I didn't buy my ZX for fuel economy, however, how many miles do most of you guys get from a tank full of petrol. So far, filled up and used 1/4 of a tank for about 50 miles around town without being a total hooligan. Am about to do a 200 mile trip later this week and wondered if how many times I need to fill up? Could be in need of a serious service tune up!

Question - is a petrol bomb combustion or an explosion ?

Does a petrol bomb combust or explode ?

Maxx, I know that Clive at RC developments was thinking about doing a chargecooler for our cars....coool....so to speak!

 

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'I hope I die peacefully in my sleep like my Grandfather and not like his

passengers....'

If your fuel burns in your engine, that's combustion. Which is nice.

 

If your fuel explodes in your engine, that's what detonation is. Which is anywhere from not nice to disastrous.

 

Sorry m8y but in this case, Paul C is precisely right. I am sure if you check with your work colleagues, they will confirm.

 

Some petrol "bombs" (eg Molotov cocktails) are just ways of getting large amounts of burny stuff to go "whoompf" all over your "enemy" (which is also not nice).

 

Some - like the new fuel/air explosive bombs (eg BLU-82 used in Iraq and Afghanistan) really do explode which explains their far more deadly force.

 

Just about anything will explode if the fuel / air ratio is right - even flour mills have been demolished if the flour dust was fine enough and in the right (wrong!) proportion to go bang.

 

Yours Gio "I was a physicist before I stopped worrying and learned to love the bomb"

 

[This message has been edited by Gio (edited 30-08-2002).]

Sorry but you are all wrong. A phenomenon/reaction can be combustion, explosion or BOTH. In this case it is BOTH.

 

You are confusing explosion with detonation. Engine detonation is where the fuel ignites/burns/combust outside of the normal combustion chamber. Use of combustion in normal everyday parlance is purely convention. If you light an open fire, THAT is combustion but not an explosion, because there is no rapid release of internal energy. In a car engine, there IS rapid release of much (for volume of fuel/air) internal energy ie. AN EXPLOSION !!

 

An explosion does not have to be destructive or unpredictable - that is not part of the definition. Explosions usually ARE destructive and unpredictable and undesirable, but they don't have to be. If you throw a petrol bomb it is desirable for the thrower that people/property are damaged !!

Sorry but you are partially right

http://www.hastingsmfg.com/Service%20Tips/detonation_and_preignition.htm

 

And I am partially wrong.

 

It says -

Detonation and pre-ignition are forms of abnormal combustion in the combustion chamber

 

It also says -

Abnormal operation may allow combustion pressures to develop so fast that the heat and pressure will "explode" the remaining unburned fuel. This produces the knock, often called "ping", carbon knock, etc. Actually this is detonation. The knock results from the violent explosion when the normal flame front runs into the secondary flame front

 

And I am sure we can all find equally knowledgeable sources so I am not trying to p*ss on your expertise or opinions.

 

But my physics tutor would take exception to:

 

Engine detonation is where the fuel ignites/burns/combust outside of the normal combustion chamber

No. see above

 

In a car engine, there IS rapid release of much (for volume of fuel/air) internal energy ie. AN EXPLOSION !!

Yes there is rapid release but that is not an explosion if it is done correctly.

 

Shall we ask Shell?

 

if you look at combustion taking place in an internal combustion engine, slowed down, it is a controled burn, with combustion taking place from the igniting spark, burning the compressed air/fuel mixture which expands and forces the piston back down the cylinder.

 

quick search from an online dictionary:

 

Explosion (n.) n.

1. The act of exploding; detonation; a chemical action which causes the sudden formation of a great volume of expanded gas; as, the explosion of gunpowder, of fire damp,etc.

2. A bursting with violence and loud noise, because of internal pressure; as, the explosion of a gun, a bomb, a steam boiler, etc.

3. A violent outburst of feeling, manifested by excited language, action, etc.; as, an explosion of wrath.

 

note the word detonation in description 1.

detonation occours when the gasses ignite in the cyl without being ignited by the sparkplug, ie extreme temperature in the combustion chamber. the 2 flame fronts collide giving the knocking sound associated with detonation.

 

description 2, nothing in the engine bursts (hopefully!!!)

 

3 dont count unless anyones getting stressed over this!!!

 

 

 

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I feel the need, the need for speed!

 

lol, i was posting mine as you posted yours Gio!!

 

glad we have the same description of detonation!!!

 

My definition of engine detonation was quoted from another source, so I was a bit wrong there.

 

The fuel and air mixture EXPLODESThe fuel and air mixture EXPLODESThe fuel and air mixture EXPLODES The fuel and air mixture EXPLODESThe fuel and air mixture EXPLODES

The fuel and air mixture EXPLODES The fuel and air mixture EXPLODES

 

 

BANG !!!!!!!!!!!!!!!!!!!!!!

Nelson m8y I promise you it is not always the case that the fuel/air mixture explodes.

 

When it happened to Yamahe OW01s, this cause "claustrophobic pistons".

 

Bet you a whole pint (beer / optimax - your choice) and a £10 to the forum that your colleagues will say combustion good, explosion bad (if we're talking car engines anyway.)

 

Anyhow - Paul C is quite right:

 

dont count unless anyones getting stressed over this!!!

So please no stress

Maybe it's HALF an explosion ?!!!

 

I'm beginning to think that because the definitions don't rule out explosions being applicable, they do not include them either. The definition of explosion is open to interpretation, and this case is difficult to call one way or the other.

 

Who cares neway ?!!

 

Peace man ! ;-)

Well I started a bit of a science test here didn't I!

 

Anyway, 250 miles trip...80 ish on Motorway and a couple of traffic jams, plus some fun down some lanes and I averaged 25 miles to the gallon.

 

Well pleased

 

Cheers

Chris

 

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The important thing about pre ignition detonation or knocking whatever is that the explosion happens too soon before the piston has finished its upstroke. It is then trying to compress the explosion which back shocks the crank and bearings and will melt the piston crowns if it persists. Good detonation is timed so that max explosion pressure arrives just after the piston has passed top dead centre. Then the energy gets translated into forward motion instead of intense heat.

Did you say EXPLOSION ?!!

FFS here we go again !!!! LMFAO

 

you are describing what happens when the timing is advanced too much (pinking).

 

ignition takes place before TDC to allow for the burn process to take place efficiently, if its advanced too far then yes pinking will occour.

 

detonation, however can also occour from other things, and is the fuel igniting away from the plug, ie extreme temp, higher boost pressures can cause this.

 

and really, no REALLY, the fuel dont explode!!

 

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I feel the need, the need for speed!