Don,
> Incidentally, I'm not tied to Rimmers or TriumphTune but I'd prefer
to buy
> from the UK because headers designed there will have been based on
> injection systems.
Don,
I've been doing some research into this of late, and have garnered
a lot of material from the list (thanks guys 'n gals!).
First off, a header is a header is a header. Unless there
are spurious ports to mount sensors, etc, there should be no difference
between a header for PI or carbs (am I right?). The task of a exhaust
manifild is to scavenge spent combustion products from the chamber, and
their design is not dependent upon the chamber input. Some exhaust
manifold scavenge better than others, by "tuning" (using exhaust
pulses to resonate inside the tubes and create low-pressure areas
adjacent to the exhaust valves, using appropriate tube diameters
and lengths) and radiusing. Other techniques may also be used, but
manufacturers are driven by the need to make a profit and satisfy
local laws and under-hood real-estate.
That said, I learned off the list that a 3-2-1 type will;
be more efficient than a 6-1 type with the PI cam (if you go with
a single-outlet).
Single or double outlet? I'm sure there will be a lot
of discussion here, but my research indicates that the single
pipe system may be better. It is documented that when Triumph
moved to the double-outlet system in 1973 (?) there was an
increase in hp. Some folk attribute this directly to the
use of the double-pipe, but I think there were a lot of other
things done to the car to help it through the ever-tightening emission
laws in the USA. My understanding is that the double-pipe broadened
the torque curve which was pretty peaky as a result of the new
timing and advance curves.
I would certianly like to hear from the more experienced
engine tuners out there, but my advice is for the Kastner-designed
header and a single pipe.
Shane Ingate in San Diego
|