|
Lynn,
I've had a look at the Turbo exhaust on the 13B and the overlap is quite a
bit more, as the extra area is in hight, compared to that of the NA
housing.
The Turbo actually opens at the same time as the NA housing but closes
later, as you alluded to.
So the Turbo housing is 'OUT' for the single
PP.
( Hope your taking notes here Rusty).
The next ting I looked at was the opening of the PP and the limitations of
the lower PP, which is the lower bolt hole - don't want to weaken that
area + I want to make the overlap as least as possible.
Probably about the same place as Jerry's PP opening.
Then I looked at the oil injection position and it's a little lower in
the NA than it is with the turbo housing.
I figure the 38mm tube is 3mm thick and the overall OD is 44mm. to get a
good position in the PP ( in this particular housing ) I will most likely
put in a sloped PP inlet, similar to one of the commercial PP suppliers. Now I
know why they did it that way! This also helps to keep the PP trailing edge low,
to limit back pressure and to miss the oil jet hole.
Probably a little lower than Jerry's PP closing.
See attached drawing ( Not to scale).
If those reading this are confused or not considering PP take no
notice - this is mainly for Rusty's information for when he converts
to PP.
George ( down under)
Kelly,
Ah so! I wasn't aware of that one and was
hoping Lynn would make some comment.
Everything affects everything. Unless there is a need to
operate the engine well above 9,000 RPM, there is no need to modify the
exhaust port to any great extent.
Later closing the exhaust port (Port cut taller) extends the
open time and increases overlap with the intake ports. This is quite helpfull
at very high RPM. The same for early opening of the port. (Cuting it lower)
there is little to be lost here at high RPM. The available work left in the
charge has been reduced to near zero, and the late opening is to help sound by
allowing more complete expansion before the charge is released. Radiusing the
opening lip of the port gets flow started along a smooth curve where much of
the flow stays along the bottom of the runner. There is some interest in
removing the exhaust flow completely before uncovering the intakes. Adding the
radius along the opening line and up the sides of the port does that.
Other than removing tooling marks and smoothing the top of
the port there is not much to do. You don't want flow from the top of the port
in either direction. So leave the top as per factory. I would reduce the
chrome and iron around the port in all directions just s few thousandths
to avoid any possibility of snagging an apex seal. Just a 16th of an inch or
so is fine.
If a chunk of anything goes through the port you can stand a
burr being stood up or a scratch along the edge of the port. In the stock
situation this would be seen by the next apex seal. If the surface next
to the "hole" has been reduced slightly you may survive that gremlin without
any drama at all.
If you want more exhaust flow, you can go wider and not
change port timing at all.
The engine suffers from exhaust dilution of the intake
charge well into the RPM range. Adding a big radius to the top of the port
opening would raise the RPM where dilution more or less stops. So I see no
point in changing it much.
Lynn E. Hanover
Yes your right the top edge of the exhaust port
is correct.
I had spoken to Lynn in the past on the bottom
edge ( leading edge) but not the top edge - I didn't know he suggested to
slightly radius that edge - if he did I can't remember.
If we are singing from the same sheet of music
- radiusing the top edge, does increase exhaust flow
characteristics. See attached drawing.
Jump inhere if you wish Lynn!
George ( down under)
George and All,
I do not
follow !! I am familar with Lynn's suggestion to add slightly more
radius to what I call the top edge of the exhaust port.........Are
you suggesting
additional work to this edge ?? Perhaps a
simple drawing would help my simple
mind visualize what you are suggesting !!
--
Kelly Troyer
Dyke
Delta/13B/RD1C/EC2
|