Headers question

[Obioban]

The was definitely a CPI headers thread on M3F. I don't remember if it was in the dyno thread of the CPI thread that we made the discovery of them not being very good. Do you remember the cause of them being less efficient?

I'm not sure we ever knew the cause.

Exhaust design is surprisingly complex/specific. They didn't let me take any pictures of it, but when I visited SuperSprint they had a full 3" binder of flow data just for e46 M3 exhaust designs. AFAIK the CPI stepped headers had no actual development-- they just took an exist general tube routing and added a step.

[Arith2]

I'm not sure we ever knew the cause.

Exhaust design is surprisingly complex/specific. They didn't let me take any pictures of it, but when I visited SuperSprint they had a full 3" binder of flow data just for e46 M3 exhaust designs. AFAIK the CPI stepped headers had no actual development-- they just took an exist general tube routing and added a step.

It's really hard to see flow inside a tube. It's crazy how they can refine so many tubes fitting in such a tight space, while also fitting to the stock location. It's awesome you got to tour their facility. Do know what the hardest part of the design was? Was it fitment or matching exhaust pulses or something else?

[digger]

It's really hard to see flow inside a tube. It's crazy how they can refine so many tubes fitting in such a tight space, while also fitting to the stock location. It's awesome you got to tour their facility. Do know what the hardest part of the design was? Was it fitment or matching exhaust pulses or something else?

post 15 mentions something about a dyno result that was addressed by CPI whatever that means...

https://www.zpost.com/forums/showthread.php?t=1048834

testing headers is hard, sometimes your not testing the change from the header but the total change of the exhaust system as inadvertently other things like collector length get changed in the process. I classify the header as the primaries and part of the the 3into1 collector, but not all of the collector. What comes after the header has bigger effect on the bottom end and midrange than the primaries can ever have due to the space available.

[Tbonem3]

What comes after the header has bigger effect on the bottom end and midrange than the primaries can ever have due to the space available.

Hence the 63.5mm piping of the SS v1s having a dramatic effect on midrange vs. 55mm diameter of all other headers? Like, it's not the steps in the primaries that have the greatest effect on power, but the pipe diameter after the collector?

Ok, so someone take stock headers, cut them after the collector, before the cat, and weld in 2.5" pipe! Wasn't PitM3 (he has s54 hellrot e36 iirc) doing that on m3f? He set up a jig and was making pie cuts. But I don't remember his pipe diameter.

[digger]

Hence the 63.5mm piping of the SS v1s having a dramatic effect on midrange vs. 55mm diameter of all other headers? Like, it's not the steps in the primaries that have the greatest effect on power, but the pipe diameter after the collector?

Ok, so someone take stock headers, cut them after the collector, before the cat, and weld in 2.5" pipe! Wasn't PitM3 (he has s54 hellrot e36 iirc) doing that on m3f? He set up a jig and was making pie cuts. But I don't remember his pipe diameter.

I’m not sure the piping size is as dramatic as people make out as seems to be at most 5-7 numbers but the length can make or break a street car. You could simply cut cats off to make it into a euro header. You could trim it in such a way to make the collector size larger as well

[Zezorro]

I think I will go with euro headers and Evolve tune . That should be really nice update for my Z4 M. Thanks for comments