Re: The best porting option for a 13b rotary engine.

"Felix Miata" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> The Raven wrote:
>
> > "Fisco" <[EMAIL PROTECTED]> wrote in message
>
> > > I am not quite sure which port to get for the following requirements,
>
> > > 1. 13b rotary
> > > 2. Turbo installed
> > > 3. For use on the street, everyday
> > > 4. around 200kws
>
> > > I will be using the car as a daily driving car and dont want a port
that
> > > is too fuel inefficient either. Rotorworx in Australia have a port
which
> > > called an extended turbo port, what kind of porting is that?
>
> > An extended turbo port is something less than a conventional extend port
(as
> > seen on non-turbos). The idea is to increase breathing without getting
to
> > much overlap. Too much overlap is bad, the turbo blows the intake charge
out
> > the exhaust (bad for performance, reliability, and emissions).
>
> Overlap? Extending a port has no material impact on overlap.

Sorry, it does affect overlap. Perhaps the extend ports used in the US
aren't as aggressive as what is seen here.

> Bridge
> ports are what create the overlap that doesn't work with a blower.

Overlap exists in most engines, including rotary. Rotary engine overlap are
determined by the port size/shape.

>
> > > Will a turbo work fine with a standard 13b port or does the port HAVE
to
> > > modified for the turbo to be effecitve?
>
> > Turboing a stock ported engine will work but it'll be heaps better with
a
> > little massaging of the ports, particularly the exhaust as I understand
it.
> > If you want to turbo now and rebuild later that's fine but I'd rather do
it
> > all up front before you fit the engine/turbo.
>
> Extending the port is exactly perfect for forced induction. It's the way
> boinger cams are ground for use with boost.

The trick is to improve the intake flow while minimising/maintaining stock
overlap.

> Just exactly how much extending is best is the million $ question.

Ahh, so true. Some local experts have "turbo ports". Generalising. they
increase the port size but avoid increasing the intake ports height. They
tend to widen it rather than lengthen (heighten) the port.


-- 
The Raven
http://www.80scartoons.co.uk/batfinkquote.mp3
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** since August 15th 2000.