Divided manifold vs not

CorneliusRox

CorneliusRox

Seasoned Rookie
Does anyone have any data showing divided vs non-divided exhaust manifold on the same setup?

My impression is that divided is going to spool a little quicker, but how much quicker, and is there any power losses/gains?

I'm planning on building a manifold (mostly for fun), but the location I want to put the turbo would make it hard to keep it divided. I'm just wondering if it's worth all the extra work to keep it divided.
 
I'm interested in this data as well.
I would assume that you could size the turbo accordingly and be golden.

Also, if I build a manifold, I want to do it similar to the way the calibrated power ucc truck's is done.
 
The manifold I made out of 3/16" steel has the turbo right between 2 and 3. Not divided and not even any type of interior diverter. With the 60mm WH1C over S475, 5x18 injectors, 191 DVs, 23* timing, some bowl work widening out the swirl ramps, and a 3 angle valve job; I hit 10psi by 1250rpm and it climbs QUICK from there.
 
Similar to stock. ID closely matched the port.

E73BBA56-50EC-4FCD-919E-75A696A13A26_zpstbc4y7t6.jpg


My A/W intercooler also sits right over the valve covers, so charge piping length is similar to a 1st gen; I'm sure that effects spool up a little too.
 
Have you considered that your manifold design may be a factor in the idle haze issue you are having?
 
Smokem said:
Have you considered that your manifold design may be a factor in the idle haze issue you are having?
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Not until literally right after I posted the picture and before you commented. LOL

But then as I sat there staring at the picture I was trying to wrap my head around how that could actually cause it?... It should be decently similar to a stock manifold... The last time I blew the head gasket, I started up the truck before bolting the turbos back on to the manifold. I could actually see the raw diesel almost like misting out. Don't think the manifold has any effect on that unless you can offer up some ideas.
 
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Hardway Performance had an article on their website about this but I can't get it to load for some reason so I can't post the link. They tested steed speed manifolds that had a wastegate insert that kept the manifold completely divided and one that left a small gap for air to cross over between the sides, the difference was pretty large for such a small gap left open. The divided manifold made more torque and it mainly shined in the midrange if I remember correctly. Peak power didn't change much. I imagine these results would only be magnified comparing a completely undivided manifold to a completely divided manifold.
 
I would like to dyno the two to compare also. We run a fully undivided manifold that we built on our puller, but it was run with an undivided housing on previous turbos. This year we will have a divided turbo housing with our open manifold.
We still have a strait flange steed speed we could compare if we ever get to the engine dyno.
 
97crewcab said:
I would like to dyno the two to compare also. We run a fully undivided manifold that we built on our puller, but it was run with an undivided housing on previous turbos. This year we will have a divided turbo housing with our open manifold.
We still have a strait flange steed speed we could compare if we ever get to the engine dyno.
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I wonder if anyone's got an old rusty divided steed lying around they'd let you swap out to do back to back runs on.
 
Even when running a turbo with an open exhaust housing. The engine will run better across the board with a divided manifold/header.
 
I would think velocity-spoolup would be greater on divided..for an open I would have to agree with less drive pressure and a slight power bump in top end Rpm's..but then again that's an all out truck..for your typical daily driver it would probably be opposite considering your fuel/heat


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The turbo spools up by a volume of air being forced into the volute, through the small opening at the end and across the turbine at a high velocity. correct? With as long of a volute the turbo has, would it be wrong to suggest that the exhaust manifold more simply acts like a pressure holding tank feeding the turbo volute and that any turbulence in the manifold does not effect the velocity at which the hot air moves across the turbine?

I can see manifold design being very important in a N/A application where you want the exhaust scavenged as quickly as possible between strokes, but when we put a huge restriction right at the manifold wouldn't all that change?
 
CorneliusRox said:
I wonder if anyone's got an old rusty divided steed lying around they'd let you swap out to do back to back runs on.
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Our current manifold puts the turbo out front so it isn't a simple swap. It still may happen this year of we feel the need to try.

I have heard the discussion both ways. One says divided makes more power, the other says as long as the manifold isn't a restriction, it won't matter. This is in a pulling application only, not street or drag racing. As with anything, I would rather get the details myself.
 

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97crewcab said:
Our current manifold puts the turbo out front so it isn't a simple swap. It still may happen this year of we feel the need to try.

I have heard the discussion both ways. One says divided makes more power, the other says as long as the manifold isn't a restriction, it won't matter. This is in a pulling application only, not street or drag racing. As with anything, I would rather get the details myself.
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What we're you trying to accomplish by moving the turbo forward like you did?
 
Nothing. We wanted it there. It is simple.
Why did your header not place the turbo in the stock location when you made it?
 
97crewcab said:
Nothing. We wanted it there. It is simple.
Why did your header not place the turbo in the stock location when you made it?
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The reason I moved my turbo had nothing to do with the exhaust side. I built the equal length header simply because I had to build something to get the exhaust to the turbo. The reason I moved my turbo is completely different than the reason you moved yours so I was curious.
 
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