Hi!

I'm building an exhaust for my 1.3GT crossflow engine and I have some questions:

1 – What is the best solution? 4-1 or 4-2-1. I heard that if you need power at higher revs you should go for the 4-1, else go for the other. Is this right?

2 –What should be the length of the tube until it connects to the other in the 4-2-1 or the other 3 in the 4-1 version. The same with the diameters of the tube after the union.

Thanks in advance for your help.

Sérgio

Dont know about the piping for the exhaust. Unless you are moving the exhaust away from that brake mastercylinder reservior, I would strongly suggest you put some heat wrap around the pipes and a shield between the pipe and the reservior.
Its just too close to the exhaust manifold, to be safe.
I think you need to protect it from the heat of the manifold pipes.

Just my 2d worth.

A 4-1 manifold will generally give the highest peak power, but a 4-2-1 will give a better spread of torque at the expense of slightly lower peak power, which is often more desirable.

The optimum lengths of the primaries and secondaries depends on the exhaust cam timing and at what RPM you want the exhaust to be tuned for.

Have a look at this for some numbers:
http://tom.marshall.tripod.com/exhaust.html

The book mentioned on that website (Performace tuning in theory and practise by A. Graham Bell) is worth getting as well.

[Edited on 10/1/08 by MikeRJ]

Hi!

The reason why I'm building an new exhaust is exactly because of the original proximity to the brake master cylinder (see photo).

Thanks for the link. I'll take a look...

Original setup



Description

Remote reservoir and some exhaust wrap would be easier and cheaper.

Not if the exhaust tubes are free...