Effects of undivided ext. gate spacer on divided manifold & turbine housing

Hurley said:
interesting - with both springs, I assume? I got antsy and installed it without using your test setup :D I love the thing, regardless!


Nick, I'm glad you took some time to spell that out.


Also, what are you guys using to lubricate the o-rings on the piston?
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yes with the springs I had in there is how I tested it
 
I wonder what would be cheaper - 'remaking' the divider or just selling and getting a new plate/pipe/flange from E.D. ...that or finding someone that would be willing to trade (that would be a gem!).
 
Joesixpack said:
Try a header manifold and get back to me on that. All the extra volume kills pulse energy.

The easy check is to cap the gate.

I'm interested how it turns out.
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I've already done just that. I increased the manifold volume by about 5-7 times, and gained 31 hp and 34 ft/lbs.

NewPicture1.jpg
 
Hurley said:
I wonder what would be cheaper - 'remaking' the divider or just selling and getting a new plate/pipe/flange from E.D. ...that or finding someone that would be willing to trade (that would be a gem!).
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I think you would be running the risk of warping the part trying to remake the divider, a trade would be ideal!
 
Joesixpack said:
I'm thinking the larger manifold plus the divider missing is killing spool from a pulse perspective.
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X2.

When I was building headers for these, my third gen version had an undivided turbo feed, and honestly it spooled like chit, from a stop. Now from 2k to 4k it spooled faster, but on the lower end it just wasnt a good deal. There are dyno sheets to prove it, it lost like 100hp on the bottom end, and gained 30hp on the top end.

Its pretty simple, more volume, the longer it takes to fill it. Pulse has quite a bit to do with spool actually, but it really just depends what you are doing. Its not such a big deal if you keep the RPM up, now street trucks will be alot more fun with the pulse being utilized. JMO
 
PASSENGER said:
And you are saying the difference in exhaust pulses vary enough that the principles no longer apply?
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no just found it kind of funny that a dyno chart from a gas burner was put up to explain how a larger manifold will not increase spool times. Even your chart shows that power dropped off down low due to less velocity of the exhaust entering the turbine wheel. This would correspond with it taking longer to spool, no?
 
GOT-Torque said:
no just found it kind of funny that a dyno chart from a gas burner was put up to explain how a larger manifold will not increase spool times. Even your chart shows that power dropped off down low due to less velocity of the exhaust entering the turbine wheel. This would correspond with it taking longer to spool, no?
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I only have this dyno of the gas burner as an example, the diesel ones I have done I don't have copies of, but the results were the same.

The power didn't drop off down below, I know its hard to see the lines but it stays on top the whole way.
The thing is, I added approx 180 inches of volume to the manifold, and it didn't spool any slower, you guys are talking about adding about 2-3 inches of volume and thinking its gonna make a big difference in spool time, it won't.

What else causes slow spool up?... restriction, and it can come in several forms, including turbulence. Which is the issue here.
 
PASSENGER said:
I've already done just that. I increased the manifold volume by about 5-7 times, and gained 31 hp and 34 ft/lbs.

NewPicture1.jpg
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With your gasser there is a lot more residual head in the exaust even at idle due to it being throttled, and a hotter burn, way more heat in the exhaust right from the get go.

One of the trucks I pull against put a chitload of time into building a equal length header, into a large collector with no divider. Was a work of art.

Spooled like chit.

More on top.....maybe, as a peak, BUT it would snuff the charger way early as well.

All that open pipe was a huge heat sink, so from that angle, lost a bunch of heat.

All the extra volume, killed the pulses.

In the end, gave it away and I see he has one of the new t4 manifolds this year.
 
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Joesixpack said:
With your gasser there is a lot more residual head in the exaust even at idle due to it being throttled, and a hotter burn, way more heat in the exhaust right from the get go.

One of the trucks I pull against put a chitload of time into building a equal length header, into a large collector with no divider. Was a work of art.

Spooled like chit.

More on top.....maybe, as a peak, BUT it would snuff the charger way early as well.

All that open pipe was a huge heat sink, so from that angle, lost a bunch of heat.

All the extra volume, killed the pulses.

In the end, gave it away and I see he has one of the new t4 manifolds this year.
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Egt's between gas and diesel engines are fairly similar, on my vw diesel I built they were the same as any small 4 banger turbo gasser. However, heat alone doesn't have much to do with driving the turbine.

The open collector is what would kill it the manifold your competitor built. Open collectors create a ton of turbulence, the volume in its self doesn't have anything to do with it. How volume is utilized does matter, a lot. A big empty chamber is of course not going to be conducive to maintaining exhaust gas velocity and density (the energy that drives the turbine).


I've built lots of tubular exhaust manifolds for these cummins and everyone makes the turbo spool sooner and increases throttle response. For the simple reason that is not restrictive, and uses proper pulse firing. Unlike BS "pulse flow" log manifolds on the market.
 
Well lets see some photos of how its supposed to be done. Know of two others on here that tried header style manifolds and both said the same, spooled significantly slower off idle.
 
Yeah I'd like to know more about this since I'm kinda struggling to believe what you're saying. Many of the Dmax sledpullers with fancy headers got rid of 'em real quick.

And I don't know about your EGT statement. I don't have a gasser with a pyro but I understand at idle they can be 800-900 F. My truck at idle is like 200F.
 
nwpadmax said:
Yeah I'd like to know more about this since I'm kinda struggling to believe what you're saying. Many of the Dmax sledpullers with fancy headers got rid of 'em real quick.

And I don't know about your EGT statement. I don't have a gasser with a pyro but I understand at idle they can be 800-900 F. My truck at idle is like 200F.
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What would you like explained?

I have/had lots of gassers with pyros. They usually idle in the under 400* fahrenheit range. There would be a MAJOR problem is a gasser was idling anywhere near 800*.
 
I know after I put headers on a gas motor truck I had, they would read about 600* if you let it idle for about 5 mins on a hot day. Thats with a lazer temp gun.
 
PASSENGER said:
What would you like explained?
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Well, you're trying to make the point that it's "about flow" and "low pressure".

Obviously if you took that to an extreme, you'd make 3" primaries and have infinite flow and nonmeasurable pressure drop. And they would spool like ass.

So somewhere in between is the balance point. I have been told by a Garrett application engineer that spool is all about gas velocity. Temperature does come into play because the loss of it, reduces the volume it occupies, which slows linear velocity if everything else is constant.

And the thing I still don't understand is how could several apprently skilled header builders have terrible luck with V-8 headers on Duramaxes to the point where you can buy pretty much anything BUT a set of race equal-length headers. That experience is the direct opposite of what you have seen on your Cummins stuff. So were they just all doing it wrong? I'm kinda skeptical on that. One guy can go off on a tangent, but a whole group?

I'm not calling BS or anything, just trying to have a good conversation on this.

Have you ever built V-8 diesel headers?
 
SPEEDSHIFT said:
I know after I put headers on a gas motor truck I had, they would read about 600* if you let it idle for about 5 mins on a hot day. Thats with a lazer temp gun.
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I've only got my readings from pyrometers, which are more accurate than laser temp guns in my experience. I couldn't tell you why you had a reading so high, iirc the 700whp 2.0l honda in the shop idles around 300-350*.

nwpadmax said:
Well, you're trying to make the point that it's "about flow" and "low pressure".

Obviously if you took that to an extreme, you'd make 3" primaries and have infinite flow and nonmeasurable pressure drop. And they would spool like ass.

So somewhere in between is the balance point. I have been told by a Garrett application engineer that spool is all about gas velocity. Temperature does come into play because the loss of it, reduces the volume it occupies, which slows linear velocity if everything else is constant.

And the thing I still don't understand is how could several apprently skilled header builders have terrible luck with V-8 headers on Duramaxes to the point where you can buy pretty much anything BUT a set of race equal-length headers. That experience is the direct opposite of what you have seen on your Cummins stuff. So were they just all doing it wrong? I'm kinda skeptical on that.

I'm not calling BS or anything, just trying to have a good conversation on this.
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I think maybe you are misunderstanding what I am trying to say. Yes you want to increase flow, and decrease pressure, this is best done by eliminating restrictions. Obviously added "unwanted volume" volume is a bad thing.

Perhaps I should explain better. Volume in itself does not make a manifold more unresponsive. However Incorrect use of volume, like open collectors, over sized primaries etc greatly slow down gas speed by rapid pressure drop and expansion, which in effect can also cause a great deal of turbulence.

Alternatively there are ways to add useful volume, like unrestrictive primaires.

The Garrett Engineer you talked to is absolutely correct, gas speed and density is what drives the turbine. Heat, as a individual variable, does not have much to do with it.

The log manifolds currently on the market kill the exhaust velocity by having a very tight turn right out of the port and merging all the ports into a narrow passage way together, instead of keeping them separated.

One thing everyone noticed that ran the manifolds I made was that when you pressed the throttle, the response was instant, like on a gas engine, on a log manifold when you blip or mash the throttle you have to wait a second for the engine to pick up.

If you could show me some pictures of the headers you are talking about, along with the specific issue they had with them it should be fairly easy to diagnose the problem.

And don't worry about questioning what I am saying. I'd be happy to answer your questions.
 
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