Funny thing is, I'm willing to bet your car will definitely be slower if you go down to a 2" restrictor instead of a high flow cat or even a stock cat. Your top end will definitely fall off compared to your other options.

That is not what I have noticed.

The restriction whether it is a "highflow cat" or a 2" hole limits total exhaust system flow just enough that you don't get boost creep.

I have noticed with the restriction as far from the turbo as possible that you get the best spool (low end torque)- perhaps that is why the top end could feel softer to you? Better low end.

 

I can say that without a doubt, removing my stock cat improved throttle response, low/high end torque, a much better top end and much faster spool time even with the restrictor plate. I would be willing to bet the car with the plate will still make more power at any given rpm than one with a stock cat, but that's just speculation.

I did end up ordering a 2in plate to try (who knows, maybe I'll get lucky). Ill test it out and have results here shortly. On a completely different note, does anyone know the exact spring rate of the factory wastegates? Im guessing somewhere between 6-8psi?

 

My car made 289 hp with 360 nm at 0,88 bar @ 6980 rpm, its didn't feel slow and it pulled nice and
strong until redline set at 8.500 rpm. The 2inch flange was suggested by Pip Gardner from WGT England, who was over ( to denmark) for a tuning session. When I ask him when he started tuning rotary engines he smiled at me and said "1979" that shut me up! Anyway its not a pissing contest
I just offer my 2cents here.

 

Update time!
Firstly the link about the flange, yeah dont buy it. Its almost half an inch thick and really only ment for 2in exhausts. I ended up having a local shop fab up a 2in plate for me instead and the results are awesome. It was a little chilly this morning so I figured it would be a great opportunity to try and induce some boost creep into the system. I started off with my ebc off and everything worked normal with 7-8psi. Turned the boost controller on and set my settings very conservative and was very happy to see boost for the most part at 10psi (much better than the constant creep to 14+ like before). After a few settings were adjusted, a 1- 3 gear run ending at 8100rpm resulted in a peek boost of 11.9 with it being 10psi most of the time and the injector duty cycle never went above a safe 79%. Im very happy with the results and think this will do just fine until winter when the motor comes out.

 

Awesome it worked out

For anyone wanting to try this to fix boost creep but finding a flange seems like a hassle...

I cut my restrictor plate out of paper thin stainless with scissors and slip it in with the gasket- works great and easy to change sizes of orifice.

 

We concur! We've been selling restrictors for 3" exhausts and now 3.5" with options for the restriction hole. Many customers have reported back that adding one in has helped with boost creep/spiking.

https://jp3motorsports.com/pages/sea...ust-restrictor