Exhaust Internal Diameter.
Turbo Mini Forums

I have an N/A 1380 engine in my car now with fully worked head, massive cam, weber, basically all the usual stuff. It will be Revved to 8k and should be producing at least 110 bananas.

My concern is the exhaust system I have, basically it is a Janspeed LCB manifold and a Janspeed backbox. But the centre section is from a cooper and is pretty small. It is also restricted by the bends which are narrow due to how they are formed.

Now the manifold is well sized as are the innerds of the back box, so what I am planning to do to remove the restriction is make up a larger centre section from some 2 inch internal diameter pipe.

Will 2 inch be too big and reduce gas speeds, or would it be better to use one of the large bore maniflow centre sections such as these http://www.minispares.com/images/products/600/C-ARA337.jpg


Thoughts please

James

I think if your going to put all this effort into an engine you may as well make sure everything else is up to par.

Judging by the quality of john k`s exhaust manifolds give him a shout. In my opinion is better then Mani-flow.

I breached 110bhp with a hiff44 on a 1293.

Have you decided what camshaft your thinking of?

Perhaps?

Swift Tune Head
Kent Cams MD310
Weber 45

Is the RC40 still about ? 2" and fairly quiet and non restrictive.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

RC40 is 1 3/4", still good for 110 bananas.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

The engine is well sorted as it is and has an 895 cam in it which is similar to the 296 apparently. I have only fired the car up at the moment but not yet driven it.

The issue really is that at the moment I can't justify spending a lot more money on another complete system, when the front and back of the existing system are good and its only a matter of time before I rip the whole lot out and dump a twink in it.

The reason I want to go to the 2 inch internal diameter is that I can make up a new centre section how I want it from components from merlin motorsport.

They also sell 1.75 inch but I would rather keep things the same size as the lcb outlet and silencer inlet the whole way through the system i.e 2 inch.

James

I have an RC40 on the end of a 2" system - is this restricting my engine ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

More than 110 bhp at the last count

The DON uses a 2" exhaust, 220bhp or thereabouts.