1QwkSport2.5r

I have many aircraft engines, two of which are 4-cycle. One 10cc and one 20cc. I have an RB Innovations HOAXcharger that I was going to try installing on one of my 4-cycles and see if it would do anything or not. We all know they're a joke on 2-cycles. It's been so cold here, I'm not in a hurry to set it up, however I have some pulleys and brackets to mess with in the mean time to get the pulley/belt geometry reasonably close.

Forced induction on a 2-stroke would have to be a turbocharger realistically, but these tiny engines are too small for the extra efficiency of a hypothetically operational turbo to be realized. Honestly, you're better off adjusting the port timing, changing the carb (larger choke area), adding more nitro (ie: using 40-60% nitro) , adding an adjustable tuned exhaust (ie: http://macspro.com/DragCarPipes.asp), machining a different head button (high nitro heads needs to be shaped differently than lower nitro heads), and the list goes on. If you're only going for the bling factor, then by all means... Bolt it on!

toolmaker7341

Super Charger for a 2 stroke " it's called a tuned pipe"

cbaker65

Lol....I agree!

My theory input...Is you really cant force more pressure in a nitro 2 cycle engine because its fixed timed port.
intake & exuast ports are in theory are fixed sizes,an are fix timed with the stroke of the piston.

A nitro engine you can only mod. so much,like razor edge piston rod,chanel crank shaft,an ports,an acource,
tuned pipe.
The filters,2 stage probably henders these engines because air restriction,but you cant run them with out
because they protect the engine.

Although,what I did hear,is to rough up the bottom of carb. throat inside the carb.this would help mix the air
with the fuel better as its entering the engine,an pollish exuast port for a smoother faster exuast exit.
This will allow the engine to breath an run better...

Well,thats my theory,an its only a theory!...

Instructor

My Feedback: (16)

Check with MAC Exhaust systems and see if they can make you a tuned pipe for your engine.......

Larry

Argess

Ahh... another supercharger discussion. Just to throw in my 2 cents, this whole idea of it not working due to both ports being open at the same time doesn't hold up.

You can't take a static picture of the engine with the piston in a position where both ports are open, and then apply a dynamic situation to this moment in time by allowing the air to escape.

Take a bucket with a hole in it. As long as we add water as fast as it comes out, the bucket will stay full. You can't freeze this situation in time, yet state the bucket will empty.

We know superchargers can work with 2-strokes. It's not really debatable.

Now, will the RBI unit work? I've seen videos where it has. But let's suppose they are faked. Doesn't mean that in principle it can't work. I say that anyone wanting to experiment with a homemade S-C is to be commended for not only following his personal interest in the hobby, but demonstrating the type of analytical research, foresight and dedication that engineers, scientists, physicists and other inventors of the ages have used to get us to the technological world we currently live in.

I’m always impressed with the lads who come up with modifications. The naysayers; not so much.

toolmaker7341

[QUOTE=Argess;11958975]Ahh... another supercharger discussion.

Turbo's have been made to work on 2 strokes but not any better than a properly engineered and tuned pipe. If they were better you would see them on racing bikes. You can prove or disprove any theory with analogy's but that doesn't make it work. The only turbo's that I know of that sorta work are on snow sleds and they have variable exhaust timing. The op didn't seem to have much IC knowledge.

phmaximus

So we would be better off asking people in the know?

i dare say the reson most people have not seen 2 stroke turbos is they problary are not working In that feild or simply have nothing to do with it..... They are not exactly mainstream

the fact is there are plenty of examples of larger 2 stroke bikes and snowmobiles out there. U just have to look.

correct me if I'm wrong. But as far as I know the variable exhaust timing does not effect if a turbo will work or not.

As far as I'm concerned.... The theory is there for It to work but the only problem is scaling down these turbo setups and retaining efficency.

phmaximus

I think if there is to be a future with forced induction on these little engines turbo is not the way to go because it the efficency vs size issue... So ideally superchargers is the way to go.....

So I wonder..... With the advances in electric superchargers and electric hybrid turbos why not apply that technology to these engines??

i think the way to go would be a electric supercharger..... Everyone knows about turbo lag, but there is never any mention on supercharger lag..... The biggest problem with mechanical superchargers is they only reach max boost at redline..... And if you over rev the motor it will over boost.... So because boost is proportional to the engines RPM at half engine speed u only have half boost...(there is more to it)
But with a electric supercharger..... U wouldent have that.... U could have max boost in under 1 second after nailing the throttle.......

the big thing im interested in knowing.... What's the average CFM rating for medium size 1/8 nitro engine?

Barracuz

The only reason a 2 stroke snow mobile/ v8 Detroit diesel/ 2 stroke 3 cyl fiat motors can use any type of forced induction is because they implement diffrent mechanisms to control intake and or exhaust flows.

The snowmobiles you take about use a reed valve on the exhaust, the Detroit diesels use normal valves like any other 4 stroke engine and the 2 stroke multi cylinder fiat (can't exactly remember the car brand) uses an overhead rotary valve setup.

Our engines are very robust in design and don't offer any control on intakes or exhaust air flows.

The biggest problem with a super charger on our engine will be the loss of power due to running the SC off the crank.

Then you also have the SC design. A turbine supercharger would need to be geared off the crank in order to achieve high rpms that are needed for the turbine to properly work. Even if go with a rotary vane, spiral,screw or roots type of compressor. All 3 of those feature very heavy moving parts and will only cause strain on the crank.

Now if you were to use a sepreate electric supercharger you would probably have a legit setup but you'll also have the weight of the motor and battery plus any circuitry you'll need to install so the supercharger works in tandom with the engine.

If there's going to be a future with rd and forced induction it's going to be with 4 strokes not our schnerule ported engines.

Barracuz

Double post.

1QwkSport2.5r

I agree Barracuz. It makes more sense to shim the head and run more nitro and use a better exhaust system. Bling factor is great, but that wears off pretty quick. Truth be told, burning more nitro will likely make more power than any power gains attained from forces induction. I look at a MACS drag pipe as more bling-worthy than a 'charger. I posted a link to the drag pipes back some posts. They are a true tuned pipe. http://macspro.com/DragCarPipes.asp

If someone tried one, and didn't like it, I'll buy it from you. I've always wanted to try one in something fast.

phmaximus

No doubt that would be a better way to gain power.... But that's boring...

Barracuz

But then you have the added weight and higher fuel consumption.

Boost is the replacement for displacement. Lol.

Weather permits I bought a air mattress inflator off the clearance rack from walmart and I shall try it on a couple of engines. Will also try to get a buddy lend me his cfm meter

Gotta start somewhere.

phmaximus

Now ya talking.... I know a lot of people will say it's a wast of time but it's all in good fun...

if it's true and we apply the bucket theory (u can fill a bucket even tho it has a hole, u just need to add more than what's leaking)
and the theory of... as boost increased the force of the exhaust pulses increases.

there should be a real good chance of keeping a positive charge within the combustion chamber.... I mean, we know there is technology around that will produce more air flow than the motor. So it's safe to say it's possible to boost a nitro at the throttle plate. But the big question is how much boost is it going to need to get that charge through the crankcase up the ports and into the combustion chamber.

i think there is a real good chance... If u think about it, the high pressure will be at the throttle plates, as soon as the crank turns that Pressure is going to dump into the crankcase by the cranks port opening and the piston moving up. As the piston moves down, the crank port closes and side ports open, the charge moves up the ports into the combustion chamber. At the same time there is a shock wave of exhaust gasses that have just bounced of the end of the muffler that are heading back up the header. This shock wave crashes into the charge of boost that just entered the combustion chamber, this creates a very high pressure spot right at the exhaust port.
On a Na engine this pressure spot is enough to hold enough of the fuel it mix into the combustion chamber.
So my thought is....the exhaust pulse should increase in force with boost, because of the increased exhause flow.... Also under boost the pressure of the fuel air mix in the combustion chamber is a lot higher than normal you would need to gradually and slowly build up boost.... Otherwise, if u were to build up boost to fast the pressure difference from the pluse to the combustion chamber might be to great and u will lose a lot of boost out the exhaust


i think the biggest hurdles are going to be the fuel system and introducing boost without introducing heat

i think the only way these basic carbys will ever work is with a draw through setup. That way they work like intended, they increase fuel flow with either throttle input or Venturi effect.
in theory the boost shouldent upset the Venturi effect too much but I have this gut feeling it will...
Something alone the line of yes there will be enough flow for the Venturi effect so in that regards it should work but the air is going to be a lot denser. And there is no way for the carby to increase its flow for denser air.....hence why nitros need tuning in different weather

then for adding boost with out heat. With a draw through setup u cant really run any type on inter cooling. The intercooler it self will attract small particles of fuel and endentially flood the engine....
And then say if we're to use a draw through setup with a ducted fan. The fuel air mix will have to pass through the fan potentially causing a fire...so in a way it needs a centrifugal air pump so there is no chance of the fuel/air mix coming in contact with the electric motor

somethink like this??? I wonder if u could fit a high KV brushless motor?? And have its esc pluged into the throttle with a y adapter?

Argess

"Fun" ? Absolutely the best reason!

Oh, and there's more than just the bucket theory. As you may know, our little engines develop more power at sea level than at high altitude. Denser air means more oxygen, so we add more fuel, maintain a good mixture and develop more power. Denser air comes for the increase of atmospheric pressure at Sea Level compared to higher altitudes.

Just to throw numbers at it, air presure at sea level is about 14.7 psi. At 4500 ft up, it's about 12.5 psi.

So... this means if we added a supercharger that created 2.2 psi of boost to an engine at 4500 ft, it would increase in power to the same as if it were running at sea level.

This leads to the question of what happens when we add boost of 2.2 psi to the engine while at sea level. No doubt in my mind there will be more power yet again.

From what I understand, the drop of power at high altitudes is fairly significant (according to some research concerning the airplane guys... their altitude being in the mountains, not the height of the plane). So why not aim for a supercharger that can supply double that, say 4 to 5 psi?

You had asked about cfm. For larger (full size automobile) 4-stroke engines, one rule-of-thumb is 1.8 to 2.0 cfm for every cubic inch of displacement. Seems to me one would need to double that for a 2-stroke. So for a 0.21 engine, the carb would draw approx 0.8 cfm. More would be needed once boost was added. If the pressure is going up 4 psi (from 14.7) that 27% increase might mean 1.02 cfm is required.

Oops... and as our little engines run about 4 times faster than an automotive engine, maybe we better increase that to about 4 cfm at 4 psi for our supercharger spec.

At this point, I admit to getting into things I'm not sure of when it comes to cfm/pressure relationships and how to design a fan that would output that cfm at that pressure at an engine driven (high) rpm, but it might help as a starting point.

sdfhsyth

I just wanted to know do you think i could get the parts to make a supercharger for my RS4 3 EVO. and how expensive would it be for me to just buy a supercharger?????

dfhhv

putting a super charger on a 2 stroke would definitely lower the power of the motor, first of all it does nothing but push air through the exhaust, it adds weight, and is belt driven, so it putting drag on the motor. completely pointless and a waste of money.

Anthoop

There is a member on the forum that tested a simple ducted fan...think he is called ziggy12345 here...
https://www.youtube.com/watch?v=0EziHOHBqAw

I do not know how much air a fan that size could move?

phmaximus

I still don't see that working with out leaning out....and it's all wrong lol

The biggest thing that's going to be effected is the air density, the air flow will increase too, but that's no problem because the carbys Venturi will supply more fuel as the air flow increases... But as for the density of the air there is no way for the carby to meter that. As soon as the air gets denser, it's going to lean out, and the denser it gets the more it means out....

Is is that a HoBao Hyper 10?

Anthoop

I agree...

I do not know what car it is...did not even look...just I can remember that video...send him a message on here and he will tell you what car...his name is Tony...he runs Rossa (the RC speed thing).
http://rossa.org.uk/

Argess

Brent Davis (a well respected engine guy and a member of this forum) says this about his video below:

My Revo with a RB supercharger and YES it worked for me, no matter what others say.

https://www.youtube.com/watch?v=SvEZN9KXTko

Snake0311

what did you use for the turbo exhaust and how did you mount it????

DieHarder

Snake0311