Jim Sower wrote:
<... a simple
way to cut down on the amount of fuel/air mixture during idle ... yet have
plenty of reserves at redline rpm ...>
So why do I need primarys and secondarys with different lengths
that screw up DIE and generally make life more difficult?
There
must be more to this than meets the eye ... Jim S.
According to the graphs Ed distributed after the presentation, on the
1990 Turbo and street ported 1991 Turbo II their primary and secondary
runners can be identical lengths.
On the 1988 NA the secondary port
runners should be about 4 inches longer than the primaries. This presumably
is for a non-street ported engine. Any porting will dramatically alter the
required lengths.
Come on, Ed. Help me out here!
Finn
Hi Jim, Finn
Good question and answer. As I hope I
made clear, the DIE effect is an adjunct to an already good intake
system. There are several other factors than DIE that carry more
weight (than DIE) in producing power. One appears to be the velocity
of the air/fuel mixture in your pipes. Too slow is apparently not good
and that depends on (among other things) on the diameters of the
pipes.
What you want/need for an automobile
installation is different than for an aircraft. An example is with the
torque, auto engines are generally tuned to produce gobs of torque at
relatively low rpms to give the vehicle that breath taking 0-60MPH
acceleration. We of course want the torque and power at different
(generally higher) rpms. Therefore we have the
different lenghts and diameters of the auto engine manifold all for
good and valid reasons.
I do not have any data one way or the other
about what changing the intake system and port timing does to the basic
breathing of the rotary. Paw Yaw's web site probably has as good as I
have seen on that aspect.
I believe (but have no data to support the
belief) that if you want the DIE effect at only one rpm, then given all else
is equal (which it seldom is) then it may make sense to port an engine to
give the same timing on both primary and secondary. I think this would
be hard (and not necessarily good) to do on the 6 port as there is a wide
difference between say the secondary and aux timing. I think it is
easier to get the two ports on a turbo block equal in timing without major
challenges.
I will be merging my primary and secondary
runners shortly after they exit the engine block on my next manifold.
My ports are already equal in timing. So hopefully with in the next
month or two, I will have this new intake fabricated and can provide some
data on the results.
Hope this addresses your question.
Best Regard
Ed Anderson