I run the 35mm also.

 

Jeremy: Sorry but what do you mean when you said the 46mm was overkill? too much??

 

You need a big wastegate if you have a big turbo (compressor) on a small engine and intend to run low (max) boost. The job of the WG is to cut off the peak of the typical narrow band turbocharger characteristic.

Now these are all qualitative terms and since the original 39 mm WG does (more than) what is called for at the relatively low standard max boost, then a 38 mm WG should be more than adequate. GURU’s modified OEM wastegates do an excellent job at the HP levels you target, so maybe that should be considered as well (it certainly fits without modifications).

Laust

 

I agree that a 38 mm wg will do the job and that a 46 mm may be overkill for our engines but not for the reasons stated above.
The wastegate needed is dependant on what exhaust volume flow it needs to pass and that is dependant on engine volume and rpm, and not on hp level (not directly anyway).
If you increase boost then, although the mass flow through the engine increases, the volume flow does not. The wastegate may even be smaller at high boost as more gases are needed to drive the turbine and the high exhaust pressure will increase the flow capability of the wg.
If you have large engine volume and/or high rpm and low boost then you need a bigger wg.

Tomas

 

Thomas and Laust: Thanks for that explanation.........

Reason why i asked is because i wanted to know if there were any differences between running the 38mm and the 46mm on a street car (except price difference)..........

Thnx for the input......

 

Pretty much exactly what Tial told me a few years ago when I spoke with them about my WG selection.

 

I am happy with the 38 mm from SFR. I am planning on a larger turbo and injectors to finish off my engine mods along with my MAF. I do not need more than 330-350 rwhp. The Tial 38 is ideal for this.
Just remember to regularly tighten the bolts. Mine loosened up about three weeks after the install and the car got significantly louder. I did not mind the noise but I had to retighten the assy so it would not fall off!