Hello guys, i am working on a header project for my Vortech SC'ed S. It will have a 4-1 design but i'm not sure about the dimensions. I'm using T1R V3 single exhaust which has 70mm. (2.75") pipe diameter so the collector of the header should have the same dimensions but i'm not sure what dimension will be optimum for the primaries

So i need your thoughts and advices because i will produce it once.

Thank you.

 

Unless your planning on resizing the ports on your head I would stick with stock size primaries. You want everything port matched to get the most efficient working system for the most power with the size exhaust your running. Thats with any kind of exhuast system.

 

So you say keep the stock diameters for primaries. How about the collector? I think, from your perspective, it's better to have a 2.75 in. collector for a 70mm. header back single exhaust because it matches...

 

Yes I would say so, and if your going with a 70mm cat back then go with the 70mm collector to match. 2.75 isnt the same as 70mm. 70mm is only 5mm shy of 3.''

I would see if anyone else chimes in on this subject too, see if you get some different opinions on the matter and if so then why and make sure they provide a good reason to back it up. Not many chiming in on this subject though. I feel pretty solid that you want to maintain port matching throughout no matter the size you decide to run with. This reduces turbulence which kills flow and flow is important for making power, you could have a big diameter pipe but it may not flow properly. I also agree 4 into 1 header is a good option for SC, and I think 70mm is a good moderate size to choose to go with this.

 

just for clarification, 70mm is 2.75583637"


do you have a 70mm cat on your exhaust right now, too?

 

[QUOTE=SuzukaBlueAP2,Jul 6 2009, 12:19 PM] just for clarification, 70mm is 2.75583637"

 

There is a lot of science behind header design. There are def. calcs for x-sectional area which you could relay to different sizes and also a lot interesting things like anti-reversion chambers and such. But like these guys said, I would trust the Honda Engineers and stick with the OEM sizes unless you're porting.

Look to Burns Stainless for premade collectors. They will take engine specs (stroke, bore, comp, ect.) and help build a collector that will best suit your needs. It may be pricey but they know what they're doing.