VR4 JSPEC Cyclone manifold - Open VS Closed

[bazeng]

Hey guys.

Just FYI.

A dyno run with the secondaries open vs closed.

thanks to gvr4.org

 

[Jonson]

bit of difference there!

 

[kayarubin]

is the engaged open? u have the opposite to my manifold where if you leave the hose off it runs the butterflies open and when its connected it runs them closed til boost is built up...

 

[rob323]

I would read "engaged" as being "operational". In others work, the extra power around 3000 rpm is with the cylcone butterflies operational.

 

[EVO-00X]

There's a bit of a dip between 4200-4800rpm when the butterflies are open? Any reason anyone thinks why this is so?
I'd like to see the difference with a bigger turbo on

 

[rob323]

There's a bit of a dip between 4200-4800rpm when the butterflies are open? Any reason anyone thinks why this is so?

It is around that rpm (4500 rpm from memory) when the butterflies in the short runners open up. It's not a dip per se but rather that's about where the long runners make the engine start to run out of power. It happens rather dramatically and the engine is right down on power at 5000 rpm when only the long runners are flowing air. It is probably also caused by a stack of turbulence caused by greatly differing air speeds as the butterflies are being opened.

Maybe that dip could be reduced by opening up the short runners a little earlier, but I'm sure Mitsi would have made that adjustment in the factory if it did make a difference.