REFLECTOR: Exhaust systems

Wed, 16 Jul 2003 14:13:17 -0500

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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