93 replies to this topic

[MatsNorway]

I am reading in a old book i found in the "archive" at work.

It shows a bunch of grafs and i found it interesting to note that there is a higher efficiency relative to the comp ratio and that if you had a comp ratio of 12:1 you could get a efficiency of just above 30%

Is that the max teoretical number possible? at that given comp?

the curve is still climbing but it has a negative umm.... proportion making me think/guess it would peak at say 50%

Its for a petrol engine. The book is probably from 1971 or newer.

Next graf shows octane and compression and to go up to 13:1 in comp you need just below 110 octane

The fun part is a list that tells octane numbers on different airplane fuels.

octane
80 small planes light red.
91/96 grade helicopters red
100/130 grade small planes green
108/135 grade civil and military planes brown
115/145 grade bigger civil and military planes Violett

what octane number would a diesel get?

There is also a picture of a variable compression device to test and label octane number on different fuels.

Btw you could run diesel in a petrol engine right? guess it would be very inefficient ofc. as the engine would not be optimised for it..

[Lee Nicolle]

Here in Oz Avgas [commercial fuel as defined by CAMS] is called 100 octane but from memory is 100-115 and is colored green. You can if you are very careful run p to 13-1 with the right chamber on it though 12- 12.5-1 is safer.
In the dim past we could buy 130 octane at a couple of petrol stations at about 20% more than normal Super grade.. Now 100 is about twice as much as normal petrol.
Some people seem to be getting good results on 98 unleaded, even on very hi performance engines. Having used both in recent times on my Ford Clevo/M engines the avgas makes more power and smoothness with 10-1 and a lot more power with 11-1

[24gerrard]

You could always brew your own ethanol and run 15 to one.
But then that is why they had prohibition in America, to stop the public 'growing their own' vehicle fuel.
Forget the 'booze' issue that was just a red herring.
Clever those oil companies, they have profited from polluting our environment for over 100 years, some con.

[Allan Lupton]

"Octane numbers" relate knock rating of fuels to a standard based on a proportion of iso-octane in a reference fuel expressed as a percentage.
It follows that 100 is the highest true octane number and the values over 100, which are obtained by extrapolation, are correctly referred to as "performance numbers"
Historically there were two methods of evaluating the knock rating, the "Motor" method (MON) and the "Research" method (RON) and for the same knock rating there is approx. 10 difference in the octane number for the two methods. That is important only when you see that in the 1930s someone's engine developed ??? h.p. on 80 octane fuel and you find it needs 90 octane post-war. That 13:1 CR on 110 would be an MON I think.
Without getting too deeply involved in the Otto (or Day, Oechselhauser, etc) cycle, I can point out that it is the expansion ratio that is important when getting mechanical power from high-pressure gas and although we refer to it as compression ratio it is both. The higher the ratio the better, from a thermo-mechanical efficiency standpoint, limited only the need to avoid detonation. That is the tie-in with the octane rating of the fuel that was the basis of the question at the beginning.
Since the diesel cycle is rather different, detonation/knock is not the problem. DERV (diesel fuel) has a cetane rating but as it's even less my field I'll leave it to someone else to explain.
As for using DERV in a gasoline (as we seem to call it now) engine it won't work. The gasoline engine operates with a homogenous fuel/air mix that fills the working space and is ignited at a suitably timed point, and DERV is not sufficiently volatile to become such a mixture. The diesel's working space is filled with air into which, when it's been compressed and is hot, DERV is injected and burns as it comes into contact with the oxygen of the unburnt air (apologies to the specialists for the simplification, but I think the question needed some answer).
The other point to make is that alcohol-based fuels have lower calorific values than petroleum distillates, so although you can use higher CRs as you don't get as much energy per pound of fuel (and as the proportion of fuel:air required is higher) you need to consume such fuels at a much higher rate. Compare the racing cars of 1957 and 1958 to see how a change from alcohol-based fuel to gasoline affected them.

[24gerrard]

The other point to make is that alcohol-based fuels have lower calorific values than petroleum distillates, so although you can use higher CRs as you don't get as much energy per pound of fuel (and as the proportion of fuel:air required is higher) you need to consume such fuels at a much higher rate. Compare the racing cars of 1957 and 1958 to see how a change from alcohol-based fuel to gasoline affected them.

Alcohol is a better fuel for an internal combustion engine than petrol, it simply means you have to carry a larger amount.

[MatsNorway]

Alcohol is a better fuel for an internal combustion engine than petrol, it simply means you have to carry a larger amount.

If F1 today could run it would the extra weight be worth it? I assume so..

Btw don`t forget my OR questions...

[Greg Locock]

There's no theoretical upper limit, each increment in CR should give you some increase in thermodynamic efficiency. But the mechanical losses accumulate with much greater rapidity as CRs increase, so you end up with a more efficient engine somewhere between 5:1 and 30:1, depending.

Octane in itself does you no favours efficiency wise, but a high octane fuel tends to knock less, so you can run a higher CR than otherwise.

[gruntguru]

what octane number would a diesel get?
Btw you could run diesel in a petrol engine right? guess it would be very inefficient ofc. as the engine would not be optimised for it..

A Diesel engine needs fuel with the highest possible "Cetane" number. Cetane number is almost the opposite of Octane number. It is a measure of "ignitability". A gasolene engine does not want the fuel to ignite easily - that would be detonation. It needs the fuel to burn smoothly and progressively. A diesel engine regulates the rate of combustion mechanically by controlling the rate at which fuel is added to the combustion process, so detonation will not occur except in the case of a fuel with a low cetane number. In this instance the fuel may not ignite instantly when injection begins ("ignition delay") so there may be some quantity of fuel spray already in the chamber when ignition occurs. This will result in rapid combustion of the entire quantity of premixed fuel - a kind of detonation and the cause of "diesel knock."

Running diesel in a petrol engine is bad. High cetane diesel has a very low octane number and would require a very low CR.

[Lee Nicolle]

Alcohol is a better fuel for an internal combustion engine than petrol, it simply means you have to carry a larger amount.

To a degree. Methanol fuel would not be nice in a roadcar but is quite good on a race engine. It makes more power, through more compression and more even flame travel though less per pound of fuel. It wears out bores and pistons more and is probably more carclogenic than unleaded petrol, not good But is far more stable in the event of a fire and harder to light too.
Ethanol blend fuels tend to have the same characteristic though are a bit more volatile in case of fire and supposedly better for the enviroment also.

[24gerrard]

To a degree. Methanol fuel would not be nice in a roadcar but is quite good on a race engine. It makes more power, through more compression and more even flame travel though less per pound of fuel. It wears out bores and pistons more and is probably more carclogenic than unleaded petrol, not good But is far more stable in the event of a fire and harder to light too.
Ethanol blend fuels tend to have the same characteristic though are a bit more volatile in case of fire and supposedly better for the enviroment also.

I hope Ethanol is not carclogenic, it is after all Vodka.
Methanol is poisonous.

[Greg Locock]

By the way Mats, buy or steal Heywood's book, it really nails down the fundamentals.

[gruntguru]

Methanol fuel would not be nice in a roadcar but is quite good on a race engine. It makes more power, through more compression and more even flame travel though less per pound of fuel. It wears out bores and pistons more . . .

Methanol is fine in a road car. Many of the problems people associate with it disappear when it is used at correct mixtures.

[MatsNorway]

I for some reason bought that book of ebay right away... It better be good. its my first propper book. apart from silly math books who i have yet to look into... Was supposed to get a plan B so i could study some more if things went bad.

I still wish i new a octane number even if its only teoretical for diesel.. how low can you go anyway? could you make 20 octane petrol? whats the natural octane number for pure petrol?

[ray b]

if they add 15% alcohol how much does that change the octane rating
or is the now pump rated 83 really lower octane as pure gasoline
and the added alcohol brings it up to 83 ??

[ray b]

I for some reason bought that book of ebay right away... It better be good. its my first propper book. apart from silly math books who i have yet to look into... Was supposed to get a plan B so i could study some more if things went bad.

I still wish i new a octane number even if its only teoretical for diesel.. how low can you go anyway? could you make 20 octane petrol? whats the natural octane number for pure petrol?

octane is part of normal gasoline

an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (isooctane) is used as one of the standard values in the octane rating scale.


along with heptane

n-Heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 point is a 100% iso-octane).

but then it gets complex with lots of different kinds of octane and heptane called isomers

Octane has 18 structural isomers (24 including stereoisomers):

* Octane (n-octane)
* 2-Methylheptane
* 3-Methylheptane (2 enantiomers)
* 4-Methylheptane
* 3-Ethylhexane
* 2,2-Dimethylhexane
* 2,3-Dimethylhexane (2 enantiomers)
* 2,4-Dimethylhexane (2 enantiomers)
* 2,5-Dimethylhexane
* 3,3-Dimethylhexane
* 3,4-Dimethylhexane (2 enantiomers + 1 meso compound)
* 3-Ethyl-2-methylpentane
* 3-Ethyl-3-methylpentane
* 2,2,3-Trimethylpentane (2 enantiomers)
* 2,2,4-Trimethylpentane (isooctane)
* 2,3,3-Trimethylpentane
* 2,3,4-Trimethylpentane
* 2,2,3,3-Tetramethylbutane




Heptane has nine isomers, or eleven if enantiomers are counted:

* Heptane (n-heptane), H3C–CH2–CH2–CH2–CH2–CH2–CH3,
* 2-Methylhexane (isoheptane), H3C–CH(CH3)–CH2–CH2–CH2–CH3,
* 3-Methylhexane, H3C–CH2–C*H(CH3)–CH2–CH2–CH3 (chiral),
* 2,2-Dimethylpentane (neoheptane), (H3C)3–C–CH2–CH2–CH3,
* 2,3-Dimethylpentane, (H3C)2–CH–C*H(CH3)–CH2–CH3 (chiral),
* 2,4-Dimethylpentane, (H3C)2–CH–CH2–CH–(CH3)2,
* 3,3-Dimethylpentane, H3C–CH2–C(CH3)2–CH2–CH3,
* 3-Ethylpentane, H3C–CH2–CH(CH2CH3)–CH2–CH3,
* 2,2,3-Trimethylbutane, CH3–C(CH3)2–CH(CH3)–CH3, this isomer is also known as pentamethylethane and triptane.[1]

[gruntguru]

Adding to that:
- 2,2,4-trimethylpentane (isooctane) is defined as 100 on the octane rating scale
- Straight-chain C7H16 (N-heptane) is defined as 0 on the octane rating scale
- Blends of the above two, are defined to have an octane rating equal to the percentage of iso-octane in the blend
- Pump petrol may have neither of the above compounds. Its octane rating is established by comparing its knock characteristics to reference fuels consisting of a blend of iso-octane and n-heptane. This is done in a variable compression fuel research (knock) engine.

[J. Edlund]

The theoretical efficiency of an engine can be written as ( Q_added - Q_removed ) / Q_added. The ideal otto cycle engine operate with four processes: 1, isentropic compressionen, 2, isochoric heat addition, 3, isentropic expansion, and 4, isochoric heat removal. This means Q_added = (Cv*T3) - (Cv*T2) and Q_removed = (Cv*T4) - (Cv*T1) where T1 is the temperature before compression, T2 the temperature after compression, T3 the temperature after head addition and T4 the temperature after expansion.

So, ( Q_added - Q_removed ) / Q_added = 1 - Q_removed/Q_added = 1 - (T4-T1) / (T3-T2) = 1 - T1/T2 = 1 - cr^(1-k)

cr = compression ratio
k = ratio of specific heats (1.4 for air)

As a result, the theoretical efficiency of an otto engine will follow the compression ratio. A compression ratio of 12:1 will for instance offer a theoretical efficiency of 63%. Increasing the compression ratio will increase the theoretical efficiency, although the higher temperatures and pressures that will follow will in reality result in larger and larger heat and frictional losses.

Gasoline is a mixture of many (several hundreds) hydrocarbons, each with its own boiling point and octane rating. The octane scale is based on n-heptane which is given the octane rating 0 and iso-octane given the octane rating 100. Octane numbers above 100 are tested using a reference mixture of iso-octane + tetra ethyl lead. Gasoline contain hydrocarbons having a boiling point from about 25 to 225 degC, and they are typically branched or ring formed, as those resist self ignition. Diesel contain hydrocarbons that have a boiling point between 180 degC and 360 degC, they are mostly straight as those self ignite easily. As a result, diesel would be a bad fuel for a spark ignition engine and vice versa. A SI engine given diesel fuel would probably not start at all due to the high initial boiling point and if it starts there is a chance of serious engine damage due to knocking. Similar, a compression ignition engine can be seriously damaged by gasoline. The lower boiling point of gasoline means that the fuel will easily vaporize, but the low cetane number means that the ignition delay will be long. As a result the fuel will burn rapidly as a homogeneous mixture, resulting in very high combustion pressures.

The octane rating is typically measured using either the research or the motor octane number test. Avgas have two ratings, one is "lean" and the other "rich". The rich rating is naturally higher.

Methanol and ethanol are both good SI engine fuel. They produce little soot when burned, the have a high octane rating, a high heat of vaporisation (cools the charge), a high flame velocity and the exhaust contain less toxic substances than with regular gasoline. They are both also bio degradeable. However, ethanol tends to form acetic acid and methanol formic acid during combustion which can demand shorter oil change intervals, and special oil addetives. Their lower boiling point do however mean that there will be less fuel found in the oil. Their combustion products can also be corrosive to engine internals by "chemical wear", particulary formic acid which is a stronger acid. This is typically less of a problem than the fuels corrosive effects on the fuel system. Formic acid is also the reason why methanol is toxic to drink. In the body, methanol will be degraded into formic acid, the formic acid can damage the optic nerve and will lower the ph of the blood, eventually resulting in death. Ingesting very small amounts of methanol is on the other hand harmless (methanol is not cancirogenic), methanol occur naturally in the body and can also be found in food, but this is of course in very small amounts.

Methanol and ethanol are both corrosive to several metals; aluminum, brass, zinc, and steel should for instance be avoided in the fuel system. For instance stainless steel could be used instead, and aluminum components can be nickel plated to prevent corrosion. Electric wires should be isolated with for instance PTFE, the fuel pump motor should use a carbon commutator instead of copper, and the fuel level sensor should be powered with AC instead of DC to prevent electrolytical corrosion. Valve seats should be made of a harder material and a coating can be required on the inlet valves. Different polymer materials can also be required in the fuel system, and alcohol-gasoline blends are usually thougher to those materials than pure alcohols or gasoline. In the case of bio-ethanol, sulphuric compounds found in the fuel due the the production process can also be an issue; this can cause the build up of black deposits in the fuel system.

Back in the early 20'th century, GM planned to use ethanol as a replacement to gasoline in their cars. But in the end, oil reserves proved to be much larger than initially thought, and the volumes of ethanol requred proved to be too large to produce. The plan was to improve fuel efficiency by first adding tetra ethyl lead to gasoline, making the oil reserves last longer, and then switch to ethanol when the supply of oil became scarce. GM researchers did however had trouble finding ethanol for their work due to the prohibition.

[Lee Nicolle]

Methanol is fine in a road car. Many of the problems people associate with it disappear when it is used at correct mixtures.

Not in my experience, even with a proper Bolaws methanol carburettor and the engine set up by very experienced people, who advised against the whole deal in the first place. It had no bottom end driveability, fouled plugs and contaminated the oil very quickly. Fitted a petrol carb and used Avgas it became a practical street hottie.But lost about 25 hp top end.
The same with modified efi systems, no bottom end power.
Because of the volume of the stuff it does not meter properly at low engine speeds, E85 is not a great deal better either though there has been a lot more manufacturer development for that and while they are lazy and thirsty it is viable in those cars.
And E85 in a race type set up does make good reliable power though once again bottom end is a bit 'basic'.
Do not use either with alloy fuel tanks, pumps and neoprene fuel lines, carby needles etc.
I have seen that stuff go bad quickly even with e10 fuels. Which somecars seem to like and other hate.

[gruntguru]

. . . carburettor . .

I spotted your problem.

and the engine set up by very experienced people, who advised against the whole deal in the first place. It had no bottom end driveability, fouled plugs and contaminated the oil very quickly

If it fouled plugs and contaminated the oil it was too rich.

For bottom end driveability carburetted, you would need some serious manifold heating.

EDIT. Actually thinking about it, the lack of manifold heating could also cause plug fouling and oil contamination.

Edited by gruntguru, 20 May 2011 - 03:53.

[Canuck]

Its carcinogenic. Fack...for a forum of rather smart folks your spelling is killing me. (invariably my iPhone and my thumbs will now conspire to mangle my next posts).

[ray b]

but alcohol added does change the octane rating

in the 70's a buddy sold mr wang's alcohol/water injection kits
to people with hi-c older cars to run on low lead lo-test
and it sorta worked as long as they refilled the mix

so is alcohol raising octane levels at 15% by how much ??

[bigleagueslider]

J. Edlund did a good job explaining the thermochemistry. It's basically work available from heat release versus net work done at the crank.

Octane rating (whether RON or ROM) gives a relative measure of a fuel's resistance to combustion detonation. Octane rating is one consideration in how suitable a fuel might be for a spark ignited engine, but there are others such as toxicity, latent heat of evaporation, vapor pressure, energy density or heat value, cost, etc.

If cost and practicality are no object, the best fuel for an SI engine overall is probably hydrogen. It has very high octane, burns very clean, and has the best mass energy density of most any fuel in liquid form. Alcohols, such as methanol or ethanol, have good detonation resistance and high latent heat values. But they also are hydrophyllic and corrosive to many metals.

The efficiency of any combustion cycle generally improves with increasing pressure ratios. The cycle pressure ratio can be increased by higher geometric compression ratio, or by higher intake charge pressures. With a normally aspirated SI engine, efficiency tends to top out at around 14:1 CR. At WOT conditions, a 14:1 engine would have detonation unless a high octane (benzene, toluene, etc.) or high latent heat fuel (methanol, ethanol, hydrogen, etc.) was used.

To make a long story short, octane rating itself does not affect thermal efficiency. But a higher octane fuel would allow an SI engine to operate with higher cycle pressure ratios without suffering detonation, thus improving thermal efficiency.

As a historical note, the reason most cars use gasoline as fuel has to do with the fact that the oil refining distillation process produces a certain amount of liquid fractions like gasoline that have very few other uses. At the turn of the century, before the advent of the automobile, oil refiners wanted kerosene for lighting. Gasoline was a useless by-product, and was typically dumped in the nearest river. Someone quickly figured out that this "useless by-product" made a good internal combustion engine fuel, and thus we use it to this day.

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[Tony Matthews]

Gasoline was a useless by-product, and was typically dumped in the nearest river.
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[bigleagueslider]

Matthews,

Why the giggling?

Rudy Diesel's first engine ran on peanut oil, Porsche's first car was lead-acid electric, and Hank Ford's first engine ran on alcohol. Now days, most oil refining is optimized for maximizing high-value products like gasoline.

Besides, haven't you heard the old joke about how John D. Rockefeller saved the whales?

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[gruntguru]

The efficiency of any combustion cycle generally improves with increasing pressure ratios. The cycle pressure ratio can be increased by higher geometric compression ratio, or by higher intake charge pressures.

I would qualify that by saying that supercharging does not increase TE (thermal efficiency). Sure the cycle pressure is increased and consequently the temperature at which heat is added is increased (by itself an indicator of higher TE). However, unless the expansion ratio is increased (eg by using an exhaust turbine with blowdown recovery) the exhaust temperature (the temperature at which heat is rejected) will also increase and this will reduce the TE.

This highlights a very important point. It is not higher compression ratio that increases TE, it is the higher expansion ratio (that normally follows when CR is raised in a piston engine).

[Magoo]

Back in the early 20'th century, GM planned to use ethanol as a replacement to gasoline in their cars. But in the end, oil reserves proved to be much larger than initially thought, and the volumes of ethanol requred proved to be too large to produce. The plan was to improve fuel efficiency by first adding tetra ethyl lead to gasoline, making the oil reserves last longer, and then switch to ethanol when the supply of oil became scarce. GM researchers did however had trouble finding ethanol for their work due to the prohibition.

A fascinating story, an excellent history of which can be found here, written by noted automotive journalist Jamie Kittman:

http://www.thenation...et-history-lead

[Tony Matthews]

Matthews, Why the giggling? Besides, haven't you heard the old joke about how John D. Rockefeller saved the whales?

A smile, not a giggle, and simply because I enjoy your writing style. There are several posters who inform and amuse, you seem to have the same facility. As to the joke, it must have passed me by.

[Lee Nicolle]

I spotted your problem.


If it fouled plugs and contaminated the oil it was too rich.

For bottom end driveability carburetted, you would need some serious manifold heating.

EDIT. Actually thinking about it, the lack of manifold heating could also cause plug fouling and oil contamination.

Manifold heating may help ofcourse, at the expense of top end power. Though a little hard to heat a Victor Jnr manifold on a SBC. Though it was not noticebly iceing up, just poor fuel atomisation.
I have seen methanol through a fuel injector on a flow bench, not a pretty sight!
EFI engines with dirty injectors are quite good at fouling plugs with petrol as the fuel does not atomise. Though at highway speeds seldom cause much problem as the intake velocity atomises the fuel anyway [though not nearly as well] And methnol through a petrol injector is much like that even with hi flow pumps. To me a very bad idea but some racing classes are using that set up.

[gruntguru]

Manifold heating may help of course, at the expense of top end power.

Most people would be surprised to see how little the top-end power is affected by sensible manifold heating - especially with Methanol.

Though a little hard to heat a Victor Jnr manifold on a SBC. Though it was not noticebly iceing up, just poor fuel atomisation.

Puddling is the main problem. Big droplets at low air velocity get added to the puddle on the floor of the manifold then when the throttle opens or the car turns a corner the puddle drowns one or all of the cylinders.

EDIT. The first time I saw Indy Cars, my first impression was the lack of Methanol smell.

Edited by gruntguru, 21 May 2011 - 06:10.

[mariner]

The military have paid for "multi fuel engines" for tanks etc. so any fuel can be supplied to the battlefield in an emergency. I beleive the two stoke OP engine used in the Chieftain tank was " Multi fuel" (albeit with apparently poor performance).

How do military multi fuel engines cope with the cetane/ octane type conflicts explained above.

[bigleagueslider]

A smile, not a giggle, and simply because I enjoy your writing style. There are several posters who inform and amuse, you seem to have the same facility. As to the joke, it must have passed me by.

Matthews,

The old joke about Rockefeller saving the whales is a backhanded slap to environmentalists. And like all good jokes, it has a basis in fact.

As you may be aware, in the late 19th century, John D. Rockefeller was the richest man in the world and the owner of Standard Oil. Environmentalists/anti-capitalists love to hate the "greedy robber barons" and "evil oil companies". Rockefeller represented both. In the late 1800's, Standard Oil's main product was kerosene for lighting, and kerosene sales made Rockefeller incredibly wealthy. The irony comes from the fact that prior to the availability of low cost kerosene for lighting, the main source of lamp oil was from hunting whales. So had Rockefeller and Standard Oil not been successful in producing and marketing a lower cost alternative to whale oil when they did, it's likely that whales would have soon been hunted to extinction.

Unfortunately, among the clueless American public, John D. Rockefeller has a bad (and completely undeserved) reputation. Besides saving the whales, he was a generous philanthropist. And most fail to fully appreciate the significant impact in peoples' quality of life and standard of living that was brought about by the widespread availability of low-cost lamp oil. Even the poor could now stay up after dark reading, writing, and talking.

So now that you know the story, does the joke make you chuckle?

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[Lee Nicolle]

Most people would be surprised to see how little the top-end power is affected by sensible manifold heating - especially with Methanol.


Puddling is the main problem. Big droplets at low air velocity get added to the puddle on the floor of the manifold then when the throttle opens or the car turns a corner the puddle drowns one or all of the cylinders.

EDIT. The first time I saw Indy Cars, my first impression was the lack of Methanol smell.

Having been involved with speedway modified sedans which are internally modified 6 cyl engines using standard 2bbl manufold and a 350 Holley on methanol icing was ever only an issue on cool autumn evenings. Some people run very restricted water heating [original equipment] to alleviate this. Only to alleviate the potential of jammed throttles. Full water flow on the dyno does affect the power quite a lot.
Cold air boxes etc are not nesecary on a methanol engine!

[bigleagueslider]

Lee Nicolle,

"puddling" of methanol in an intake manifold can be a serious problem, but not for the reason you might imagine. Methanol is highly corrosive to many metals, especially the metals racing intake manifolds are usually made from, such as magnesium or aluminum. While Indy cars no longer run on methanol, back when they did, the crews would have to purge the methanol from the fuel system (referred to as "pickling" and was done using gasoline) at the end of the day to prevent corrosion damage to the engine parts.

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[24gerrard]

Lee Nicolle,

"puddling" of methanol in an intake manifold can be a serious problem, but not for the reason you might imagine. Methanol is highly corrosive to many metals, especially the metals racing intake manifolds are usually made from, such as magnesium or aluminum. While Indy cars no longer run on methanol, back when they did, the crews would have to purge the methanol from the fuel system (referred to as "pickling" and was done using gasoline) at the end of the day to prevent corrosion damage to the engine parts.

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Ethanol used to play havoc with my chainsaw and ride on mower carbs and manifolds.
Stainless was the answer.
Teflon coating on the piston crowns.

[Magoo]

Unfortunately, among the clueless American public, John D. Rockefeller has a bad (and completely undeserved) reputation. Besides saving the whales, he was a generous philanthropist. And most fail to fully appreciate the significant impact in peoples' quality of life and standard of living that was brought about by the widespread availability of low-cost lamp oil. Even the poor could now stay up after dark reading, writing, and talking.

Well, as one of your clueless Americans, I'll note that he was a pioneer of the oil industry, and he did be become a great philanthropist, but he was still a robber baron in the classic mold, a relentless monopolist, and a chiseling bastard by all accounts, much of a muchness with his contemporaries in steel, coal, and railroads who led the gilded era. Historian Allan Nevins once famously observed that Rockefeller's was arguably "the least tainted of all the great fortunes of his day," which might be the ultimate left-handed compliment in the annals of biography. I don't think we can say that Rockefeller made it possible for children to read their schoolbooks at night, but we can state with some confidence that John D. generally got his nickel whenever they did.

[J. Edlund]

Not in my experience, even with a proper Bolaws methanol carburettor and the engine set up by very experienced people, who advised against the whole deal in the first place. It had no bottom end driveability, fouled plugs and contaminated the oil very quickly. Fitted a petrol carb and used Avgas it became a practical street hottie.But lost about 25 hp top end.
The same with modified efi systems, no bottom end power.
Because of the volume of the stuff it does not meter properly at low engine speeds, E85 is not a great deal better either though there has been a lot more manufacturer development for that and while they are lazy and thirsty it is viable in those cars.
And E85 in a race type set up does make good reliable power though once again bottom end is a bit 'basic'.
Do not use either with alloy fuel tanks, pumps and neoprene fuel lines, carby needles etc.
I have seen that stuff go bad quickly even with e10 fuels. Which somecars seem to like and other hate.

The fact that you state the engine suffered from fouled plugs and fuel contamination of oil makes me suspect that the carburettor wasn't able to control the air fuel ratio over the whole range.

E85 fueled cars are actually developed from earlier M85 fueled cars. Increasing oil prices in the seventies meant options to gasoline became interresting, and several methanol fuel programs were started. When oil prices dropped during the eighties most of these were canceled as making methanol from natural gas would be more expensive than gasoline. But in the nineties they resurfaced again, now with a new purpose; reducing smog. Car manufacturers such as GM made a large number of M85 fueled vehicles, mostly sold in California, which worked fine with exception from some early problems with clogged fuels systems due to incompatible materials found in fuel station equipment. Aside from cold start difficulties there were no driveability issues with these cars that I'm aware of. These M85 fueled cars were then the starting point for later ethanol, E85, fueled vehicles using essentially the same hardware but with new software. The smog reducing effect of the methanol was eventually replaced by reformulated gasoline, but methanol is still used in some places. China for instance produce fuel methanol from coal.

A naturally aspiranted engine converted to E85 improves the energy efficiency of the engine by about 3% and tests conducted by AVL have shown that an engine can offer an approx. 2 point efficiency increase compared to using RON 95 gasoline (36 to 38% maximum efficiency). There is no significant impact on engine output with naturally aspiranted engines, although turbocharged engines can use the higher octane to boost output.

With modern multilayer plastic tanks or the latest stainless steel tanks and the correct fuel system hardware, compatibility with ethanol and methanol is not a problem. It can however cause problems if unsuitable materials are used in the fuel system.

I can see no reason why methanol should be more difficult to "meter" due to the volume of fuel needed. All fuel injectors lose accuracy with short opening periods, but the effect on the air fuel ratio should be about the same regardless if we use methanol, ethanol or gasoline unless the injectors aren't sized properly. Clearly this can be a problem with any fuel where the injectors have to be very large compared to the fuel need at idle, but this is also easily solved by using two sets of injectors. With direct injection I don't think there will be any problem at all since these can adjust the fuel pressure depending on the need.

The military have paid for "multi fuel engines" for tanks etc. so any fuel can be supplied to the battlefield in an emergency. I beleive the two stoke OP engine used in the Chieftain tank was " Multi fuel" (albeit with apparently poor performance).

How do military multi fuel engines cope with the cetane/ octane type conflicts explained above.

In modern times the "multifuel" capability usually means that an engine can operate on both diesel and jet fuel. That way, a single fuel in the form of jet fuel can be used by all military engines, simplifying fuel distribution which can be a significant problem in a war zone. Jet fuel is similar to diesel, the main difference being the poor lubricating properties of jet fuel.

[ClubmanGT]

A high compression A-series will struggle on anything below 95 and really needs 98 to run properly. It's a little older technology than the engines you're talking about (late 60s vs early 70s) but even at a small scale, the fuel does tend to make quite a large difference.

[cheapracer]

Recently my Mazda's transmission has decided it doesn't like anything less than 97.

Any Mazda (2005 Mazda 6) experts out there?

[gruntguru]

Recently my Mazda's transmission has decided it doesn't like anything less than 97.

Try putting oil in it.

[johnny yuma]

Jet fuel is basically kerosene,is "cruder" than diesel,comes out of the crude oil earlier (colder) than diesel in the catalytlic cracker and has less btu s. If you run out of petrol in a 1950s car with 6:1 or 7:1 compression,it will run on kerosene for a while till the residual petrol is gone, it cools down and gets very unhappy.

Forget that demon Rockerfeller,the Abbasid Caliphate was burning kerosene in lamps in 850AD ...about the time the Arab world were holding human knowledge during the Dark Ages in Europe.

[Lee Nicolle]

Jet fuel is basically kerosene,is "cruder" than diesel,comes out of the crude oil earlier (colder) than diesel in the catalytlic cracker and has less btu s. If you run out of petrol in a 1950s car with 6:1 or 7:1 compression,it will run on kerosene for a while till the residual petrol is gone, it cools down and gets very unhappy.

Forget that demon Rockerfeller,the Abbasid Caliphate was burning kerosene in lamps in 850AD ...about the time the Arab world were holding human knowledge during the Dark Ages in Europe.

About 35 years ago during a National Fuel Strike the place I was working for procured a 44 of power kero.The work vehicles were a FB Holden ute and a Chrysler Royal wagon. Both around 8-1. Which both ran very well on kero though they stunk. particularly the Chrysler, which would actually start cold on kero.
The Holden was 'primed' with a little bit of 2 stroke to make that start cold.
That drum got us out of trouble in the worst of Goughs years.

[gruntguru]

They must have pinged their brains out. I ran a stock 850 mini on kero/petrol once and it knocked violently if you so much as breathed on the throttle.

[24gerrard]

They must have pinged their brains out. I ran a stock 850 mini on kero/petrol once and it knocked violently if you so much as breathed on the throttle.

It would have run better if you had loosened the Lucas distributor and turned it a few degrees counter clockwise.
I have run most fuels in the A series, usualy test engines of 1290, 1340 1430 0r 1445 cc based on the 1300 version and the Cooper S versions.
With a 649 cam and the centrifugal weights in the distributor replaced with a solid base plate and 'S' 32 ounce points, with no vacume advance ******, adjustment was enough.
With the high overlap cam any basic fuel type can be run fairly OK without 'much' pinking if you are careful.
Better still with 1.2 ratio offset rockers.
I even ran one on powder straw and a TR4A engine in an old grey ferguson tractor (fast plowing that one)

[gruntguru]

It would have run better if you had loosened the Lucas distributor and turned it a few degrees counter clockwise.

If only I'd had a 7/16" spanner. It was late at night and had run out of real fuel - just needed to get the car home.

[24gerrard]

If only I'd had a 7/16" spanner. It was late at night and had run out of real fuel - just needed to get the car home.

There you go then, the distributor clamp has a seven sixteenth captive lock bolt.

[johnny yuma]

Same fuel strike (early 70s) a mate had a 1928 Oldsmobile ragtop.His older brother was a bit of a guru,recommended kerosene with mothballs added, and as the merry Oldsmobile had advance/****** on the steering column (love to have that) you could tune as you drove.Smelt of kerosene AND mothballs,ran OK --but never went that well even on petrol anyhow !

Interestingly the "Firepower" rip off seems to have had mothballs (naptha) as it's only active ingredient (except unscrupulous greed).

BTW Lee was that Chrysler one of the old side valve jobs ?

[Lee Nicolle]

Same fuel strike (early 70s) a mate had a 1928 Oldsmobile ragtop.His older brother was a bit of a guru,recommended kerosene with mothballs added, and as the merry Oldsmobile had advance/****** on the steering column (love to have that) you could tune as you drove.Smelt of kerosene AND mothballs,ran OK --but never went that well even on petrol anyhow !

Interestingly the "Firepower" rip off seems to have had mothballs (naptha) as it's only active ingredient (except unscrupulous greed).

BTW Lee was that Chrysler one of the old side valve jobs ?

313/318 Sawtooth engine. I dont think our Royals had sidevalves did they? Kingsways did of course. I am sure that Ray will know.

[Spaceframe7]

Hi Canuck, and to the North American contributors to this forum. Apologies if this has been questioned before, but is there any research that you know of, or advice you can provide on the maximum compression ratio that should be considered for a road going sports car - using Super unleaded gasoline - in Canada? The engine, in the process of being re-built, is a 1600 c.c. Ford Crossflow fitted with Weber carbs and the head has been professionally modified for use with unleaded fuel (hardened exhaust valve seats, and higher grade valves). I have searched a number of sites from the U.K., but have noted that U.K. fuel and fuel rating is different from that in N. America. I do not want to burn a hole in the pistons (not yet purchased), or damage any other part of the engine by going overboard with too high a c.r. I read an article in our local paper some time ago that Avgas is not recommended for road cars as it is intended for an engine that normally runs at a constant rpm, and stays at those revs for most of its running time. (note: the article quoted some aero engines running on Avgas at possibly 3600 - 4000 rpm max., but I may be right out to lunch on this as I've used these numbers from memory).

Would approx. 10:1 be considered the max., for a road use engine, or does anyone suggest lower c.r. than this? I would think that the F.F. racers here in N.A., running with mandatory 9.3:1 using a double choke Weber carb, would be using Super unleaded (are they allowed to use hardened exhaust seats and valves or perhaps fuel enhancer?) or do N. American racers have access to leaded fuel somehow? Advice please. SS7

Edited by Spaceframe7, 26 May 2011 - 22:05.

[gruntguru]

I don't have a lot of knowedge on these engines, but those that do would probably like to know your camshaft specifications (timing) in order to recommend a CR.

[Greg Locock]

I read an article in our local paper some time ago that Avgas is not recommended for road cars as it is intended for an engine that normally runs at a constant rpm, and stays at those revs for most of its running time.

I'd be inclined to use that newspaper for some other function than supplying information. AVGAS is extensively used as a cheap form of high octane fuel for mototrsport in the USA and Australia at least.