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And for reference, I'm dumping my hx30 at 28 gate started to open, 32 fully open(bottoming against the roof of the exhaust housing, so it physically opens as far as possible). That's from 25-28, big difference in power, faster overall spool up
 

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Discussion Starter · #22 ·
I started somewhere near that but as I kept tinkering later seemed better but there was a point where the stop was needed just to keep the two from having issues as to which one was gonna lead the "dance", once I added the exhaust manifold pressure gauge it became easier to visualize what was really happening.
My biggest concern has been high 1st stage temps causing compressor wheel failure and this might be a bigger issue in my head that is is for the wheel...
What are you seeing as far as manifold pressure differences are you seeing at cruise and WOT?
 

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I started somewhere near that but as I kept tinkering later seemed better but there was a point where the stop was needed just to keep the two from having issues as to which one was gonna lead the "dance", once I added the exhaust manifold pressure gauge it became easier to visualize what was really happening.
My biggest concern has been high 1st stage temps causing compressor wheel failure and this might be a bigger issue in my head that is is for the wheel...
What are you seeing as far as manifold pressure differences are you seeing at cruise and WOT?
Fair enough, I never have had a exhaust manifold pressure gauge so I really have had no idea.
I did run my set up for many years with no turbo failures, nothing burst. I did run my hx35 over h2e at 65 psi for 50,000 kms. I would not have been surprised if it did go boom tho!!!
Cruise on flat with the hx30/hx35 I'm seeing around 10 psi boost. Wot would be 40 psi, but I had a very bad boost leak from the compressor housing of the hx35, so i never pushed it real hard this last year. I'll know more in a month or so when I get her back on the road. Towed good, but it was squeeling like crazy, sometimes I'd get close to 1200 degrees on mountain passes. Hopefully I can push it a bit harder this year and keep some of that boost in the system
 

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The turbo wheel concerns would seem like a good reason to externally wastegate before the high pressure turbo and dump the heat into the bigger lower pressure turbo. Wouldn't you get lower drive pressure on the high pressure turbo and lower the peak heat it sees? Plus, all that heat/pressure would goto your bigger low pressure turbo so it would not be wasted. Sounds like alot of work, but probably simpler than piping in another CAC/intercooler and running spagehti intake pipes around between the two turbos and the CAC. The piping mess was the main thing persuading me to stick with a single.
 

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The turbo wheel concerns would seem like a good reason to externally wastegate before the high pressure turbo and dump the heat into the bigger lower pressure turbo. Wouldn't you get lower drive pressure on the high pressure turbo and lower the peak heat it sees? Plus, all that heat/pressure would goto your bigger low pressure turbo so it would not be wasted. Sounds like alot of work, but probably simpler than piping in another CAC/intercooler and running spagehti intake pipes around between the two turbos and the CAC. The piping mess was the main thing persuading me to stick with a single.
External gates are the best way to fully waste gate the high psi turbo, but too aggressive wastegateing leads to sequential turbocharging rather than compounding. It's a fine line to walk to get a compound set up to optimal place and its different on every engine, every truck. I'd rather hold my high psi on a bit longer, gives me a bit better mid end power. It does sacrifice top end, but my truck is heavy so it works.
 

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Discussion Starter · #27 ·
Since I last replied I have lowered the PIS to open the 1st stages waste gate to 18 I have also lowered the gate on the second stage to 38 that required a little change it the stop on the 2nd stage gate to keep manifold pressure from dropping too much which just increases the boost creep above 2,100 rpm. Now I'm seeing 40 max at the manifold and it holds steady in 3rd, 4th and 5th I'm still seeing as high as 23psi from the 1st stage above 2,100 rpm if I hold WOT, however WOT in no longer needed to hold 75mph up my test grade which is 6% starting at 5,000' up to 6,500' it will hold speed unloaded with 2/3 throttle. Drive to manifold PSI is +/- 10% under normal loading and drive is ~20% over manifold while building boost and dead even under a steady WOT condition, I'm happy with this and even though 1st stage WOT boost is a little higher than I would really like whit things as they are I'm never there for any real length of time so I "think" I'm safe enough. At this point I'm up to nearly 16MPG from the 14.5 before tuning so a Win/Win in my book.
 

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Discussion Starter · #28 ·
The turbo wheel concerns would seem like a good reason to externally wastegate before the high pressure turbo and dump the heat into the bigger lower pressure turbo. Wouldn't you get lower drive pressure on the high pressure turbo and lower the peak heat it sees? Plus, all that heat/pressure would goto your bigger low pressure turbo so it would not be wasted. Sounds like alot of work, but probably simpler than piping in another CAC/intercooler and running spagehti intake pipes around between the two turbos and the CAC. The piping mess was the main thing persuading me to stick with a single.
The charge air temp the 2nd stage is fed is a combo of the ambient temp at the inlet of the first stage the 1st stage compressor wheels efficiency and the PR it's working at, so keeping the 2nd stages inlet temp down will require you to keep 1st stage boost to a manageable level so feed it outside air is #1 then if you need/want more that 20/25 psi from it add a IC between 1st and 2nd stage for me there is simply no room on the passenger side of the engine compartment as the air intake, airbox/filter and plumbing required to keep the inlet vacuum within spec has consumed it all but the Goblin is right after having compounds I would NEVER build a diesel with a single turbo even if high boost was not in the plan with compounds you see whatever your systems max boost between 1,300 and 1,400 under load and being able to cleanly use heavy fueling that early in the torque curve make your driveability so much better...$.02
 

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Discussion Starter · #30 ·
Well, I am tempted. But for now I am just gonna have to live with a single.
the engine compartment in my Bump Side have moor room that your Waggy does and I still needed to redo the inner fender wells to fit it all in and even after that things are still rally cramped. When I was running the 221 the truck was not underpowered even weighing 8K and pushing all that wind so you should be more than happy with your performance even toeing any load that belongs behind it.
 

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Discussion Starter · #31 ·
Over the last 1,000 miles of normal driving with 30% of that on the interstate I got 17.12 MPG and I'm extremely happy with that number and doubt I can do any better without a change in my final drive ratio as I spend a majority of my time at 70mph or above and 70 equals 2,000 RPM. Looks like with my D44/D60 combo I could go to 3.23/3.25 and keep the 33's or move up to 35's the next time I need tires, the gear change would be best and 35's would be even harder on my brakes but not sure it's worth the time and coin...
All in all the time spent really paid off as I lost no power with the changes and gained 2.5 MPG, quite a surprise that it turned out like it did just goes to show what can be done with what I thought was already a good running setup.
 

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Discussion Starter · #33 ·
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