Ex.Chamber Science

[Tomtall]

Gotta thank Jeff Lytle for finding this one.Cool site Jeff! http://kawtriple.com/mraxl/expansionchambers.htm

http://kawtriple.com/mraxl/chambers.gif

[Seagull 170]

But I can't work out why his reeds are chuffing at the end of the inlet stroke, give me that M6 spanner I want to have a look at them.

[kws]

somethings just make you hmmm
makes me wonder why they called them expansion chambers and not a packing chambers

[Mark75H]

The term "expansion chamber" actually pre-dates the late 1950's MZ tuned pipes. I was quite stunned to see it in literature from the early 1950's. At that time it simply refered to a closed area for exhaust gases to expand in. It would be very interesting to learn how the phrase "expansion chamber" came to be associated with tuned pipes .... could have been a misnomer by some boat racer or perhaps Carl Kiekhaefer himself. I think a query to Mssrs. Strang and Rose is in order.

The first outboard I've seen with closed end pipes is the 1961 Carniti V-4 500cc racer, followed by Königs a year or so later .... after 2 years of the Carniti dominating 500cc racing in Europe. I think Carniti took the 500cc World championship 2 years in a row before König switched to loop charging and expansion chambers. König's switch to loop charging is what drove Christner to produce the Quincy Looper. You have to fight fire with fire sometimes.

[kws]

i think i read somewere the germans played with expansion chambers in the 20's. but i could be very wrong lol have slept many times since i read that.
but one thing is for sure that is a great illiustration
if a picture is worth a thousand words, a moving colorized picture might be worth 10,000 words lol

[Mark75H]

A German developed loop charging in the 20's. Expansion chambers were also invented by a German, but it was the late 1950's.

[Mark75H]

The basics of how an expansion chamber works:

The first section works the same way an open megaphone works:
Exhaust bursts out into the pipe when the exhaust port opens, then
it progresses thru the pipe with that initial burst of speed continuing
beyond the length of pipe necessary to clear the cylinder of exhaust ...
actually pulling fresh charge from the crankcase up into the cylinder ....
sometimes with even enough force to reopen reed valves that have
sprung shut.

The middle section of the pipe is just a length of pipe to get the timing right
for the grand finale ... at the end of the pipe the sound wave echos off
the final cone .... heading back to the exhaust port and sheparding some of the
gasses in the pipe with it. An open megaphone tends to over scavenge
the fresh charge out into the megaphone or at least the header leading to it;
so does the first cone on an expansion chamber. The more or less hard reflection
from the final cone pushes the over scavenged fresh charge back into the
cylinder just before the exhaust port closes (but well after the transfer
port has closed).

One more part: The "stinger", bleed resistor or muffler
the last section of an expansion chamber is a restriction that further increases
the pressure in the pipe. The cone sections of the pipe work so well that
the expansion chamber actually can release the exhaust and pull in the fresh
charge while the average pressure in the pipe is higher than atmospheric pressure.
This allows that final jamb back of pressure into the cylinder before the
exhaust port closes to significantly increase the cylinder pressure ....
just like a supercharger.

As long as the average flow out the bleed resistor is equal to the total
flow out the exhaust port you can continue to increase the average
pressure in the pipe and the motor. Too little flow from the outlet and
you will cook the motor ... too much flow and you are giving away free
horsepower .... it is a fine balance that depends on variables from the
carb to the prop.

The smallest usable outlet is the one that allows the motor the most rpm
your prop and set up allow, but no more .... this will yeild the greatest power. Change
props, motor height, angle, significant weight of driver and you may go over
the edge and not let enough exhaust out .... cooked motor!

:(

[Mark75H]

The length, size and taper angles of each part affect the way the pipe causes
the exhaust sound waves to affect the motor.

Early expansion chambers had longer mid sections and shorter
final cones. It was soon learned that the short final cones
cause the pipe to work well at only the very highest rpm. A change
was made that extended the effective upper rpm range where
the pipes worked .... longer final cone, slightly shorter middle.

The next major change was to allow the pipe's whole length to
be changed by having the pipe slip over the header pipe. This allowed
the pipe to have 2 major rpm range's where it worked well instead of
one.

Non-sliding pipes will work dramaticly only in the single rpm range where
the length agrees with the motor rpm .... maybe 9,000 to 11,000 for a
Konig, Konny, Rossi or Yamato PRO motor. Allow the pipe to slide out to
a longer length and it can also work at 6,000 to 8,000 when it is long.

[Mark75H]

Sliding pipe:

[Mark75H]

Oh my you say .... won't the exhaust escaping from the slip
joint affect the operation? Well, it could if it was a very sloppy
and loose fit, but keep it tight and you can easily make up for it
by reducing the exhaust stinger size or increasing the stinger length
a little bit. The exhaust escaping the slip joint is normally of no
concern at all.

The exhaust outlet doesn't even have to be at the tail end of the
final cone. GoKarts use an opening in the middle of the middle section.
Some special high ground clearance motocross bikes used a snail
shaped expansion chamber with the stinger off the middle of the
middle section. My brother saw one of those 25 years ago and made
one himself and it worked as good or better than the original expansion
chamber for that bike.

[Mark75H]

Remember I said that every dimension of the pipe affected the action in
some way? Well, a larger volume middle also favors accelleration and
mid rpm power. Smaller volume middle favors high rpm power.
How about changing the middle length and volume of the pipe instead
of the whole pipe by sliding it at the middle/back instead of the front?

Harry Pasterzak made pipes like that 25+ years ago. Here's an xray
view:

[Master Oil Racing Team]

Very interesting. I didn't see where this conversation started, but we experimented with ZAK STAKS extenstively in 1970. They were fixed and we changed stinger sizes with a tool to remove and replace strong springs that held the stingers in place. That Zak STACK era was a transition from the can (I'm only speaking of Konigs here because it was prior to Yamato and before Quincy water injection} to the sliding pipes. I hope the previous sentence isn't too confusing.

When I first found this site (thanks to Joe Rome), and I surfed around I thought about an interview I did with Dieter Konig in 1975. I had recalled him telling me about how he accidentally found a horsepower increase when he hooked up a device to funnel exhaust fumes out of the room where he tested motors. He claims to be the first one to harness horsepower from pipes. I never researched to see where the origins lay, but I do know I saw him open up a drawer and pull out an old dog-eared diary and turned to the page where it was recorded. It was all written in German but there was a sketch of what he had hooked up and a description of how the engine responed.

In my mind the revolutionary exhaust designs are what sparked the need to build boats to handle the increased horsepower and corresponding speeds. I never wrote the article about Dieter I intended to and never listened to the tape again, but I thought there was some stuff there that this audience would be interested in. I rewound the tape from where my interview stopped (not in Dieters office, but at the Berlin boat show 1975) and when I went to play it back I found out that it stripped from the spool.

I am going to try to put it back together to play because what I remember he told me was a significant step in two cycle history. Since it was thirty years ago I want to confirm what I remember.

(A side note) I did listen to a good part of the tape as I was rewinding it and it include Karl Bartel, Kurt Mischke, Hans Krage, and Jerry Drake. It was the first time I met Jerry. He was still living in South Africa.

[Peter Crowley]

The "Zak Pipe" that Sam illustrated above is the same as what was on the 250cc Harrison/Yamaha (1984 vintage) engine that I had. I bought a 250ccH rig from Kay Harrison that had a '84 Pugh boat and the Harrison engine. I ran this rig for a couple of years (1987 & 1988)and ran that engine through the Kilos on my laydown runabout.......

[Mark75H]

Here is a schematic of an early Carniti racing outboard expansion chamber

[Mark75H]

An early (probably 1963) Konig with expansion chambers

[Master Oil Racing Team]

Here's some Zak Stacks on Bob Rhoades' backwards motor

[smittythewelder]

Those pipes on Rhoades' engines had no sliding elements, but Zak did supply a set of extensions about 2" long that could be bolted between the aluminum elbows and the steel cans.

I used to race an A Konig like the one pictured. The first version of that engine was brought to the States by Konig about 1956 or '57, and had megaphones pointing straight out each side (ugly!). Konig kept tweaking that engine for decades!

[Dan M]

Ray Hardy had the first set of Zak pipes with the internal sliding cone. Harry's pipes were made to fit the original "round block" Konigs. When Dieter changed his castings to make the center to center distance of the bores tighter, square block, Harry's cast aluminum parts would no longer work. Harry still did a lot of pipe development for a lot of people. He really understood what made a 2 stroke run well. :)

[Mark75H]

Konig kept tweaking that engine for decades!

I'd prefer to say he replaced the original A deflector with an all new A looper in 1960 ... and the looper was the engine he tweaked for decades. ;)

Smitty is right, they looked real funny at first with the pipes going STRAIGHT out the sides ... anyone have any pics of those? A little later they decided they could bend the pipes a little .... like these:

[Tomtall]

Some theory by - George Grabowski @ "HPT Sport USA"
http://www.hpt-sport.com/tunedpip.htm

[smittythewelder]

My e-mail just alerted me that someone had posted here, after a long period of inactivity. After looking at Tom's entry, I looked back at some others.

Sam, are you still here? You indicate that the A Konigs were deflector motors before 1960, but I have a copy of Boat Sport from 1957 which has an article on the "new" A Konig. It looks just like the ones from the early '60s (other than the pipes, and having the carbs mounted vertically), and the engine internal drawing shows it to be a looper. If anyone here is restoring one of these engines and has no good access to Boat Sport, give me a PM and I'll shoot you a copy of the article.

I think I have what's left of one of these first-version blocks. You wouldn't believe it: all of the water jacketing is formed by drilling in from the deck surface, parallel to the bores!! The funny thing is, none of these holes are interconnected, except by a shallow channel around the inside of the head. The water just kind of shook in place!! This first A was rated at 25hp, which might have been optimistic, and maybe not for long. By the mid-'70s, Ron Anderson was getting something like 67hp from the single-pipe A of those days, with considerable longevity (he and Lee Sutter were running it) which is surprising, considering how spindly those crankshafts were. At one time I had what I took to be a second-generation block (raced by Jack Livie, and now in the hands of Buzz or Alan Thorsen, maybe). This version had much better cast-in water jacketing, and looked about like the early-to-middle '60s engine shown in the photo above except that it had no boost-port, just the two transfer ports and the exhaust.

[Mark75H]

Smitty, I think you are right ... 1957, not 1960

Santa brought me a book about MZ motorcycles & Walter Kaaden ... looks like Kaaden had expansion chambers on the MZ's a little before 1958 ... but really brought it together in '58 with a 20hp 125cc (10ci) racing motorcycle that had rotary valve intake, hemi/squish band cylinder head and 3 transfer ports instead of 2 ... all this to optimize the power boost from the expansion chamber

[Tomtall]

Nice format. Lets see if this link works.

http://fpp.hamradio.si/roost/software/exhaustcalculator2.zip

May require unzipping. However I was able to just run formate as is. Click on "Exhaust calculator2" folder.

[Mark75H]

Wow, Tom ... if you surf off of that guy's links you hit some of the mother lode of 2 stroke information

Here's the Mac version (macro'ed up Excel stuff) Link to Mac version of the pipe/motor calculator (http://www.macdizzy.com/2_stroke_calc.sit)

[Tomtall]

This site offers some very cool software and theory. :cool:
http://www.bimotion.se/

[Mark75H]

This week it occurred to me why it was Germans that discovered the expansion chamber ... The V-1 rocket engine was an exhaust pulse tuned motor. The only compression it had was the reflection of the previous exhaust pulse leaving the end of the tube.

Here's the run down on the V-1 engine:

The fuel was propane. At the front, a group of check valves allowed a gulp of air to enter the combustion chamber which was bulb shaped. Tailing off the other end of the combustion chamber was the tuned exhaust pipe, open at the back. That's it, nothing else, (except for an on/off valve on the fuel and maybe a check valve in the fuel line).

The engine was started by opening the fuel valve and igniting the first pulse with a spark plug. After initial ignition, the spark plug was not needed ... the returning exhaust pulse hit the next fuel/air charge with enough force to cause compression ignition; the intake check valves kept the explosion from going out the front of the engine. As the exhaust traveled down the exhaust pipe, it created a vacuum that pulled in the next gulp of fresh air to the combustion chamber ... the exhaust pulse returned and ignited that ... over and over again at the rate determined by the length of the exhaust pipe .... br-r-r-r-r-r-r-r-r-r-r-r-r-r

There must have been hundreds of German engineers that knew how this worked ... they applied it to the exhaust on 2 strokes and Kaaden combined it with the correct rotary valve timing and porting for more power than anyone thought possible with a 2 stroke motor with it's exhaust port closing so late in the cycle.

[smittythewelder]

Fun to see old dormant threads revived!

Here's a boat-racing/expansion-chamber/pulse-jet connection. Jim Hallum, who engineered Gerry Walin's record-setting Anzanis in the Sixties and early Seventies, was one of the early Reg. 10 experimenters with expansion chambers (first on roadracer Jimmy Dunn's motorcycles and on somebody's racing chainsaw). In the early Fifties, while wrenching on his dad Val Hallum's A Hydro (Evinrude power), Jim's own hobby was racing control-line model aircraft. Some other boatracers were avid model aircrafters, including Bob Wartinger, who was a control-line racer before getting into outboards while getting an aeronautical engineering degree at the U. of Washington, where I met him. And after Ed Karelsen retired from building boats, he took up radio-control flying; maybe still does it for all I know. Anyway, Hallum bought a Dyna-Jet Redhead pulse-jet model airplane engine . . . invented by Bill Tenney. Jim got his plane going 150mph, went back to a big meet in the Midwest, met Tenney, found out about Anzanis (this info is only roughly reliable; if strict accuracy is essential, get hold of Jim).

Anyway, today Jim has returned to his early hobby, and builds and flies pulse-jet powered models. How's that for a tie-in, Sam?!!

[Powerabout]

Maybe we should look into Dieter Konigs family to see what they were doing during WWII

[Mark75H]

Maybe we should look into Dieter Konigs family to see what they were doing during WWII

Its in the Konig History thread ... not involved in any of that.

[OUTBOARDER]

But I can't work out why his reeds are chuffing at the end of the inlet stroke, give me that M6 spanner I want to have a look at them.

As the piston is on it's way down the pressure in the crankcase builds up and at some point overcomes the inlet pressure wave thru the carb and the reeds slam shut. The air/wave that was flowing thru carb rebounds of off closed reeds back out of carb as a result. "Chuffing"
Happens more at certain rpms than others, typically at lower rpms.

After getting on plane the 45ss the engine has fuel puddled in lower pan from this.

Can cause a 2-stroke engine to load up with gas mixture from picking up fuel twice thru carb.

Ideally the over rich condition can help with engine accelerating, like what a accelerater pump does in a automotive carb. The rich condition also lowers egt temp and lowers tuned rpms of the pipe which helps with making effective rpm range larger.

[Powerabout]

they all do the reverse fuel thing
Get an engine in a test tank and use a timing light just in front of each barrel of the carbs.
There is always fuel in front of them
( try it at night!)