i am thinking of getting the new mega or the sirio evo 2. has anyone tried both? is either better than the other? also, i heard the carb is no good in the evo and to use a novarossi carb, is this true? thanks in advance.

they are both good engines, I have them both and honestly the mega race legal goes fine against the 5 port evo 2, both carbs are good but with time the o rings get tired, they´re both composite, while the novas are aluminum, some people prefer them, some not. they work fine anyway

Anyone have an idea?

All I know is that it is the plug Sirio suggests for their engines, but i'm not sure if it is the same as the Nova C7TGF or C7TGC.
I think it should be between both, since they don't offer two types of S7. It must be an allround 7 plug.

AFM

Yeah thank AFM, I just want to know if the novarossi gold C7TGF plug is better than the sirio S001720127 S7 plug.
I can readily get the nova C7TGF plugs compared to the sirio plug.

You can't go wrong with the Nova plug....I personally used the C7TGC in all my Sirio and Collari engines (high humidity here), and now keep on using it on my STS D3R with exelent results and reliabilty.

AFM

Anyone think the Sirio Evo 2 5 port will run with an RB Rody 3 port Turbo? I kinda doubt it. I wan't something fast and inexpensive with part support. The LHS does have it I believe for the Sirio, but eh I dunno yet.

sirio evo 2 runs hott
 

i am running a sirio evo 2

my engine runs too hot and i cant figure it out, it is broken in and has good top end, a little slugish in the md range but i cant tell is it because of the temp or not. its running 235-250 degrees in 50 degree weather. when the tepm hits the 90's my motor will be toast if i cant get the carb right, its idles fine and runs good. just too hot. can i get some starting points on all the needles, (my mid range needle is kinda hard to turn).

Guess I won't get the Sirio. My MT12 is doing great now. :)

hey the sirio is a monster motor for the money, it just comes with little directions as far as tuning, there isnt a better motor for the money, just look at the last couple of big races, the motor is a beast im just a novice tuner. OS motors come with step by step info, the sirio's dont. dont take my info as the info to go by just ask around

Re: sirio evo 2 runs hott
 

Gentleman

Your problem is a combination of factors related to glow plug selection, head shim, and weather conditions, which affects carburetion.
For starters these are the base needle settings for the Sirio Evo2. If you haven’t touched the mid range needle just leave as it came from the factory.

Sirio .12/15/18 (General Carburetor Settings)
High Speed - 5.5 turns
Low Speed - 3-1/2 (Generally this should be flush with the end of the slide)
Mid Range - Flush then one turn out.

Now, following are some articles that might help you out understand better what you have to do.

Have fun

AFM

1.- WEATHER MAKES THE BIGGEST DIFFERENCE

The atmospheric pressure, temperature and humidity all affect the density of the air. On a hot day, or at high altitude, or on a moist day, the air is less dense. A reduction in air density reduces the amount of oxygen available for combustion and therefore reduces the engine’s horsepower and torque. For tweaking the fuel/air mixture and compression ratio, the air density is the most important consideration.

Inputs:
The Air Temperature should ideally be the temperature of the air that is going into the intake of the engine.

The Absolute Pressure (also called actual pressure or station pressure) is the ambient air pressure.

Relative Humidity is a measure of how much moisture is in the air compared to the amount of moisture that the air could hold at saturation. Relative humidity is a function of temperature and therefore changes as the temperature changes, even if the amount of moisture in the air remains constant.

The air density is the actual weight of a given volume of air. This is a key parameter for engine tuning.

Resuming:

When the air density increases, you will need to richen the air-fuel mixture to compensate. When the air density decreases, you will need lean-out the air-fuel mixture to compensate.

Use the following as a guide to correcting your setting when the weather changes:

Air temperature: When the air temperature increases, the air density becomes lower. This will make the air-fuel mixture richer. You must lean the mixture to compensate for the lower air density. When the barometric pressure decreases, the opposite effect occurs.

Humidity: When the percentage of humidity in the air increases, the engine draws in a lower percentage of oxygen during each revolution because the water molecules (humidity) take the place of oxygen molecules in a given volume of air. High humidity will make the air-fuel mixture richer, so you should lean the mixture.

Altitude: In general, the higher the altitude the lower the air density. When driving at racetracks that are at high altitude, you should lean the mixture and increase the engine's compression ratio to compensate for the lower air density.

2.- ENGINE SHIM TUNING (by Dennis Richey)

Experience dictates that just by lowering the head (more compression) you gain more power especially in lower rpm range, idle quality can suffer, but the engine also runs cooler . Also, that a higher head (less compression) will increase top rpm speed on bigger tracks.

A decrease in head shims (an increase in compression ratio) will increase torque because as the compression ratio goes higher, the actual ignition timing occurs sooner. However there is a point of diminishing returns where detonation occurs or engine temps can soar, and if this happens a colder plug can help.

A colder plug will also increase torque, except in the instance of a colder plug the ignition is slowed until a greater point of compression build occurs.

When you increase head shims (a decrease in compression), top end is enhanced as the ignition timing is retarded and occurs later. Generally a hotter plug is needed to advance the ignition cycle so that timing does not occur to late in the cycle, but at this point you end up over leaning the engine to get it to rev properly and the engine life will suffer dramatically.

On a .12 engine we would only advise going 0.10mm over or under 0.46mm, so that is 0.36mm or 0.56mm, of total head clearance
Generally on a .12 engine 0.10mm will change the compression ratio about 3/4 to 1 point..

We should also state that the comments with regards to plugs and head shimming are when both are used together. Used alone a hotter plug will rev harder and a colder plug will make more torque.

One last comment. never assume that the head shim that is on the engine is the actual head clearance. in many cases you will find that the engine actually has 0.20mm to 0.15mm without any head shim. Novarossi's are 0.20mm without one, and the factory installs a 0.30mm shim, giving the engine 0.50mm stock head clearance. This has not always been the case but 99% of the time it is. When in doubt measure the head button register and the piston to the top of the liner at top dead center and subtract, to determine proper shim. This is the only way to really know.

You can safely use 30% Nitro on the stock head clearance. Using a C8TGF you can go up to 40% Nitro, and If you don’t over lean it, the engine life will not suffer dramatically.

Someone asked about plug fatigue: plug fatigue can occur under high sustained RPM's, and this is where the plug stays shiny and the wire just fractures for no reason. This is why we have always run Novarossi plugs, as they don’t do this. When this happens it is usually not a carb. tuning or head clearance problem. If you see the wire start to pull out of the hole this means that the engine is scavenging really hard and when this occurs the engine is making serious power.

3.-ABOUT TURBO GLOW PLUGS


Turbo Glow Plugs where designed to give more performance to an engine, for the following reasons:

·It forms an uninterrupted combustion chamber.
·The advantage of better heat transfer or heat dissipation, and a leak proof seal, generated by the conical seat of the plug.
·Greater choice of thermal ranges, that allow for more precise tuning according to variations in weather conditions (temperature, humidity, height, barometric pressure, etc.).

The numbers and characters on the plugs, are the product number, wire thickness, and thermal range of the plug’s body. Example: The Novarossi C6TG (F) or (C)

§ Product: C (Candele)
§ Wire Thickness: 6
§ Plug Type: T (Turbo)
§ Plated: G (Gold)
§ Thermal Range: F (Fredda = Cold)) C (Calda = Hot)

The plugs with cold thermal range F(Fredda), have a body with thinner walls and shorter body, so they dissipate heat better and faster to the engine head.

How to select the proper plug, regardless of Nitro %

·When the ambient temperature is high, we have to use a plug with thicker wire.
·Humidity determines if we use a Cold (F) thermal range, or Hot (C) thermal range.
·With high humidity percentage we should use a Hot (C) thermal range plug.
·If we have high temperature and high humidity, we should use a plug with thick wire and a Hot(C) thermal range.

The best instrument to determine which Turbo Plug to use, is those weather panels they sell for Yachts, that have Temperature, Humidity and Barometric Pressure on them. Have it calibrated at your local weather station. That is the key to success or failure tuning engines with Turbo Glow Plugs, because they are so sensitive to weather variations that is unbelievable.

Following is a selection chart for Novarossi Turbo Glow Plugs

Type Thermal Range Nitro% Temp.C° Humidity%
C5TGC Hot/hot wire 10-20 0-10 70-100
C6TGC Hot/average wire 10-20 10-16 70-100
C7TGC Hot/cold wire 20-30 16-25 70-100
C8TGC Hot/ultra cold wire 20-30 25-up 70-100
C5TGF Cold/hot wire 20-30 0-10 40-70
C6TGF Cold/average wire 20-30 10-15 40-70
C7TGF Cold/cold wire 20-up 16-25 40-70
C8TGF Cold/ultra cold wire 20-up 25-up 40-70

Going with AFM's advice, I am looking at purchasing the Sirio S12 200006 pipe for my WRXLC12PRO3. Does anyone know where I can find these pipes for sale online? The 3 main sites I use in Hong Kong dont list it :(

Any advise appreciated.

Regards
Andrew

mid range
 

does the mid range needle play a big part in engine temp, and are they hard to turn, or is it just mine?

Re: mid range
 

Yes it is hard, and if you start playing around with it you might develop air leakage on that Sirio carb, because o'rings will fail.
But any way I'll explain the best I can, how does the mid range
needle work (actually it is the main jet).

The screw inside the slide body is really the low-end needle, and it plugs into the main jet (the needle in the opposite side called the mid range needle), without closing it completely, to allow a little fuel to pass when the low-end needle plugs into it, to allow the engine to idle.

The dimensions of the jet (mid range needle), its position relative to the venturi, and the dimensions, ramps and shape of the low-end needle dictates the fuel curve of the carburetor (or how much fuel enters by each cfm of air drawn into the engine at a relative carb opening).

At idle speed, the engine is controlled by the low-end needle and how much air passes into the engine via the position of the barrel. But when you start to move the barrel to allow more air to pass , in fact you're moving the low-end needle, allowing at the same time more fuel to pass too.

Depending at which opening of the barrel the jet (mid range needle) is totally uncovered, and the carburetor starts to being mandated by the adjustment of the high-end needle, and how much fuel it lets to pass, rather than being governed by the low-end needle, can be varied, and the power band of the engine too, but slightly, by screwing or unscrewing the jet (mid range needle) and readjusting the low-end needle.

But be careful screwing the jet (mid range needle) too further into the venturi can lead to mix and temperature problems (in fact, you're leaning the mid rpms, where the engine operates at partial opening of the carb, this can lead to problems and erratic operation). THIS IS WHY ON ALMOST ALL ENGINE BOOKLETS THEY WARN YOU NOT TO TOUCH THIS ADJUSTMENT.

The position of the jet (mid range needle), relative to the venturi, changes also the position of where is the vortex of air when it enters into the carb, and varies how much or how finely is the fuel sprayed into the air that enters.
Fuel is converted into a mist for being burned, a drop, no matter how little it is doesn't burn, and can create many and serious problems, like conrod breakage (common), or piston breakage (not common but seen some) due to hydro lock.

There you have it, hope it helps

AFM

Hi,

This is the new Racy exhaust system I be using with my Sirio

http://www.centralrc.co.jp/racy/RTG264.jpg