tag-RCU

My Feedback: (1)

What is the difference in running 10% or 20% fuel? Is one more tunable than the other? I have a 2.5 T-Maxx.

Thanks
tag

ManicMechanic

You should break your truck in with 10%. It contains more oil and will protect the engine more during the break in process. The more nitro a fuel has, the hotter the engine will run, and you don't want this while your breaking it in as it could cause damage.
I've just finished breaking in my ofna hyper .21 on 10% nitro, I've run a gallon through and now I'm going to 16% nitro. I'll keep you informed of any changes if you want.
Mat.

packfan88

My Feedback: (2)

you used a whole gallon of 10% to break it in?

ManicMechanic

I could only get it in gallons, so yeah. I only use it for bashing and at the time, the shop I went to only had 10% or 25%.
I've got a gallon of 16% now.
Gonna try that when I can get hold of a hitec 645/945 servo.
They are like rocking horse poo in the UK!!!

bigbadbowtie

How do you know the 10% had more oil content???
Most of your CAR fuels dont even list oil content???

Just asking?

Manufacturers suggest breaking in your car on the fuel you re going to run.

ManicMechanic

Err, it gives the oil content on the side of the can. I'm in the UK don't forget and I buy a regional hobby shops own brew.

bigbadbowtie

aaahhhh.. see here in the US.... 75% of the Car fuels don't list there oil% on the bottle. Its Like some BIG secret....


Im sure another cat is being killed as we speek.(inside joke)

Madd_Maxx

Have you ever tried any of the morgan fuels ?? I have tried several brnads of fuel: top fuel 10% - trininty monster horsepower(can't remember the %) - wildcat 15% - cool power 15%.
Trinity wasn't to bad but I had problems getting it dialed in with it. Top Fuel ran ok but after-run oil was a MUST as it seemed to corrode everything inside the motor without it. Wildcat was a VERY BAD PURCHASE it ran hot - major tuning problems and killed TRX motors FAST (just over a gallon)!!
I came back to cool power 15% by morgan fuels (15% nitro and 18% oil) it's the first fuel I ever tried over 2 1/2 years ago with my first generation T-Maxx and it's been the best fuel for all around use for me. It runs great in my planes as well as in my 2.5 rustler and 2.5 T-Maxx.....not to mention alot of hobby shops here carry it for the airborn r/c crowd.

Did I forget to mention cool power is CHEAP....$12 bux a gallon -vs- the 20+ a gallon for any of the car fuels. Some people suggest not to use plane fuels in cars I don't agree with this idea at all (just my opinion on this....don't flame me for it) the old trusty TRX .15 ran in my first generation T-Maxx for over 9 gallons without a rebuild or bearing problem.....untill all those donuts on wet concrete finally killed it. THAT WAS MY FAULT not the fuel I was using at the time or the motor !!

Sorry for the long post I seem to always get carried away once I get started !!
Madd_Maxx

pirate man

I have to agree w/ madd maxx. I fly helicopters (raptor 30) and use the same fuel on my pirate monster hyper 21 w/ no problems, so far 4 gal and runs like a charm. 20% synth oil 15% nitro. I know it's higher than rc car/truck fuel and plane fuel but I can run it a little rich for the extra umph and still run cooler due to the higher oil %. plus it runs me 15$ a gal. I'm eventually I'm going to 30%. I'll see how that goes on the hyper .21 8 port. I asked the lhs, why cant I use plane/heli fuel and they say the carb holes are to small for the oil %. that it can glog it . well no problems yet. and for the price on rc truck/car fuel I think they are trying to push the more expesive fuel !!!. so if in doubt give it a try. 4 gal on my hyper 21 w/ no problems. JUST MY 3 CENTS.

cowboysfan
(GO SPURS)

bigbadbowtie

I like Morgans fuels too but I pefer to run the Omega because of the casdtor synthetic mix. The castor has around 200 higher burn point than that of synthetic. I like the idea of added protection during a lean run.

bobjones

My Feedback: (1)

i wouldnt switch between nitro percentages after break-in. The point of a break-in is to get your piston and sleeve mated and to get your engine used to the fuel. You should always break-in your engine with the same fuel you plan to drive with. Specifically, the TRX 2.5 doesnt need any special fuels during break-in as stated by their DVD. Just stick with what you run.

Also, i would use the 20% nitro. It offers a lot more power while still giving you the even wear and long life of weaker fuels. The duration ends at 20%. 25% is better suited to racers who use multiple engines and have a larger budget to work with. Once you go over 20%, be prepared to see a lot of power and spent a lot more time buying new pistons and sleeves.

bigbadbowtie

Bobjones

I switch between fuels all the time. In fact I emailed OS engines about this same subject and they said all you need to do is tune it to the new fuel.

As far as Higher nitro % causing more wear. My experience says different. With higher nitro%'s you can run the engine at a richer setting and still make gobs of power. A richer setting wil provide more fuel,more fuel = more lubrication. I saw no difference when switching to 30 % as far as temps go. I did get a HUGE gain in power. I have 6 gallons of 30% through my current big block and it still screams.

bobjones

My Feedback: (1)

Well, that just goes to show you how different engines are. I just prefer to stcik with my fuel and 20% always gave me the performance I needed.

P.S. Traxxas urges owners of the TRX 2.5 to stay with the same percentage, so it probably is just a difference in engines.

Ledgendary

This article appeared in
the premier issue of RC Nitro.
This issue is no longer available.
The topic of RC nitro fuel sparks intense debate: how much nitro should you use? How much and which type of lubricant should the fuel contain? Will you get more power with fuel that has a higher nitro content? Can you switch to higher-nitro-percentage fuel without harming your engine? Is it a bad idea to switch fuel brands? These are legitimate questions, and a shortage of information adds to the confusion. I enlisted the help of Jerry Conley of Wildcat Fuels to shed light on fuel-related issues so that you'll be able to make an informed decision when you buy your next gallon of fuel.
Jerry has degrees in mechanical and aerospace engineering from Florida State University. He was involved in the development of fuel systems for the Air Force and the automotive industry and has consulted for the USAF, NASA, Nissan and Toyota. Jerry is president of Wildcat Fuels; his experience in the hobby industry spans 27 years.

The methanol used in most RC fuels is very pure and of a consistently good quality. Methanol is a fuel like gasoline but is less volatile yet produces more power; it also costs a heck of a lot more!

The nitro in RC fuel varies in quality; very pure nitro runs cooler and more cleanly than less pure nitro, and the difference can be significant. RC nitro fuels have a certain percentage of nitro mixed with methanol and lubricant. A gallon of fuel with 25 percent nitro is one quarter nitro; methanol and lubricant make up the rest of the mix.


FUEL BASICS

RC fuels differ most with respect to their lubricants. The lubricant (oil) is essential to keep the engine's moving parts working freely and to remove heat. Lubricants used in RC nitro fuel are either purely synthetic or a blend of synthetic oil and organic castor oil. A coating of oil prevents metal parts from rubbing against one another, and avoids heat buildup and excessive wear. The type, quantity and blend of lubricants in a fuel are the most closely guarded secrets in the business. A few manufacturers disclose lubricant content, but most of them leave you guessing.
Conventional wisdom says the castor oil promotes cooling while the more dynamic synthetic oil protects engine components from wear. Few fuels contain only castor oil; most contain either both types of oil or only synthetic oils.

The flash point—the temperature at which a lubricant will burn—varies with lubricant. Lubes with a very high flash point tend not to burn at all and leave the engine awash in oil. This certainly helps keep an engine well-lubed, but it can cause excessive oil discharge in exhaust. Lubes with a lower flash point tend to burn with the fuel, and this leaves a cleaner combustion chamber for the next cycle.




WHICH NITRO PERCENTAGE SHOULD YOU RUN?

This is an “It depends who you ask” question; in fact, no fuel is ideal for every application. Nor is it a given that a higher percentage of nitro results in better performance. The correct percentage of nitro and its effects on engine performance are rather complex issues, but I'll try to cover the basics. To understand how nitro content affects engine performance, it helps to have a basic understanding of nitro. A derivative of propane, nitro can be considered an oxygenator; suitable as a fuel by itself, it carries its own oxygen component. Nitromethane contains nitrogen and oxygen, which provides more “fuel” for the combustion process; more oxygen allows more fuel to be burned in the same amount of space. More fuel plus more air typically equals more horsepower—much like the benefits a turbocharger or supercharger give a full-size car engine. There is a great deal more technical complexity to nitromethane, but this explains why you can produce more power with it.




NOW, HOW MUCH NITRO SHOULD YOU RUN?

Maximum performance means an engine is running at maximum efficiency with maximum horsepower. The bottom line is that using high-nitro fuel that far exceeds the parameters of your engine may only net a slight gain in horsepower, but overall performance is compromised; so, more isn't necessarily better where nitro content is concerned.

When engineers design an engine, one of their primary considerations is the type of fuel to be used. The compression ratio and the timing and duration of the intake and exhaust ports take fuel composition into consideration. For example, Fedération Aeronautique Internationale engines—popular in model airplane competitions—are designed to run on pure methanol. The competition rules specify that fuel must not contain nitro. Adding nitro to the fuel used in these high-compression engines usually results in poor performance and high running temperatures.

Similarly, RC car engines are designed to run with a certain percentage of nitromethane. An engine designed to run on fuel with 20 percent nitro is configured for a certain compression ratio and a fuel/air ratio that provides ideal performance. Introducing a considerably higher concentration of nitro allows a greater overall amount of fuel volume. It can result in higher compression (air is the only compressible component in the fuel mix), detonation (when fuel explodes rather than burns) and higher operating temperatures. These outcomes show the fuel exceeds the design limitations of the engine. Even if none of these symptoms are patently obvious, combustion is compromised, and that prevents fuel from being completely burned. It can create an unstable idle and erratic fuel-mixture settings. These conditions are common in engines running on higher than recommended percentages of nitromethane. Essentially, the answer to the “How much nitro?” question is that you should follow the engine manufacturer's recommendations.

There is a “window” of about 5 percent both above and below the recommended percentage of nitro you can have in your fuel before engine performance will be noticeably affected. If a manufacturer recommends 20 percent nitro, you can get away with 25 percent. Go beyond that, and you are likely to wind up with an engine that runs hotter, gets poor fuel economy and is more difficult to tune. If your engine's manufacturer doesn't recommend a specific percentage of nitro, you may have to experiment to establish the proper balance of horsepower and efficiency.


CAN YOU CHANGE THE AMOUNT OF NITRO
IN FUEL WITHOUT DAMAGING THE ENGINE?

Yes and no. Yes, you can change the percentage of nitro in your fuel safely, but you must not make a change and run the engine hard right away. Every engine undergoes a process called “hysteresis.” In hysteresis, the engine components slowly acclimate to the specific cylinder pressure and engine temperature that result from burning a particular type and blend of fuel. A change in fuel changes the whole picture for the engine. An engine that is accustomed to a certain amount of expansion using its usual fuel might now have to cope with increased cylinder pressures and the additional expansion caused by higher temperatures. Simply pouring a new fuel into the tank and “letting 'er rip” places undue stress on the engine components.

If you use a different blend of fuel, your engine has to go through a second “break-in.” Run the fuel mixture slightly rich and ease into the throttle for a few tanks before you nail it. If you fail to follow this procedure, your engine will still survive 99 percent of the time, but it will last longer and run stronger if you make a gradual change to a new fuel. There is also a break-in period during which using less nitro presents a new set of parameters for the engine.

STORAGE

Methanol-based fuel is hygroscopic. In plain English, that means it sucks in moisture like a sponge. If you leave the cap off a methanol fuel bottle for a couple of minutes, you'll see moisture accumulate inside the bottle, especially in humid conditions.

Since methanol also evaporates very quickly, it's important to keep the cap on your fuel and filler bottles. Even with the bottle capped, dramatic changes in temperature accelerate evaporation and moisture accumulation. If you have to store fuel, even for a short period, keep it out of the trunk of your car and off the cold basement floor. Try to keep fuel in an area where temperature remains relatively constant. If you must store it in a basement or garage, insulate the bottle from the floor with a piece of scrap carpet or lumber. If you are careful, and avoid conditions that make fuel go bad, you'll be able to safely store fuel and use it up to two years later!

Diesel Racing

Hey Legendary,
I've read you post about fuels and this is the information I was searching for. What a helpful article that you read! Thanks for taking out the time for posting this. I haven't broke in my truck yet, I'm waiting for the mailman! But I went out of my way to buy some supplies and gear, so when he arrives, I'll be ready to go! I was contemplating on what kinds of fuels and %'s and what not! I just so happen to buy some Wildcat eliminator 20% at my LHS! I was really impressed with their website (www.wildcatfuel.com) and how they laid out everything in the open. There's nothing to hide and they talked about the processes about making fuel. They listed every ingredient in the bottle! I was very impressed! When you said that Jerry got his degrees from FSU, then I realized this is the fuel for me! (lol) Basically in fuels, you want to pay more attention to the content and %'s vs. the brand correct? All of the fuels will start a daggum motor, just what will produce the best efficiency in the long run! I could type all day long about this, but i'm gonna save my fingas for my contollers! Thanks again for your input!

sledmanass

My Feedback: (2)

now my hobyy shop when i got my first rc told me to use 20% monster trinity, and that all i have used and its been working great, 20% will also have a little more power then 10%.

diirtbag

My Feedback: (3)

higher nitro content will cool youre motor but make it pull harder therfor shortening its life but thats where temps come in if youre running it over 270 to get the power you want switch to a higher nitro fuel and re tune I have found going from 20 to 25 droped my temp by about 30 degrees and gave a bit more power I know some manufacturers recommend low nitro for break in but I wouldnt buy less than 20 the 25% I buy is 18% oil.you must re tune with different nitro content to achieve proper performance