REFLECTOR: Exhaust systems

[Mike Pollock]

You know Scott, I am not as stupid as you must think I am, but frankly I
don't care what you think.  You need to read the questions below before you
start your comments on slamming people.

I was answering a question that "YOU" did not ask.  Yes, I should have added
more to the information, but I was speaking of an aircraft engine, not a
helicopter!

By-bye!

Michael Pollock
Flying Velocity N173DT
Building Cozy MKIV #643
EAA #411862
EAA Chapter #1246
Technical Counselor #4357
Based at TKI / NE Dallas Metroplex



-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
Behalf Of Scott Derrick
Sent: Wednesday, July 16, 2003 1:09 PM
To: reflector@tvbf.org
Subject: Re: REFLECTOR: Exhaust systems


Thats right & wrong..  MAX RPM is 2700, not max HP.

Its that at 2700 RPM(max recommended rpm) it is producing 200 HP, at sea
level on a standard day. At 2800 RPM its more, at 2900 RPM its even more.

Scott

Mike Pollock wrote:
> Lycoming Max HP is rated at 2700 RPM for an O-360 or IO-360.
>
> Mike
>
>
> -----Original Message-----
> From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
> Behalf Of Brian Michalk
> Sent: Wednesday, July 16, 2003 8:48 AM
> To: reflector@tvbf.org
> Subject: RE: REFLECTOR: Exhaust systems
>
>
> At what RPM does the Lycoming make its peak horsepower?
>
>
> My glossy PZL sales brochure shows:
> At 2800 RPM, HP is 205, the certified max horsepower.
> At 2700 RPM, HP is about 198.
> At 2600 RPM, HP is about 192.
> At 2500 RPM, HP is about 184.
> At 2400 RPM, HP is about 175.
>
> If there are other references indicating otherwise, please inform me.
>
> The sales brochure is a little confusing.  The HP curve I gave you is
> labelled, "HP full throttle".  It peaks, and then they make another curve
> going down, below this one labelled, "HP prop load."  I'm assuming the
> bottom curve is the one obtained by setting a constant torque equal to
where
> the max horsepower is, then closing the throttle.
>
> One graph is full throttle, variable torque, graph below is constant
torque,
> variable throttle.   I could be wrong.
>
>  Brian Michalk  <http://www.michalk.com>
> Life is what you make of it ... never wish you had done something.
> Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
> musician, home-brewer, entrepreneur and mostly single
>
>
>
>>-----Original Message-----
>>From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
>>Behalf Of Mike Pollock
>>Sent: Wednesday, July 16, 2003 7:23 AM
>>To: reflector@tvbf.org
>>Subject: RE: REFLECTOR: Exhaust systems
>>
>>
>>"The point I was trying to make is that the Franklin is 10 cubic inches
>>smaller than the Lycoming, yet it has more certified horspower. Why?"
>>
>>Because RPMxTorque = HP and the Franklin is getting its HP at the higher
>>RPM.
>>
>>Mike
>>
>>-----Original Message-----
>>From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
>>Behalf Of Brian Michalk
>>Sent: Tuesday, July 15, 2003 4:15 PM
>>To: reflector@tvbf.org
>>Subject: RE: REFLECTOR: Exhaust systems
>>
>>
>>Certainly, fuel burns at a specific temperature at a specific condition.
>>I was comparing carbureted engines(O360, not IO360) on purpose, because
>>there doesn't exist a certified fuel injected Franklin against which to
>>compare.  I could cite someone's homebuilt fuel injected Franklin
>>dyno data,
>>but that's only a single data point, and is not very relevant to the
>>discussion.
>>
>>The point I was trying to make is that the Franklin is 10 cubic inches
>>smaller than the Lycoming, yet it has more certified horspower.
>>Why?  It's
>>in the compression ratio, and the cam design.  Although the original topic
>>was exhaust gas temperature, I'll keep my comments focused mainly on
>>compression ratio, because I feel that is the reason for lower EGTs, and
>>most of the power difference.
>>
>>Increasing the compression ratio increases horsepower for the
>>same amount of
>>air/fuel.  But you are right, there is no free lunch.  The
>>tradeoff is that
>>the Franklin can only use 100 avgas.  Not good considering the future of
>>100LL. It's either that, or retard the timing to make sure detonation
>>doesn't happen.  Retard the timing, more burning mass goes out
>>the tailpipe,
>>higher EGT's.
>>
>>The Franklin is just a very efficient engine.  It keeps the fire
>>inside the
>>cylinders longer, and scavenges better, meaning a much better
>>intake charge
>>for the next bang.  EGT and BSFC usually are inversely
>>proportional.  I can
>>look up my engines book as it was run on the factory dyno and give you my
>>BSFC.
>>
>>The most efficient engine would have an EGT that is the same as the intake
>>temperature.  That would mean 100% energy extraction from the fuel.  Where
>>can I get one of those?
>>
>>If you want, I can provide references.  I have a copy of Taylor, and
>>Heywood.  I'm sure I can find a chart somewhere in the text relating some
>>combination of EGT/torque/compression ratio/BSFC.
>>
>>As a side note, I was talking to a NASA engineer years ago about
>>experimental engines they were testing.  The engine was mostly
>>carbon fiber,
>>and ceramic.  There was no oil, and no cooling system.  Completely self
>>lubricating.  They wanted to let the engine come up to combustion
>>temperatures to extract as much energy from the fuel as possible.  He said
>>they got some good BSFC numbers, but had problems with engines
>>siezing, due
>>to the expansion of various materials.  The fuel was very
>>expensive too.  It
>>had to resist pre-ignition due to the incredible heat.
>>
>>
>>>-----Original Message-----
>>>From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
>>>Behalf Of Scott Derrick
>>>Sent: Tuesday, July 15, 2003 2:06 PM
>>>To: reflector@tvbf.org
>>>Subject: Re: REFLECTOR: Exhaust systems
>>>
>>>
>>>Well, my IO360 is 200HP, so not much difference there.
>>>
>>>I think there's something fishy in Denmark about this A&P's remark.
>>>
>>>We are also not talking about cruise RPM's but takeoff rpms, which are
>>>considerably lower.
>>>
>>>Any way you cut it, a specific air-fuel mix at a certain pressure burns
>>>at a certain temperature. I don't care if its in a magic
>>
>>Franklin or not.
>>
>>>Scott
>>>
>>>There's No Such Thing As A Free Lunch!
>>>
>>>Brian Michalk wrote:
>>>
>>>>Franklin engines are 10.5:1 compression ratio with 350 cubic
>>>
>>>inches, and are
>>>
>>>>rated at 220 horsepower, normally aspirated.  Compare this to
>>>
>>a Lycoming
>>
>>>>0-360 rated at 180 horsepower.  More heat(energy) goes into the work.
>>>>The second thing that could cause low EGT is the very high
>>>
>>>valve overlap.
>>>
>>>>There is a lot of scavenging going on in a Franklin cylinder, causing
>>>>volumetric efficiencies of 103% at the cruise RPMS.
>>>>
>>>>
>>>>
>>>>>-----Original Message-----
>>>>>From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
>>>>>Behalf Of Scott Derrick
>>>>>Sent: Tuesday, July 15, 2003 11:09 AM
>>>>>To: reflector@tvbf.org
>>>>>Subject: Re: REFLECTOR: Exhaust systems
>>>>>
>>>>>
>>>>>This sounds very odd.  I think av gas in a near optimal
>>>>>mixture(Stociometric?) burns at 1500+ F. It doesn't matter whether its
>>>>>in your Honda Civic, your lawn mower or aircraft engine.
>>>>>
>>>>>Maybe its the placement of the EGT probe.  The absolute temp is really
>>>>>of not much concern because where you stick the probe in and how the
>>>>>exhaust flows in the pipe will effect the probe temperature quite bit.
>>>>>Its the trend that is of prime importance.
>>>>>
>>>>>Scott
>>>>>
>>>>>John Dibble wrote:
>>>>>
>>>>>
>>>>>>I just spoke with an A/P that works on Franklin engines.  He
>>>>>
>>>>>says I should not expect
>>>>>
>>>>>
>>>>>>my EGT to exceed 1000 F.  Franklin engines run cooler.
>>>>>>
>>>>>>John
>>>>>>
>>>>>>steve korney wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>John...
>>>>>>>
>>>>>>>In that case your running way to rich...You should see temps of
>>>>>>
>>>>>about 1250
>>>>>
>>>>>
>>>>>>>to 1300 (f) on take-off...
>>>>>>>Maybe that's the reason it stumbles so much on run-up...Lean it
>>>>>>
>>>>>out...Keep
>>>>>
>>>>>
>>>>>>>the temps above 1150 on the ground or you won't vaporize the
>>>>>>
>>>lead in the
>>>
>>>>>>>fuel and it will foul your plugs...
>>>>>>>
>>>>>>>Best... Steve
>>>>>>>
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