I don't start too many threads on this forum, but thought I would share. I had contemplated fabricating a 4" exhaust for my GTR, but then decided to go forward with a design I had in my head for some time regarding a new midpipe. It's not a new concept to run a dump off the midpipe and I have seen others do the same with either electric valves or wastegates. However, I wanted the dump to be the primary exhaust flow path and have the bypass portion be the stock routed exhaust. I figured if I was going to run a dump I should either go big or go home.
I removed my Cobb midpipe and used it to create the jig as shown below.
I next started fabricating the new midpipe, which is two 3.0" primaries that merge into a 3.5" merge collector and then transition to a 4" tube. I added some bullet mufflers because I wanted to somewhat tame the noise prior to the dump.
I next added the flex sections followed by the merge collector. You can also see the 3.5" to 4.0" transition on the outlet of the merge collector. Unfortunately, the merge collector I ordered was too long so I sacrificed the collector on the Cobb midpipe for the new design. I'll just rework the Cobb midpipe to add in the longer merge collector.
The next task was to integrate the 4.0" piece that came with the http://www.loudvalves.com, which is a 4.0" pipe with a 4.0" Y-merge. You can see from the pic below that after the 4.0" Y-merge I use a 4.0" to 3.5" transition to allow me to connect to the 3.5" 2-bolt exhaust flange. You can also see in the pic below the massive 4.0" boost actuated dump valve.
I next tacked together the 3.5" pipe to the 3.5" 2-bolt exhaust flange and then guaranteed that it bolted to the car with no fitment or clearance issues.
The final step was to weld the valve to the midpipe and weld the turndown to the valve.
I was able to take the car to the track Friday and improved on my previous time from before, which was a email@example.com. Unfortunately, I did not get a chance to run it with valve closed, which I hope to do this Friday.
It is definitely LAF inside the car, but based on the video below a lot more tame on the outside vs what I thought. Overall I am happy with the new midpipe as well as the results and the final item is to hook up the valve to a Mac 3-way solenoid in line with a 10psi Hobbs switch so I can cut this on and off. The Hobbs switch is because the valve starts cracking at ~2psi so I want it to open much later. Below is a link to one of my runs....firstname.lastname@example.org.
Edited by 240Z TwinTurbo, 28 August 2017 - 09:00 AM.