Odds and ends
Due to the way the TD04HL-16T exhaust housing and flange mated I wasn't sure if it needed a gasket to seal. After starting it up it was easily apparent that it did need one so I hunted one down and picked it up.
I had to take apart a few things but I got the gasket installed and no more exhaust leak.
Because I flipped the exhaust manifold to point up and due to the design of the secondary turbo exhaust housing and how I was positioning it I had one corner that I could not bolt down. I thought about a couple of different ideas to get some clamping force on that corner. I decided to make some kind of external clamping force instead of drilling new holes or welding additional flanges to the manifold and housing. Regular turnbuckles are not strong enough for the short space I had. I figured I'd try to make one with left and right handed nuts and rod ends. Left handed nuts were pretty difficult to come by and a coupler nut that was tapped for both could only be found on the internet. I fabbed up something simple that would fit the space and give me some clamping force for that last corner.
I made a bracket that is held in place by the manifold bolt and that allows a rod end to pull down on one of the exhaust housing's studs.
With the angle of the manifold's mounting surface for the turbo the clamping force is pretty close to straight down. I double nutted the rod end to keep it from loosening up.
For boost reading locations on twins to help for tuning you want a total boost reading and a Primary turbo reading. Total boost can basically be picked up from anywhere after the boost leaves the secondary turbo. I used the same place I had set up when I ran a single turbo which is off a port on the intake manifold. For a Primary reading it needs to be after the compressor outlet on the primary but before that pressure enters the secondary.
Here is where I drilled and tapped a hole on the HE351vgt for primary boost reading. I used some 1/4 line I had left over from my front locker project to act as a sleeve to protect the actual boost line.
Everything together for test drive. I plan to move the air filter from it's current location but needed an extra part to make that happen. That's been ordered and should show up soon but this will work for testing. The 90 u bend I thought I was going to use to connect the two turbos didn't fit how I needed it to fit so I reused my 90 silicon hose with a 90 exhaust bend. All my pressure side intake is 2.5". I took that u bend after I hacked it up and pieced it back together to connect to the intercooler. With the bend in it I hope to be able to clear an AC compressor in the future.
Another shot of downpipe clearance.
So I have been driving it for a week and took it out to the mountains for a shakedown. For tuning before I drove it all I did was set timing at 17 degrees, turn one full turn in on the full power screw, spring gate on the secondary set at 3 turns out from being full tight, primary exhaust housing set at what we calculated as 14cm, and re-leveled idle rpm. Incredibly with twins it was still pretty smokey for my tastes and didn't spool like I hoped. Definitely spooling faster than the single but not instant response. I only hit a max of 32 psi total with 15 from the primary. I definitely have more tuning to do as I didn't really scratch the surface but at least I have a place to start. Even at that boost it feels strong and willing to pull. It was pulling hills well but I popped the intake pipe out of the intercooler. I realized that the paint was finally getting warm on the piece I painted and was acting like a lubricant making it hard for the boot to clamp down and get a good seal. I cleaned off the paint but broke a compression clamp putting it back together on the trip so I used lesser clamps in the tool box and kept my foot out of it for the rest of the trip . My good clamps were at home.
Warning: if you don't like math, don't read any further. Here's the math part needed to know how the turbos are sharing the load. This is simplified to get an idea of what's going on as there are other factors that go into it. You must get it into PR (pressure ratio) to see what's going on.
Formulas:
PR = (PSIg + At pressure)/At pressure
PR = pressure ratio, PSIg = gauge boost pressure reading, At pressure = atmospheric pressure (this changes depending upon your elevation, I'm only a couple hundred feet in elevation so the standard 14.7 works for me).
For my readings:
Total PR = (32 + 14.7)/14.7 = 3.18
Primary PR = (15 + 14.7)/14.7 = 2.02
Then take Total PR/Primary PR to get the secondary PR
Secondary PR = 3.18/2.02 = 1.57
Then to get secondary psi work the formula backwards
Secondary psi = (1.57 * 14.7) - 14.7 = 8.3 psi
What this says is that my primary is doing more of the work. Depending on the turbos used you may not want them to share the load equally. In my case I do want my primary to share a little more of the load. Since I am aiming for a total for 50 psi WOT this is what I'm looking for:
Total PR = 4.40
Primary = 2.4 to 2.6 PR range which translates to 20.6psi to 23.5psi on the gauge
Secondary = 1.83 to 1.69 PR range which mean it's putting out 12.2psi to 10.1psi
So to look at it very simply as I'm tuning the spring gate and fueling I am looking for 20-24psi on my primary gauge and about 50psi on my total boost gauge. That will help me know how the turbos are sharing the load at whatever fuel I'm throwing at them.