i might say nova base engine is more reliable. go to os tz thread to have more info about the engine

i havent try N12LL3 but i have N12LL5. tuning is not that difficult. easier than the previous nova. it's a long stroke engine means for high speed power. spend some time n patience on the break-in and running-in to get the max power n life span

need somebody to explain about the ventury at the carb air intake. there's several size (5.4mm, 6.5mm) and how does it works. i normally run without install it.

VENTURIS

Internal combustion engines require three things to produce power - fuel, oxygen and heat -- and they need them in specific ratios. Running in situations in which the air is denser (contains more of oxygen) an engine produces power with ease. In situations in which the air is less denser (less available oxygen), an engine will not be able to burn as much fuel as it does at higher density air situations. Less fuel means less power, and that means slower speeds.

What can you do to minimize the effects of less denser air. Compression creates power, and when the air is less dense, there is less fuel/air mixture available to compress.
To recover some of the lost compression, you can use a fuel containing a higher percentage of nitromethane, or reduce engine-head clearance to increase the compression ratio.

To compensate for less density air, you need to adjust your needle valve to a leaner setting to maintain the proper fuel/air ratio. The opposite is true for higher density situations. The idea is to maintain the optimum ratio of fuel and oxygen by adjusting the fuel volume to compensate for ambient air pressure.

Now, if you have the appropiate compression, and still need some more fine tuning for lower density situations, that is where the different sized Venturis come in handy.

A venturi such as a model engine carburetor's works on the vacuum principle: as air rushes through the venturi, it accelerates and creates a vacuum at the spraybar. This vacuum draws fuel from the spraybar and fills the crankcase with a mixture of air and atomized fuel; at very low density situations, less air accelerates through the venturi and past the spraybar. This reduces the vacuum at the spraybar, so less fuel is drawn through it, and the mixture becomes too lean.

There is a way to compensate for this: Switch to a venturi with a smaller area.

When you have a smaller venturi area, the airflow velocity through the venturi is increased. This also increases the vacuum at the spraybar, which, in turn, draws more fuel.

Obviously, you have to experiment to learn which combination size of Venturi best suits your model, and ambient situation.

AFM

thanx a lot afm.

AFM : I thought removing 5.4mm restrictor actually should increased power ? Because more airflows are less restricted going into the carburetor. I should remind you the diameter below or underneath the slider is narrower ( maybe 4mm dia. and this is the point where the airflow acceleration begin ). While the diameter at the opening hole is wider, ( 6.4mm or 5.4mm ) So 6.4mm venturi ( without 5.4 restrictor ) it allows the engine to suck more air and thus produce more power.

BTW, Xtreme RC Cars, March 2005, page 170, article " Can I get some power ? " have engine dyno data confirming with or without the restrictor.

With restrictor ( 5.4mm ) : 0.45 HP / 21.000 RPM

Without restrictor ( 6.4mm ) : 0.60 HP / 22.000 RPM

Sorry Sir, you got it wrong this time :smile:

No i didn't. If you read carefully, the question was how do Venturis work, not if they give you more or less power. That is another issue. I've just explained how and what they do.

And your statements and figures from Xtreme magazine are valid for the ambient conditions on where they did the tests. If you take that same engine to higher altitude (lower air density) you'd be surprised that it will have more power with a Venturi than without one.

Another consideration is that for legal sanctioned races you are limited to 5.5mm (IFMAR/ROAR) and 5.4 (EFRA)....so what is the point on having engine figures without restrictors...on the other hand you should learn to tune your engine according to your local weather sistuation using different sized and shaped Venturis within the rules by which you race.....sorry no hurt feelings, but it is you who has it wrong.

Bye
AFM

AFM : peace man :smile: ........ Instead of killing each other.... let me write these:

I know you are the expert and you always make very good explaination about things.... including how venturi works.

I made that comments because you wrote these : "There is a way to compensate for this: Switch to a venturi with a smaller area. When you have a smaller venturi area, the airflow velocity through the venturi is increased. This also increases the vacuum at the spraybar, which, in turn, draws more fuel. "

Mie3R or even myself take the words "Switch to a venturi with a smaller area" , "increases the vacuum at the spraybar" is something like : "5.4 venturi is better than 6.5". This is not true if I compare it with the article in Xtreme RC Magazine. Moreover Mie3R live in Johor, low altitude city ( in this case, he is correct NOT to use the 5.4 restrictor, but at the same time, his engine will be illegal under a sanctioned race ).

Of course at the end, you also mentioned the word "ambient situation" and that part I didn't read it....... hehehe :D.... :blush:

Anyway, Mie3R ? How's Malaysia ? I'm from Jakarta..

Peace on you too.....just clarifying the issue.....yes i said "Switch to a Venturi with smaller area......"....but in the context of the whole idea

........at very low density situations, less air accelerates through the venturi and past the spraybar. This reduces the vacuum at the spraybar, so less fuel is drawn through it, and the mixture becomes too lean.

There is a way to compensate for this: Switch to a venturi with a smaller area.

When you have a smaller venturi area, the airflow velocity through the venturi is increased. This also increases the vacuum at the spraybar, which, in turn, draws more fuel.

Now let me give you the practical track proven results with different sized Venturis on legal sanctioned races:

Smaller Venturi will give you more top end at the expense of loosing some bottom end...and also fuel consumption increases a little.
Bigger Venturi will give you more bottom end and a little less top end...and a little less fuel consumption.

There you have it...

AFM

Forgot to add that these findings are at sea level (hugh density situations):

Smaller Venturi will give you more top end at the expense of loosing some bottom end...and also fuel consumption increases a little.

Bigger Venturi will give you more bottom end and a little less top end...and a little less fuel consumption.



AFM

afm

i have a ns3 and the middle needle has been moved and the motor runs pretty good but it runs hot, 270 and higher sometimes on hot days. i know if i get it tuned right i'll get more speed at a lower temp. how do i get the carb set back to a more default setting

Best thing is to place so called mid range needle back to flush with the carb's body, then adjust your low and high needles accordingly (I guess you know how to by now).

I asume you have your head clearance set to the Nitro contents of your fuel.

So what is left is to have the appropiate glow plug. (I asume you are using Turbo plug). It is unbeleivable how sensitive this engines are to wrong plug selection.
If where you run has 70% or more humidity, you need to use hot bodied turbo plug I.E. Novarossi C7TGC...but if humidity is below 70% you need to put a cold body plug I.E. Novarossi C7TGF. It is like night and day how engine temps will drop when using correct plug type.

I personally use a Casio digital table Clock with humidity and temperature readings. In the mornings humidity in my track is about 62%, so I use cold body plug. In the afternoon humidity is like 82% so i use hot body plug. If I don't do this change, my engine temp just goes wildly high in either case.

Of courdse i am asuming you have the correct gear ratio also, because if you are using a longer ratio than your track allows, you are forcing the engine and it will also heat up.

AFM

thanks alot, have u ever seen a ns3 with a standard button. it has a standard plug in it but i will have to check my selection. (cold/hot)

20% nitro with stock shims i beleave. i think its just my lack of tuning knowledge. what is a good running temp for my motor, it has been in the 90's almost every race day and 115 track temps, very humid but i dont know exactly how humid

ns3
 

i took the head off my ns3 and i have no shims and a oily build up under there, can i find the right number of shims on the nova site? and its a standard button, is that wrong?

Gent. Yes i have, don't worry. it is better for you to have a standard plug if you are still learning.

I'd suggest you put a Novarossi 7G or a Mc Coy 9 for 20 % Nitro and just leave the aluminum shim (0.30mm). Takae off the copper shims(s). If you look closely therea re shims on that head, you jaust think there are none because they are so thein and you are probably looking at at the almunum one and think there's none. Take an Xcto knife and try taking them out and as I said just leave the aluminum one.

AFM


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