Exhaust design discussion

[Will L.]

Something else that has had me wonder a long time on hotrodded single side mounted turbo-
Building the turbo side header like Nate did is a challenging task. Working in the tight areas all the twisted spaghetti so tight... so not everyone chasing that and the thermal losses of cast iron to steel pipe- I get it.

But what about the driver side. Use mega thick pipe- which is also readily found and cheap. Long tube header coming down, (long tube helps torque more also) using a 2+2 configuration and add the scavenger type x pipe between them to speed up flow more. That 1 bank has a long way to travel to match the other. Thats why Heath did his one cam design that way- slow down passenger and speed up driver sides to get more balanced flow to turbo. And crossing up the tubes would help with the odd delay in matching cylinder order.
18726543. But that side is really like 3,1,pause,7, double pause,5. So if someone gets into building their diy passenger header- dont just stick them next to each other. Mix so the one can draught the other, and use scavenger x pipe principle. We cant scavenge close to turbo because of back pressure, but this side can. It wont speed engine cycle but it will speed up exhaust flow to the other side so faster turbo spool snd smoother flow through the turbine, right?

Using heavier pipe anybody with a 120v buzz box stick welder could diy it. Yes it might warrant a physical support like a bracket of the block, but so what?

Back directly to Chris’s build- how many people want to guess how much time he spends porting and polishing that turbo side banks manifold before it gets coated? Haha.

 

[n8in8or]

If you're just changing the shape .going from round to oval then back to round..it's no different than moving water the same amount can pass through the same area since you're not changing the overall diameter of the pipe.. here's a crude example..I'm posting two pictures of the end of a styrofoam cup.. the first one is its original shape perfectly round... Second one is when I squeeze the sides which make the opposite sides push out farther.. mathematically I'm not changing the overall area of the opening.. so the same volume should be able to pass through it..
Bonus 10 points for the first person who can tell me what's wrong with these pictures..

You're confusing circumference with area/volume. If you fill your cup to the top with water and then do that same squeeze you will see that. Your circumference stayed the same, but when you squeezed it you decreased the cross-sectional area and therefore the volume of the cup. That's why you need to go to a larger oval tube to have the same cross-sectional area as a round tube.

But what about the driver side. Use mega thick pipe- which is also readily found and cheap. Long tube header coming down, (long tube helps torque more also) using a 2+2 configuration and add the scavenger type x pipe between them to speed up flow more. That 1 bank has a long way to travel to match the other. Thats why Heath did his one cam design that way- slow down passenger and speed up driver sides to get more balanced flow to turbo. And crossing up the tubes would help with the odd delay in matching cylinder order.
18726543. But that side is really like 3,1,pause,7, double pause,5. So if someone gets into building their diy passenger header- dont just stick them next to each other. Mix so the one can draught the other, and use scavenger x pipe principle. We cant scavenge close to turbo because of back pressure, but this side can. It wont speed engine cycle but it will speed up exhaust flow to the other side so faster turbo spool snd smoother flow through the turbine, right?

Back directly to Chris’s build- how many people want to guess how much time he spends porting and polishing that turbo side banks manifold before it gets coated? Haha.

I have thought about this as well. However I don't think it's scavenging that this would apply to since everything is under positive pressure pre-turbo, it's more about providing equal pulses to the turbine (which you said with your "3,1,pause,7, double pause,5" statement) and to not cause excess pressure back down the exhaust port as another cylinder is exhausting. In my mind, that's why I like individual tube turbo headers.....however, in practice (especially for the 6.5 and our power levels) I really wonder how much of a difference it makes. People make a crap-ton of power with a simple log manifold. I have some alternate designs in mind that I want to test my bundle of snakes passenger side manifold against and see if any differences show up. And also see if there's much merit in making a change to the driver side manifold or not. One would think there would be differences, but then again, at our power and pressure levels, will it?

I also wonder about the downpipe. Is the 3" downpipe holding us back any? Again, the big boy Duramaxes make a double metric crap-ton of power with a 3" downpipe, but my question is are they making that much power despite the 3" downpipe or could they be making even more power with a larger downpipe? A while back I was noticing that when I floored the Tahoe my exhaust would turn from a V8 exhaust note to whooshing sound - that made me think I had an exhaust restriction (just my theory). My first thought was the 3" downpipe. But I also have that resonator/muffler and a second muffler in my exhaust, so any of those things could be the culprit. What I would need to do is put some ports and gauges in my exhaust at various locations and see if I'm finding higher pressure in the system.

I'm really missing having the Tahoe operating to mess with (a problem of my own making to be sure). I'm hoping to get another truck this fall that I can put the Hoe's drivetrain in so I can once again enjoy it and commence tinkering while I continue to renovate the Hoe's body and chassis. And since it isn't my daily anymore I could get a little more extreme with the tinkering/testing so hopefully some of the stuff I've been wanting to do can begin happening. For what it's worth.....

And yes, I have NO DOUBT Chris will make that manifold sweet before it gets installed. I can't wait to see how that 351VE performs, it should be awesome!

 

[Twisted Steel Performance]

This thread seems to have sparked a little interest in a few...

All have given good thoughts as well, Thanks...

It will be a while before I start this part of the project but I will update when I have it under way...

 

[schiker]

Stoney that is not the case. I think you are thinking of conservation of mass. Yes, the same amount of water or air will pass through something that goes from round to oval and back to round (just measuring individually) but the drag through a change of shape is somewhat like a direction change so different than leaving it the same shape. Round is the most efficient. It has to do with the amount of air that sticks to the inside wall of the shape (round gives the most crosssection vs perimeter) and somewhat that air is compressible. Trying to reduce pressure required to flow through a round to oval back to round would require the oval to be bigger than just squashing a pipe. Squashing a pipe might be analogous to making a nozzle on the first side and funnel on the second the more the squash the worse the restriction. If you want to visualize it flatten the end of a garden hose through tighter ovals (water is not compressible) and the nozzle effect will spray the water faster. The nozzle portion is a restriction.

Yeah, the duramax's are leaving power in the exhaust but not near as much % wise. Probably not worth chasing it for them. Well not worth the factory chasing it economically. They can post pretty big HP gains with cobra heads and the like but the gains are not there for daily driving avg joe.