120 big green! er wait its actually half that

 

When my bike was stock, it gave about 70. With the 351 kit , stock carb and pipe but both modified, it returns 58-62.

 

I don't carry gasoline on my back, either.

 

I always seem to around the 60mpg or better. Average mileage is 100 miles before RES. I also always fill up with 91 US octane. But this time, from my trip in New York, I got a full tank of 95 US octane. Mostly because of the hill climbs that KLX had to pull while I was there, it started to knock even with the 91 US octane.

 

Unless you have changed your compression I think putting in 91 or 95 is less power than 87 octane. You should get more power from less octane with our bikes compression. Less octane means more gas and less additives to give a higher octane.

 

WTF does that mean? Explain.

 

I needed the higher octane for the trail riding that I was doing. Even with the 91, it was starting to knock as I went WOT up 45+ degree slopes. So I used the highest octane I could get, which was the 95. Thou New York's fuel also contains 10% ethonal while the usual Oklahoma fuel is 100% gasoline. I wonder if that made a difference.

 

I think it's a condensed way of saying the higher 'octane' rating is only because of the extra additives which are mainly anti-knock additives.

Higher 'octane' pump fuels -at least in stateside pumps- are not higher octane in the true sense of the word.

 

Some interesting reads. If you have time.


What is octane?
Octane number is a measure of the antiknock quality of petrol. That is the ability of the petrol to resist knocking (otherwise known as detonation) when it is burned in an engine. There are two laboratory tests to measure octane which are run in a single-cylinder engine operated under different conditions: Research octane number (RON) and Motor octane number (MON).


Benefits of running Ellf BFK-07 (98 octane race fuel) in bikes and karts:
Elf fuels are blended to very tight parameters to ensure a consistency between batches.

The fact that BFK-07 contains no Benzene is also an advantage. Benzene is a natural enemy of rubber so using a fuel with no Benzene will mean that rubber components like carburetor diaphragms, fuel lines etc will last much longer, Go karts crank seals will not fail, a common cause of engine failure.

The other known fact is that Benzene is a cleaning agent so whilst you are in the case of a two stroke adding oil to your fuel for lubrication, the Benzene is trying to clean the lubricating oil off the moving parts. (i.e. big end, main bearings, piston etc.) This situation does not exist in Elf BFK 07.

All of this will result in a consistency in tuning, engine performance and engine life.


How can the true octane rating of Pump Fuel vary?
Because of the variety of engines it is possible for a petrol manufacturer to come up with a fuel that has a high RON, but a lower than expected MON. Although it looks normal on the pump, and is labeled “98 octane” it may perform badly. However on another day the same company may make its fuel out of a different blend to get the same RON but a different MON.

The cause of the variance in quality is due to the fact that Australian Oil companies are producing millions of litres of fuel for the purpose of supplying road cars in everyday transport. The motorsport market is very small when compared to the total quantity of fuel sold. To improve the production/quality control process would simply be too expensive. Very little consideration is given to the fact that the pump fuel is going to be used in racing.

98 octane pump fuel is the best quality fuel available to Australian Motorists. Motor racing participants need to understand however that independent testing and analysis has shown that even the highest quality pump fuels may loose octane rating over time and batches of pump fuel may vary.


RON and MON – The background into fuel standards.
The need to ‘rate’ the quality of fuel was first identified by the Aviation industry during World War I. The Aviators (like Australian racers) had a problem, many engines would suddenly self destruct through detonation. An engine might run fine on one batch of fuel but blow holes in the pistons on the next batch. The fuels seemed the same, weighed the same and may have even come from the same factory.
The fuel companies then tried to employ standards for the aviation fuel being used, but were still unable to weed out the bad batches. A standard test engine with a variable compression facility was built and the fuel to be tested run through it. This heavy duty, single cylinder engine would be warmed to a standard temperature and at a set rpm the compression increased until engine knock occurred this would give its Highest Usable Compression Ratio. Two reference fuels were later used to further improve the process.
Motor Spirit is usually rated using the Research or Motor test methods. Both use the same heavy duty, single cylinder engine but under different conditions:

Motor Octane Test (MON)
Inlet air temperature: 148.9 C
Engine jacket temp: 100 C
Engine RPM: 900

Research Octane Test (RON)
Inlet air temperature: 65.6 C
Engine jacket temp: 100 C
Engine RPM: 600

The Motor Octane Test employs a higher temperature and RPM and hence is a better indicator for a racing engine. The Research octane test gives a higher number and that's why the Australian manufacturers quote it (RON) in their marketing programs.


What to consider regarding RON and MON when tuning race engines:
The Research Octane Number (RON) gives a good view on Knock properties at low RPM (slow corner, beginning of re-acceleration). For example, RON is important for Motocross because they are always in re-acceleration.

The Motor Octane Number (MON) gives a good view on Knock properties at high RPM (speed races). The MON is important in competition where speed is the main target.

Tuners should be aware that high octanes are not required for all kind of race engines: Turbo and 2 stroke engines need high octanes, but 4 strokes engines with high RPM need a higher speed of combustion than octane.

When tuning with octane ratings in mind (Turbo and 2 strokes engines), the main parameters are ignition advance and Air/Fuel setting for the mapping parameters, and turbo boost or compression ratio for the mechanical settings.