Henry William French

A couple years ago I tried to a performance test on different nitro percentages using my OFNA ULTRA MBX which has a OFNA Hyper 21. No it isn't the 8 port version but anyways I found that with the 35% fuel my engine would turn much more RPM than the 20%. Also with the 35% I could not get the same low end punch as with the 20%. Of course I was tuning the carb needles properly and warming it up and such. I liked the 20% for offroading and 35% for the road. With the 35% nitro, I would have to lean the high speed needle to start it each time and as it warmed up I could richen it up again for performance. Fuel economy was also worse with the 35% as I said it needed FAT settings. I tried to be as acurate with my test as I could but I ain't no Mythbusters. Anyone else have this experience? Seems some people think more nitro means more power across the board.

dicko

did you just add nitro to an existing fuel? if so you oil content would have also changed & made all your results scewed.

i mix my own fuels and have messed with oil contents as well as nitro contents. running more nitro will also lower the temp your engine runs at. using different types and amounts of oils will also play a huge part in engine performance and temperatures.

Henry William French

Yeah, I dumped the fuel out of the tank each time I swiched. I didn't empty the fuel lines or play with the oil content. I was using Odonel fuels. You mentioned oil content, I believe higher oil content adds to people trying to lean their engines out too much. Someone here posted that I think and made lots of sense. Higher oil gives a little less performance which makes it seem rich then they try and lean it out to get the power back... get it? What do you think??

SManMTB

The only thing I can say regarding nitro is this:
More nitro = more power, higher fuel consumtion and more broken engines . But it was fun.

This is based on RC boat racing with nitro blends from 5 to 60%.

dicko

by my comment above i wasn't asking if you drained yor tank, i was asking if you had a bottle of fuel as a base that you were adding nitro to, or if you had 2 seperate fuels with the same oil content and the only difference was the nitro - methanol ratio. this will make a difference.

if you add oil you need to richen the needle, oil isn't there to be burnt, it's there to lubricate, so when you add more oil to your fuel you need to still get the same amount of combustible fuel for the airflow, so you need to richen your mix.

adding nitro to your mix also widens your tuning band & makes it much easier to tune your engine. but as SManMTB said above, more nitro tends to end in a thinner wallet.

Unbreakable207

My Feedback: (1)

I will only run 33% top fuel, it's super good stuff, and it keeps your engine very well lubricated. The thought that higher nitro content equals less life is a common misconception, as long as you buy suitable fuel, your engine should last just as long as it would with any other nitro content. Many engine modifiers back this up, and they know engines.

SManMTB

I'm not saying 33% reduces life because it doesn't. When you go up to 50% you might run into problems with broken rods and stuff just because you are making lots of power. It doesn't wear the piston/liner faster.

Unbreakable207

My Feedback: (1)

Yep, exactly. Oil content is also crucial, fuels with less oil are going to make your engine more prone to insufficient lubrication.

Henry William French

I had 2 seperate bottles of nitro fuel. I still think high oil content encourages over lean settings. More oil is not an answer to anything.

Reindeer

My Feedback: (25)

One thing that could also be skewing the results is switching back and forth between nitro content. Different nitro content means different heat content which means a different rate of expansion, and therefore different wear characteristics. That's why when increasing the nitro content, it is not recommended going back to the lower percentage fuel.

SManMTB

[sm=confused.gif]
What are you talking about? Different rate of expansion..... of what?
Could you please explain more?

Reindeer

My Feedback: (25)

Thermal expansion of the sleeve and piston. Increased nitro introduces more oxygen into the mixture, which in turn means adding more fuel to compensate. More fuel means more heat, and the additional heat will cause additional expansion of the metals in the combustion chamber.

SManMTB

Yeah and how exactly is that related to nitro content?

Piston/Liner expands exactly the same amount for each degree the temperature is increased no matter what nitro content you run.

Reindeer

My Feedback: (25)

A given quantity of fuel contains so many BTUs/calories of energy, right? When you increase the quantity of fuel being burned, you increase the amount of energy being consumed at a given time. The energy being released is in the form of heat.

SManMTB

You can still run your engine at 240F with no Nitro.

The Nitro content has nothing to do with how much the piston/liner expands. It's about the temperature, nothing else. That's why the statement 'That's why when increasing the nitro content, it is not recommended going back to the lower percentage fuel' is wrong.

Running your engine at 240F (for example) with 30% nitro will cause the same expansion as running it at 240F with no nitro. Going from high to low nitro content is not going to change the rate of expansion.

dicko

i've got to agree with SManMTB on that one, if you increase your nitro you'll actually reduce the temp of your engine if you keep the same oil content (nitro has a lower ignition point), as long as you keep your engine in the recomnded temp range you'll be OK, heck my engine temps vary more depending on the ambient temp & climate changes than it does on nitro content.

Reindeer

My Feedback: (25)

First Law of Thermodynamics: Total energy output is equal to the amount of heat supplied.

Second Law of Thermodynamics: It's all gotta go somewhere

SManMTB

Yup, it's just that the energy you supply with nitro is not all going to be converted into heat, you forgot the mechanical energy that actually moves your car forward.

JJJEEEFFFFFF

A higher nitro content normally runs cooler 'cause there is more unburnt fuel going through the engine taking the heat out. But in saying that if you increase the nitro content you normally run cooler there for the piston/sleeve expands less and wears in a different way. its not a bad thing to change nitro content its a bad thing to run your motor at different operating temps. If you've run it for 6 gallons at 300 you should keep running it there, 'cause its to late to change it to running at 240.

just my 2c

dicko

that's why you should run your engine in with the fuel you intend on racing with.