REFLECTOR: Exhaust systems

Scott Derrick reflector@tvbf.org
Wed, 16 Jul 2003 15:00:32 -0600 

Yes if you put 10.5 to 1 pistons in a Lyc O360 you would get about the 
same HP at the same RPM as you do in a Franklin 6A-350-C1R

EGT's would not change much.  < 50 degrees F

Scott


Brian Michalk wrote:
> Okay, so for a carbureted Lycoming O-360,      max horsepower is 180 at 2700
> RPM.
> And,     for a carbureted Franklin 6A-350-C1R, max horsepower is 198 at 2700
> RPM.
> 
> I'm not Lycoming bashing.  I was originally trying to make a clarification
> on why EGTs are lower on a higher compression engine, and what higher
> compression does for performancem but the discussion degenerated into
> differences between Lycoming and Franklin.
> 
> 
>>-----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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>>>>>>>
>>>>>>>
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>>>>>>>>
>>>>>>>>
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>>>>>>>
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>>>>>>
>>>>>>
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>>>>>
>>>>>_______________________________________________
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>>>>
>>>>_______________________________________________
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>>>
>>>
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>>
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> 
> 
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