Compound turbo(two compressor wheels)

[specialagentPK]

After reading the thread about the new powerstroke the turbo they are using has peaked my interest.

I want to know how it works and what its advantages and disadvantages are to a two turbo compound system.

Is there anything in the works for the Duramax crowd or are these turbos out there that would work?


Can the compressor wheels be different sizes?


Can it be done without using variable vane technology?

 

[McRat]

I'm interested as well. Garrett, Holset (now Cummins), and Borg Warner all have been playing with them, and there are numerous patents out there. Best I can figure the buzzword is multi-stage, and the ones for diesels will be VNT, and have progressive valving between the two compressors.

But I have not seen pictures of any of them. Supposedly there are some tractor pullers who have used them, but that's internet talk.

 

[specialagentPK]

Hmmmm wonder if this is the future of turbos then? Guess we wont really know until more hit the market. I can see how they could be better than a two turbo system but a good question is the turbine technology advanced enough to drive a 66mm/GT47 multistage compressor side. Guess where I am going is can they make the turbine small enough to get the 66mm part lit fast and then open it up enough to give the top end flow of a GT47 or would that big of a gap between compressors be too much for a one size turbine to drive efficiently?

 

[WolfLMM]

I'm surprised that its took this long for these to come about. Multi-stage turbos should be more efficient than compounds, ie one less turbine creating back pressure.

 

[JoshH]

...but a good question is the turbine technology advanced enough to drive a 66mm/GT47 multistage compressor side. Guess where I am going is can they make the turbine small enough to get the 66mm part lit fast and then open it up enough to give the top end flow of a GT47 or would that big of a gap between compressors be too much for a one size turbine to drive efficiently?

From the picture, it looked to me like the turbo used in the new Power Stroke uses the same size wheels for both compressors. I'm not sure how having them run off the same shaft changes the requirements for different wheels.

 

[Fingers]

As being used on the new power stroke, it is not really a compound. Both compressor wheels dump into the same Scroll. It is more like parallel twins.

 

[Fingers]

Did anyone else notice that this turbo has a waste gate?

 

[McRat]

I'll admit I'm confused.

Gated and VNT? Dual turbine inlets.

Looks sequential. Appears that there are two inlets for compressors, but only one outlet. Wild guess, they run one inlet for low rpm, then open the second inlet.

 

[MadMaxx61]

Dual turbine inlets.

Would that not mess up the flow and shape of it?

 

[maxaholic]

Did anyone else notice that this turbo has a waste gate?

Just a wild guess but could it be because that once the vains are open all the way to relieve DP, that the waste gate opens. Or that the gate is just another way to keep it in its efficiency range.

 

[Fingers]

I'll admit I'm confused.

Gated and VNT? Dual turbine inlets.

Looks sequential. Appears that there are two inlets for compressors, but only one outlet. Wild guess, they run one inlet for low rpm, then open the second inlet.

My take and a WAG at that....

With one inlet throttled, the response would be rather quick. (less load) But it could also over speed, thus the waste gate. (you have enough turbine to run two compressors after all) As you need more air for higher RPMs, you unblock the second intake and allow more total air to enter the "spare" compressor section.

Put another way. Think of having two turbos plumbed in a unique way. The compressors are parallel, but the turbines are sequential. One of the turbos is gated. This sets one turbo up as the work horse whereas the other is the make-up turbo when more volume is needed. This allows both turbos access to all the engines exhaust flow.

This isn't for high boost numbers, it is to broaden the CFM range and reduce drive pressures.

 

[duramaximizer]

IDK shit but fingers explaination sounds great to me.:hug:

 

[Dzlnut]

This shows it is compounded..

 

[Fingers]

This shows it is compounded..

Look again at the cutaway that I posted before. It is NOT a compound, it is parallel on the compressor side.

 

[Killerbee]

I don't know if it applies here, but I have felt for some time that the smart money would put a wastegate in combination with variable geometry.

It would be a good longevity decision, and dummy proof max vane issues that destroy turbos now. Alternatively, some kind of shaft speed sensor that limits top end overspeed by spilling open the vanes...a governor of sorts.

Interesting Idea of dual compressors, makes a lot of sense for the high flow rate niche. Presently, there is no doubt, induction heat climbs steeply as we try to maintain 25+ psi rates into the 3400 rpm range. It is a serious problem, with post CAC temps running very high on grades.

 

[Fingers]

Assuming the center section is about the same as the current VVT's, the compressor inducer bore on this turbo is tiny!

 

[mytmousemalibu]

FYI, Dual turbine inlets are old, Detroit used them on there diesels.

 

[dmaxfireman]

where can i get one? sooo tempted right now....... gotta keep thinking house and mortgage... you mods have a button that will stop me from spending money on truck stuff lol :spit:

 

[WolfLMM]

What does Garrett say? Looks to be compound to me as well.

 

[JMK777]

I seen a real cutaway of this turbo in reno last year it's a very trick unit we would need to make a vnt controller but outher then that the unit is small.