About nitro percentage.

About nitro percentage.
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About nitro percentage. - 4/29/2004 1:57:15 PM

coolguy234

Posts: 140
Joined: 4/26/2004
From: Quatre Bornes, MAURITIUS
Status: offline

Hi Guys,

Can you please tell me what will happen if I run my engine on less nitro % than recomended by the manufacturer? I mean fuel consumption, running temperatures, engine wear and performance, and anything I forgot to mention. The engines are buggy ones and the fuel is homebrew.

Thx.

Post #: 1

RE: About nitro percentage. - 4/29/2004 4:26:22 PM

impactiq

Posts: 800
Joined: 6/1/2003
From: genoa, IL, USA
Status: offline

You will loose performance. Your fuel consumption will go down a tad.... engine wear will wear about the same considering the average car/buggy engine only lasts for 8-10 gallons worth of fuel before rebuilding. Of course the last statement depends on how hard your are on your engine.

(in reply to coolguy234)

Post #: 2

RE: About nitro percentage. - 4/29/2004 6:01:57 PM

Rodney

Posts: 4889
Joined: 12/8/2001
From: FL
Status: online

You will find very little difference at the high end. The idle may be harder to adjust to a low value with less nitro.

(in reply to impactiq)

Post #: 3

RE: About nitro percentage. - 4/29/2004 9:55:52 PM

FlyNBHappy

Posts: 274
Joined: 7/21/2002
From: Peanut Gallery, USA
Status: offline

quote:

ORIGINAL: coolguy234

Hi Guys,

Can you please tell me what will happen if I run my engine on less nitro % than recomended by the manufacturer? I mean fuel consumption, running temperatures, engine wear and performance, and anything I forgot to mention. The engines are buggy ones and the fuel is homebrew.

Thx.

The following is my experience with airplane engine:

Fuel Consumption: You'll get more flying time per tank. I gain about 30-50% running time in .40 size engine, from 15% to 0% nitro, 10 oz tank.
Running Temp: I don't have a temp gun so I don't know for sure, but I'm guessing it is about the same as with nitro or it is minimal in difference.
Engine wear: Since the engine runs at lower rpm, I say the engine lasts longer..... but engine wear is dependent on quality of engine rather than nitro content. Plus nitro rusts bearings, so if you don't use after run oil or there is fuel with nitro left in engine.... more problems.
Performance: Definitely less rpm with no or lower nitro..... but unless you're into racing, who cares about an extra couple of hundreds rpm when you're saving .... see below. I agree that your lower idle will be harder to tune, but who flies at idle anyway.
Costs: Savings of about $4-$8 per gallon of fuel. Depending on nitro content. Once you figure out costs of homebrew, then you'll cry at how much money you've been giving to commercial fuel manufacturer per gallon.
Ease of Homebrew: Methanol & Oil (either castor or syn) are readily available. Nitromethane is costly and hard to obtain (mostly due to federal regulations).
Laughed at by your flying buddies because they swear by 10 or 15% nitro, while you laugh at them for spending more money.

Sorry I don't have any experience with buggy engines. Please let us know how your engine runs with lower or no nitro.

(in reply to coolguy234)

Post #: 4

RE: About nitro percentage. - 4/30/2004 4:35:40 AM

FHHuber

Posts: 4931
Joined: 1/1/2003
From: gone, , USA
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some of the smaller engines that are intended for high nitro have a lower compression ratio than those intended for FAI or low nitro fuels. Some manufacturers include a head shim to put in if you intend to use above a certain nitro percentage...

If its a lower comperssion engine, then the low nitro will make performance abysmal. You'll feel like you are feeding it water instead of fuel.

The engines that list 10% to 20% as the recommended nitro content tend to do OK on 5%. But you will see a loss of power. FAI (no ntro) fuel may not work well at all.

Nice thing is.. if the low/0 nitro fuel doesn't work... get some high nitro fuel and mix the cans... you can use it up that way. Just volumn weighted average the percentages. (3 quarts 20% + 1 quart 0% = 60%/4 = 15% multiply the quarts by thier percentages... add the results, divide by total quarts)

(in reply to FlyNBHappy)

Post #: 5

RE: About nitro percentage. - 4/30/2004 5:25:41 AM

downunder

Posts: 3271
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline

I agree with No2Nitro but maybe it should be pointed out that there's very little difference between a "high" compression (about 11:1) and "low" compression (about 9.5:1) engine. I've yet to find any engine that won't work perfectly well on zero nitro.

But if you read No2Nitro's comment on fuel consumption you can see why the needles are more sensitive to tune. You're controlling a much smaller fuel flow so a 1/4 turn of the needle has much more affect than it does with nitro in the fuel. This lower fuel flow also means a lower flow of oil through the engine and is why I wouldn't use anything less than 20% oil. I've got one engine (ST G51) that's so economical I have to use 25% oil to stop it from overheating.

IMO nitro is only useful for competition use where all out power is needed. At any other time it's a waste of money.

(in reply to FHHuber)

Post #: 6

RE: About nitro percentage. - 4/30/2004 11:28:34 AM

coolguy234

Posts: 140
Joined: 4/26/2004
From: Quatre Bornes, MAURITIUS
Status: offline

Well thanks for the replies. I did run one of my car on 2-3 % nitro with 18% castor oil and didn't see any big difference. It wasn't too difficult to tune my 1st engine and after it was tuned it could stay idle all day, a Kyosho GS.21 on a landmax. It also ran great except that I was beaten by another racer with the same engine but who ran on 20% nitro, but at the end of the day he blew up his engine. I just got a new buggy, an EB4 S2 and I didn't even start break in, I will in November (School Holiday). I gave some races the same fuel to run, most of them run OS Engines here, and they didn't have any problem neither.

To No2Nitro: I'm only 19, and I'm in Nirto RC only since some months, so I didn't yet spend a lot of money on fuel. Don't worry I won't cry even through I realised how much money it's gonna save me 2 mix my own fuel. LOL.

Here is a post to where find nitro:
http://www.rcuniverse.com/forum/Where_to_find_nitro%3F/m_1763637/tm.htm

(in reply to downunder)

Post #: 7

RE: About nitro percentage. - 4/30/2004 12:23:52 PM

twostroker

Posts: 651
Joined: 7/13/2002
From: Ionia, MI, USA
Status: offline

Some time you guys give good advise, sometimes you are off by a mile. So far, I think you are off by a mile.

The engine maker will recommend the nitro content range for their engine, start with the highest. The highest will create the most heat which will make the cylinder/piston fit the best due to the amount it swells from the heat. If you start a new engine and run it on less than recommended nitro you will not get as much heat in the combustion chamber, making the cylinder/piston fit tighter than it should be, creating more wear.

Once you notice the engine has been run for a season or two, you may notice the performance isn't what it used to be due to wear. Then it is time to drop back on the nitro content, which makes less heat, so that the piston/cylinder fit tightens up yielding more compression.

I do not know what nitro content has to due with fuel economy. I feel fuel economy is controlled by the size of the engine and size of the thumb on the throttle stick.

(in reply to coolguy234)

Post #: 8

RE: About nitro percentage. - 4/30/2004 3:47:45 PM

downunder

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From: Adelaide, AUSTRALIA
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Well here's a mile for you to catch up with

Nitro content has very little affect on running temps and certainly won't give enough difference to let you accomodate wear. You're better off running a worn out engine in winter when the temperature gradient between the air and the cooling fins is highest

To answer why nitro affects fuel consumption. Methanol gives max power when tuned to an air/fuel ratio of between 4.5 and 6.5:1 (compared to petrol which is about 13:1). Nitro gives max power over a much wider range and that's up to 2.5:1 (it can be as rich as 0.5:1). The higher the number the less fuel is needed for the same volume of air.

From these figures you can see that nitro at a MINIMUM will be used nearly twice as fast as methanol (comparing the leanest nitro figure of 2.5 with the richest methanol of 4.5). Now when you blend the two together you end up with a correct air/fuel ratio somewhere between the two. But it should be remembered that when you go up in nitro content you displace the same amount of methanol so the proportion of nitro to methanol increases very rapidly.

An equivalent thing is when a gas engine is converted to glow. Because of the widely different air/fuel ratios between petrol and methanol the carb's jets have to be doubled in area so it can flow enough methanol. The converted gas engine then goes through fuel twice as fast.

Now to tie together the two points about running temps and fuel flows. A great deal of the cooling of our engines comes from internal cooling which is done by the evaporation of the liquid fuel vapours. This is latent heat of evaporation. Nitro is nowhere near as good as methanol but, because of the (comparatively) huge amounts of nitro passing through, it more than makes up for it's lesser ability to cool. So nitro gives more power but more cooling and all at the expense of higher fuel consumption.

(in reply to twostroker)

Post #: 9

RE: About nitro percentage. - 4/30/2004 3:55:56 PM

Sport_Pilot

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Joined: 1/21/2002
From: Acworth, GA, USA
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I agree with downunder. People confuse the fact that nitro has more heat with temperature. Temperature is to Voltage as Heat is to Current. Not the same thing.

(in reply to downunder)

Post #: 10

RE: About nitro percentage. - 4/30/2004 8:40:00 PM

FlyNBHappy

Posts: 274
Joined: 7/21/2002
From: Peanut Gallery, USA
Status: offline

Downunder,
You tell them.

Twostroker,
You are soooooooooooo wrong. Maybe to the point of trolling for a response. If you truly believe in what you posted, there's no helping you now, so more power to you. If there is room for discussion then I say this:

I have not read an engine manual that says to break in an engine with the highest allowable nitro content. All the manuals I've seen says to break in an engine with 0 or low nitro, then increase as desired to maximum specified by the manufacturer.

As for temp difference, Downunder says it best.

< Message edited by No2Nitro -- 4/30/2004 2:56:48 PM >

(in reply to twostroker)

Post #: 11

RE: About nitro percentage. - 4/30/2004 8:51:45 PM

Sport_Pilot

Posts: 7828
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline

BTW, I have always upped the nitro on a worn engine. Makes up for the power lost from wear.

I have never noticed nitro rusting bearings. I think this has some validity in a four stroke (but not that much), but almost none in a two stroke.

(in reply to FlyNBHappy)

Post #: 12

RE: About nitro percentage. - 4/30/2004 10:17:18 PM

twostroker

Posts: 651
Joined: 7/13/2002
From: Ionia, MI, USA
Status: offline

Not a troll! I guess there is no hope for me.

(in reply to Sport_Pilot)

Post #: 13

RE: About nitro percentage. - 5/1/2004 1:24:13 AM

downunder

Posts: 3271
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline

There's always hope....

I didn't take it as being a troll but there are a lot of urban myths floating around and some get repeated so many times that they seem to take on the air of being the truth but there's never any hard and fast evidence to back up what they say.

Oops, so I'd better back up what I said

For the stuff on air/fuel ratios go to http://www.holdfastmac.com.au/tech.html and find the link on fuels. OK, so it's the web page I do for my club but the tech stuff comes from a BP chemist.
For info on temps go to http://www.modeltechnics.com/glowplug/firepower.html and compare their results with the same engine on different fuels.

(in reply to twostroker)

Post #: 14

RE: About nitro percentage. - 5/1/2004 4:05:53 AM

jessiej

Posts: 1808
Joined: 7/6/2003
From: STATESBORO, GA, USA
Status: offline

Good info Downunder!

jess

(in reply to downunder)