octanes,the power limit of an engine is air not gasoline

[raaaid]

i heard a lot on how spit i and 109 are porked for using low octanes, well:

what limits the power of an engine is how much air you can put on the cylinder, thats why turbocompressors are cool

if theres one mol of 02 you can get a limited amount of mols of H2 and C burning

if theres no enough air in the cilinder it doesnt matter you rise the octanes or put more fuel it wont burn

in other words it has identical effect on terms of power inject more gasoline to inject less with higher octanes :)

edit:

methanol injection i guess its different, its a different reaction which with the same amount of O2 you get more heat

but more or less octanes dtermines the proportion of H2 in the fuel

you can put in the cilinder lot of h in litle fuel or litle h in much fuel, its the same

what has me clueless is water injenction, anymbody knows the advantage

whay cars not use water injenction to save fuel?

[T}{OR]

If it only was that simple. :)

Both water injection and high octane levels have one purpose/advantage - greater compression ratios (http://en.wikipedia.org/wiki/Compression_ratio) and largely eliminating the problem of engine knocking (http://en.wikipedia.org/wiki/Engine_knocking) (detonation).

Methanol injection has an added bonus of cooling the engine as well.

[Ze-Jamz]

If it only was that simple. :)

Both water injection and high octane levels have one purpose/advantage - greater compression ratios (http://en.wikipedia.org/wiki/Compression_ratio) and largely eliminating the problem of engine knocking (http://en.wikipedia.org/wiki/Engine_knocking) (detonation).

Methanol injection has an added bonus of cooling the engine as well.

True Dat..

[Longbone]

i heard a lot on how spit i and 109 are porked for using low octanes, well:

what limits the power of an engine is how much air you can put on the cylinder, thats why turbocompressors are cool

if theres one mol of 02 you can get a limited amount of mols of H2 and C burning

if theres no enough air in the cilinder it doesnt matter you rise the octanes or put more fuel it wont burn

in other words it has identical effect on terms of power inject more gasoline to inject less with higher octanes :)

edit:

methanol injection i guess its different, its a different reaction which with the same amount of O2 you get more heat

but more or less octanes dtermines the proportion of H2 in the fuel

you can put in the cilinder lot of h in litle fuel or litle h in much fuel, its the same

what has me clueless is water injenction, anymbody knows the advantage

whay cars not use water injenction to save fuel?

Hi mate
read this
http://autospeed.com/cms/title_Water-Injection/A_107970/article.html

EDIT: How can this solve our problems ? Higher octane == higher FPS ??? :rolleyes: :):):)

[Kurfürst]

i heard a lot on how spit i and 109 are porked for using low octanes, well:

what limits the power of an engine is how much air you can put on the cylinder, thats why turbocompressors are cool

Essentially power output of the engine depends on how much fuel can be burned, and how efficiently. The rest is just a chain of requirements:

- to burn more fuel, you need supply oxygene
- to add more oxygene, you need to compress it so it would fit the given volume of the engine*
-- above a given air compression level (boost, manifold pressure) as it heats up the air mixture as it is compressed, you will need
--- fuels with better anti knocking properties (higher octane)
--- or to cool down the air mixture by
---- intercooling
---- water injection (to prevent water from freezing, you need to add some kind of alcohol: ethanol or methanol, for example)
---- or even fuel injection. Evaporating fuel can cool the charge down just as well, though its a bit expensive way for that..
-- or all of the above
- In the end, it also greatly limited by the mechanical stress the engine could take. This was greater limiting factor than fuel octane ratings...

*
You can also burn existing fuel more efficiently, by increasing compression ratio of the engine. This way x amount of fuel burned makes more useful work (piston moves more) However this will require better anti knocking properties

Sidenote: If you think about the above mechanism, you will realise why the German engines never got so much into superchargeing and high octane fuels. To achive the same amount of power, you need a given amount of fuel burned, with a given amount of oxygene supplied. Since these engines were of much larger displacement, it meant you did not have to use such highly compressed air to fit the same/u] weight of fuel/air mixture into a [u]smaller burning chamber. Less compression meant that less demands were made on fuel anti knocking abilities.



methanol injection i guess its different, its a different reaction which with the same amount of O2 you get more heat

what has me clueless is water injenction, anymbody knows the advantage

MW-50: Methanol-Water 50%-50% mixture. "methanol" and "water" are the same things referred. ADI on Allied planes is the same mixture as MW50 on German planes.

The water is used to cool things down by evaporating, and drawing heat away. When its injected into the supercharger, it cools down the charge, making knocking less likely. What water remains evaporates in the engine, and cools the engine from the inside by drawing away heat. (just like coolant flowing through the engine does). Heat is energy that is used to boil the water away.

Methanol or Ethanol is added as an anti freeze agent. It also burns like fuel on its own right, being an alcohol. Works like VERY high octane benzine, with less energy though. Prime reason to add is that at 30 000 feet, you will have -50, -60 Celsius around you..

[Hexcaliber]

A higher octane rating results in smoother engine running, it is a measure of how prone a fuel is to pre ignition, the higher the rating the better. In terms of performance, as already mentioned, a poor octane number results in pinking, or knocking, this throws off engine timing, results in poor compression, and causes excessive wear and damage to an engine even over relatively short periods.

The better the octane rating of a fuel, the better the compression ratio that can be used, an important factor when determining engine output and directly affecting relative engine performance.

Piston engine performance relies on more than a simple chemical interaction of hydrocarbons and air at the cylinder face. For the technology available during the early part of WW 2 the performance advantage of the higher octane fuel was significant. It allowed better compression ratios, meant lower maintenance over heads due to reduced wear and allowed engines to perform as close to optimal as was possible, for longer periods of time.

While water injection helps offset pre ignition, it also means the engine is far more susceptible to damage, and brings an entirely new set of problems to the table when considering fighter aircraft.