REFLECTOR: Exhaust systems

Wed, 16 Jul 2003 12:16:05 -0500

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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