How would having an open downpipe effect my performance on a 35r ?

 

There is almost no increase in power over a full straight through exhaust.

 

So no decrease also?

 

i notice faster spool up running a cutout

 

The open exhaust might help you. It will depend on the power the car is making now and how good your exhaust system is.

 

The car will be insanely loud though, like over the top loud

 

^^^agreed...hopefully you are planning on doing this for the "track only" cause on the street your car would be super duper loud....the benefits dont outweigh the megatives on this one.

If you want a better flowing exhaust just go to a 3.5"/4" exhaust...youd probably see similiar gains

 

I was wondering about this as well. What if you have a full 3" Turboback but add a cutout as well. Would you have to have two seperate maps. Say one for the 3" Turboback and then when you open up the cutout have another map or would one map work for the both of them?

 

As a side note. My RS with our full 3" turboback exhaust, Vband design with our single bullet muffler on it ran 9.77 at 148.27 mph yesterday.