Twin Turbos

[RobG]

Ever since I went to the HX-40/16, I've been wondering if a twin turbo setup might be the best overall route to take with regard to lowering EGTs AND regaining the low-end lost with the bigger turbo. The thing is, on my truck, I don't see any boost to speak of until nearly 2000 RPM, and when cruising, if I floor it AT 2000 RPM, I can only keep my foot in it for a few seconds before the SPA's high EGT warning lamp lights at 1275 deg.



I wish I'd taken more photos of HVAC's twin setup, but I've been thinking about such an arrangement for my truck, and wanted to ask some questions and bounce some ideas off of everybody.



First... Am I correct in assuming that I'd need to (a) build a new manifold or (b) build an extension to the current one, so that the exhaust gasses would pass through both turbos? I'm thinking that if I could move the HX-40 (which I'd upgrade to an 18cm2 housing) aft maybe 2-3" and even down a bit, in case I were to build an extension to the manifold (sort of a y-pipe).



I was thinking that if I had a new manifold made, would it work to run, say, four cyls into the big turbo, and two into the little one?



Without having another turbo to test fit with, and without looking at the engine bay, I'm thinking the smaller turbo (What'd he use, an HX-20??) with a nice, small housing, like a 9cm2 or smaller, would go 6-8" ahead of the big turbo, and maybe off to the left a bit, too, to make room for the outlet pipe to run from it to the inlet on the big turbo. Or would the outlet Y- into the intercooler plumbing from the big turbo, and the big turbo's inlet would also be from the air filter? That's one thing I'm not clear on.



It'd also have to sit downward a bit so that the exhaust pipe could clear the big turbo and Y- into the big turbo's downpipe. There's probably less room to work with than I"m thinking, as I do remember Nowell's setup did appear pretty cramped.



I'd also move the passenger side battery back to the firewall, where the Psychotty filter sits now. This would give me a place for a big air filter ahead of the smaller turbo, and hopefully not require any funky fender cutting. Another alternative would be to install one of those Ram-Air hoods and make it functional.



This is entirely speculation at this point, but I wanted to see if I have the plumbing correct. I haven't given much thought to the oil feed or drain yet, but they should be much easier to work with than the rest.



So, am I completely nuts?



Rob

 

[Bad340fish]

Not an Expert Here but from what I understand you have your plumbing idea wrong . I have understood that the exhaust feeds the small turbo %100 and the exhaust coming out of the small turbo is then rooted to the larger one(or maybe its the other way around?). Not running all 6 cylinders to either turbo would make an EXTREME amount of lag. Now I am not sure what to do on the intake side of things. Just my . 02

 

[HEMI®Dart]

The Wiz was trying to put together a Twin Turbo package a few months back. Price was supposed to be reasonable. I have not heard much on them lately.



https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=5650&highlight=Twin+turbos

 

[Gonzo 1066]

Staging turbos

When running twin turbos for high boost and quick responce you Stage them. That is the exhaust goes from the manifold to the first turbo and then is routed to the inlet side of the second turbo. The intake is the same, from the aircleaner the air enters the second turbo compressor and exits to be compressed further by the first turbo. the #1 turbo dosent know that it is getting compressed air so it just compresses it further. There is better efficency in a twin setup (less heat produced) than a large single providing that the stageing is done properly. A excellent book is Hugh McHinnes "Turbocharging" Stageing is not a novice game there is more to a good setup than just bolting on another turbo. I had been a mechanic and owner of a 3 stage International Harvester Pulling tractor and it can be a NIGHTMARE when things go wrong. Can you imagine the last turbo compressor exploding and then that mess feeding through the other turbos? The amount of dibris entering the engine is staggering. Bit when they work well WOW!!!!!!!! 200 to 250# manifold pressure. 2000+ HP from a 436 Ci inline 6. The 5. 9 has been barley touched for its HP capability.

 

[drawson]

Here are my thoughts on twin turbo set up. Use a HX-35 12CM2 at the manifold modify the waste gate opening bigger, alot bigger to cut down obn back pressure. Then plumb it to a HX-40 or bigger. Adjust the waste gate on the 35 to open above say 25 PSI, by then the 40(or bigger) should be past it's lag point. I think this would give the best of both worlds.

 

[Diesel Freak]

HVAC is running an HX-40 in series with an H2E.

 

[MikeR]

Hey Hemi Dart,



I don't think we'll be hearing form WIZ for a while. Last I saw,he was on the Ford site telling them what POS his Dodge was and that he was going back to a PSD.



RobG,

I've seen HVAC's setup,and going to a twin is an extreme performance step. More than adding a couple psi of boost at cruise,you're now gonna have to give it enough fueling to spin two turbines. Wasn't mileage a concern on your rig? From what I've read in your posts you're after practicality,not the world record quarter mile.

If you have no boost psi at highway speed,have you ever had your intake system pressurized to check for leaks or problems?



Let us know exactly what you're after... killer mileage or killer speed?



One thing I'm wondering is,will a 17:1 compression ratio ETH engine take the increased cylinder pressures?



-Mike

 

[RobG]

Mike:



I'm not after speed; the 6-speed and the fact that it's impossible to shift quickly negates any need for that. If the truck was an automatic, then I'd be more inclined to say "gimme gimme gimme!" since it'd be more practical to take to the drag strip.



What I was after with the twin setup was better low-end response and lower EGTs. The HX-40 has not provided the dramatic reduction in temps that it has been alleged to make. All it's done for me is cost me low-end, and maybe helped a little with temps (100 deg. tops). If it wasn't such a PITA to switch back to the HX-35, I'd do that, with a 16cm2 housing, to see what the difference was.



As for power, I'm gonna get me an Edge Comp or DD UPM, so that'll take care of my power needs for good. I'll leave it powered off or on the first setting for towing, and then turn it up for when I'm unloaded and need some extra ooomph. That'll do it for my power mods, at least until something lets go, like a head gasket, or the pump or something.



Rob