What type of gas does everyone use

[Bob Denman]

I have no idea what you just built...
But it looks cooler than a bus full of cheerleaders; on their way to a Water Park!

[PMK]

I have no idea what you just built...
But it looks cooler than a bus full of cheerleaders; on their way to a Water Park!

Bob, FWIW, in regards to internal combustion engines, there is no such thing as precombustion.

It happens on all sorts of forums that discuss engines.

The words precombustion, predetonation, and more terms that do not exist, but get used by people.

I'm sure the guys post meant preignition.

PK

[Bob Denman]

Are "pre-ignition" and "detonation", the same thing?
If not; can they have the same consequences?

[jcthorne]

Not the same but related. Pre-ignition is when the fuel air charge in the cylinder starts burning sooner than desired, sometimes before the spark plug fires, and the charge burns too quickly that the flame front fills the cylinder before the piston reaches top dead center. This is caused by heat in the cylinder and a fuel that burns to quickly or easily.

This pre-ignition leads to rising cylinder pressures before top dead center of piston travel. Detonation (the ping you sometimes hear in an engine with this condition, is the energy of the combustion trying to slam the piston back down the wrong way while the crank shaft absorbs the impact load and continues on its upward thrust. Its violent and uncontrolled combustion at the wrong time in the cycle and it does do damage.

[PMK]

Are "pre-ignition" and "detonation", the same thing?
If not; can they have the same consequences?

Bob, JC gave a good description. I would change it slightly though.

Preigniton is as he described. Burning of the fuel prior to the spark plug igniting the fuel. Preignition begins as the fuel burning, ignited by anything from hot carbon, to a sharp metal edge and so forth and hopefully continues as fuel burning.

With detonation, the fuel does not burn, but rather explodes. This violent explosion is almost instantaneous and creates huge stress within the engine.

A normal engine burns the fuel in a controlled manner. Terms such as flame front are often used. In comparison, a flame front could be considered similar to a weather front. Rather predictable and following a path.

Preignition compared to weather may be a front traveling along a path. Let's say expecting to drop rain in the city late in the day. As the weather moves, it is forced to travel over the mountains, this change lets the front begin to drop rain early. Bad example but maybe the idea of something other than the spark plug igniting fuel is realized.

Comparing detonation to weather sort of. Consider an earthquake. All seems good at one moment, the next moment it's as if a huge force disturbed everything.

Often, people are unaware of the technical differences. Engine tuners, from Kart racers to Nitro Funny Car racers know all to well of detonation. Preignition is not that common.

Ultimately much of this relates back to internal cylinder pressures. Variables such as throttle setting, ignition timing, fuel quality can come into play, and fuel air ratio mixture.

It is also possible for an engine to begin a proper burn of the fuel. However if the fuel was ignited by the spark plug at the improper time (advanced timing), the fuel could begin its burn, then as the pressure inside the cylinder increases, the possibility exists to detonate.

Hope it helped.

PK

[sddinnh]

I just can't see any reason to disregard the MFG recommendation on this issue. So I use anything at or above 91 and then just forget it and ride

[Dgjason]

I just can't see any reason to disregard the MFG recommendation on this issue. So I use anything at or above 91 and then just forget it and ride

Agree. I'm really not cheap in my old age (although being poor at one time in my life does make you think twice on the cost of things) my bike calls for 91 octane but can only find 87, 89 and 93. The price difference is 30 cents between each grade. Each time I fill up I think "would 89 be ok." It hurts but I go with the 93.

Dennis

[ChasCS]

I would love to take two equal sized jerry cans to my neighborhood Petro-Can station, or Shell. To buy equals value amounts of regular and high test fuel. Just to see how much we miss for those few extra cents a fill up of (94 octane) instead of a lower octane. Learning how much or little it actually differs, may sway some Spyder owners, to switch to a slightly lower octane. Keeping back some of that extra large government tax revenue.

It may be a real pain in the derrière. I don't know what hurts more, ryding with an over stuffed wallet or coasting along with a thin bill fold broke from the last gas stop encounter. Yeah, or hopefully it's only thin, from beings full of hundreds and not tens and twenties... ;-)

Reality sets in fast, and it's understood there is nothing left to laugh about.
We either stay home and live vicariously through others actions, by just sitting back to watch vids of other lucky people living it up... Or we can suck it up, put on our big boys pants, and fill theese tanks on a regular basis, because we ryde that much. and having a huge ball ourselves.

I was amused watching American Pickers, last night. One of their picks, included finding an old gas station sign. The price for gas was 4 1/2 cents for the gas and 6 cents government tax.
So yeah, imagine that? Even way back there, in the nineteen twenties, for 10 1/2 cents a gallon, the tax outweighed the actual price of the fresh petrol. My how times have "changed"
The price of petrol gas risen WAY high, and the tax has stayed relatively the same, but less than the current fuel costs associated.
Ok now I'm meandering... Enough said.

Chas