Today's Message Index:
----------------------
1. 12:13 AM - Please Make a Contribution to Support Your Lists... (Matt Dralle)
2. 03:33 AM - Re: Crossover exhaust (jrc)
3. 04:44 AM - Re: Crossover exhaust (Gary Casey)
4. 06:09 AM - Re: Archie's expertise on tuning (CardinalNSB@aol.com)
5. 06:14 AM - Cross-over exhaust (Gene Smith)
6. 06:31 AM - Re: Re: Crossover exhaust (jrc)
7. 09:35 AM - Re: Re: Crossover exhaust (n223b@comcast.net)
8. 08:21 PM - Re: Re: Archie's expertise on tuning (Archie)
Message 1
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| Subject: | Please Make a Contribution to Support Your Lists... |
--> Engines-List message posted by: Matt Dralle <dralle@matronics.com>
Dear Listers,
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Message 2
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| Subject: | Re: Crossover exhaust |
--> Engines-List message posted by: "jrc" <jrccea@bellsouth.net>
----- Original Message -----
From: "DEAN PSIROPOULOS" <dean.psiropoulos@verizon.net>
> Parallel valve Lycoming 4 cylinder engine. Is there a reason the front
> two
> pipes have to cross over before they go out the cowling?
They don't have to. You will probably lose about 5% of your available power
if you don't crossover, though.
> Another fellow Q200 builder
> did the same thing with his 0-200 Continental engine and says there has
> been
> a noticeable difference in under-cowl temps
As you know, the O-200 has a different firing order than a Lycoming, so the
optimum exhaust layout doesn't use a front crossover.
> What wives-tail or urban legend says the exhaust has to crossover?
It sounds as though you've already made up your mind about the need for the
crossover. If power isn't important to you, there is no problem in omitting
it.
All the best,
JimC
Message 3
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| Subject: | Re: Crossover exhaust |
--> Engines-List message posted by: Gary Casey <glcasey@adelphia.net>
Another comment on this - as Archie and others have said the idea is
to get even exhaust pulses in each pipe, but at the low rpm's we are
running there isn't much room to get the pipe length that would make
tuning work. There is a tuned system that fits in 172's and that one
has pipes that go back and forth a couple of time - probably no room
for that. Then look at the Subaru engine - they do care about
tuning, high rpm hp and such, but they obviously gave up or thought
it wasn't worth the effort to build a tuned exhaust. the run both
exhaust together in a very small manifold. The result, though is a
"funny" exhaust note reminiscent of an old VW. I doubt if that would
be very noticeable in an aircraft application, so it might be
reasonable to just keep each side separate and go with it, saving
space, weight and lowering cowl temperatures. I think they did it
that way on the J-3.
Gary Casey
Message 4
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| Subject: | Re: Archie's expertise on tuning |
--> Engines-List message posted by: CardinalNSB@aol.com
Archie,
The hot rod magazines are full of articles on "fine tuning" to get a few
percent extra horsepower out of stock engines-checking rocker arm length, making
sure butterfly opens all the way, etc., playing with a few degrees of timing.
Can you direct me to a source that might help my ap fine tune a carbeurated
Lycoming 360?
Thanks, Skip
Message 5
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| Subject: | Cross-over exhaust |
--> Engines-List message posted by: "Gene Smith" <esmith6@satx.rr.com>
Testimonial: If you remove the crossovers and go to four pipes (obviously one
for each cylinder) you will notice an increase in power and acceleration ability
and a slight drop in fuel consumption...The downside is you create a little
more noise...This is a Lyc. 0320 160HP in a RV-4...................CHEERS!!!!
Message 6
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| Subject: | Re: Crossover exhaust |
--> Engines-List message posted by: "jrc" <jrccea@bellsouth.net>
J-3's mostly use small Continentals. Different firing order, so no need for
a crossover.
JimC
----- Original Message -----
From: "Gary Casey" <glcasey@adelphia.net>
Subject: Engines-List: Re: Crossover exhaust
> , so it might be
> reasonable to just keep each side separate and go with it, saving
> space, weight and lowering cowl temperatures. I think they did it
> that way on the J-3.
>
> Gary Casey
Message 7
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| Subject: | Re: Crossover exhaust |
--> Engines-List message posted by: n223b@comcast.net
Continentals cylinders are numbered differently from Lycomings. The layout of
all flat four cylinder engines is the same. The front two cylinders are 180 degrees
of crankshaft apart and the rear two cylinders are also 180 degrees apart.
In a four stroke/cycle engine each of these two sets of cylinders must fire
either at the same time or 360 degrees of crankshaft rotation apart. Since
a complete cycle of a four stroke/cycle engine is 720 degrees, two cylinders
firing 360 degrees apart is an even firing order. The two rear cylinders also
fire 360 degrees apart but they are offset 180 degrees from the front two cylinders
resulting in an even firing power pulse occuring each 180 degrees of crankshaft
rotation. The numbering of the cylinders and the sequence of those numbers
designated as "firing order" does not change this essential reality.
Connecting the two front cylinder exhaust pipes puts the exhaust pulses as far
apart as possible thereby minimizing the positive pressure spike inside the exhaust
pipe. If the pipe is the correct length one pressure pulse can actually
create a slight negative pressure wave that can assist in scavenging the next
pressure pulse. These two features of a crossover system can produce a measurable
power increase over an exhaust system that connects the two cylinders on
each side. Is the increase significant? That question is above my pay grade.
Clearly some engineers have coucluded no, because there are certified airplanes
with simple exhaust pipes connecting side cylinders. But that doesn't mean
that those motors wouldn't benefit from a crossover system.
There is a thorough study of this matter on the CAFE foundation web site. Their
study also appeared in Sport Aviation over six years ago, but the data is still
correct and appropriate to this discussion.
Bob
-------------- Original message --------------
> --> Engines-List message posted by: "jrc"
>
> J-3's mostly use small Continentals. Different firing order, so no need for
> a crossover.
> JimC
>
> ----- Original Message -----
> From: "Gary Casey"
> To:
> Subject: Engines-List: Re: Crossover exhaust
>
>
> > , so it might be
> > reasonable to just keep each side separate and go with it, saving
> > space, weight and lowering cowl temperatures. I think they did it
> > that way on the J-3.
> >
> > Gary Casey
>
>
>
>
>
>
Continentals cylinders are numbered differently from Lycomings. The layout of all
flat four cylinder engines is the same. The front two cylinders are 180 degrees
of crankshaft apart and the rear two cylinders are also 180 degrees apart.
In a four stroke/cycle engine each of these two sets of cylinders must fire
either at the same time or 360 degrees of crankshaft rotation apart. Since a complete
cycle of a four stroke/cycle engine is 720 degrees,two cylinders firing
360 degrees apart is an even firing order. The two rear cylinders also fire
360 degrees apart but they are offset 180 degrees from the front two cylinders
resulting in an even firing power pulse occuring each 180 degrees of crankshaft
rotation. The numbering of the cylinders and the sequence of those numbers
designated as "firing order" does not change this essential reality.
Connecting the two front cylinder exhaust pipes puts the exhaust pulses as far
apart as possible thereby minimizing the positive pressure spike inside the exhaust
pipe. If the pipe is the correct length one pressure pulse can actually
create a slight negative pressure wave that can assist in scavenging the next
pressure pulse. These two features of a crossover system can produce a measurable
power increase over an exhaust system that connects the two cylinders on each
side. Is the increase significant? That question is above my pay grade.Clearly
some engineers have coucluded no, because there are certified airplanes with
simple exhaust pipes connecting side cylinders. But that doesn't mean that
those motors wouldn't benefit from a crossover system.
There is a thoroughstudy of this matter on the CAFE foundation web site. Their
study also appeared in Sport Aviation over six years ago, but the data is still
correct and appropriate to this discussion.
Bob
-------------- Original message --------------
-- Engines-List message posted by: "jrc" <JRCCEA@BELLSOUTH.NET>
J-3's mostly use small Continentals. Different firing order, so no need for
a crossover.
JimC
----- Original Message -----
From: "Gary Casey" <GLCASEY@ADELPHIA.NET>
To: <ENGINES-LIST@MATRONICS.COM>
Subject: Engines-List: Re: Crossover exhaust
, so it might be
reasonable to just keep each side separate and go with it, saving
space, weight and lowering cowl temperatures. I think they did it
that way on the J-3.
Gary Casey
_-
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Message 8
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| Subject: | Re: Archie's expertise on tuning |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
Not really, Skip.
The items you mention are automatically covered in a "good" engine build.
Many of the items incorporated to obtain high HP from opposed aircraft
engines
go against FAA and manufacturer's recommendations, and I choose not to get
involved in some of that banter.
Bolt on items that have been approved such as the Aerosance (Continental)
FADEC system, and Powerflow exhaust are FAA accepted items which produce
noticeable power,
better fuel economy, easier starting, etc. An aftermarket oil sump with more
precisely
equalized intake tubes is also a plus.
Picking up a 30+ hp increase is doable, but is cost prohibitive, unless you
just want bragging rights.
One engine I did for testing produced better than 50% more, but the end
product was still primitive
by today's automotive standards.
Catch me at Oshkosh, and I will tell of some of the methods employed.
Archie
----- Original Message -----
From: <CardinalNSB@aol.com>
Subject: Engines-List: Re: Archie's expertise on tuning
> --> Engines-List message posted by: CardinalNSB@aol.com
>
> Archie,
>
> The hot rod magazines are full of articles on "fine tuning" to get a few
> percent extra horsepower out of stock engines-checking rocker arm length,
> making
> sure butterfly opens all the way, etc., playing with a few degrees of
> timing.
>
> Can you direct me to a source that might help my ap fine tune a
> carbeurated
> Lycoming 360?
> Thanks, Skip
>
>
>
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