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Hi Ed,
So should probably keep the alum
flange(s) and alum tube runners. Actually the primary runners are
0.016 alum plate rolled to fit the oval ports and 30 mm round
velocity stacks inside the plenum, wrapped with glass and epoxy
resin to prevent them from collapsing.
I was thinking about replacing my 1/4"
plywood plenum box with a more rounded shape in polyurethane
resin. The box distance from engine ports are limited where it
hits the cowling with the upper rear box corner. Being able to
mold the plenum with round corners I should potentially be able
to lengthen the runners about an inch. Would be a lot of work
and then there's the plenum strength issue.
The urge for more horsepower is
there but in truth I rarely, if ever, run anywhere near full
power, except at takeoff. Too cheap to see the fuel flow above
7-8 GPH for any extended period of time.
Yeah, I miss the good ole days!
Finn
Hi Finn,
I doubt that you could make the entire intake using polyurethane
resin and still keep weight lower than your 5.87 lbs. I think
the thin aluminum tubes will weigh less than resin tubes.
However when it came to making the two channle throttle body
mount to convey the intake air into the four aluminum tubes
going to the manifold, I think resin is the way to go.
I flew mine from before the time of the article (2007)
until I sold it a few years ago and never had any problem with
the resin throttle body mount. Did have to reweld one side of
an aluminum tube where its welded to the manifold. But, that
was the only "problem" I ever incountered. I think the design
was responsibe for my old 13B hitting up to 6200 rpm on a cold
morning take off swinging that 72x80 prop on Tracy's 2.85 gear
box. Really make for great take off.
Ed (Rotary Ed from the good ole days 😁)
------ Original Message ------
Date 1/27/2024 10:32:08 AM
Subject [FlyRotary] Re: Milling exhaust manifold flat?
Thanks Stephen.
Did you use a carbide end mill
to mill the flanges?
Looking forward to the photos.
In order to keep it light I may
just keep my existing intake. It's 5.87 pounds including
throttle body, plenum, flanges and primary injectors.
Finn
Hi Finn
We modified the OEM headers by welding a new flange to the sawn off version with a sweeping bend back to the exit through a resonator (see photo).
We discovered that the flanges warped and the gasket leaked. We had the flanges milled but the same thing has happened.
As we have a slip joint down stream from that flange I’m about to remove most of the flanges OD back to round and weld the flanges together.
This will reduce weight and allow me to wrap the wend back to the headers more effectively.
As far as intake manifold, you could purchase the aluminium section of an old 4 port OEM intake and cut it back and weld on some new runners.
I used the existing OEM secondaries while welding new primary's to the siamese flange/plate.
In the photo you can see where I cut the secondaries and turned the upstream section through 180 deg and rewelded the secondaries.
This made the manifold point down rather than up. You can see the new primaries that meet the secondaries at the VDI valve manifold (I cut off the SSV Secondary Shutter Valve).
I had to lengthen a grinding stone shaft but managed to smooth the weld (that penetrated the secondary runners) nicely in the end.
I’ve been meaning to put a cable on the VDI valve and see if opening the valve gives me more power above 6500RPM.
My primaries and secondaries ended up different lengths so the VDI might not work very well.
If I had my time over I think I would weld new straight runners onto a cutoff OEM flange with an intake plenem and TB. A bit short but simple.
Hoping your mods work well Finn.
I’m retesting my new cooling system tomorrow hopefully.
Last test revealed best H2O coolant cooling but Oil was way hotter.
I realised that I hadn’t refitted some fairings at the cowl exits that I’m hoping messed up the exit air flow and so are retesting tomorrow. Hoping for a better result.
Photos following
Cheers
Steve
On 27 Jan 2024, at 4:08 am, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:
When I welded on my stock Renesis exhaust manifold the end I welded the 270 deg bend on got warped.
It's about 0.04" bent away from completely flat at the top flange at flywheel end.
Doesn't seem to have been an issue during the 100+ hours the engine has run.
But for peace of mind I'm wondering if I should mill the three flanges flat.
Is it true that I'll need a carbide end mill to do this? Even a 1/2" carbide end mill is close to $30.
Finn
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