>>> >>> 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 Renesis
>> engine 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.
Final
>> sunk 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
> > Took long enough Doug!
> George (down under)
> > For the new guys here is the Guru racing beautiful p-port
> pictures again.
> > I don't know how much HP this beast has :)
> > Paul Lamar
George,
Yes you are correct but I had a few more variables to contend with. I was
planning to use the early front housing like shown in the Guru Racing
photos
and also mount the pump remote. This housing appears to be very robust.
I don't know if Guru's P-port manifold can be made to work with our
applications. I can't seem to find a way to contact them to ask either. Do
you have their email address?
Paul definitely over 300Hp judging by the fact that Mazda accomplished that
number with carbs. long ago.
DougFir
Well maybe on carbs. The racing engine most used in the 1980's had
mechanical fuel injection and a slide throttle.
Paul Lamar
This may complicate this discussion, but I was impressed by
the Mistral effort on Digital Engine Management, DEM:
See:
http://www.mistral-engines.com/index_files/Page1101.htm
And the PDF presentation on that page.
As Paul mentioned the engine Mistral had at Oshkosh had direct port
injection.
From the site:
http://www.rotaryeng.net/pp-injector.jpg
So my point, "Intake design," DEM, etc. is still evolving.
Steve Reed
Thanks Francois for fixing the web site. I can now access it
Firefox. I really like this chart. I hope you don't mind
my uploading a copy here. Does this include the cooling system
heat exchangers and coolant? It does not say so.
No question about it. It is a very sophisticated system. Probably
the best on the market for the rotary. I think it should work with P-ports.
Paul Lamar
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