You are correct, George.  Unless you go to variable length/volume induction systems, the peak power can be fairly narrow.  So that is why I tell folks they have to make decision about where they want the power peak.

 

I personally chose take power 6000-6200 rpm – because I never (well, only to test) fly at WOT, burns too much fuel, I’m too cheap and don’t have to be anyplace in that much of a hurry.  I always say if you don’t clear the trees, top speed doesn’t matter.  Clearly you need to chose the operating environment you plan operate in and select your tuning to match it.

 

Ed

 

 

Yup.... But. The design parameters are alot different for an application that need usable power from 1500 to 9000 rpm, Like in a car.. We only need good performance around 5500 - 7000,  plus or minus a little,,who the heck cares how the thing idles or pulls strong at 8900. . That narrow powerband for aircraft applications is what I was speaking about. YMMV

Ben Haas
www.haaspowerair.com



 

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To: flyrotary@lancaironline.net
From: lendich@aanet.com.au
Date: Thu, 1 Apr 2010 07:55:40 +1000
Subject: [FlyRotary] Re: Tuned lengths?

Ben,

I agree tuning is necessary all designs are slightly different.

On the subject of intake design, I don't think Mazda came up with their fancy Renesis intake by chance, I'm pretty sure that would be a computer proven design, well before production.

George (down under)

Lynn does such a great job at painting a very clear picture of the dynamics of an internal combustion engine.. Thank you sir... As a side note those of us using an engine in close to  a steady state application are very lucky because tuning the intake is alot easier then in a application that has a wide powerband range. A coupleof sharp motor tuners and a day or so on a good repeatable dyno can zero in on acceptable intake design that should set a good baseline for what really works. You can sliderule / use fancy computer programs and other methods of determining optimum designs but nothing trumps real time data in a running engine. Just my .02 cents worth.
 
Ben Haas
www.haaspowerair.com

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To: flyrotary@lancaironline.net
Date: Wed, 31 Mar 2010 01:09:18 -0400
From: lehanover@gmail.com
Subject: [FlyRotary] Tuned lengths?

A "tuned" intake covers a wide Varity of techniques ranging for Hermholtz,
RAM, Dynamic Intake, Inertia, etc,.  There are basically three conceptually
different approaches although they tend to merge under certain conditions.
You have the resonant tuning, the pulse tuning and the inertia turning
concepts.  However, truth be known all three phenomena occur in most intake
systems - it's a matter of emphasis.

The thing that really complicates it is the fact that within any induction
or exhaust system you have Finite Amplitude Waves - the power of these pulse
makes a 135 db sound wave very puny - these pulses can actually pound metal
apart.  They do not interact linearly as do "sound waves" - in fact they can
respond in what at first seems to be weird ways.  For instance they may
reverse there "polarity" depending on whether they encounter an open or
closed termination.

It has only been with the advent of digital computers has it been practical
to even try and model the effects of these waves in an induction system.  I
find them fascinating.

Here are a few references that some of you might find interesting.

http://home.earthlink.net/~redcat/pulse_ram/theory.html

http://www.motionsoftware.com/simtech.htm

http://www.proracingsim.com/dynomationmainpage.htm

http://www.audietech.com/DMfeaturetable.htm


Ed Anderson

Side intake port engines produce different tuned effects than do Periphery ported intake engines.

 

Side exhaust ported engines produce different tuned effects than do periphery ported exhaust engines.

 

The most powerfull engine would be the Periphery intake and exhaust ported engines.

 

Although the intake and exhaust open and close events are reported in degrees of crankshaft rotation

just like a side port engine, the periphery ports never actually close. So, tuned lengths produce bigger changes than in the side ported engine. So, one end of the tune length is virtually open all of the time, and worse one end is exposed to changeing pressures all of the time.

 

The overlap (Intake and exhaust open at the same time) is huge. So exhaust back pressure can poison the intake quite badly.

 

In the side intake ported engine one end of the column is closed solid by the side of the rotor. Intake and exhaust overlap may be minimal or extensive. Column lengths produce crisp tuning. Overlap with peripheral exhaust ports may have less effect. Exhaust back pressure can remove much power.

 

Side intake and exhaust Renesis) may have no overlap at all. The center exhaust ports share an exit that is too large right at the port face. Even with no overlap, the intake can be poisoned by exhaust gasses being held in the chamber by a poor exhaust system. Exhaust system has three outlets

 

Possibly less sensitive to back pressure than other designs When converted to a Periphery intake port, may still have low overlap.

 

Lynn E. Hanover.

 

 

 

 

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