Exhausts And Manifolds

[jimbo07g41]

One of the important things with the manifold is the diameter of the pipes. As Martin says, unless they are matched to the head the manifold will just make a nice noise. When I was playing with bikes, we use to have to sort out fuelling issues, by using bigger jets in the carbs or piggy back ECU's on some. You can use a progammable ecu to improve things but you would be better spending your money somewhere else first,

 

Small bore exhaust for small power and headwork and big bore for over 190 bhp. I think PTP use to have some info on their site (goes off to check).

 

Yep look at PTP but big bore for engines over 190ps not 180 (edited).

[Martin R]

Dont whatever you do read another well known site regarding small v big bore exhaust manifolds. It will do your head in and you will be non the wiser. Some say a big bore will improve things on all K series engines.

 

As Jamie says some say small up to 180ish and big bore after. You then get to if a flexy section reduces the torque versus a solid manifold. It gets silly complicated IMO.

 

I have took the advice of a man who has done a lot of testing and i respect his opinion. I am going for a big bore EBD without the step in the primaries by the head. This is to make allowences for possible future upgrades.

 

If you think about it the purpose is to get the gases out of the head as quick and as efficent as possible. A bigger diameter then the exhaust port should not restrict the outward flow. A diameter smaller certainly will. This is why they need matching.

 

You then get to the theory that some K series need some back pressure in the exhaust system, especially a VVC head apparently. Confused ? You will be. As ever you pay your money and take your chance. Read as much as you can and make your own choice would be my suggestion.