Muffler Tech

[Bearded Baldy]

2 inch secondaries into 2.25 collector, 2.25 the rest of the way would be my first choice. With primaries slightly larger (2mm ish) than port size.

 

[ThePog]

The setup is 4 into 1 on the current manifold, I cut it off just before the massive cat box in the front of the engine. What is left is actually pretty nice. That hole at the collector pretty much suits a 2.5" pipe, and I kinddof want to use it for simplicity, although if it comes to it I will build some proper headers as it isnt super ideal.

I guess the question really is: will the 2.5 to 2.25 transition cause issues?

[Bearded Baldy]

How long can you make the transition?

Guessing not much room for a long cone shape reducer? Say 300mm?

Not basing of any engineering principles. Just things i have seen.

[ThePog]

I have room for that yes. I guess thats better than an abrupt drop in diameter.

[kpr]

Just put a big reso  after the headers. then you can do whatever sins you like after that.  

Ideally  a smaller pinch point at the header merge,  then diverging cone out, will maximize midrange 

But  2.5" from headers to a reso,  then drop down to 2.5 after that  or just before your 2.25" mufflers.  it wont really matter