> > The reason I am so grumpy about this subject as I have
> been battling with people for many years about the intake
> design. I had a brief friendly discussion with Bill Eslick at
> OSH this year on this subject. Bill has 400 hours on his
> engine and he has changed the intake design at least once.
> He seemed resigned to having a 150 mph airplane.
> I know he is interested in going fast as he entered the
> Dayton to OSH race last year. He did not do well. Three hours
> and eighteen minutes or 142 mph. Most RVs are averaging around 200
> mph in this race and Dave Anders did 244 mph in his RV4
> this year. Bill's current intake is a long dynamic chamber which
> I stated over and over again a few years ago is not
> the right thing to do. Even Tracy abandoned it after he convinced
> a lot of people it WAS the way to go. Chuck Dunlap's airplane
> had something similar with equally disappointing results.
> > Mistral spent a lot of dyno time and money on the side port intake
> and they got only 190 HP at 6000 rpm or so.
> > People think the RX8 engine is a magic 240 HP engine all
> by itself regardless of the intake. It WILL generate 240
> HP at 8500 RPM with the right intake system. That is 28 HP
> per 1000 RPM. So 7500 is 212 HP and 6500 is 184 HP.
> No getting around it. Putting it another way the max torque
> on the side port engine is about 160 foot pounds maximum no matter
> what you do. It is, after all, only a 160 cubic inch engine.
> > The p-port on the other hand is an easy 200 HP no matter
> how you mess up the intake system. 200 foot pounds of torque
> is no problem. Moving the torque peak up by shorting the
> length of the runners results in a lot more HP. 300 HP at
> 9500 RPM with 2 inch diameter runners and a slide throttle
> is no problem at all. We demonstrated 240 HP at 6500 RPM
> on the dyno using about 2 inch runners and a carb no less.
> > The other major factor is the skin friction drag inside
> the runner tubes. Four, 1.5 inch diameter runners, have four
> times the surface area and skin friction drag as two 2 inch diameter
> runners if my arithmetic is right. Probably more as the
> air velocity could be higher. This increases the pumping losses.
> The high power RX8 six port/runner engine is even more of a
> nightmare. Mazda had to do it to get more torque at 2000 and
> 3000 RPM for car use. The four port/runner RX8 engine is worse
> as the breathing is becoming limited over about 6000 to 7000 RPM.
> > A p-port intake system is easier to build as there is no flange
> bolted to the side of the block. Just use the slide throttle
> design on the web site.
> > Ironically there is no BSFC advantage with the side port.
> Probably on the contrary as the pumping losses are higher
> with the side ports and multiple runners.
> > Don't get hung up on low RPM. Forget everything you know about
> piston engine RPM. The rotary is a different animal. It is
> more akin to an electric motor than a piston engine.
> There are no parts that jerk back and fourth, fatigue and
> crack. Forget the 2.17:1 gear box. It is ancient history.
> Go for the 2.8:1 gear box or even 3:1. Also go for a constant
> speed prop if you want a lot of MPG.
> > I'll be talking more about props soon.
> > Paul Lamar ...No rotor no motor.

Paul,

In your defense of the P-port.
As a P-port convert I recently went over two years and many folders of print
outs and notes.  It was obvious to me my early interest for the Renesisengine was based on information pertaining to automobile usage and the
'newest is best' mindset.  For those of us after the big horses (over 240Hp)
in a small package, the  P-port manifold is the least complicated and
lightest manner to get the required volume of air in the engine. This is a
fact not opinion. Mazda engineers have told me as much repeatable. Finalsunk in I guess.

I found it useful to make long lists evaluating my needs, the possible
engines configurations, PSRU ratios, and propellers to accomplish the job.

Excuse the evangelizing. New converts are usually the most  enthusiastic:)

DougFir

Would one get reasonable test data for a proposed intake manifold by
taking an RX-8 car, putting it on a chassis dyno, then repeating the run?

Scott Gettings

Sure. I think you have an RX8 car don't you Scott?
Sounds like a lot of work. Mazdatrix has a dyno and an RX8 engine.
Perhaps you can send your manifold to them for a dyno test.
There would be a lot less man hours involved.

Paul Lamar ...No rotor no motor.

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