airraptor

My Feedback: (66)

Why are you running av gas in your DLE?

AV gas is designed to run in an engine at near full power for extened times, not in a up and down power requirements in our model planes.

Tired old man what are your thoughts on the AV gas with 100 octane rating?

I think the High octane rating is also way over kill and will add to the carbon build up in the engine.

My thoughts on timing is they should be adjustable for max power by the user for his needs. If your engine is making the best power on lower timing then you have a great chamber design. i on my race quad i am running three spark plugs with seprate ignitions so that i can reduce the negative torque the engine see's. My best timing at 9,000 is just under 25 BDC.

I am having a a hard time deciding on the DLE20 or DLE 30's for a F-7Ftiger cat. I want the engines to run very well and no issues. with this 20 have crank problems sounds like i should go with the 30's

Waco

My Feedback: (265)

Now this is amusing one guy has a crank problem and now all DLE20s have crank problems, come on one engine that breaks a crank does not mean they all do. Every brand will have some problems here and there at times and many times it is not the product but the user that is at fault.

Kweasel

My Feedback: (29)

Start a poll for mechanically failed engines. This may be a one time event, or maybe not. Remember the early DA50s.

Craig 01

I believe there are only 3 crankpin failures reported here within rcu.

Tired Old Man

My Feedback: (1)

My "thoughts" about the use of avgas in our engines has remained unchanged for years. Don't do it. The stuff is also called 100LL. LL stands for low lead. "Low" is used as a comparative term. The lead content is low compared to the amount of lead auto gas had before unleaded fuels were incorporated. That was back in the 1980's. Engines that used leaded gas had things like valves and valve seats, and the metal chemistries used in engines was different then. Sealed bearings weren't used in areas that would collect residual lead.

Our little engines do not meet any of the qualifications that require leaded fuels. Our spark plugs load up with lead after a period of time, especially in engines that will run for long periods of time. Residual lead becomes trapped at wrist pin and rod bearings. Some is forced inside of sealed bearings.

If someone really believes they need 100 octane fuel for an engine that was designed for octanes between 70 and 90, then recing fuel with no lead is available. Eventually they'll figure out their low compression engine doesn't have the power his buddy's engine does. The reason is because his buddy is using pump grade regular unleaded and all the fuel is being burned during the combustion cycle, while his engine is not using the full charge because the high octane is maintaining a slower burn. His buddy is also getting his gas for $2.00 a gallon less than he is, and can buy it on any street corner.

But what the heck, some people figure, wrongfully, that more octane equals more power. Others figure that because a fuel is intended for a real airplane that it must be better than our pump gas. That's not the way things work.

Lnewqban

If higher octane gasoline is used, at least increase the compression ratio of the little engine accordingly to obtain the benefit of the higher price.

Lifer

My Feedback: (1)

Does higher octane fuel affect the engines operating temp?

rangerfredbob

My Feedback: (13)

the guys I know that use 100LL do it for the longer shelf life compared to the ethanol blends

a1pcfixer

My Feedback: (7)

Avaiation grade gasoline is also blended differently from automotive grades (such as anti-knock, etc). As such they can shorten the life of automotive engines and R/C types.

Back in the 70's - 80's I raced 1/4 mile. Several of my Chevy 350 V-8's had 11:1 cr domed pistons. I asked a mechanic
at our airport about using high octane aviation grade gas, as Sunoco 260 was being phased out. He said NOT to do it, as there was a very high probability of burning holes in my pistons. Back then low octane aviation gas was similar in octane to premium leaded gas, and high octane aviation gas was well beyond premium automotive gas.

Using aviation gas when we only need regular no-lead automotive gas, is like putting 12 gallons of water into a 10 gallon aquarium.........just a waste.

I have however seen where a few of DA's newer engines state premium.

Tired Old Man

My Feedback: (1)

So how much gas does one have to buy for a full season of flying? Do people feel they have a need to bunker 50 gallons of gas or so? Just how difficult is it to fill a can at a gas station one every couple of weeks? I put gas in my car once every week or two and have no probelm doing that. 100 LL still has a tremendous amount ot TEL, even considering the LL identifyer.

How much extra work is there in filling a 1 gallon gas can every couple of weeks? If you're flying a large twin that steps up to a 2.5 or 5 gallon can once a month. Just how long does model fuel need to be stored? How long will it last when stored out of the sun in a sealed container after mixing with 2 stroke oil? 4 months? 6? I've flown gas close to 8 months old with no evident effects of aging. So how long can you park your car with a tank of gas before you drain the tank to replace the old gas. Get real people! The two stroke oil you mixed in the gas is a stabilizer.

There are evidently a lot of people thinking they are being smart but in reality don't have a clue. Worse, they don't have any capacity for reasoning. My buddy does this, or people say to do that. I'm sure gald I'm not standing next to them on a cliff.....

captinjohn

AV gas is not needed in low compressionRC engines. It is great in the high compression engines & is worth th exta cost. Example...my snow blower (a 4 cycle) starts & runs so much better...it is unbelievable. Also the exhaust fumes have no stinky smell. My wife always said she could smell the fumes left on my coat. She was right and the fumes did bother my sinuses very bad. I had some AV gas for my cycle so I filled the snow blower with it. That blower runs & starts so good...from now on that is what I will use. It is also very good storage fuel for about any engine. The multi carbs on a motorcycle will not get gummed up while setting. Av gas is a good storage fuel for 2 cycles also...no stink...it does not turn bad. I would not be afraid to use it in any engine. If carbon does build up...clean the carbon out...which will not be often. Capt,n

Tired Old Man

My Feedback: (1)

Lead is the problem, not carbon. I dare anyone to try cleaning tetra ethyl lead out of a two stroke bearing. Been there, couldn't do it. The plugs were hard enough.

captinjohn

I am learning...what does the tetra ethyl lead to do the 2 cycle bearings? Is it both the ball type or the needle or roller type of bearings that are effected? Thanks Capt,n

a1pcfixer

My Feedback: (7)

Lifer

Detonation is the #1 issue, followed by lead.

This might help explain a bit;
http://www.osbornauto.com/racing/race2avgas.htm

More importantly, why bother with avgas at all?
Just use what the mfg recommends, regular unleaded pump gas.

Lifer

My Feedback: (1)

A1pcfixer,

Thanks for the response. The reason I asked is that I ran some premium gas in my 40 cc last year and it acted like an engine running hot. Someone else confirmed to me that premium will make our engines run hotter. I switched back to regular and all was normal again.

Any confirmation from the more learned?

Tired Old Man

My Feedback: (1)

That doesn't make sense at all, unless the compression ratio is so low that the combustion cycle never concludes, but that's more like pre-ignition or detonation. You had something going on that doesn't make sense by itself.

captinjohn

Back in post #61...I forgot to mention my snow blower is over 25 years old & my Motorcycle is 31 years old. They where built back in the dayswhen engineswas built to last &had pertty good power output too. I will miss em...but they go to go.Its time to stop messing with that stuff & put the $$ into my next RC airplane & engine. Maybe a 55cc DLE. Going to do more flying, insteadof working on everything. Capt,n

Truckracer

My Feedback: (19)

I believe this is explainable .... low compression ratio combined with high octane fuels and late timing could create a condition where combustion is still well in progress when the exhaust port opens. For the most part, you're belching raw flame into the exhaust system and overheating the lower part of the jug. This would move heating lower into the jug where there are often fewer or smaller cooling fins to disipate the heat. And forgive me for calling our cylinders jugs ... I learned that term years ago and refuse to call them "heads"!

I learned this first hand when racing circle track small block Chevy engines. Too high octane fuel combined with late timing would make headers glow red every time. And I was running 14:1 compression ... far higher than our airplane 2 strokes so I was creating a cylinder environment that was friendly to high octane fuel. But timing was everything when it came to making the whole package work.

I have no clue why some modelers insist on using high octane fuels ......or the very low octane fuels for that matter. One is as bad for our engines as the other. Odor is the most common reason and that is not valid in my mind. Low odor, medium octane, non leaded racing fuels are available everywhere in this country. Ya just have to pay the shipping costs.

Lnewqban

It could have been the difference in ethanol contained in both the premium and the particular regular gasolines that you used.

Each lb of gasoline generates 20,000 BTU of heat when burned.
Each lb of ethanol generates only 12,000 BTU of heat when burned.
Hence, gasoline mixed with ethanol contains less energy per pound or gallon, and will generate less heat in any engine.

Some good reading for the detonation resistance properties of the gasoline according to the octane rating:

http://en.wikipedia.org/wiki/Octane_rating

Truckracer

My Feedback: (19)

A simple twist of the HS needle valve offsets any differences in the energy content of the fuels used. Just about everybody on this earth that has ever been around any internal combustion engine understands that alcohol blended fuels have to be run at a richer mixture than a straight gasoline fuel. None of this really matters though if the engine is tuned to the specific fuel it is currently burning.

captinjohn

This chart is very interesting.<hr />Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.

[edit] Examples of octane ratings

The RON and MON of n-heptane and iso-octane are exactly 0 and 100, by definition. The following table lists octane ratings for various other fuels.<sup id="cite_ref-Purdue_Coal_3-0" class="reference">[4]</sup><sup id="cite_ref-IUPAC_4-0" class="reference">[5]</sup>

Fuel	RON	MON	AKI
hexadecane	< -30
n-octane	-10
n-heptane (RON and MON 0 by definition)	0	0	0
diesel fuel	15–25
2-methylheptane	23
n-hexane	25	26	26
1-pentene	34
2-methylhexane	44
1-heptene	60
n-pentane	62
requirement for a typical two-stroke outboard engine<sup id="cite_ref-5" class="reference">[6]</sup>	69	65	67
Pertamina "Premium" gasoline in Indonesia	88
n-butanol	92	71	83
n-butane	91
"regular" gasoline in Australia, New Zealand, Canada and the US	91–92	82–83	87
Pertamina "Pertamax" gasoline in Indonesia	92
Shell "Super" in Indonesia	92
Pertamina "Pertamax Plus" gasoline in Indonesia	95
Shell "Super Extra" in Indonesia	95
Shell "FuelSave " in Malaysia	95
ExxonMobil Avgas 100<sup id="cite_ref-6" class="reference">[7]</sup>		99.5 (min)
"EuroSuper" or "EuroPremium" or "Regular unleaded" in Europe	95	85–86	90–91
Shell "V-Power 97" in Malaysia	97
"SuperPlus" in Germany, Great Britain, Slovenia and Spain, "SP98" in France	98	89–90	93–94
Shell "V-Power Racing" in Malaysia	100
iso-octane (RON and MON 100 by definition)	100	100	100
benzene	101
"BP Ultimate 102 - now discontinued"<sup id="cite_ref-7" class="reference">[8]</sup>	102	93–94	97–98
t-butanol	103	91	97
ethane	108
propane	110
toluene	111	95	103
E85 gasoline			100–5<sup id="cite_ref-8" class="reference">[9]</sup>
xylene	117
isopropanol	118	98	108
ethanol	129	116	122
methanol	133	105	119
methane	135	122	129
hydrogen

captinjohn

More Data on fuels<hr />Methanol and ethanol<dl> <dd>Main articles: Methanol fuel, Ethanol fuel </dd></dl>

Methanol and ethanol can both be derived from fossil fuels, biomass, or perhaps most simply, from carbon dioxide and water. Ethanol has most commonly been produced through fermentation of sugars, and methanol has most commonly been produced from synthesis gas, but there are more modern ways to obtain these fuels. Enzymes can be used instead of fermentation. Methanol is the simpler molecule, and ethanol can be made from methanol. Methanol can be produced industrially from nearly any biomass, including animal waste, or from carbon dioxide and water or steam by first converting the biomass to synthesis gas in a gasifier. It can also be produced in a laboratory using electrolysis or enzymes.<sup id="cite_ref-0" class="reference">[1]</sup>

As a fuel, methanol and ethanol both have advantages and disadvantages over fuels such as petrol (gasoline) and diesel fuel. In spark ignition engines, both alcohols can run at a much higher exhaust gas recirculation rates and with higher compression ratios. Both alcohols have a high octane rating, with ethanol at 109 RON (Research Octane Number), 90 MON (Motor Octane Number), (which equates to 99.5 AKI) and methanol at 109 RON, 89 MON (which equates to 99 AKI).<sup id="cite_ref-1" class="reference">[2]</sup> Note that AKI refers to 'Anti-Knock Index' which averages the RON and MON ratings (RON+MON)/2, and is used on U.S. gas station pumps. Ordinary European petrol is typically 95 RON, 85 MON, equal to 90 AKI. As a compression ignition engine fuel, both alcohols create very little particulates, but their low cetane number means that an ignition improver like glycol must be mixed into the fuel with approx. 5%.

When used in spark ignition engines alcohols have the potential to reduce NOx, CO, HC and particulates. A test with E85 fueled Chevrolet Luminas showed that NMHC<sup id="cite_ref-2" class="reference">[3]</sup> went down by 20-22%, NOx by 25-32% and CO by 12-24% compared to reformulated gasoline.<sup id="cite_ref-3" class="reference">[4]</sup> Toxic emissions of benzene and 1,3 Butadiene also decreased while aldehyde emissions increased (acetaldehyde in particular).

Tailpipe emissions of CO₂ also decrease due to the lower carbon-to-hydrogen ratio of these alcohols, and the improved engine efficiency.

Methanol and ethanol contain soluble and insoluble contaminants.<sup id="cite_ref-4" class="reference">[5]</sup> Halide ions, which are soluble contaminants, such as chloride ions, have a large effect on the corrosivity of alcohol fuels. Halide ions increase corrosion in two ways: they chemically attack passivating oxide films on several metals causing pitting corrosion, and they increase the conductivity of the fuel. Increased electrical conductivity promotes electrical, galvanic and ordinary corrosion in the fuel system. Soluble contaminants such as aluminum hydroxide, itself a product of corrosion by halide ions, clogs the fuel system over time. To prevent corrosion the fuel system must be made of suitable materials, electrical wires must be properly insulated and the fuel level sensor must be of pulse and hold type (or similar). In addition, high quality alcohol should have a low concentration of contaminants and have a suitable corrosion inhibitor added.

Methanol and ethanol are also incompatible with some polymers. The alcohol reacts with the polymers causing swelling, and over time the oxygen breaks down the carbon-carbon bonds in the polymer causing a reduction in tensile strength. For the past few decades though, most cars have been designed to tolerate up to 10% ethanol (E10) without problem. This include both fuel system compatibility and lambda compensation<sup class="noprint Inline-Template" title="The text in the vicinity of this tag needs clarification or removal of jargon from May 2009" style="white-space: nowrap">[clarification needed]</sup> of fuel delivery with fuel injection engines featuring closed loop lambda control. In some engines ethanol may degrade some compositions of plastic or rubber fuel delivery components designed for conventional petrol, and also be unable to lambda compensate the fuel properly.<sup class="Template-Fact" title="This claim needs references to reliable sources from August 2008" style="white-space: nowrap">[citation needed]</sup>

"FlexFuel" vehicles have upgraded fuel system and engine components which are designed for long life using E85 or M85, and the ECU can adapt to any fuel blend between gasoline and E85 or M85. Typical upgrades include modifications to: fuel tanks, fuel tank electrical wiring, fuel pumps, fuel filters, fuel lines, filler tubes, fuel level sensors, fuel injectors, seals, fuel rails, fuel pressure regulators, valve seats and inlet valves. "Total Flex" Autos destined for the Brazilian market can use E100 (100% Ethanol).<sup class="Template-Fact" title="This claim needs references to reliable sources from October 2010" style="white-space: nowrap">[citation needed]</sup>

One liter of ethanol contain 21.1 MJ, a liter of methanol 15.8 MJ and a liter of gasoline approximately 32.6 MJ. In other words, for the same energy content as one liter or one gallon of gasoline, one needs 1.6 liters/gallons of ethanol and 2.1 liters/gallons of methanol. Although the volume of fuel consumption doesn't increase as much as energy content numbers indicate because the alcohol fuels are more efficient.

Methanol fuel has been proposed as a future biofuel. Methanol has a long history as a racing fuel. Early Grand Prix Racing used blended mixtures as well as pure methanol. The use of the fuel was primarily used in North America after the war.<sup class="noprint Inline-Template" title="The text in the vicinity of this tag needs clarification or removal of jargon from May 2009" style="white-space: nowrap">[clarification needed]</sup> However, methanol for racing purposes has largely been based on methanol produced from syngas derived from natural gas and therefore this methanol would not be considered a biofuel. Methanol is a possible biofuel, however when the syngas is derived from biomass. In theory, methanol can also be produced from carbon dioxide and hydrogen using nuclear power or any renewable energy source, although this is not likely to be economically viable on an industrial scale (see methanol economy). Compared to bioethanol, the primary advantage of methanol biofuel is its much greater well-to-wheel efficiency. This is particularly relevant in temperate climates where fertilizers are needed to grow sugar or starch crops to make ethanol, whereas methanol can be produced from lignocellulose (woody) biomass.

Ethanol is already being used extensively as a fuel additive, and the use of ethanol fuel alone or as part of a mix with gasoline is increasing. Compared to methanol its primary advantage is that it is less corrosive and additionally the fuel is non-toxic, although the fuel will produce some toxic exhaust emissions. From 2007, the Indy Racing League will use ethanol as its exclusive fuel, after 40 years of using methanol.<sup id="cite_ref-5" class="reference">[6]</sup> Since September 2007 petrol stations in NSW, Australia are mandated to supply all their petrol with 2% Ethanol content

TimT2000

My Feedback: (1)

This is a good read and backs up what Jody has been saying.
http://www.sea-doo.net/techarticles/oil/oil.htm

It tells what the types are for.

cheers Tim

Tired Old Man

My Feedback: (1)

Truckracer,

I work a fuel where adjusting the needles will not compensate for the difference in energy content. This fuel is a broad spectrum fuel that encompasses a wide range of cetane ratings. If one starts out with a well tuned engine using a higher cetane rating then switches to a lower quality/cetane rating they will not be able to compensate for the difference at the carb needles. The best one can hope for is a considerable loss of RPM while delaying knock, and increased fuel consumption. This applies to carbureted engines only.

a1pcfixer

My Feedback: (7)

Unfortunately, not all types of engines allow the range of adjustment to do so.

I miss adjusting Holley carbs. Swapping out jets on those was somewhat of an art form.
Doing the same on a GM Quadrajunk was a science unto itself......and a nightmare.