2 barrel carb

[Nigtmare]

i think i have too much time on my hands! and by the looks of it, the winter's going to be very long. being an auto mechanic, i've been thinking a little out of the box. :blink: i dont know if this has been done before on an r/c engine but im thinking it will work. im thinking of having a 2 barrel carb made so that it will run on a primary carb until a certain rpm, then the same linkage will kick in a secondary carb, providing more air and fuel to the engine. B) i dont think its a hard thing to do if you have a machine shop and a few hours to play around with. it will work at the same principle as the 4 barrel gm carb. the primary will open up the secondary, which at the same time will open up the Don Ferrette valve :lol: :blink: to provide more fuel to the secondary barrel. what do you guys think? am i going insane or should i invest the time or money? do some of you guys want to try this? here's a picture that i drew. im not an artist, so please dont laugh! :lol: can this be the next "100 mile 21 hydro"? :lol:

 

[Bob Finn]

Charlie WIlliams in Dallas built one of these about 10 years ago for a 40 mono. He did manage to make it work succesfully, but I think it proved to be about equal to a stock carb in performance. He is a master machinist and does some beautiful work.

 

[Mark Poole ModVP]

I have seen something similar done on a 40 outboard. Manifold built to accept two carbs. This engine also had two tuned pipes! It ran but was not very fast. The old Johnson Stinger 3 cylinder outboard could be modified to accept 3 two barrel carbs instead of 3 one barrels. But part of that mod was seriously enlarging the intake tract to make good use of all that extra fuel and air. Making more fuel and air "available" does not always mean more power on a two stroke engine. Crankcase volume, cylinder volume and RPM limitations will dictate how much the engine can suck in and blow out. Your linkage idea is interesting.

 

[topfuel443]

heh heh heh...... Mark said suck and blow.....heh heh heh

~James

Interesting idea Nightmare

 

[Tom v.d Brink]

at the moment i am doing a simplified steady state study of inlet tract discharge coefficients using cfd simulation and i think you will find that the junction and double inlet opening will cause more extra loss then the gain of having an extra carburettor open. also the inlet tuned length will need to be lengthened to accommodate two carbs side-by-side otherwise the bend will become to sharp so it will probably become to long.

on my study so far I found we could put some more effort into the inlet shape off the current velocity stacks.

 

[John Knight]

heh heh heh...... Mark said suck and blow.....heh heh heh

Sick mind! You are looking at a long winter indeed, in Germany!

 

[dwb2620]

Charlie WIlliams in Dallas built one of these about 10 years ago for a 40 mono. He did manage to make it work succesfully, but I think it proved to be about equal to a stock carb in performance. He is a master machinist and does some beautiful work.

Bob beat me to it. h34r:

David

 

[Nigtmare]

Charlie WIlliams in Dallas built one of these about 10 years ago for a 40 mono. He did manage to make it work succesfully, but I think it proved to be about equal to a stock carb in performance. He is a master machinist and does some beautiful work.

Hey Bob. I didn't know that someone try this thing.it just looks to simple not to try I think 10 years later and the INTERNET we shout be able to make things work. B) Nick

 

[HTV Boats]

Jetting a single needle is tough enough to tune and the transition without some sort of accelerator pump would be hard. If you want a simple project try making a tune pipe with a slide mechanism to ajust the length. Old stock and alky outboard racers would "pull the pipe" to shorten it in straightaways for top end, and longer out of the turns for acceleration.

 

[Nigtmare]

at the moment i am doing a simplified steady state study of inlet tract discharge coefficients using cfd simulation and i think you will find that the junction and double inlet opening will cause more extra loss then the gain of having an extra carburettor open. also the inlet tuned length will need to be lengthened to accommodate two carbs side-by-side otherwise the bend will become to sharp so it will probably become to long.

on my study so far I found we could put some more effort into the inlet shape off the current velocity stacks.

Tom. sometimes things don't work on paper.I have found in the auto industry,that you need to try to succeed.I worked next to 20 mechanics (we do alot of electrical work and trouble shouting) I'm the only one that didn't make or have any notes.I tried things out on the bench and the only thing that can happen Is i f*** up Then I go back and try again . Maybe the outlet needs to be in two parts and have the intake see a primary and a secondary.I think the cfm needs to be calculated, and the pipe has to match the "suck and blow" as Mark said the runners behind the barrels play a big part whether the engine would have a lot of rpm or torque or both. The stock velocity makes a difference in shape and length but not as drastic as behind the barrel. At the v point (behind the barrel) a divider can be inserted in a form of a steel plate and this will let the two sides operate individually. So far, our little engines are running fine the way they are and since we can not go into turbo charge and super charge engines I think increasing the cfm is the other route to take. I wish I had a place that I could sit and make this thing and I'm pretty sure its going to work and be an improvement too.Remember that you need to work the pipe and carb at the same time. Nick

 

[Joe Warren]

i think i have too much time on my hands! and by the looks of it, the winter's going to be very long. being an auto mechanic, i've been thinking a little out of the box. :blink: i dont know if this has been done before on an r/c engine but im thinking it will work. im thinking of having a 2 barrel carb made so that it will run on a primary carb until a certain rpm, then the same linkage will kick in a secondary carb, providing more air and fuel to the engine. B) i dont think its a hard thing to do if you have a machine shop and a few hours to play around with. it will work at the same principle as the 4 barrel gm carb. the primary will open up the secondary, which at the same time will open up the Don Ferrette valve :lol: :blink: to provide more fuel to the secondary barrel. what do you guys think? am i going insane or should i invest the time or money? do some of you guys want to try this? here's a picture that i drew. im not an artist, so please dont laugh! :lol: can this be the next "100 mile 21 hydro"? :lol:

Save your energy & read some theory on 2 stroke engines. The intake & exhaust duration & Pipes of differnt sizes & shapes is where the performance is. The barrel valve type carbs of various sizes are good for what we are using them for. Remember its a game of Weight vs HP when you begin construction of the boat. ON Hydros Different angles on the sponsons release the boat off the water. While other angles help keep it from flying away..... John finch wrote some excellent books on this of years ago, but it still applys to todays engines & boats ADVANCED RC MODEL BOATING a good book on theories of boats & engines. He is on this board maybe he can tell you where you can still purchase it? POINT::: Work on the entire package Not just the carb.

 

[Wesleys Custom Graphics]

instead of 2 carburators, what about 2 in line? I have a friend who modifies carbs for f-4 I (600cc croch rocket engines) for sprint cars. I told him he was silly when he tried to install injectors in front of the carb and after the air filter. I told him a motor will only accept so much fuel and the rest is wasted. I WAS WRONG! He has sold probably 100 of these units along with the re-maping software for the computer and these things dominate wherever they go.

 

[El Zorro]

Back when I was still in high school, I was working in the local hobby shop and knew everyone who came through the door that flew airplanes and had boats, etc. I had been flying controline Combat and Rat Racing for a few years and was getting better at making the engines run better than stock. I was also learning to fly R/C Pattern airplanes. This one hot shot Pattern guy wanted to try his hand at Pylon Racing. K&B had just come out with their "Series 69" engines and the .40 size is what was used in the R/C Pylon and the ukie Rat Race events. This engine had a bolt on front and rear plate. My big idea was to take a rear rotor racing engine and adapt a front rotor housing to it, making an engine with two intakes. All I had to do was make a drive pin to press into the crankpin of the front rotor crankshaft and it was ready to go. We put this engine into this guy's Pylon Racer. To set the needle valves I would turn the front needle out about 2 1/2 to 3 turns and do all of the fine tuning on the rear needle. These engines didn't use a tuned pipe, but used a "mini pipe". They were a straight piece of thin aluminum tubing about 7/8" in diameter and maybe 5" long. This airplane was FAST!!! None of us had ever seen anything go that fast. I would guess it was going about 150 MPH. This turned out to be much more airplane than this guy could handle and eventually he strained it through the pine trees on the other side of the runway. You could hear it going through the trees and only the fuselage came out the other side!

Moral of the story is that when you can pack more air and fuel into an engine ( it's a pump, remember? ) its going to go faster. I believe an engine will "unload" more in an airplane than it will in a boat, so I don't believe there would be an advantage to this or two carbs in a boat. One of the guys in the ODMBA club built a supercharger for a boat engine many years ago.............anyone remember that?

Dick Tyndall

 

[Tofastformellow]

wouldnt it be easyer to fit a glow plug to a die grinder ??

pressured fuel injection will yeild more power than twin carbs.

i think that with a 30 psi fuel pressure alloy pressure tank and a stainless fuel injector we could increase the venturi size a large % and still have an out of the box reliability ...

there is much to be had... ive played with efi on race cars enough to know you can have big power and drivability ...and HUGE venturis , you can tune the ' BIG 'stutter out of the progression

but efi 's no good here.. mech inject . now ., thats a subject i want to talk about !!!

now whos going to build small lightweight mech gear drive fuel injection for my cmb hr91 ???

belt drive the pump , of the flywheel ?

would the preformance of a sliding tune pipe , and mech injection off set its weight , you could push larger hull i suppose ,

but if the injection were built into the motor.. ... hummm

couldnt you just run an open venturi , and richn the fuel mix to launch and slow the boat down ??? & flood it to quit

thanks

Jason

 

[El Zorro]

Back in the late 1980's ( 1980's technology, anyone? ) I played around with a .21 Mono and pressurizing the fuel tank with crankcase pressure from the engine. From what I can remember now, crankcase pressure is somewhere around 2 or 3 times more than typical pressure from a tuned pipe. Only drawback to using crankcase pressure was that you had to incorporate an on-off valve between the remote needle valve and the carburetor. This valve was operated with the throttle servo. When the engine was operating at full throttle the valve was shut, allowing pressure to build up in the tank. When you started closing the throttle, the valve would open which would allow pressure to bleed off from the tank. If all of this extra pressure stayed in the tank when you throttled back the engine would flood and cut off. Initial runs showed that the system did indeed work, but I didn't really see enough gains in performance to warrent the extra work in putting this in the boat. Just something else to go wrong, you know? Another idea from my controline flying days..............

Dick Tyndall

 

[jayt]

IC engines don't run on fuel, they run on air and fuel. Too much fuel/not enough air and the power goes down. Increasing power is not a game of getting more fuel into the engine, it is all about increasing the volumetric efficiency of the engine so it can ingest more air/fuel. That is what a supercharger does, it packs more of both air and fuel into the combustion chamber. If I set the mixture too rich on my blown Dodge, the dyno shows less power. Set it too lean and the engine temperature climbs and detonation sets in. Pro Stock drag cars (no blower) can have volumetric efficiencies above 108% with the right setups. 2-cycle engines can have over 100% VE too.

The engine doesn't care what size or how many carbs it has, just how much of the correct mixture is directed into it. There may be small potential power increases by better intake tuning - or we may find out that the short intakes we now have are best for top end power. Either way, I just can't see normally asperated glow engines driving an R/C hydro above 140 mph. The energy in the fuel is the limiting factor now.

.

 

[Mark Poole ModVP]

Yeah James I said suck and blow. The ENGINES! It was all about the ENGINES!! :lol:

 

[Wesleys Custom Graphics]

IC engines don't run on fuel, they run on air and fuel. Too much fuel/not enough air and the power goes down. Increasing power is not a game of getting more fuel into the engine, it is all about increasing the volumetric efficiency of the engine so it can ingest more air/fuel. That is what a supercharger does, it packs more of both air and fuel into the combustion chamber. If I set the mixture too rich on my blown Dodge, the dyno shows less power. Set it too lean and the engine temperature climbs and detonation sets in. Pro Stock drag cars (no blower) can have volumetric efficiencies above 108% with the right setups. 2-cycle engines can have over 100% VE too.

The engine doesn't care what size or how many carbs it has, just how much of the correct mixture is directed into it. There may be small potential power increases by better intake tuning - or we may find out that the short intakes we now have are best for top end power. Either way, I just can't see normally asperated glow engines driving an R/C hydro above 140 mph. The energy in the fuel is the limiting factor now.

My friend that modifies the F 4 I motors doesent gain alot of extra horse power but it is more efficent at atomizing the fuel air mix for better response from mid to high rpm. That is where his big gain is. Just think, if you could creap up to the start line and take off like a dragster to beat everyone to the turn.

.

 

[jayt]

Just think, if you could creap up to the start line and take off like a dragster to beat everyone to the turn.

Oh, you mean just like an electric boat can do?














J/K, no flames please! We are all R/C boaters here - the power source is less important than the fact that we all run boats! B)

.

 

[Bob Finn]

Back in the late 1980's ( 1980's technology, anyone? ) I played around with a .21 Mono and pressurizing the fuel tank with crankcase pressure from the engine. From what I can remember now, crankcase pressure is somewhere around 2 or 3 times more than typical pressure from a tuned pipe. Only drawback to using crankcase pressure was that you had to incorporate an on-off valve between the remote needle valve and the carburetor. This valve was operated with the throttle servo. When the engine was operating at full throttle the valve was shut, allowing pressure to build up in the tank. When you started closing the throttle, the valve would open which would allow pressure to bleed off from the tank. If all of this extra pressure stayed in the tank when you throttled back the engine would flood and cut off. Initial runs showed that the system did indeed work, but I didn't really see enough gains in performance to warrent the extra work in putting this in the boat. Just something else to go wrong, you know? Another idea from my controline flying days..............

Dick Tyndall

In the early 70's, Leland Morton and I had a 2 stage fuel valve in a B Proto ship that was centrifugaly operated. It had a primary jet for takeoff and a secondary that opened when the centrifugal force overcame the spring.(When it came on the pipe after takeoff). We flew that setup sucessfully for about a year and half. It worked well at times, but didn't have consistancy. The KISS principal is the winner in most cases. In my experience, you also can't give up the velocity in the venturi, or make the case so large that it suffers for lack of base compression. Bigger is not always better. It still has to pump.