law if my ole memory about physics is still with me.

 

So not even the 10.5 T is going to help us then oh well time to start saving up

 

Good thread that should be a sticky

In end boost in higher RPM's will have diminising returns after a certain point.