"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more."

 

Harleys with fuel injection and ECU's do have knock sensors.

"With the Delphi EMS, the key features and functions of the 2001 Softail
platform include:
* Hybrid ECM technology for compact and rugged applications.
* Cylinder-independent sequential port fuel injection.
* Cylinder-independent spark timing control.
* Synchronous manifold pressure sensing of engine load.
* Predictive load estimation for accurate transient control.
* Control of idle air for turnkey starting and idle speed control.
* Cylinder identification without the use of a camshaft sensor.
* Barometric pressure compensation for operation at any altitude.
* Knock control using "ion-sense" technology.
* Engine speed-governing control.
* Engine management systems diagnostics.
* Communication interface to instrument cluster, security module and
service tools.

"Harley-Davidson customers demand reliable and durable and engine
performance," said Meier. "Our new electronics technologies assure these
requirements are met. We are proud to be on the Harley-Davidson team as a
supplier.""

 

Wrong.
Octane rating enhancing substances slow the flame front, resulting in a controlled burn.
Spontaneous combustion without being initiated by a spark, is pre-ignition.
Thanks for the third-grade Mr. science reference though.

 

I stand corrected. I didn't associate the 'ion sensor' with traditional knock sensors.
That being the case, there should be no instances of ping, since the ECU manages spark advance/retard.

 

Here's a good, easilly digested explanation of the combustion process by a friend of mine. He formulates high performance fuels as a hobby.
http://polariswatercraft.com.au/fuelforthought.htm

 

Wrong again

Think of it in terms of a diesel engine the low octane diesel fuel doesn't need spark plugs to ignite it only high compression, most diesel motors are at least 14:1 compression ratio or higher,, now with the lower rated octane fuel say 87 rated in a higher compression gasoline motor 9:1 or higher it can ignite the compressed mixture before the spark plug can thus pre detonation and the knock comes from the pre ignition of the fuel which tries to force the piston back down as it comes up to the full compression stroke. Worst case ( usually higher compression gas motors over 11:1) if the detonation continues it can actually melt the piston and rings along with valve train damage on the higher compression gas motor resulting in a seized piston or major motor damage.

Lower octane burns hotter and is good for emissions on a lower compression gas motor thanks EPA, but you give up the power, power on a built motor comes from the higher compression and the amount of fuel you can get into the cylinder on the intake stroke not the high test gas but you need the high octane to prevent pre detonation so the motor will live.
__________________

 

You guys really seem to be stuck on this notion of spontaneous combustion. This usually only takes place AFTER combustion chamber temperatures have been increased to the point that spontaneous ignition is LIKELY to occur. Detonation occurs in the last 50% of flame propagation and resluts in wildly increased temperature and pressue.

 

if our bikes have ion sensors why do alot of people comlain of pinging?

mine does ping if i lug it on the highway. at least i think it does. sounds like

peagravel hitting the fender at wot at 2000rpm in 6th un till i back off or down shift.

 

Ya'll are starting to sound like Dems and Reps with the I'm right you're wrong crap. Who cares...if your bike runs well on cheap then good for you. This is like the discussion on posers or chrome vs black...no one cares...do what you want. Isn't that the point of riding anyway?

 

+1....All I know is I have to run 92-93 octane in my RK. It has extensive engine mods. and runs like chit with anything else.