Man accused of pumping aviation fuel into car at California

[scrambled_legs]

Man where's the mechanics in here?? I hate reading discussions on octane, cause no-one really understands it. Knock sensors throttling back for you??? A higher octane is not harmless and a high octane with lead is lethal.

Manufacturers determine the octane required for your vehicle. They ensure that the engine will run without pre-ignition (ignition prior to TDC) causing pinging knocking. The higher the octane, the harder it is to light and it provides a slower and smoother explosion than low octanes. Your engine engineers, will determine the octane required based on pressure, temperature and engine spark advance.

Pressure is simply your compression ratio. The ratio that the air sitting in the cylinder is compressed. If the piston is at BDC (bottom dead center) and there is 100cc of air in the cylinder and at TDC there is 10cc, then the compression ratio is 10:1. Turbo chargers and super chargers will also increase this by providing already compressed air at BDC. Another thing that effects your compression ratio that people don't pay attention to, is altitude. The higher you are, the less ambient air pressure. So you're starting with less compressed air than at sea level. You'll notice that places like Denver will run a lower octane on their regular unleaded then San Diego. If you live in Denver and are filling up for a trip to the coast, throw in some mid grade gas instead of regular.

Temperature is simply the inside cylinder temperature that your engine operates at. This can also be affected by carbon deposits which will heat up red hot and act as embers in a fire and ignite the gas prior to the spark. Just another reason why running engine cleaner's are more important than running high octane.

The last thing is your engine spark advance. The amount of time between the spark prior to TDC. There's a delay between the time the spark ignites the gas and the time that the pressure from the exploding gas, provides a force to the piston. The spark plug is fired as the piston is traveling upwards still, so the gas ignites and starts forcing the piston down just after its started back downwards. Running higher octane takes longer for the gases to ignite providing a slower smoother pressure downwards. If your ignition is significantly advanced, you have to run high octane so it doesn't ignite quickly and create a sharp downwards force on the piston while its still traveling upwards. This is where knock sensors come into play. If it senses engine knock, it'll retard the spark. This sensor only works when the preignition is soley due to timing. If the timing is caused by too low an octane causing preignition before the spark fires, it'll do nothing. The same thing happens if the preignition is caused by carbon build up by a cold running engine. The knock sensor is helpless to prevent it other than turning on the check engine light.

Our stock car engines are generally not designed for high octane and running it simply makes the engine less efficient will cause it to run cooler and thus create more deposits in the cylinders and a greater chance for pre-ignition. Pre-ignition is anything but harmless and can easily destroy your bearings causing your engine to eventually blow. Even if you don't have enough carbon for it to occur, the fouled spark plugs/injectors/valves will cause enough minor problems to still be a headache.

Now take the lead additive and add it to the equation. Engines designed to run on lead have significant differences then the engines designed to run without. It's not simply a fuel pump, it's the whole design. All your tolerances in a lead engine are far greater as the lead acts as a lubricant as it runs through the engines. Todays engines have far less tolerances and running lead will cause lead deposits to be left in areas that don't have enough room for it. The valves will start sticking and pretty soon your engine won't start when its cold or will start but have no power until the lead warms up and the valves start opening and closing. Eventually it'll build up to the point that the valves won't open and close at all. I used to fly a plane where we had to run mogas once in a while to clean the lead deposits out of it. If we never the valves would stick and it'd never get full throttle until fully warmed up or worse.

So you take the combination of low temps and lead and pretty soon your engine will stop running one way or another. Just hope its because of the deposits that can be cleaned relatively easily and not from pre-ignition, cause that'll be a new engine.

PS we used to have drag racers filling up on our 100LL to cheap out on racing fuel, until their engines had a little bit too much lead run through them. Those engines were designed to run on 100 octane but not the lead.

Confused yet??? Bottom line trust the engineers and only run what your car/plane is designed for.

[Big Pratt]

Excellent briefing you gave there scrambled_legs!

One thing I'd like to add is that it's not the octane per say, but the octane RATING that you're all talking about.
It's just a scale of reference to indicate the resistance to knocking of a given fuel batch as compared to a mix of iso-octane and heptane.
The octane rating being the percantage of iso-octane in that mix, that would provide you with the same resistance to knocking as the fuel tested.

And there are two widely used ways to determine that rating that are averaged to give you the rating displayed on the pump.

If you were so inclined you could determine the octane RATING of a cheap hooker's perfume!

BP

[Four1oh]

my 1973 nova with the 350 in it loved the taste of 100LL

[scrambled_legs]

my 1973 nova with the 350 in it loved the taste of 100LL

For how long and did you ever switch back and forth getting the mogas to clean out the deposits? It could be that the engine was so loose that the lead deposits helped tighten things up. Being a 73 Nova I imagine it was rebuilt and given a compression ratio boost, so the 100 octane maybe wasn't such a bad thing.

Big Pratt thanks and good point. You can have the same Pump Octane Number (PON) even though the RON (Research) and MON (Motor) are on opposite ends of the scale as its an average.

[Meatservo]

Never mind the chemistry... Wouldn't the news people be interested if they found out about aircraft being operated on automotive fuel?

[. ._]

My 1979 Suzuki GS750 ran on 100LL for a summer. I found it was slightly harder to start, but when she was warmed up had a bit more power. I could be imagining the more power bit.

Went for a ride once, and the guy following me on his bike said after the ride, "Hey man, your bike smells like a Zlin."

-istp

[KAG]

forgot to mention the beetle has a few engine modifications

vnt17 turbo upgrade
huge .216 injectors
boost controller
ecu flash (unitronic)
cat-back straight pipe

puts out 160hp and 305 ft-lb torque and still gets amazing mileage without any difficulty starting in -40 weather

You on freds TDI forum?
I was wondering about Jet a in a diesel, I currently have 2 myself. What do you recommend for diesel additive or will any do. I was running stanadyne but now just using power service.

[imarai]

Regarding the removal of the zinc-based additive. Yes, it can reduce cam lobe and valve stem/guides/lifter life in some engines. L*c*s makes both a fuel tank and crankcase additive that can substantially reduce that problem. It can be found in most Ukrainian Tire stores.

Good points on octane and cetane on the previous threads. It is hard to get by the pervasive myth that higher octane always translates into greater power and torque. Remember: THE HIGHER THE OCTANE, THE SLOWER THE FLAME FRONT SPREADS AFTER IGNITION. HIGHER OCTANE PROVIDES FOR A SMOOTHER, MORE EVEN IGNITION/COMBUSTION, THEREBY ALLOWING FOR HIGHER COMPRESSION RATIOS, AND A MORE ADVANCED IGNITION TIMING.

[Track]

forgot to mention the beetle has a few engine modifications

vnt17 turbo upgrade
huge .216 injectors
boost controller
ecu flash (unitronic)
cat-back straight pipe

puts out 160hp and 305 ft-lb torque and still gets amazing mileage without any difficulty starting in -40 weather

You on freds TDI forum?
I was wondering about Jet a in a diesel, I currently have 2 myself. What do you recommend for diesel additive or will any do. I was running stanadyne but now just using power service.

im not a member of any diesel forum except beetle.org (but i do read fred's occasionally)

you'll get better info on there, but i use stanadyne also (8$ bottle can serve approx 5 full tanks) and ive never had any complaints...cant remember which product i was using before but ive noticed an increase in economy since the stanadyne

[Hedley]

My 1979 Suzuki GS750 ran on 100LL for a summer

I have had poor results, running 100LL in non-aviation engines, I
suspect because of it's poor atomization. You don't want
vapour lock at FL240, after all.

If you want a really good gasoline, I might humbly suggest
cocktailing Sunoco 94 and 100LL, using roughly 75% mogas
and 25% avgas. This will result in a much better gasoline
at sea level, IMHO. The lead in the 100LL will help increase
the octane rating of the Sunoco 94.

[scrambled_legs]

If you think higher octane = more horsepower... you don't know the first thing about combustion. You want the lowest octane that doesn't produce pre-ignition, in order to get the most horsepower and best operation of your engine. Why do you think racing fuel isn't 500 octane?

[Four1oh]

my 1973 nova with the 350 in it loved the taste of 100LL

For how long and did you ever switch back and forth getting the mogas to clean out the deposits? It could be that the engine was so loose that the lead deposits helped tighten things up. Being a 73 Nova I imagine it was rebuilt and given a compression ratio boost, so the 100 octane maybe wasn't such a bad thing.

Big Pratt thanks and good point. You can have the same Pump Octane Number (PON) even though the RON (Research) and MON (Motor) are on opposite ends of the scale as its an average.

i'l'l guarantee you it was loose, since it was all original, never rebuilt. I did rebuild the 4 barrel carb though.