Don't get pissed off at me again, please.....but the 2" o.d. runner
has an i.d. of 1.875." The cross sectional area is 2.8 sq. in.
The 1.625 i.d. that I am using has a cross sectional area of 2.1. And
my runners will not be too short or too long. They have the
additional advantage of having a 2.5 radius bend that will allow a
fairly close fit over the top of the engine. Jerry
I have the 2003 Burns catalog right here and the largest 6061 U bend
with a 2.5 inch center line radius is 1.625 OD or 1.5 inch ID.
Page 5. Are you reading it right?
Also there is no room for a proper plenum with alt air that will fit on
top with the right length runners. An inch change in the length makes
a big difference. The alt air is your requirement.
Why are you hung up on going over the top?
I spent a lot of time doing 3D's that fit under your cowl
that use two inch tubing with a 3 inch center line radius.
The Russell design's four injectors are a long way from the exhaust.
The ram air opening comes out in just the right place for the stock
cowl cheek opening. Here is the long Russell again that will work with
a 2.17:1 PSRU. The short Russell fits just as well if you move the starter.
Note the width of the rads.
No snorkel required. What is not to like about it?
You tell me it is easy to raise the cowl top. Do it! And then
I will give you a design with the plenum on top.
I can understand why you don't want to go to a 2.85:1 gear box as
you might already have a 2.17:1. If you are serious about selling P Ports
you need to make them pay off big time for the customer and go to two inch tubing
like the Le Mans engine we have dyno curves for and assume they are also using
a 2.85:1 PSRU. Other wise they will port a six port, a third gen four port
with high compression rotors, a Cosmo engine with high compression rotors
or an RX8 high power engine and have close to 200 HP if not quite a bit
more. In the case of the high power RX8 properly around 220 HP at 7500 RPM.
Don't dick around. Go for the 270 HP at 7500 RPM! Make it worth the risk
of a P-port.
Paul Lamar
Paul,
Here's a fabrication idea. Instead of horseing around trying to get the right bend and right radius and right yada yada, why not just cut two pieces of flexible pipe insulation to the length of
runner you want. Wrap them in something suitably smooth. With the plenum fixed in position, bend them into position and hold them there (or you could fill the pipe insulation core with small
diameter soft copper tubing to do the job of holding them in position). Now, here's the step that all the you aluminum-bending-rivet-junkies will hate: Wrap them in fiberglass and let harden.
Dissolve the male mold cores with something (it will depend on whatever you made the male mold from). Voila! You've got composite runners that have been molded to be the exact same length.
If you are from the church of the 1.5" runner, use the pipe insulation for 1/2" pipe, which has an O.D. of 1.375. If you want to imitate the LeMans 2" manifold, use the pipe insulation made for 1"
copper or 3/4" iron pipe, which has an O.D. of 2". If you don't like pipe insulation or want some other wierd diameter, you could use those "pool noodle" things if that fits.
Will it be as smooth inside as the metal version? I dunno. Depends on the skill of your welder to weld from tube one side flawlessly compared to your ability to lay up fiberglass. The quality of
your male mold will determine your interior finish.
Concerned about high temps? Use carbon cloth and high temp laminating resin. It's what some of the auto OEM manifolds are made from these days.
There are some downsides, of course. No fun with welding all those wonderfully varied turns. No picking through catalogs looking to match the right radius with the right diameter or figure out how
to weld and cut metal donuts. And I think you'd have to sleeve it in metal if you wanted to have the trombone-adjustable version that adjusts in length.
But you can have whatever diameter you want, on whatever radius you think will work, with runners perfectly matched from the beginning to be identical lengths.
Barry Gardner
Wheaton, IL
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