Charles Perdue
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YOU CHEATED, that just proves that a Zoom carb will make ANYTHING run. :lol: You win, buy yourself a sixer and send me the bill, I will pay it. :blink:
Charles
Charles
Super Charged .21
- Thread starter dwilfong
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dwilfong
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I knew you would pull the zoom carb card. <_<
Hell with the beer.
How abouts you make me a carb.
Charles thanks for being a good sport. It is a honer to win a bet with some one of your caliber.
David
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Charles Perdue
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I will have to try that with an engine on my NEW TOY when I get it finished. This is what is taking up all of my carb building time.
I think that we used the same decorator in our shops, yours looks like mine on a good day.
When we meet, we will have to bend an elbow together.
I think that we used the same decorator in our shops, yours looks like mine on a good day.
When we meet, we will have to bend an elbow together.
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Charles Perdue
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Oops, here it is.
L
lohring
Guest
Nice inertial dyno, Charles. You can learn a lot.
Back to supercharging. Two strokes can be supercharged to a power that is only limited by the mechanical strength of the engine. Examples are:
Nearly all the big marine diesel two strokes that modern ships use
The Rolls Royce Crecy V 12 aircraft engine (test single cylinders developed up to 300 hp)
The Napier Nomad
Many snow mobile engines (the one pictured develops around 800 hp)
The Eco Motors engine
(see pictures below)
The important thing about all these engines is the exhaust back pressure is raised along with the intake pressure. Since simple two strokes (some of the engines pictured aren't simple) will have the exhaust port open after the transfer ports close, it's impossible to raise the cylinder pressure by increasing the intake pressure alone. In a two stroke, raising the exhaust back pressure doesn't do negative work on the piston since it all happens around bottom dead center. If you do that on a four stroke, the piston makes a full 1/2 stroke against the pressure.
Can you mechanically supercharge our little engines successfully? Probably, but it's going to be hard. I think time would be better spent working on the design of the simple turbocharger we have, the tuned pipe. It does all the things we need with no moving parts. It drops the cylinder pressure to increase the incoming charge and then magically increases the exhaust back pressure for a supercharging effect. Mechanical turbochargers suffer from scale effects that make small sizes inefficient. Even displacement superchargers have scaling problems. Good luck, though.
Lohring Miller
Back to supercharging. Two strokes can be supercharged to a power that is only limited by the mechanical strength of the engine. Examples are:
Nearly all the big marine diesel two strokes that modern ships use
The Rolls Royce Crecy V 12 aircraft engine (test single cylinders developed up to 300 hp)
The Napier Nomad
Many snow mobile engines (the one pictured develops around 800 hp)
The Eco Motors engine
(see pictures below)
The important thing about all these engines is the exhaust back pressure is raised along with the intake pressure. Since simple two strokes (some of the engines pictured aren't simple) will have the exhaust port open after the transfer ports close, it's impossible to raise the cylinder pressure by increasing the intake pressure alone. In a two stroke, raising the exhaust back pressure doesn't do negative work on the piston since it all happens around bottom dead center. If you do that on a four stroke, the piston makes a full 1/2 stroke against the pressure.
Can you mechanically supercharge our little engines successfully? Probably, but it's going to be hard. I think time would be better spent working on the design of the simple turbocharger we have, the tuned pipe. It does all the things we need with no moving parts. It drops the cylinder pressure to increase the incoming charge and then magically increases the exhaust back pressure for a supercharging effect. Mechanical turbochargers suffer from scale effects that make small sizes inefficient. Even displacement superchargers have scaling problems. Good luck, though.
Lohring Miller
dwilfong
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Lohring
The SC will gust be used to scavenge the eng and load the pipe. with the right pipe it will slam it back in.
Talked to MR. Conley about this and he will see if he can find one of his 427 SC that work on glow fuel for lube.
This is some where no one has gone before so its all BS till I give it a whirl.
David
The SC will gust be used to scavenge the eng and load the pipe. with the right pipe it will slam it back in.
Talked to MR. Conley about this and he will see if he can find one of his 427 SC that work on glow fuel for lube.
This is some where no one has gone before so its all BS till I give it a whirl.
David
Charles Perdue
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Thanks Lohring for the compliment. My dyno can be used as an inertia or torque brake, the torque brake uses a hystersis type electric brake. It will be able to make a run with the inertia flywheel side and turn a round and make a torque brake pull back to back, or vice versa. Should be able to learn a lot.
Not too bad for us with ZERO ABILITY.
Charles
Not too bad for us with ZERO ABILITY.
Charles
L
lohring
Guest
Another historical note on two strokes from the very interesting book, Stealing Speed. It illustrates the success of the tuned pipe, Schnerle scavenged, disk valve two stroke after a lot of attempts with complex, supercharged engines by DKW among others. See the picture below.
Lohring Miller
When Ernst Degner stabbed Walter Kaaden in the back and sold his master's two-stroke secrets to the Japanese, the two-stroke had yet to win a motorcycling world championship. From the first year of grand prix racing in 1949 to the year of Degner's defection in 1961, the four-stroke won 52 world titles, the two-stroke won nothing. Over the next 13 years, as Kaaden's wonder technology percolated through the capacity classes, the four-stroke won 35 world crowns, the two-stroke took 30. Over the following 27 years the two-stroke assumed a position of total domination, winning 104 titles, while the four-stroke won a big fat nothing. Only a change of rules in 2002, permitting 990cc four-strokes to compete against 500cc two-strokes in the elite class, allowed the four-stroke to win again.
Lohring Miller
When Ernst Degner stabbed Walter Kaaden in the back and sold his master's two-stroke secrets to the Japanese, the two-stroke had yet to win a motorcycling world championship. From the first year of grand prix racing in 1949 to the year of Degner's defection in 1961, the four-stroke won 52 world titles, the two-stroke won nothing. Over the next 13 years, as Kaaden's wonder technology percolated through the capacity classes, the four-stroke won 35 world crowns, the two-stroke took 30. Over the following 27 years the two-stroke assumed a position of total domination, winning 104 titles, while the four-stroke won a big fat nothing. Only a change of rules in 2002, permitting 990cc four-strokes to compete against 500cc two-strokes in the elite class, allowed the four-stroke to win again.
Michael Costanzo
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that is great! have seen it done many years ago,but there it is,the proof is in the pudding!
Hydro Junkie
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Just to drop in my .02, some(if not all) of the full sized Detroit V-8 two strokes use no intake valve but rather a large number of vertical intake slots around the bottom of the sleeve that, like our nitro motors, are closed by the piston skirt. The difference between the Detroit and our nitro motors is the Detroit uses direct fuel injection with an exhaust valve to hold the turbocharger raised airbox pressure in the cylinder until the piston rises enough to seal the intake slots. At the same time, no glow plug is used as compression alone creates the required heat to start combustion
scott bouchie
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Charley was the 1st one I know of to make a Dyno
for rc boat engines.,it was in about 1977 he used a power steering pump
for rc boat engines.,it was in about 1977 he used a power steering pump
Charles Perdue
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That was a LONG time ago. The dyno was crude but it worked. I used a GM power steering pump mounted so that it would pivot in bearings mounted in a frame. I installed a valve between the pressure line and the return line and as I closed the valve, it would cause the pump to pivot, the force of this was picked up by a homemade load cell and this was read out on a gauge as inch ounces of torque. It used a DC motor as a tach generator for the RPM. The pump was under driven with small gear belts that reduced it down at a 10:1 ratio.
It was surprisingly accurate. I think that I still have it somewhere.
The new one that I am building now will be computerized, with readouts.
Charles
It was surprisingly accurate. I think that I still have it somewhere.
The new one that I am building now will be computerized, with readouts.
Charles
L
lohring
Guest
Charles
The combination of an inertial and brake dyno allows you to take advantage of the features of both types of tests. It's very advanced. We are much cruder with a friction brake on the inertia wheel. It's good to be able to change flywheel sizes. We've tested gasoline engines with 2 to 12 hp, but testing 67 nitro engines with the same flywheel melted pistons. I think they are on the edge of detonation and the high load of our flywheel was too much. Other engines just took longer to spin up the flywheel.
There are two scavenging types used in two strokes, loop and uniflow scavenging. Uniflow scavenging is used with an external blower and loop scavenged engines often use the crankcase as a pump. Both types can be supercharged, usually with power from an exhaust turbine. Uniflow engines like the Detroit Diesel and the big two stroke in my first post have the advantage of independent control of the intake and exhaust valves. This gives higher scavenging efficiency and can allow a slight supercharge. Loop scavenged engines like ours are simple, compact, and inexpensive. The tuned pipe has made them competitive with the uniflow engines in all but the largest sizes and highest powers.
Electronic engine management combined with direct fuel and oil injection has made two strokes competitive with four strokes in emissions as well. See the two stroke
for sleds and big outboards. Scooter engines are getting there as well. Pretty soon California weedeaters will have simple electronic engine management. Time for another class at the local community college.
Lohring Miller
The combination of an inertial and brake dyno allows you to take advantage of the features of both types of tests. It's very advanced. We are much cruder with a friction brake on the inertia wheel. It's good to be able to change flywheel sizes. We've tested gasoline engines with 2 to 12 hp, but testing 67 nitro engines with the same flywheel melted pistons. I think they are on the edge of detonation and the high load of our flywheel was too much. Other engines just took longer to spin up the flywheel.
There are two scavenging types used in two strokes, loop and uniflow scavenging. Uniflow scavenging is used with an external blower and loop scavenged engines often use the crankcase as a pump. Both types can be supercharged, usually with power from an exhaust turbine. Uniflow engines like the Detroit Diesel and the big two stroke in my first post have the advantage of independent control of the intake and exhaust valves. This gives higher scavenging efficiency and can allow a slight supercharge. Loop scavenged engines like ours are simple, compact, and inexpensive. The tuned pipe has made them competitive with the uniflow engines in all but the largest sizes and highest powers.
Electronic engine management combined with direct fuel and oil injection has made two strokes competitive with four strokes in emissions as well. See the two stroke
for sleds and big outboards. Scooter engines are getting there as well. Pretty soon California weedeaters will have simple electronic engine management. Time for another class at the local community college.
Lohring Miller
Charles Perdue
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Lohring, thanks for the spread sheet matching the size of the flywheels to the size of the engines. That's going to help a lot. I took that into consideration when I designed my dyno, I can change flywheels in about 15 minutes.
Charles
Charles
Jim Allen
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Charles,
I am truly impressed with your effort. Every question about any two stroke; pipe design; carburation; transfer exhaust geometry & timings; head design; etc., etc., can easily be answered with this tool. Congratulations!!
Jim Allen
Charles Perdue
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Thanks Mr. Jim. Coming from you, I consider that a real compliment. It has and continues to be a labor of love.
Charles
Charles
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Sweet!
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