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Quick Spool Crossover Pipe
- Thread starter 6.2 turbo
- Start date
NVW
Well-Known Member
From everything I've heard 2 1/4" is as small as you want.
BBB82
Member
That would give you more lag I would think.
buddy
Active Member
The less volume before the turbo the less to pressurize, so it should work better for spooling with smaller pipe.
At our local exhaust shop they built a bigger cross over for a 6.5 and the customer hated the slow spoolup, so they went back to a smaller one. Can't remember the size though. Also one of my friends has diesel shop and they tried bigger up pipes on duramax and he said it killed it,and are not nescesary untill about 800hp. I may have to try different sizes to find a happy medium,or just keep going smaller untill drive pressure at max rpm is higher on the left than on the right. The only thing that bothers me is that the pipe might be to long to make so small.
buddy
Active Member
Another something to consider is using a lower S intake, because it has the EGR channels that meet in the middle. I dont know how the EGR is routed through the heads, if it catches just a couple cylinders, but that would be a short route and may help equalize pressures from side to side. Just plug the part that comes up to where the valve would be.
chessie 6.5
Member
how about welding some sort of cone shape , or a 2 1/4 to 2 inch exhaust adapter to the inside end of pipe or weld to a flat spacer that would sandwich between pipe and manifold. That way you could remove it and modify it if needed. That should accelerate exhaust flow right at the turbo inlet. Do good welds with no slag that could come loose.
iamdave0887
Here Comes Chaos.....
FWIW the Banks crossover pipe is ~1 7/8" ID If i remember correctly. It uses a 2" clamp as it's a 2 piece crossover.
I also thought of making a turbo flange/adapter that would be divided. It would have to stick down in the manifold a good ways,and would divide 6cyls and 2 cyls. The turbo I got for it has a divided housing. On my Cummins with a HX35, I removed some of the divider and it made the turbo spool 300 rpms later. I thought it would help since it was divided 4 and 2 . It also made the exhaust quieter. Some time I would like to build a 6.5 with a center mount turbo,and van or hummer turbo manifolds,this would have to be way better.
Acesneights1
New Member
You know that is interesting, I had a bigger one made for my 93 and it spools slow.
iamdave0887
Here Comes Chaos.....
Tell me if this makes sense. Asking myself if it makes sense doesn't work so well. :rof:
A larger pipe would mean the gasses could cool off and contract.
A smaller pipe would mean the gassers cannot cool off as quickly and therefore cannot contract as much.
It makes me wonder if this is why the EGTs are strangely low on my 96, yet i know it's getting plenty of fuel. Hmmm......
ak diesel driver
6.5 driver
probably has more to do with velocity smaller pipe= faster flow
buddy
Active Member
The smaller pipe would only be advantageous on intial spooling, less volume to pressurize, but the engine under load will reach and maintain the same peak pressure once the larger pipe is pressurized behind the turbo. The larger pipe would likely help with less backpressure under the no and low load scenarios though. And even though they can pressurize to the same level, you can have more flow at load with the larger pipe at the same pressure. The choke point is the same, or adjustable with wastegate, but fluid dynamics is not a weakest link in the chain kind of equation.
Acesneights1
New Member
You should get 2 different sizes made up, and test them. I am watching this as I will be tring a super HX40W with a 18^2 turbine housing on it, I need it to spool around 1500 or so?? I think I will need to change the size turbine to get that, will see once I finish my build tho.......