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Want your thoughts...

Twisted Steel Performance

Anything worth doing is worth overdoing.
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Alright folks, my aluminum sheet metal intake project is coming along nicely, I don't have any pics to show just yet by the way but soon....

I am working on my next project along the way as time permits, my question for the masses is.....

If a TRUE scavenging turbo header were to be attempted, what would the combo for the tubes need to be to best pull exhaust out of each cylinder.. ie - cyl 1 & 8 ran together so the exhaust pulse from one would pull and NOT push on the other cyl...

I have what I think would be best, just would like to see what others think.. and for now, my preliminary drawings have a crossover on the front & rear of the motor tied to a turbo flange on the p/s of the motor..

yea, I'm a fabricator by trade and purchased a new tig rig for home so I'm getting ready to make some art LOL......
 
Flip a coin as you simply can't do much worse than the GM airflow mess the SUV/Pickup 6.5TD's have now.
 
yep..... on paper it's doable as a one off thing for me anyway I'll attempt it..

I know someone here knows enough about scavenging cylinders to see if my thought process is close ....
 
Can't help but wonder if the scavenging effect is somewhat nullified by the back pressure of a turbo
Yes it does, but when the turbo is at 1:1 or better the effects become less and less meaning the higher back pressure, scavenging is impeded more. The better the exhaust flow through the turbo, the more scavenging takes place.


@Twisted Steel Performance
I have some of the math worked out, but it will be a while before I can dig it up- and it isn’t all that much info.
I was trying to do it as rear center mount and could swear I found 1 side of each should swap into the other header by the timing.

Thinking of side mount at the time would be easier fix than what I have room for, I figured that 2 long tube headers merged into a single up pipe before getting to the to the t3/4 flange would be a strong possibility.

And the more I been fighting wanting a real turbo on mine, the desire of a custom trumpeted sheet metal intake on mine gets more and more like an option. I am dying weighing buying a good tig vs fixing my a/c and heater in the hummer. Turns out more budget would help- haha! I really might make one out of mild steel...SMH.

Rule #1 everyone: NEVER sell any of your tools without replacing them with better ones first.
 
The scavenging you're thinking of is the vacuum in the exhaust system created by pulses traveling down the pipe to pull remaining exhaust gasses out of the combustion chamber. My understanding from the Killing A Duramax series was that scavenging occurs when you have a sub 1:1 drive to boost ratio. The pressure on the intake side is greater than that on the exhaust side, thus pushing the remaining exhaust gasses out of the chamber during valve overlap. I believe Gale likened a high drive to boost ratio as "poor man's EGR" because so much exhaust gas is being trapped in the combustion chamber by high drive pressures.

Building a scavenging turbo header system to that length IMO would be overkill, but I do believe that a set of headers that flow better than the stock manifolds would still be a benefit to the platform. So when you develop those with an HE351VE flange, I'll be the buyer for set #0002. 😁😁😁
 
To do a proper scavenging exhaust system all the pipes must be equal length to keep the pulses even. Since the 6.5 doesn't alternate firing each bank your going to have a mile of tube under the hood. You will have to connect equal length pipes from both sides to feed into the turbo. I've seen a few guys do it on a V8. Mostly turbo ls stuff.

Turbo inline engines all do this from the factory. But its easy for them. Factory v8 turbo engines just collect from each bank in a divided system feeding a twin scroll housing. It's not the ideal way to do it since your not alternating pulses evenly. But it has benefits over an open system.

Getting 1:1 boost to drive pressure ratio is ideal like others have stated. Also I would consider tightening up the LSA on the cam too. With a more efficient turbo the stock cam shaft could use some adjustments in my opinion.
 
Yes, tuned exhaust makes perfect sense for N/A motors. In the aviation 4-banger world, going to a tuned exhaust (from OE) is known to immediately bump power by 10% on the motors that I am familiar with.

From the category of knowing just enough to be dangerous, the question is whether the incremental benefit is there for what the 6.5 delivers. As a possibly crude example, in the Navistar 7.3 turbo diesel (direct injected) motor, going to a tuned exhaust is reported to have too small a benefit for OE level powers, or even when pushing moderate power increases over OE. Only people whom report a real benefit are the folks that up the power by ~100% to the ~1K+ ft/lb range.

Alternatively, if a tuned exhaust on the 6.5 can translate in to better breathing and lower EGT's, then this is a big win for towing.

Am definitely not looking to stop creativity, and am just offering some thoughts to play with from my simple bean counter mind :)
 
Naw... I can do better than a coin toss.....

Someone, ANYONE, just needs to make something that's better than the GM setup. Not sure there is money in it, but, a few may be interested in buying one. @n8in8or should send you his to copy and knock out a few. I am just saying that sometimes getting bogged down in "details" for perfection kills the project. 90% better is still better than the OEM mess. The bar is so low that better is a cakewalk. Look at perfection and then what one could knock a dozen or so out of.

You make a kit for a Hummer to drop a better turbo on and IMO it would sell. Esp. with your turbo preference.
 
The poor stock side mount 9cm2 turbo exhaust system IMO is further diminished by the installing of a larger x-over pipe when leaving the stocked sized would be more beneficial driving the turbine.

Nates header is a great upgrade however; turbine size and down pipe diameter are more important to enhanced performance, as scavenging a turbocharged diesel goes the turbine is the barrier to that concept.
 
Someone, ANYONE, just needs to make something that's better than the GM setup.

Good point.

The 6.5's exhaust is so messed up that anybody can hear it at the tailpipe. At first I thought there was something wrong with the engine as it was an odd harmonic. After I realized that the noise was cyclic and learned more about the exhaust flow, it was clear that the sound was collision of exhaust pulses from the crossover and #8.
 
The parts are there for something better if you have the skills to fabricate the rest.

I'm running the van/hummer center mount manifolds. Got NOS pair for less than $100 on at a military surplus store. I picked up a up pipe manifold from a 7.3 ford. Just need to figure out the turbo placement and make the up pipes to connect it all. It's in a square body so I have more room than a gmt400.

A equal length system would be killer. But common rail guys are pushing huge HP numbers with just standard up pipes on the duramax. I see no reason to do anything different on a 6.5. And it should be a huge improvement over the stock design
 
Well my intent isn't to have a so called perfect manifold, just as good as I can, I know the tech behind a well flowing tube manifold, "some" can translate into a more better design for our motors.

This is not something I have any intent producing to sell, same with the intake, this project is something for me alone, is the intake & manifold a must, well yes and no.. I have built sheet metal intakes and headers for others over the years, both are not easy nor is their money in it in my area, me likes doing it....

I like making one off things so it's time I do some for myself and maybe inspire someone else to think outside the box, in my case will all this work and not to mention the cost be worth it... who cares right....

Give me a couple weeks and I'll post a few pics of the intake parts, I have a shop full of other folks work right now I need to finish by the end of the year...

Thanks for all the responses everyone...
 
The van and hummer intakes for center mount (there are a couple styles btw) have a descent chamber size, but no trumpets which is what make the chambered intakes better than a spider runner intake like the factory intake on trucks and n/a hummers. Then to tune the flow those trumpeted intake runners have to be tuned by length so the pressure waves help instead of hurt.

I ran n/a intake open air and the larger chamber van/hummer intake both open air without turbo for fair comparison- the truck intake had faster acceleration of 0-60 by over one second. That proved to me hands down the runner length isn't right. I even tried with and without the center section- No noticeable difference btw.

Want it slower- use van intake. Cant be to help
Solely top rpm because all hummers have governor set lower than in a pickup. I cant say all vans do, but the db2 vans were. Idk about ds4 vans top rpm.
 
Fact is for a forced induction motor the runner design isn't so much about harmonics as it is about velocity, the "velocity stack runner" used in na motors doesn't gain much and is used in round ports that we don't have..

The head intake port/gasket measures 25mmX 55mm , my runners are 175mm long and taper from 25X55mm up to 55X80mm.. so a rectangle funnel larger at the top down to the size of the ported runner or gasket dimensions. This should create a bit more velocity entering the chambers, or that's my thinking, I plan to check things on a flow bench once it's done and compare stock to this new one..
 
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