Advantages and Disadvantages

[VTec1987]

What's the advantages and disadvantage of having a secondary butterfies in the b18c gsr motor.

[dudeling7]

well i know that its good in that when the butterfly is closed you have short runners giving u better low end torque and response. then when you get into the high rpm and hte secondaries open this gives you better topend response, so rather than a compromise its giving you best of both variables.

aftermarket IM like skunk2 are permanantly open to give u better up top but you loose down low a little.

[locote]

I ripped the butterflys of my and it runs way better but im using a powerFC

[VTec1987]

Anyone else?

[VTec1987]

Better with it or without?

[aaronng]

Disadvantage - Time take to switch between short and long runners. When you are using the long runners, the air in the short runner is stagnant. So when it switches to the short runner, you get a little bit of a torque dip for that instant that the air takes to start moving.

Also, because you've got both long and short runners in that small space, the design is less idea than say a Type R intake manifold with only short runners. The VTIR one might have a smaller diameter because there just isn't enough space to put in bigger runners.

If you are planning to live at the high RPM above 5000, then just use the short ones. If you want drivability below 3500rpm, then keep both.

[VTec1987]

So for performance, is it better with it or without?

[aaronng]

For high RPM performance, you want short and big runners.

[VTec1987]

so I should keep it on? If i want performance

[DLO01]

Long intake runners for low rpm

Short intake runner for high rpm

Duel port design is prodominatly for street drivability. Its trying to make the best out of both worlds. You run off your long runners at low rpm and at a cirtain rpm the shorter runners open.

For the ITR and it being designed with the track in mind. A simplified single port design is used.

http://i13.photobucket.com/albums/a265/DLO01/Temp/rparts6.jpg

[aaronng]

so I should keep it on? If i want performance
You want performance at low RPM, high RPM or throughout the whole RPM?

[VTec1987]

Whole RPM

[aaronng]

Stick to dual length with butterflies, what you have now and go for proper racing headers instead.

If you are after top end only, get a Type S manifold then.

[VTec1987]

Guess i should get it connected then, my car feel laggy at low rpm with out them