Sorry if this topic has been beaten to death over and over again but I couldn't find any answer using our search function.

I am actually running 70mm single exhaust with 63.5mm test pipe...

Would upgrading to 70mm free extra hp?

Dyno would be good but any answer will be fine as well

Thanks,

Erik

 

I don't know if it'll give you more horsepower. But your exhaust gases will flow better since your not "bottle-necking" it.

 

it should flow better probably give you 2-3 more hp

 

Two questions:

1. if the outlet of the collector of the header is 58mm (just made a number up), the test pipe diameter is 63.5mm, and the catback is 70mm, wouldn't the exhaust gases have a smoother, more efficient, less turbulant trip out of the exhaust system?

a gradual change in diameter instead of an instant change from the 58mm (hypothetical) of the header outlet and the 70mm of the test pipe and catback?

i couldnt find the diameter of the outlet of the stock header, but 5zigen's s2000 header has a 60.5mm outlet.

you catch my drift? almost on the same path of how a very large diameter exhaust system is inefficient and loses power on a relatively stock NA engine.


2. 57udl3y is there hard evidence behind what you posted or is it just an estimate or "i think" post like many of your other posts? not trying to attack you, just trying to figure out how you got these numbers or if you have actually seen an increase of "2-3 more hp," and where you have seen it.

 

dROO,

I know where you are coming from.. that is my logic as well but it's still a theory unless someone can prove that smoother transition will be better than just simply slapping 70mm test pipe on 70mm exhaust.

FYI, my collector is either 60.5mm or 62.5mm and I'm not running stock header.