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Everything that Racing Beat says is correct. However, the header is being
sold for a street driven vehicle and it features all of the hookups for
pollution controls and then dump into stock reactors. And it can never be used
on the street in California, (Wink Wink, Nudge Nudge) So the header is short.
Probably better for higher RPM than aircraft would use. (5,000 to 6,500) RPM.
The stock Renesis goes to 9,000 RPM. Also the center exhaust port is shared
between housings and is a flow and tuning disaster. Also the center iron appears
to run hotter as it flows about twice as much gas as the end ports.
So, if the runners were a bit smaller (higher velocity) and a bit longer
for the lower aircraft RPM and ended with a great flowing muffler could you beat
4 HP? I think so.
Or, Siamese the center pipe and collect both sides from each housing
and run the two collected pipes out to the tuned length and collect them at the
muffler. Lighter and probably as good power wise. The Renesis has no overlap in
order to pass the California Air Resources Board idea of exhaust gasses. Mostly
kittens, daises, pure water and oxygen may be expelled but not much of
anything else. The rotarie's unburned hydrocarbons are the problem. Low speed
and back pressure in the exhaust add up to unburned fuel getting out the tail
pipe in the earlier engines. Note the great lengths gone to for getting a
number of ideal intake lengths in the stock intake manifold. Note also that
those runners are all very small diameter. (Higher velocity).
Lynn E. Hanover
In a message dated 4/11/2016 6:03:06 P.M. Eastern Daylight Time,
flyrotary@lancaironline.net writes:
Len, I bow to your superior knowledge &
experience. But when the Renesis first came on the market, one of the
big rotary speed shops did everything they could with custom exhaust systems
(headers) and IIRC, the most HP gain they got over the stock Renesis exhaust
manifold was 7 HP. (The only custom exhaust header I see for the Renesis has a
claimed increase of 4 HP. http://www.racingbeat.com/RX8/Exhaust-Headers/16133.html
) Their conclusion was that with the Renesis' zero intake/exhaust
overlap, all that mattered on the exhaust side was keeping back pressure to a
minimum. They concluded that the only 'tuning' available on the Renesis was on
the intake side, since the exhaust couldn't contribute to increasing intake
flow like it does on 'normal' engines with overlap. Do you disagree with this?
(Remember, I'm only talking about the Renesis, with zero
overlap.) Charlie On 4/11/2016 2:38 PM, Lehanover
wrote:
For intake lengths, the ideal is the enemy of the good. There is only
one perfect length and diameter for each full throttle RPM. So a very large
number of lengths and diameters work very well for AC use. Tracy's Race
winning engine had rather short compact tube lengths and outran everybody.
My racer has 170 HP at 6,500 RPM and 250 HP at 9,600 RPM from a 12A engine
with 2292 CCs. This with a very large bridge port. The 13Bs you are building
are bigger with 2,606CCs.
The engines tune like a 2 cycle dirt bike. The exhaust system makes a
far bigger difference than does the intake design. My Drummond built race
engines us a stock intake manifold gasket. The intake runners are polished
but NOT enlarged. You want the highest possible intake flow velocity at
every RPM. The intake manifold to mount a Weber 48 IDF has a plenum below
each throat so the actual runner length is very short. This in turn
tunes a bit better at stupid high RPM but works well enough to deliver good
performance above 6,000 RPM. You would not have to add much length
beyond the stock lower manifold to be about perfect for aircraft use. The HP
is in the exhaust system. The side port engines have fewer degrees of
overlap than does a Pport (Massive overlap). Renesis has no overlap at all.
Smoother the idle for less the overlap.
Lynn E. Hanover
Racing rotaries since 1980.
Actually on paper I’m still the CEO of the company but
all the day to day operations are handled by Laura since my
retirement. She has been a great business partner.
Tracy
Sent from Mail for Windows 10
Actually,
The company is owned by Laura, Tracy's EX. (reminds me of the
license plate of a Mercedes, in my area," WAS
HIS"
Although
they don't have aviation parts any more, they still stock a complete line
of Tracy's seals, rebuild kits etc.
Sorry
for lack of detailed info; I was away from home & pecking at my phone
to reply.
Wayback machine:
https://archive.org/web/
Tracy's old
website was:
http://www.rotaryaviation.com/
which no
longer has aviation info on it (currently only car performance parts under
different ownership).
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