Since it's come a long way to get here, I'll just put a quick summary:
-Family bought 1990 MX-6 GT in 2003ish
-Decided I liked it and claimed it
-Original engine and turbo die honorably
-2nd, used engine installed, added a used 16G turbo and immediately cracked a piston or two. Oil dipstick blew off with anything above 7-8 psi
-2005, bought an F2T block someone else was building with larger, forged pistons and forged rods, polished smooth crank and balanced with fidanza flywheel.
-2006 new engine all installed, 196 hp/208 ftlbs on dyno...
...then the head gasket failed
-2007 new head installed, ported, shaved, almost every hole heli-coiled including spark plug threads, all new guides, springs and valves, fastest 1/4 mile was 14.49 at ~98, more than 1/2 second faster than the last head at the same PSI.
New Head Gallery
That brings us to 2008. In late January/early February I noticed a sudden appearance of black/blue smoke from my exhaust. It first started when I pulled away from a stoplight, and right away I knew something was wrong, as the engine had never burned oil or had anything but a clean exhaust since the new head was installed. I thought the turbo had gone bad, as they tend to have few warning signs before they start leaking. The engine sounded the same, had the same power as far as I could tell, but the smoke was definitely burning oil.
Then just a day or two later on my way home from work, I found there was no boost response at all. The boost gauge wouldn't go into positive pressure, and I had to floor it just to get the car to highway speed. I knew the turbo had seized, and was certain now the 16G had gone bad. A few minutes from home it did start working again, but there was an obvious lack of power now, as if something had broken.
I decided to stop driving my car until it could be replaced, and started looking at my options. My brother Ryan has a VF30 on his Probe, and a VF series was tempting. However looking at prices, it just wasn't reasonable for me. I was going to just get another 16G, when I discovered a better option; an EVO III 16G. It has the same external dimensions, so I knew it would fit, but it is lighter and has a larger compressor wheel, as well as other tweaks that make it flow almost as much as an 18G.
I started to get excited at the prospects, and decided to go for it. I bought an EVO III 16G from Slowboyracing.com with a larger wastegate flapper, and started planning how to install it.
On my last setup, the 16G was welded directly to the manifold.
It never cracked or leaked, but this time I wanted to be able to separate the two if needed. I considered building a manifold, or modifying a stock Evo one, but I wasn't willing to eliminate my EGR valve since I needed to be able to pass emissions.
So I modified a stock manifold by designing a flange for the turbo that had a shallow tilt to it, and had the manifold cut to bring it up higher:
The manifold was heated with a torch, and welded together inside and out:
It doesn't stop there of course. As is, 16Gs have threads in the exhaust housing, because the Evo manifolds have bolt holes that go from the top down through to screw into the exhaust housing. Since that's not an option for me, the threads had to be drilled out, and the housing itself cut/shaved to make flat spots for nuts:
This was tricky of course, since the EVO III 16gs have thinner exhaust housings, and if the cuts are too deep then suddenly you have a useless exhaust housing. It turned out quite well though, and bolts securely to the manifold perfectly lined up.
Now comes the next hurdle; I decided to clock the center and compressor housing on the turbo to better position it inside my car. If you look at my old setup, and this:
You can see that the compressor outlet is VERY close to the manifold, and required a pipe with a sharp bend in it to lead to the intercooler. This was the biggest annoyance, as it made installing or removing the turbo/manifold really difficult, not to mention it was just plain ugly and made everything hard to get to. So I bought a stock 14B/16G outlet pipe:
Surely this would work, right? The other part to this, was I wanted to keep using the internal wastegate, but now it wouldn't bolt up correctly since the compressor housing was clocked. Enter the ugly but functional adjustment bracket:
Right, that'll do. Moving on... Another issue with my old setup, was even though I had upgraded the manifold bolts to thicker studs, the top ones broke 3 times, forcing me to replace them. This is part of the reason I wanted the EVO III 16G, since it's overall lighter than the regular 16G. I was also determined to make a brace to hopefully eliminate broken studs, so one was made:
Again, it's ugly but it works. There are two bolt holes on the back/underside of the exhaust housing, and this attaches to both. It's built on the stock turbo brace and bolts to the same spot on the block. This will prevent the turbo/manifold assembly from flexing at the exhaust side of the head. The weird shape is mostly due to the spare metal I used to mock it up, and also to ensure the wastegate actuator isn't hindered at all.
So with all this, I was ready to install when June came around. The manifold, the turbo, the brace, it all fit together perfectly. I also had a 2.5" O2 housing to build a downpipe on, and all the fittings and hoses from the old 16G would transfer over without worries... mostly. So I drove it one more time to Ryan's shop, set everything out, and got ready to install.
Then it became clear WHY the 16G had failed, and forced a whole new aspect to this project.