Fuel Facts

[ATF]

I hope to clarify better the differences in fuel as addressed by another topic Benzine vs Ethanol which has gone off on a tangent.

All fuels have a Research Octane Number (RON) and Motor Octane Number (MON). In Thailand only the RON is stated which can be 8-10 points above the MON rating which is a more accurate measurement of the combustibility and inherent energy of the fuel contained in the octane level. This is why you notice differences in gasohol and benzine from different oil companies even though they all have the same stated RON number i.e. 91/95. Therefore 91 gasohol could actually have a true octane level of only 81. Another factor to be taken into consideration is altitude so if you are living at sea level it is best to use fuel with a higher octane level because this will give you more power by being able to burn efficiently due to the extra oxygen, in the air at sea level, and not running the engine lean. Lean running makes the engine hotter and reduces it's life. The reverse is true if you are living in Chiang Mai, which is 1200m or 4000ft above sea level. Your engine will run rich reducing your BHP by up to 30% due to the diminished oxygen, although the cooler air may compensate slightly. So unless your vehicle has had your Air Fuel Ratio (AFR) retuned for higher altitude you would be better running 91 RON to maintain the stock AFR.

To complicate matters further there is an Anti-Knock Index (AKI) number which is posted in some countries which is the median between the RON and MON numbers It may also be called the Pump Octane Number (PON).

Generally speaking Benzine will NOT give you better performance over Gasohol, but your vehicle MUST be Gasohol compatible. You cannot use E20 in a regular vehicle which is Gasohol compatible ONLY E10. However Benzine is a must for European and American bikes. Most Japanese big bikes are correctly configured to run on Gasohol but always check your handbook. Most handbooks are online.

I suspect some Benzine gets tampered with in Thailand and other countries too for that matter. That's why I always get the best performance out of my bike when I fill up at a Caltex outside the Rayong refinery. They pay jack in delivery charges so messing with the Benzine isn't a priority.

Methane (Natural Gas) has a 120 RON 120MON and 120 AKI. Impressive. Propane (Cooking Gas) has a 112 RON and 97 MON again pretty impressive. Obviously NGV cars are not being tuned for performance but economy.

[VocalNeal]

OK what I know!

A properly tuned engine will produce more power on alcohol than on "benzine" a fact that can be confirmed by looking at the specs of any Brazilian Flexfuel car. BUT you will use a greater volume of fuel. You will use about 30%+ more volume running on alcohol. E10. E20 etc.. use less volume that E100 but still more than pure "benzine"

.

Fuel injected bikes have sensors that measure barometric pressure. temperature etc.and maintain the correct AFR. So living in Chaing Mai will have no effect on a bike what so ever. This can be confirmed by looking at EFI "cheater boxes" that fool the system into believing that it is at sea level and in a cooler climate thereby changing the mixture accordingly.

[ATF]

OK what I know!

A properly tuned engine will produce more power on alcohol than on "benzine" a fact that can be confirmed by looking at the specs of any Brazilian Flexfuel car. BUT you will use a greater volume of fuel. You will use about 30%+ more volume running on alcohol. E10. E20 etc.. use less volume that E100 but still more than pure "benzine"

.

Fuel injected bikes have sensors that measure barometric pressure. temperature etc.and maintain the correct AFR. So living in Chaing Mai will have no effect on a bike what so ever. This can be confirmed by looking at EFI "cheater boxes" that fool the system into believing that it is at sea level and in a cooler climate thereby changing the mixture accordingly.

Yes you are correct drag racers use 100% ethanol and tune their engines accordingly.

Methanol is 108.7 RON 88.6 MON and 98.65 AKI Ethanol is 108.6 RON 89.7 MON and 99.15 AKI Almost identical.

Some bikes have barometric sensors and/or wide band o2 sensors to compensate, however others do not. More octane or fuel does not equate to more power or better performance, neither does more air. It is the correct balance of the two at different revs/speed which brings maximum results.

A cheater box is a simple device which does not take into account gear, speed etc. They will not produce a proper fuel curve. A Power Commander with Autotune is needed for that after the bike has been properly dyno mapped.

[AllanB]

OK what I know!

A properly tuned engine will produce more power on alcohol than on "benzine" a fact that can be confirmed by looking at the specs of any Brazilian Flexfuel car. BUT you will use a greater volume of fuel. You will use about 30%+ more volume running on alcohol. E10. E20 etc.. use less volume that E100 but still more than pure "benzine"

.

Fuel injected bikes have sensors that measure barometric pressure. temperature etc.and maintain the correct AFR. So living in Chaing Mai will have no effect on a bike what so ever. This can be confirmed by looking at EFI "cheater boxes" that fool the system into believing that it is at sea level and in a cooler climate thereby changing the mixture accordingly.

Fuel injected bikes have sensors that measure barometric pressure. temperature etc.and maintain the correct AFR. So living in Chaing Mai will have no effect on a bike what so ever.

That statement cannot be completely true, the system will alter the FAR to maintain the correct mixture, but a loss in air density will have a detrimental effect on performance. So the bike will run okay, possibly use the same amount of fuel (possibly less), but bhp will be lower due to amount of combustible gas entering the engine to be burned.

However, I am not sure whether there exists some form of "detuning program" limiting bhp, to extend the life of the engine, in which case this could be used to compensate for the lack of power at altitude, in which case you are totally correct.

Edited March 20, 2014 by AllanB

[ATF]

Any engine will keep pumping the same amount of fuel into it's cylinders regardless of the enviromental conditions unless it has appropriate sensors to compensate. The more oxygen it receives the more fuel it is capable of burning. Loss of power at high altitudes comes from too much fuel entering the cylinder which can't be fully burned, which is noticeable by a chug chug feeling, loss of acceleration and the smell of fuel when you stop the bike.

If you're riding a Harley it probably won't be that noticeable but on a high revving sportsbike you will definitely feel it. AFR at sea level should be around 13.2-13.8:1 . My bike works best with an average 13.5:1 AFR That's 13.5 parts of air to one part of fuel. At higher altitudes you could go 13.8 to 14.6:1 but again every bike and riding style is different so knowing your fuel curve is of the uptmost importance. What target AFR was you current vehicle pre-programmed for? Remember when cars had manual chokes? This was to increase the amount of fuel on cold days because cold air is very dense so more fuel needs to be burned.