Sent: Wednesday, September 17, 2003
11:01 AM
Subject: [FlyRotary] Intake
questions
Greetings,
I'm probably about to
prove that I haven't paid any attention to any of the intake construction
threads, but here goes... I know there's special length that will
tune the intake to make more power. Ed knows what this is, but if he
tells us, he has to kill us (a slow painful death, involving 60
slides) :-)
power band, so I started wondering if I could
"tune" it with individual pipes on the inlet side of the
TB.
Thanks,
Rusty (Scotty, I need
more power!)
Hi, Rusty.....I
purchased the short intake manifold from Dave Atkins. He claims he has
more than adequate power with his, and that idle is also good. Look
at all the race cars and racing motorcycles that have the carbs or
throttle bodies right next to the engine. They seem to generate a
lot of power that way. For what it's worth.
Paul
Conner
Paul is correct.
There are any number of intake configurations that will produce adequate
power for the RV-6. I am told that Dave Atkin's intake permits him to
generate approx 160HP which is certainly adequate for an RV and could even
provide thrilling performance in a low weight RV
I'll have to
say I've flow an RV with adequate (whatever that means)
performance while producing as little as 120HP. The cruise
was around 180 TAS which was adequate because even today I generally
elected to cruise at 170 TAS to conserve fuel, but take off and climb with
120 HP in my somewhat heavy bird were agony!
Paul, not
disputing what you say at all, but you have to consider the different
application. you are making the same assumption that I
made with my first intake. Yes, I listened to the Racing guys and
I'm certain that their advice was just peachy for racing - if you are
turning over 7000-8000 rpm. Than rpm range means short runners and
large diameter inlets are the cats meaow.
But, I can tell you
from personal experience that if you think you are going to put a curise
prop on your RV-6 with that set up and think you are going to turn
7000-8000 rpm with a 2.17:1 PSRU you are going to be sadly
disappointed. Tracy Crook turns as high an RPM with that set up as
anyone I know (has hit 214 mph TAS) and maxs out at around 6400 rpm.
His tubes are 1.25 and 1.5" in diameter as best I recall and wrap over the
top of his engine so that is air intake sits on the top middle of his
cowl. So the tubes are not short.
The auto and
motor cycle guys have one advantage - they have gear boxes which permit
them to wind the engine up into those higher rpm ranges with a lighter
load (lower gear) before shifting to the next ratio (where you do indeed
generate more power), but we can't wind our engine and then shift gears
(at least not yet).
Bill Eslick initially
use a very short induction system which provided very disappointing
performance results. His report (earlier on the list this
week) indicates that once he went with a different (read - longer
intake, copied after Tracy's as was mine) his performance improved so that
he now keeps up with the 160 HP Lycoming powered RV-6s.
You have to select
the induction system parameters that is realistic for your
application! What sucks for us - works for the race guys, what works
for us -would suck for the race guys. Its like apples and oranges
(so to speak) {:>)
Now, I will be the
first to say, if you want to experiment or if you find for cost,
configuration or convience reasons you want to try some particular intake
configuration, please do so. I've been wrong before and I am certain
will be in the future - but, do it with your eyes open and understanding
of what performance might reasonably be expected.
Best
Regards
Ed
Anderon
Hi, Ed.....thanks for
the post and education. I guess I was kinda thinking that if Dave Atkins's
RV performs that well with his short intake manifold, my aerodynamically
cleaner canard should perform equally to, or hopefully better? The
primary reason I liked his intake was because it is truly "bolt on" and
go. I tried to buy the wrap-over manifold from Powersport, but their
reply was...."sorry, we can't help you". I'm sure that experimenters
such as yourself, who know and understand intake systems better than I,
can tweak more power out of these engines. The latest effort I am
going to attempt is a wrap-over system similar to Paul Lamar's, but with
only two intake runners. The intake manifold I ordered is cast so that the
four intakes go into two almost immediately, and from there I will make my
aluminum tubing wrap over the top of the engine (as close as possible for
cowling clearance) and then terminate with my TWM throttlebody with the
built-in injectors. )(Also purchased from Dave Atkins, because it was
another "bolt on"). Did I mention that I like bolt-ons?
I truly appreciate the time and effort you invest into improving these
rotary installations for aircraft. Thanks again. Paul
Conner