MasterMechainc5

My Feedback: (10)

Im a tech at hobby town and iv heard people say that the higher the nitro content the cooler your engine runs and also that once you use 30% nitro in your engine you shouldnt run 20% because your engine wears in differently and will run like crap if you go back to 20%.
I think that nether of these make sense the first one because the higher nitro % your fuel has the more power it makes and more power = more heat and the secound one i think as long as you retune your engine after switching back to 20% you engine should run fine[8D]
So what do u guys think is this stuff myths or fact?

ThunderbirdJunkie

My Feedback: (3)

nitro content doesn't really affect running temperature. oil content affects that, mostly because any extra oil in the fuel will displace methanol. methanol is the cooling agent in nitro.

MasterMechainc5

My Feedback: (10)

but oil reduces friction so wouldnt more oil = less heat?

amec

I have found using 30% i havent gone looking for the last little bit of power to be had by leaning the hsn. Therefore running cooler.

l3asher

Running 30% gives you more compression which equals more power. The P/S expland more so thats why they say dont go back down because with 20% you will not get as much explansion.

ttoks

when you run 30% nitro you have to add a shim to lower the compression so that you don't stuff the glow plugs, so you dont get more power from that.

when fuel is combusted roughly (and i use roughly very loosely as it depends on the mechanical efficiency of the engine and the efficiency of the exhaust and cooling systems) 1/3 of the energy stored in the fuel gets lost to the cooling system, another 1/3ed get's lost in heat out of the exhaust, and the other 1/3ed get transfered into usable mechanical energy.

(gasoline engines typically get around 20-30% efficiency, diesel can get from 25-45%, and triple compound steam engines have been known to get up to 85% efficient, engines running on methanol are known to get around 25-35%)

so logically thinking, higher nitro % means more total energy and therefor more heat.

the only way changing fuel will effect the performance when switching back is if you run the engine to cold and it wars down the piston and sleeve more then it should, that is purely user error, nothing to do with the fuel.

ThunderbirdJunkie

My Feedback: (3)

no, because AGAIN, methanol is the cooling agent in nitro fuel. pay attention oil doesn't combust as well as methanol or nitro, and methanol evaporates rapidly, too. all extra oil does is make your truck messier and run hot.

black mamba

Yes, the higher the nitro percentage, the greater the heat released. More nitro means a bigger, hotter bang inside the combustion chamber. This heat is a result of increased cylinder pressure, and that is what gives you the power increase. Nitromethane is a oxidizer, just like nitrous oxide, and they both make their power from increased cylinder pressure, which is a byproduct of their combustion. This is why you have to richen the mixture when running higher nitro content........the nitro itself can't make additional power without additional fuel-same goes for nitrous oxide. When increased cylinder pressure is present, you have to retard the timing and run a colder plug to avoid detonation. This is why you have to run a colder plug when going higher in nitro-it retards the timing and dissipates more heat so everthing stays zen in the chamber. Most all nitro big blocks these days are designed to run on 30, so no shim removal is needed. On a small block, removing a shim is mandatory.

No, you shouldn't switch back and forth between higher and lower nitro content. Pick a level and stay with it for best longevity and performance. If you need or want to, only go up, never go down. Why? Because of the differences in heat production. This alters the sleeve and piston fit, enough to where if you went from 20 to 30, the engine (piston and sleeve) is actually breaking itself in again on the 30. This is why it takes a couple of tanks to "feel" the increased performance/effects of the 30. Don't believe me? Think about it. If your sleeve and piston are now fit for 30, what do you think happens when you drop down?

Codeblack

this makes all the sense now

myrcsupply

Im with you on that one. thats been my take on it for quite a long time. good oil amounts prolong the engine. Although iv heard the argument that noobs have a harder time tuning with the fuels of higher oil content. iv not had an issue with our customers.

However methanol also acts as the cooling agent. so without actually testing it (which im thinking about doing) im really not sure on that one, but im really interested to test it out.


now for your myths.

I feel the same way, i have ran a few 30% fuels in my engine, and also went back to 20. with no issues. just a retune. sleeve and pistion looked brand new.

from what i can see with those that have had issues, and claim that they believe it was them running a 30%. it seems that they are running the truck too lean, or not keeping the filter clean enough. becuase im always finding bad scaring on the sleeve, and i cant jump to conclusions saying that its nitro % being the root cause, becuase where as my engines always do fine.

azzman

IMO no, in the sense that your engine can only use so much oil for lube then the excess is just being a pain in the ***. Look at it this way...when you wash yourself (assuming you do ) you put on some soap and lather up...not enough and you dont get clean...too much and it just turns into a horrible soapy mess, and your no cleaner than when you used the correct amount.

ThunderbirdJunkie

My Feedback: (3)

oil DOES NOT cool the engine, in any way shape or form. run a high oil content fuel and a low oil content fuel back to back without a retune, and note the temp DECREASE when you go back to the lower oil content.

MasterMechainc5

My Feedback: (10)

oil is a lubricant which reduces friction, friction creates heat therefore oil does cool the engine by reducing friction[8D] If you dont believe me go run your engine on straight methanol and nitromethane you will have a seized engine in a couple minutes[sm=wink_smile.gif]

SpikeX

I believe oil does cool the engine, when you have the right amount. Too much oil content bogs the engine down, which brings the temps back up again. So the trick is you need the right amount of oil, not to little, not too much.

ttoks

oil is hot when it exits the exhaust because it has absorbed some of the heat in the engine, oil does help cool the engine, but methanol is more effective.

the only thing that effects the fit of the piston and sleeve is the temp, if you run at similar temp it doesn't matter what nitro you run, or if you switch from more to less nitro, temperature is key not nitro content.

black mamba

Combustion temps are DIRECTLY affected by nitro content. Increased cylinder pressure DIRECTLY affects combustion temps. Both go hand in hand here and they are all directly proportional to each other. Believe it.

MasterMechainc5

My Feedback: (10)

Yup, i agree completely oil is still needed to cool the engine (methanol too) but when there is too much oil you are bogging it down increasing the load and therefore making your temps rise Also nitro content effects engine efficiency and temp, more nitro = bigger bang = more heat and performance[8D]

CWC

Its called diminishing return once you have added enough oil (about 8%-12%) you are now simply replacing the cooling agent (methanol) with oil, now adding more oil will not remove the "rest" of the friction but simply displace methanol!
More nitro = bigger bang = more heat and performance, Yes probably but more cooling agent. I stand with 46u, TBJ and gravediggerracing also I HAVE done the back to back runs with hi oil content (16%) and lower oil content (8%) and I saw about a 40 degree drop in temps when I went to the 8%oil fuel.

All4_Nitro

i believe oil reduces heat by small ammounts, and methonol reduces heat more than oil... nitro makes your bang. so running 30% nitro and 18% oil would only make an exaust mess and kind of boggy engine... running 30%nitro and 12% oil would make a bit more sense with a slight lower temp at idle speed... =less mess and more power!!! plus the cooler motor, but!!! oil does cool the motor BUT!!! this dosent mean the more oil the cooler.cause a bogged motor means a heat factory[:@]... so if you run just enough oil to lube the motor and 30% nitro and then let the methonol do its cooling job then you should have pretty good fuel.[:-] although you have to know how to tune correctly or otherwise you can kill a perfectly good engine... heed my advice...lol

black mamba

Keep in mind that methanol is a fuel, not a cooling medium and neither is the oil-which is a lubricant. They both cool to a point indirectly, but their main purpose in a engine is not for cooling. Methanol's characteristics just happen to allow engines to run cool. Oil extracts some heat from the components it is lubricating, but in a 2 stroke where there is no oil pan to hold and cool the oil, nor a oil pump to circulate oil, it's a moot point. Back to methanol. It's why all 1:1 drag cars, monster trucks, etc that run on methanol do not need to use cooling systems (radiators, fans, etc) like a gasoline or racing fuel (gasoline based) powered engine would have to. That's also why RC engines in conjunction with a heat sink cooling head can "maintain" a running temperature without burning up/overheating.[8D]

ttoks

yes combustion temp is directly affected by nitro content, that is the point of tuning, but since 30% nitro give off more energy, and therefor more heat when combusted, that means that the piston sleeve expands more then with 20% nitro fuel, therefor less of the piston and sleeve would have to be worn away to break the engine in, so if thats the case then your logics would sugest that it is okay to switch to a lower nitro content fuel, but not back up to the higher percentage, because lower nitro fuel produces less energy, thus less heat and so the piston and sleeve expand less, so when the temps rise in your theory due to using higher nitro fuel, there would be a gap between the piston and sleeve because the sleeve would be expanding more.

the temperature at the glow plug, in a correctly tuned engine running whatever nitro percentage, is what is important, in a correctly tuned engine this will be similar weather running 20% fuel or 30% fuel.

so either way this would mean that your assumptions are flawed weather it be that nitro content effects the fit of the piston and sleeve, which it wont running just 10% difference in nitro content, you may notes maybe a 20 degree increase in temperature, but that isn't enough to cause a large enough change in the expansion of the piston and sleeve to effect performance or engine life (as long as the temperature is kept within the recommended operating temperature), but if it did it would mean running higher nitro content would shorten your engine life, bu it doesn't effect it enough to be a major factor in engine longevity.

nitro content, if anything will effect the power band of the engine by the exhaust gases being hotter and thinner which increases the speed of sound moving the optimum RPM for that particular pipe up a few thousand RPM.

amec

This thread was getting boring until your post ttoks.

All4_Nitro

well ttoks is right... or i should say i like his theory.

DaveG55

Good greif!!!
Theories, ideas and opinions are worth about as much as the myths themselves.
The only two people that have posted in this thread that claim personal experence have been totally ignored. One said that 30% fuel DID make his run cooler and the other said that his ran 40% cooler with lower oil content.
You work at a hobby shop for goodness sake, buy three or four quarts of fuel with different nitro and oil contents and try them for yourself. Then post the results. That would make for a useful thread rather than this crap of people pissing back and forth about whos opinion is right.

munro300

Amen.