24 replies to this topic

[Guess-Works.com]

just had a read of wikipedia about 'free radicals' and the following sentence jumped out at me..

Tetraethyl lead was once commonly added to gasoline, because lead itself deactivates free radicals in the gasoline-air mixture. This prevents the combustion from initiating in an uncontrolled manner or in unburnt residues (engine knocking) or premature ignition (preignition).

So on that statement... Isn't Adding 'free radicals' to the mix is actually going to make matters worse not better ???

[cap'n crunch]

just had a read of wikipedia about 'free radicals' and the following sentence jumped out at me..

Tetraethyl lead was once commonly added to gasoline, because lead itself deactivates free radicals in the gasoline-air mixture. This prevents the combustion from initiating in an uncontrolled manner or in unburnt residues (engine knocking) or premature ignition (preignition).

So on that statement... Isn't Adding 'free radicals' to the mix is actually going to make matters worse not better ???

is it just me that has read that the other way around... to me it looks like they added tetraethyl lead because "lead itself" (which i read to mean normal or lead on it own) "deactivates free radicals"? it then goes on to say the lack of free radicals "prevents the combustion from initiating in an uncontrolled manner"

or have i got the wrong end of the stick?

Edited by cap'n crunch, 11 June 2008 - 07:35 PM.

[Guess-Works.com]

Wrong end of stick.... I think.

I look at it this way... pre-ignition (pinking) is bad... anything which supposedly introduces something which is going to increase to possibility of pre-ignition therefore must also be bad...

Tetra-thingy Lead is what's in 4 star... it's not pure lead in petrol, you can't just chuck a lump of lead in your tank and expect it to make the fuel leaded ( as has been tried by many of these in tank lead additives ) as lead does not dissolve in petrol.

Edited by GuessWorks.co.uk, 11 June 2008 - 07:58 PM.

[paulrockliffe]

Tetraethyl lead was once commonly added to gasoline, because lead itself deactivates free radicals in the gasoline-air mixture. This prevents the combustion from initiating in an uncontrolled manner or in unburnt residues (engine knocking) or premature ignition (preignition).

That could go either way the way its been written, though the "prevents the combustion from initiating....." bit belongs to the addition of Tetraethyl -lead, not to the reference to lead when the paragraph is constructed this way. But thats not necessarily what the author intended, their english could be C**p.....

[cap'n crunch]

from wikipedia

"Uses of tetraethyl lead as an antiknock agent

Tetraethyl lead was once used extensively as an additive in gasoline (petrol) for its ability to increase the fuel's octane rating. A high enough octane rating is required to prevent its detonation during the compression stroke ("knocking") in the engine.[1] Anti-knock agents allow the use of higher compression ratios for greater efficiency[2] and peak power. The use of TEL in gasoline was started in the US while in Europe alcohol was initially used. The advantages of leaded gasoline from its higher energy content and storage quality eventually led to a universal switch to leaded fuel. One of the greatest advantages of TEL over other anti-knock agents or the use of high octane blend stocks is the very low concentrations needed."

to me that sounds like i did get the right end of the stick...

[Guess-Works.com]

No.... what you've got in your fuel line is something which is apparently increasing the number of free radicals in the fuel

Quote from above

The System 4 fuel cells initiate improved combustion by the creation of free radicals

TEL was added to fuel to prevent the early combustion of the fuel, in other words counteracting the effect of the free radicals.

I'll repeat this bit again... It's NOT LEAD in petrol when you talk about LEADED Petrol, it's TEL which makes petrol LEADED.

Look up Thomas Midgley, as I remeber him from QI a few weeks ago, he's known as the man who has single handedly caused the death of the most people...

Not only did he discover the usefulness of TEL, but also was the person who gave us CFC's...

[poisonberry]

Okey .. properly confuzzled now.

Does all this mean that if I cant get hold of 4 star, I should use the high octane 98 fuel at the pumps (with additive 'course) in stead of the 95 octane?

I was forced to put some high octane in my car yesterday( there was nothing else save diesel at the pumps), and now whenever I slow down she hacks and sputters like an old maid

I have a 200mile return journey to do with her tomorrow, but am as nervous as nobody's business. Have recently had the engine out and cleaned and stuff replaced, and checked over at a garage last thursday, took her up to Forest of Doom the last weekend everything went great ... but now this ... should I be worried?

[Guess-Works.com]

No just use regular unleaded with valvemaster plus, not only does this introduce an additive which replicates the effect that the Lead ( read Lead as TEL ) use to provide, but also is an octane booster which brings the effective octane level of the fuel upto what 4 star is rated at.

Basically means you need do nothing to your engine.

[poisonberry]

Thanks John

on reading another thread .. I now suspect that my clutch have become contaminated .. ffffffffffff*magicword*K

[pantera2075]

FWIW Tetra-ethyl (or Tetra-methyl) lead when added to petrol, both lubricates the valves and raises the octane level of the fuel.

To clarify octane levels: The higher the octane level, the more stable the petrol becomes - effectively meaning that it is more difficult to (and takes longer to ) ignite. This is where the ignition timing comes into it: Heat and pressure, and the spark are present in the combustion chamber, to a point where using low octane fuel would make the mixture explode before the piston had reached the top of the compression stroke and spark has triggered - hence, pre-ignition. You have to retard the spark slightly to run unleaded to make it fire closer to TDC - as it burns easier.

Additionally, if you want to raise compression to make more power, you need a higher octane rating, as the pressure in the combustion chamber will be higher , and will thus again promote pre-ignition.