Spec me a nitro RC buggy....

[SkodaMart]

Better to get it now tbh, you want that engine to get the best while it's running in. 10% will just make it run too hot and you don't want it going much over 200f until it's bedded in. Car engines don't get the benefit of the cooler air that the plane engines get and they tend to go through a bit more abuse.



It's 2wd isn't it? It'll just be the rears locking up and making it spin.

Thanks for the reply.

How does less nitro make it run hotter? You are not the first to suggest this.

Yes it is 2WD, feels a fair bit like a very twitchy Kart.

 

[andy_mk3]

As far as I know, the nitro carries some oxygen with it into the engine. So the higher the nitro percentage, the more oxygen in the engine and the more fuel you can burn, as you'd have to richen up the needle on the carb. So the more fuel going through the engine, the cooler it will run because the fuel cools to engine to a certain extent.

 

[SkodaMart]

Souce, the interweb!

"Hardly a month passes that someone doesn’t call to ask, "I hear more nitro will make my engine run cooler. Is that true?" Nope. The higher the nitro content, the higher the operating temperature. Fortunately, in most of our sport engines, the difference in operating temps between 5% and 10% is negligible, and there are lot of other factors (proper lubrication, etc.), that are much more important."

http://www.geistware.com/rcmodeling/glowpower/fuelfact3.htm

 

[Ash-Lee]

I always assumed Nitro fuel was a mix of fuel and oil/lubricants. (Similar to 2 stroke)

Therefore the higher % of fuel means a lower % of lubricants.

I own a HPI Bullet 3.0 MT with the stock HPI G3.0 engine and it happily runs on 20% mix.

 

[Kenai]

Souce, the interweb!

"Hardly a month passes that someone doesn’t call to ask, "I hear more nitro will make my engine run cooler. Is that true?" Nope. The higher the nitro content, the higher the operating temperature. Fortunately, in most of our sport engines, the difference in operating temps between 5% and 10% is negligible, and there are lot of other factors (proper lubrication, etc.), that are much more important."

http://www.geistware.com/rcmodeling/glowpower/fuelfact3.htm

I would say that goes against conventional engine wisdom where by leaning out the AFR temperature will increase. It is for this reason most cars run slightly richer than the optimum AFR (for power), to keep exhaust temps in check.

Some different interweb disagrees with your interweb about Nitro though:

Question: What are Lean and Rich as Applied to Nitro RCs?

Nitro or glow engines use nitro fuel but it's actually a mixture of fuel and air that goes into the engine. The right air/fuel mixture keeps the engine running at its best. The wrong mixture can cause overheating and vapor lock, excessive wear, or cause the engine to stall. This fuel/air mixing takes place in the carburetor.

Answer: Lean and rich refer to the mix of fuel and air. To lean out or richen a nitro RC engine means to adjust the mixture of fuel and air going into the engine. Lean is the addition of more air to the air/fuel mixture. Rich is the addition of more fuel to the air/fuel mixture.

Lean
When you lean out a nitro engine you are adjusting the air/fuel mixture so that there is more air going into the nitro engine than there is fuel. This provides a little more horsepower but can result in very high engine temperatures. If you are not careful leaning out a nitro engine you could run it too lean. This will wear out the glow plug prematurely or cause engine failure.

Rich
When you richen the nitro engine's mixture you're adding more fuel than air to the nitro engine. This can give you better results for some kinds of races because this method, unlike leaning out, will give you cooler engine temperatures. But if running too rich you can not only bog the engine down and stall out but also flood it and foul the glow plug.

When to Lean Out or Richen a Nitro RC
You might be running too lean if the engine dies while idling, you don't see a light stream of blue smoke from the exhaust, or the engine gets so hot that a drop of water on the engine immediately starts sizzling and popping.

Too much blue smoke or a lot of unburned fuel from the exhaust and an inability to reach top speed are some some signs that you may be running too rich.

How to Lean Out or Richen a Nitro RC
Engine tuning and adjusting the air/fuel mixture involves adjusting the high-end (high speed / engine temperature) and low-end (low speed / idle speed) needles on the carburetor. This is also called dialing in your engine. There are usually base-line settings for each nitro engine that provide a good starting point for adjusting the needle settings. You'll turn each needle in very small increments to lean out or richen the fuel.

Turn clockwise to lean out or add air and counterclockwise to richen or add fuel. The low-end needle controls idling and low speeds. The high-end needle controls how the engine accelerates and runs at high speed and has a greater effect on engine temperature. See closeup illustration of fuel/air mixture needles.

Lean, Rich, and Engine Temperature
You want to adjust the air/fuel mixture so that your engine runs at an optimal temperature which is generally somewhere between 225-250 degrees Fahrenheit for most nitro engines. Much over 250 degrees could cause a lot of damage and also shortens the life of your nitro engine.

Check your nitro engine's temperature often to keep it at optimal temperature for longer runtimes and overall better life for your nitro engine. If the running temperature is less than 200 degrees you need to turn your high-end needle adjustment clockwise to lean out the mixture a bit to get the temperature up a little. If your temperature is above 250 degrees you would bring it down by adjusting the high-end needle to richen the mixture by rotating the high-end needle counter-clockwise. The ambient temperature outside and the elevation according to sea level will adversely effect the nitro engine's temperature so adjust accordingly.

 

[SkodaMart]

@Kenai
Isn't that information you have posted about air/fuel mixture ratio?
i.e. Rich vs Lean?

With aircraft, you always set the needle on the rich side as things lean off as the tank gets lower, also things like flying inverted can cause it to go lean.
If you set the needle correct on the ground, it tends to cut out in the air.

I suspect that cars run high nitro, to improve power and slow running, A car does not have the huge flywheel an aircraft does (propellor) therefore high nitro will help them idle smoothly.

I may be wrong?? But with sports aircraft you can fly with any nitro content that you can achieve reliable running with.
In summer you can even get away with 0%, as aeromodellers tend to have short arms and deep pockets! but generally most use 5 - 10%

I always try to run my engines with the needle on the rich side, I don't mind a slight power loss and this way you ensure good lubrication, which is important when using a sythentic fuel like Prosynth.

 

[Munkyman]

Souce, the interweb!

"Hardly a month passes that someone doesn’t call to ask, "I hear more nitro will make my engine run cooler. Is that true?" Nope. The higher the nitro content, the higher the operating temperature. Fortunately, in most of our sport engines, the difference in operating temps between 5% and 10% is negligible, and there are lot of other factors (proper lubrication, etc.), that are much more important."

http://www.geistware.com/rcmodeling/glowpower/fuelfact3.htm

That's for model aircraft engines though isn't it? iirc, aircraft engines are designed slightly differently to car engines and the fuel made to suit due to the different application.

Manufacturer Recommended Fuel Percentages
When choosing nitro fuel percentages it is best that you first look in the manual that came with your nitro RC. Check to see what percentage is recommended for your specific nitro RC. If the manual doesn't list what percentage of nitro to use, it would be a good idea to ask your local hobby shop what they think, because most of the employees in a hobby shop either have worked on or own RCs and they also have ways of getting the info you may need. There are many different brands of nitro RC fuels out there. There is no consensus as to which one works best -- it's more like trial and error to find out which one works best for your nitro RC.
Engine Size and Nitro Fuel Percentages
One thing to keep in mind (beyond the advice in the manual) is that the Nitro RC engine size does matter when deciding what percentage of nitro to go with.

• Engines that are .12 - .18 generally use 10% to 20% nitro fuel
• Engines that are .21 - .26 or .27 generally use higher percentage nitro fuel in the ranges of 20% to 40%.

 

[SkodaMart]

I can honestly say, I don't know why they state a much higher nitro content for cars than they do for aircraft.

I have asked one of the RC club sages and await his advice.

 

[SkodaMart]

Reply from a guy in the RC club:

"It allows for more power, and also makes tuning easier, it can help with the idle, making it smoother, that way the idle can be set a bit lower which can in some cases mean the difference between the clutch disengaging or dragging. I used anything I could get my hands on, but you should be ok with 10% on a 3.5cc, anything smaller and I use 15% and 20%."