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Anzani Next Gen Expansion Chambers By Bill Tenney
This is a rare picture of the racing expansion chambers that Bill Tenney had constructed for either a class A - 250cc or class B - 322cc Anzani Alky. It is unkown if they worked well. Unfortunatley these exhausts are lost. Above them are a set of conventional Anzani crescent shaped exhaust most commonly used on most Anzanis in North America other than the stock racing wrap around type.
These next generation expansion chamber pipes are very different from the configuration used by the Andersons of Region 10 on their engines seen in other picture posts here on these Anzani threads. These Anzani expansion chamber exhausts are single pipe bolt up so they could be a generation newer than the Region 10 Anderson experimentals that would start on a megaphone open pipe and then be mechanically gate switched to the ramshorn like expansion chamber pipes commonly called "bounce pipes" back then. Comparing the pictures between the Tenney built pipes and the Anderson built Region 10 pipes both show some profound design to pipe differences.
Interesting stuff.
Enjoy the picture. :)
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A rare find,secured for restorations in the USA.
The following pictures are of a cache of parts secured after Bill Tenney passed away of later 1950s British Anzani Mark 1 major components. These parts are now in the hands of a USA restorer for re-assembly of at least one Alky engine from that era as well as parts for Anzani stock outboard racers that very rarely if ever seen run in USA waters.
*It was a recent Mark 2 Anzani (1960s) B stock engine that was restored and run in Florida this last January, 2009 by Rod Champkin (United Kingdom (GB)) and USA's RC Hawie (FL) at a northern Florida AOMCI meet that are here on BRF pictorially and on short videos on the internets "Youtube" for views of it in live with sound video.
Enjoy the pictures. :)
**If anything that looks like any of this in these pictures turns up sitting on some shelf or under some work bench gathering dust and doing nothing, please contact me at catwerx@htomail.com as we are cooperatively always looking for parts to put these engines back together again both in North America and in the UK. Anything will help no matter how seemingly insignificant. Thanks for the consideration.
**We also treat the Anzani cousin the HRP (Harrison Racing Products) class A and B engines with the same ferver so if the parts don't quite look like British Anzani they very well could be its American cousin the "Harrison" please get a hold of me for the same purposes. It is nice to see these restored engines anywhere we can get them from.
About expansion chambers, Anzanis and gasoline performance.
Hearing an Anzani class B Stock racing gasoline fueled engine light up on Youtube in the capable hands of Twister and RC sure has produced some rather startling comments akin "what an animal", "what the" and "I never knew" coming out of people! This stock racing engine from the United Kingdom that shares its kinship with the 2 stroke motor cycle engine, air cooled predecessor did not have any custom racing exhausts just the standard built for the engine factory header system that directed, collected and tossed it out at water level. No one in UK ever dreamed that this snarling engine importted to the USA by Bill Tenney would not be allowed to run in the USA stock outboard classes which by then was dominated by the Mercury 20H Deflector custom made at the factory racing engine no different than Anzani was. It was the two different technologies in collision where if the Anzani was allowed to stay would have meant obsolete Mercs so it was not allowed in and kicked virtually into the Alky classes where it immeidately took over. The takeover was so profound it triggered a basic industry change to loop charging technologies on a world wide basis in mass.
We know the engines that were created to use the same technologies that then took over in their own times to where they are today while Anzani as a company pettered out but not before it set records stunning that racing community at the time. As one racer said it was horrible to see a class B Alky Anzani runabout entered in class F and competing with them too which horrified the big boats in class F.
The whole point though of this posting is not so much the track record of the engine but whether expansion chamber exhaust pipe development ever touched on the engines as 250cc, 322cc or 350cc using gasoline as a fuel back then when expansion chambers started turning up in the 1960s in methanol fueled Alky class racing outboards?
Immediately when Anzanis starting using racing fuels other than gasoline in the Alky classes the weak crankshaft setup that was adequate on gasoline proved to be quite tricky to keep maintained running on methanol and nitro mix fuels. As the 1960s wore on to the 1970s the amounts of nitro mixed in exceeded 30% produced over 90 and 100 mile per hour records for class A and B Alky on these engines. This was all done on megaphone pipes as it was found very early that on expansion chambers that no nitro could be used what so ever without damaging the engine early on with expansion chambers and only methanol and lube the Anzanis still ran into crankshaft problems so the engine stayed away from expansion chambers and stayed on megaphones and nitro where most engines departed for the new technologies of expansion chambers where they are today. Anzani did not go there with them and eventually died anyway as the company wound down.
It was in more recent times that UK's & BRF's Twister mounted an expansion chamber system on a highly developed 250cc Anzani on gasoline to do record runs in the UK with pipe development in its infancy in the effort. In all cases of two stroke engines the only difference between a good engine and a great engine is locked up with the exhaust system. Most megaphone systems produce from 15% to 20% a power increase to a otherwise stock block type racing engine. When expansion chambers are properly built and installed to match all characteristics of a stock racing engine the increases can be from 50% to 100%. Change the factory racing engine to a custom re-engineered racing engine and the power goes over a 100% increase to where something generally gives out limiting how far the engine could be pushed. Expansion chambers on Anzanis though experimented with expasnion chambers back in the 1960s never got into todays standards of exhausts on methanol fuels nor were they specifically developed on gasoline where comparably displaced engines in the snowmobile, racing motorcycle and related industries in gasoline fueled racing exceeded 100 horspower for a 250cc and as high as 140 horsepower for 344cc engines all to of the liquid cooled varieties used in racing like Zenoah etc.
Given that crankshaft techologies of Anzani are weak and Harrison crankshafts are very few and neither available anymore it would seem that safer horsepower development for this engine as a classic would lie in the use and tunning to racing gasoline and expansion chambers to produce the horsepower somewhat safer with more predictability in the fuel they could back in the 1960s using highly corrosive and temperamental methanol and nitro mix Alky fuels. Other than Twisters expansion chambered 250cc gasser Anzani any other version anywhere else from the era when the engine was in development to produce records do not seem to exist, but really was that the case? It remains unknown and untested to this day if someone did anywhere else in the USA or Canada? Anyone?
Expansion chamber supercharging effects negated the use of nitromethane.
No Sam:
The "supercharging effects" of sonics in the expansion chambers (then called bounce pipes) negated the need for any nitromethane in the methanol based fuel.
In your previous posts, your one liners did not say enough to explain anything to anyone, anyone could learn something from. Excessive words? I hold a university level adult educational certification and taught hundreds higher level staff across this country. That says plenty. :)
For those so inclined to learn more about pipes.
For many readers who want to learn more about 2 stroke exhaust systems both very early to late model from the days of Straight pipes, Coannda effect pipes, the Burnoilli effect, Megaphones and then all manner of Expansion Chambers evolution has brought us today, just using the Google search engine or other suitable internet search engine will bring up a huge amount of the theoretical all the way to the types and kinds of formulas that can be used to build exacting 2 stroke pipes for at least three kinds or more of performance and racing applications. Though much has been written about exhaust making, it is not longer the black art it used to be and with the advent of computerization we enjoy today even less so hard to understand and easier designed and built. The simulations out there on the internet are amazing to watch and enjoy.
Enjoy your searches and readings. :)
I am not a mechanical, aeronaughtical or related engineer.
Mark 75H:
Interesting information. I am not a mechanical, aeronaughtical or related engineer which is the perview of those that use such information other for me which is general interesting information where some ideas might come from and be used sometime. I am heavily university educated and field tested. I learned how to do basic machine work in high school as an option class using a Atlas lathes and Bridgeport milling machines before they had digital readout capabilities. I am an enthusiast first and foremost with an associated to our sports background, always willing to learn, exhange information, comment and debate and post, with enthusiasm. That is the essence of BRF to stick to and that is all. :)
All makes for interesting views doesn't it? Soon 18,000 and more!
It sure makes for interesting views and postings on the fly here that make these threads such interesting places that increases viewers interests to come to BRF to look around, see, recognize and enjoy! :)
How a tuned expansion chamber racing pipe would work on an Anzani
How a Tuned Pipe (Expansion Chamber) Works:
When the engine fires it detonates the fuel mixture in the combustion chamber, pushes the piston down, opens the exhaust port and allows the burnt gases to escape along with the sound wave produced when the engine fired. The negative sound waves pull the exhaust gasses out of the exhaust port, and sucking the fresh inlet mixture through the transfer ports, filling the combustion chamber and some fresh inlet mixture go out into the header of the exhaust .
The positive sound waves, reflected back from the convergent (baffle) cone, force the extra fresh fuel mixture (that is now inside the exhaust pipe, and would otherwise been lost) back into the combustion chamber through the exhaust port moments before it is finally closed, (and since after the transfer ports was closed) thus acting effectively as a supercharger turbocharger on your 2 stroke engine.
This happen at very close tolerances individual to each engine specifications and with the correct dimensions can boost Horsepower by up to 40% above standard tune depending at the present state of tune of your engine.
Factors you need to know about your engine to build a expansion chamber racing pipe.
The following are factors you need to know about your engine as input values into most expansion chamber formulas to produce a 2 stroke engine pipe based on loop charging (same technology just different lingo) loop scavenging technologies. (loop technology pipes and deflector techology pipes are different so these values and their roles for deflector pistoned engines are different so what works for loop engines will not necessarily work for deflector engines).
It only generally requires these few INPUTS to design loop engine expansion chambers.
*Number of Cylinders
Enter the number of cylinders this engine has.
*Cylinder Bore in mm
Enter the cylinder bore in mm
*Engine Stroke in mm
Enter the cylinder stroke in mm
*Exhaust Open Period (Deg.)
Enter the total period the exhaust port stay open in degrees. The best way is to measure this accurately with a degree wheel.
*Main, Secondary & Boost Transfer Open Period (Deg.)
Enter the total period the main transfer ports stay open in degrees. The best way is to measure this accurately with a degree wheel.
*Target Power Developed in kW/hp
The power you aim for this engine to develop in kW or hp. (Select if value is in kW or hp with the radio button, next to the input.)
*Target RPM @ Peak kW/hp (Power)
The RPM (rounds per minute) this engine will produce its maximum Power at. This could easily be 20% more than the engine did in "stock" form, depending on the state of tune and modifications made (porting, reed-valve, carb. etc.)
*The Exhaust Port Exit Diameter in mm
Measure the exhaust port diameter in mm at the point where it exit the casting (the size at the exhaust gasket position)
*Fuel Type
Simply choose the fuel you will use.
Methanol
Ethanol
Gasoline
Java Pipe Program Webpage with info and downloads - automated
The following webpage contains excellent information on making a java pipe in your computers environment providing your operating systems are up to snuff.
http://www.mh-aerotools.de/airfoils/javapipe_en.htm
or do a Gordon Jennings Pipe as follows:
Tuned Pipes
Unlike four stroke engines, in which intake and exhaust valves retain fuel in the combustion chamber, a two stroke engine depends on the header and tuned pipe to retain fuel in the combustion chamber.
It has been said that the single most performance gain that one can achieve on a two stroke is made by strapping on a tuned pipe. This is very true if it is done properly. Don't just go down to your hobby shop and purchase a pipe marked ".15 Tuned Pipe" or ".21 Tuned Pipe". It's not that easy unless of course the pipe happens to be manufactured by the same company that made your engine. Which still doesn't guarantee that you will achieve optimum performance for your application. What are the sections of a tuned pipe called? What does each section of the pipe do? What are negative and positive sound waves? What won't a pipe do? These are some of the questions we'll try to answer here.
Sections of a Tuned Pipe
Header - Although not part of the tuned pipe, the header plays an important role in the overall tuning of your engine. The header attaches to the engine and is the straight or slightly divergent (opens up 2-3 degrees) section of the pipe. It helps to suck the exhaust gases out of the engine. The header pipe cross-sectional area should be 10-15% greater than the exhaust port window for when maximum output at maximum RPM's is desired. In some cases the area of the header pipe may have a cross-sectional area 150% of the exhaust port area. The length should be 6-8 of its diameters for maximum horsepower, for a broader power curve 11 times pipe diameter may be used. This is the part you trim lentght to tune the header.
Divergent (Diffuser) Cone - The section of the pipe that attaches to the header and opens up at an angle like a megaphone. It intensifies and lengthens the returning sound waves thus broadening the power curve. The steeper the angle the more intense the negative wave returns, but also the shorter the duration. The lesser the angle, of course, returns a less intense wave, but for a longer period of time (duration). The outlet area should be 6.25 times the inlet area. 7-10 degree taper angle.
Belly - Located between the divergent and convergent cones, it's length determines the relative timing of the negative and positive waves. The shorter the belly the shorter the distance positive waves travel and the narrower the RPM range. This is good for operating at HIGH RPM only. The longer the belly the broader the RPM range. The diameter of the belly has little or no effect.
Convergent (Baffle) Cone - Located after the belly and before the stinger, reflects the positive waves back to the open exhaust port and forces the fresh fuel mixture back into the combustion chamber as the exhaust port closes. The steeper the angle the more intense the positive wave and the gentler the angle the less intense. 14-20 degree taper angle. The taper angle primarily influences the shape of the power curve past the point at which maximum power is obtained.
Stinger - Located at the opposite end of the pipe from the header and after the convergent cone, it is the "pressure relief valve" of the pipe where the exhaust gasses eventually leave the pipe. The back pressure in the pipe is caused by the size (diameter) or length of the stinger. A smaller stinger causes more back pressure and thus a denser medium for the sound waves to travel in. Sound waves love denser mediums and thus travel better. A draw back to a small stinger is heat build up in the pipe and engine. DO NOT USE TOO SMALL A STINGER! The stinger diameter should be .58-.62 times that of the header pipe and a length equal to 12 of it's own diameters.
When your engine fires it detonates the fuel mixture in the combustion chamber, pushes the piston down, opens the exhaust port and allows the burnt gases to escape along with the sound wave produced when the engine fired. The negative sound waves pull the exhaust gasses out of the exhaust port. The positive sound waves, reflected back from the convergent (baffle) cone, force the fresh fuel mixture back into the combustion chamber through the exhaust port thus super-charging your engine.
Here are some formulas from Gordon Jennings' "2-stroke Tuners Handbook" (1973)
http://www.maxxtraxxusa.com/Tuned_Pipes_3608.cfm
When using the formulas above for designing or calculating what parameters the pipe to buy should have, the first step is to calculate D1. When you calculate D1 with the D1 formula above, remember that the number is in sq-in and must be converted to the diameter of the header pipe. Do this by dividing your calculation by Pi and then taking the square root. This will give you the radius of the header. Just multiply it by 2 to get the diameter. What you are doing is working the formula for the area of a circle backwards (Area of a circle = Pi r^2). From this point on, no other conversion should be necessary unless you use metric (Multiply numerator of LT formula by 83.3 and use 518.16 m/s for VS to get mm instead of inches) instead of English.
To compare, here's another set of formulas from Martin Hepperle (1997):
If you use both formulas, you'll see a slight difference, this may be due to new research between the dates of publishing (1973 Vs. 1997).
Selecting a Tuned Pipe
An ideal tuned pipe is thought to have a gently divergent header pipe to keep exhaust gases at a high velocity near the exhaust port opening, then a second medium diverging cone and a third high diverging cone attached to the belly. In reality it is what works for you. So how do you determine all these things? One at a time. Let's look at setting up an engine for course racing.
What do we want?
1) Quick acceleration
2) Broad RPM range
3) Broad to lower power range
This means we are probably not going to turn the maximum RPM's that the engine is capable of anywhere on the course. If our engine is capable of turning 25,000 RPM's, we will probably only use up to 20,000 RPM's. Look at each section of the pipe in the above descriptions. The Header cross-sectional area should be at least 10-15% greater than the area of the exhaust port. Length at this point doesn't really matter (at least 8 diameters), but make sure it is long enough to work with. The divergent cone would be at a medium angle for a broad power curve at lower RPM's. The belly would be medium to long for a broad RPM range. The convergent cone would be at a gentle angle because we want the duration of the positive wave to be longer.
How long is the pipe? If we review the formulas and get the formulas for Exhaust Systems Tuned Length and Length of Curved Pipe (if you need to calculate a curved pipe) we can calculate closely the pipe length. The formula for determining the length is:
Lt = (Eo x Vs) / N English OR (83.3(Eo x Vs)) / N Metric
Where:
Lt = tuned pipe length, in inches OR millimeters
Eo = exhaust open period, in degrees
Vs = wave speed (1700 ft/sec OR 518.16 Meters/sec at sea level)
N = crankshaft speed, in RPM
Let's say, for example, we have an engine that will turn 25,000 RPM. We calculate that we will only use 20,000 of those RPM's and our exhaust duration is 180 degrees. Then we substitute in the formula:
Lt = (180 x 1700) / 20,000 OR (83.3(180 x518.16))/ 20000
Lt = 15.3 inches OR 388.46 mm
Now this is where you need to make a personal decision. Some people say that this distance is measured from the exhaust port opening and some say that the distance is from the center of the cylinder. The choice is yours, but I take the longer distance, which is from the exhaust port opening. Remember that this is not the total length of the pipe. This is the length from the (in my choice) face of the piston at the exhaust port to the center of the convergent cone including the invisible intersection of the convergent points not just what you see. Go back and reviews the formulas for the Baffle Cones to determine this point.
Tuning that Pipe
Now comes the fun part! We get to go to the track again, unless of course we have our very own dyno. Not! So we have set the pipe up so that we have an optimum length. Well take it off! That's right, take it off. First we want to get the right prop, right fuel and right needle before we even mess with that pipe. You see this is where the "What a pipe can't do?" comes in. A pipe cannot make up for poor engine setups and crappy gear ratios. A pipe also cannot make up for bad engine timing and some engines are timed so poorly that no pipe will increase performance.
Ok, we make a few (2-3) passes without the pipe. We have the right gear ratio, the right needle setting and this is the fuel we are going to be racing with. Put the pipe back on richen the needle a little (1/4 turn) and make a run. We pay close attention to what the engine is doing. If the engine turns slower, something is wrong. If the mixture is correct the pipe is too long. Shorten it by 1/8" at a time until the revs start to rise (this can be done at the exhaust coupler). If the pipe is too short the motor will run harshly and the needle setting will be unstable and critical. Add 1/8" to the length at a time (again, at the coupler). When the pipe is at the proper length you will experience the thrill of a lifetime. You will hear the engine and pipe become one in resonance. You will see your car accelerate like you walked behind it and gave it a kick in the rear. This as known as being "on the pipe".
As indicated before there is a lot of information out there with manually run to compterized formulas. Lots to see and lots to work with.
Though these examples run the extremes of age from the older to the newer, to make a suitable pipe for an Anzani on gasoline, on ethanol or methanol, these routes point the way in terms of getting there.