I realise that the conditions are better for the Boxer engines than here in Africa, however I would like some input from UKGSer members.
Seems we have scratched a wound here in SA that's not going to heal quickly - unless BMW comes to the party and helps to resolve the issue.
For now - my bike's sitting in the garage under covers and I'll not ride her until they have sorted the problems we have discovered.
Around 20 GS & GSA's were tested on Saturday 22nd May - what we found was staggering.
ALL the bikes were running far too lean for our conditions, with Air/Fuel mixtures set from 14.6:1 to a whopping 15.1:1 and we use 95 Unleaded.
The slightest bit of load and warm outside temperature and the bikes ping through all the gears and rev's. The anti-knock of the engine does not work.....
The critical area is between 4000 & 4500 rpm when you're doing around 140km/hr on a hot day. Here the engine can self-destruct as it's running so lean and so incredibly hot that the valves and pistons decide to go "south".
Anyone knows anything about engines (and aviation) would realise that the fuel/air mixture is critical and if not right can cause serious damage to the engine.
With the results now being verified of the testing - other test centres all over South Africa have agreed to get groups of GS riders and test their bikes.
Our request to BMW is very simple - we live in the Southern Hemisphere - we are not part of the EU - our air pressure and temps are different and our fuel's totally crap - PLEASE allow us to change the ECU mapping to alter the Air/Fuel ratio to 13.5:1
Do any of the UKGSer's have any info or suggestions that could help (our bikes are under warranty - Power Commander is an option, but would void the warranty)....?
FYI
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AIR FUEL RATIO
See also
http://www.bristoldyno.com/tech/airfuel.htm
The stoichiometric air-fuel ratio is the ratio at which all oxygen is used up and all fuel is completely burnt. This ratio is a basic property of a fuel and is the result of its chemical composition.
When the composition of a fuel is known, this method can be used to derive the stoichiometric air-fuel ratio. For the most common fuels this however, is not necessary because the ratios are known:
• Gasoline: 14.7
http://www.brighthub.com/engineering/mechanical/articles/15235.aspx#ixzz0okRcMBEA
The "Perfect" Air to fuel ratio is 14.8 parts air to 1 part fuel. That is the point at which perfect combustion happens. This ratio is also called the Stoiciometric ratio. In the real world this ratio is too lean for normal combustion engines and produces way too much heat which does nothing for efficient production of power. The heat produced by a lean mixture can also cause engine damage.
The "Optimum" Air/Fuel ratio is somewhere right around 13 parts air to 1 part fuel (Between 12.5 and 13.Cool. This mixture produces the highest horsepower with a safe amount of heat. The richer the mixture (lower air number) the lower the heat production. If the mixture is too rich, too much cooling takes place which reduces horsepower as well.
http://www.maxlean.com/motorcyclepages/engine/fuelmanage.htm
Traditionally, the greatest tendency to knock was near 13.5:1 air-fuel ratio, but was very engine specific. Modern engines, with engine management systems, now have their maximum octane requirement near to 14.5:1. For a given engine using gasoline, the relationship between thermal efficiency, air-fuel ratio, and power is complex. Stoichiometric combustion (air-fuel ratio = 14.7:1 for a typical non-oxygenated gasoline) is neither maximum power - which occurs around air-fuel 12-13:1 (Rich), nor maximum thermal efficiency - which occurs around air-fuel 16-18:1 (Lean). The air-fuel ratio is controlled at part throttle by a closed loop system using the oxygen sensor in the exhaust. Conventionally, enrichment for maximum power air-fuel ratio is used during full throttle operation to reduce knocking while providing better driveability [38]. An average increase of 2 (R+M)/2 ON is required for each 1.0 increase (leaning) of the air-fuel ratio [111]. If the mixture is weakened, the flame speed is reduced, consequently less heat is converted to mechanical energy, leaving heat in the cylinder walls and head, potentially inducing knock. It is possible to weaken the mixture sufficiently that the flame is still present when the inlet valve opens again, resulting in backfiring.
http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html#ixzz0okQM4yfI
Air/Fuel Ratio Limits
6.0:1 Rich run limit
9.0:1 Low power, black smoke
11.5:1 Rich best torque at WOT (Wide Open Throttle)
12.5:1 Safe best power at WOT
13.2:1 Lean best torque at WOT
14.7:1 Chemically ideal
15.5:1 Lean light load, part throttle
16.2:1 Best economy, part throttle
18-22:1 Lean run limit
Most engines will not run at the extreme ends of this scale due to individual design limitations of each engine.
AUTO-IGNITION
The greater the extent to which gases are compressed the more they tend to heat up. Sometimes this causes ignition before the spark is produced. This is intended in a diesel engine, where there is no spark plug, but in a petrol engine the occurrence is called auto-ignition or knocking or pinking.
An increase in ambient air temperature of 5.6C increases the octane requirement of an engine by 0.44 - 0.54 MON [27.38]. When the combined effects of air temperature and humidity are considered, it is often possible to use one octane grade in summer, and use a lower octane rating in winter.
http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html#ixzz0okQkP4xs
R1200GS 2010 SPECS
Thanks to efficient knock control, both models are able to run on premium (plus) fuel with an octane rating of 95-98 RON (maximum output is measured at 98 RON). Under certain conditions there may be a very small loss of torque and a slight increase in fuel consumption as soon as knock control cuts in. On long tours where the rider might be required to use inferior fuel, the engine may also run on 91 RON regular fuel, using specific running data available as special equipment free of charge straight from the factory.
http://www.totalmotorcycle.com/photos/2010models/2010-BMW-R1200GS.htm
http://news.motorbiker.org/blogs.nsf/dx/bmw-updates-r1200gs-motorcycle-for-2010.htm
BMW KNOCK CONTROL SYSTEM
BMW Press Release, Spring 2004
The BMW R1200GS introduces a new system of knock control, never before used in a motorcycle engine. Knock combustion is recognised by a solid-body sound sensor matched specifically to the cylinders. Receiving appropriate signals, the electronic engine management will recover the ignition angle (i.e., it retards the angle) and protect the engine from possible damage. Engine temperatures are also taken into account in evaluating the signals and help to supplement the safety function.
Benefitting from knock control, the geometric combustion ratio on the engine has been increased to 11:1, certainly a remarkable figure for an air/oil-cooled engine with cylinders of this size. Fuel consumption also benefits - the R1200GS being almost eight per cent more fuel efficient than its predecessor in the EU2 test cycle.
Designed for unleaded fuel (RON 95) the engine, thanks to knock control, can also run on lesser fuel qualities (RON 91) sometimes found in other countries, without requiring any kind of manual intervention or adjustment. Within available limits, knock control adjusts the ignition angle automatically to the fuel on which the engine is running.
Interacting with a wide range of sensors, knock control adjusts to even the most extreme conditions and requirements, for example with the engine having to withstand extremely high temperatures and thermal exposure in desert areas. To provide this reliability, the electronic engine management adjusts engine operating parameters to ensure supreme reliability under all conceivable operating conditions.
http://www.r1200gs.info/pressrelease.html
HOWTO "FOOL" THE EMS
The ReCyclizer is a means for tuning the BMW GS. The fuel system is governed by the Motronic engine management, which is pre-programmed to inject an exact amount of fuel at a given throttle position, air temperature, RPM, etcetera.
The Motronic, based on input signals, will adjust the air-fuel ratio to approximately 14,7:1, which will make the engine run 'clean' and fuel efficient, with the drawback that this lean mixture will also make the engine run less smooth and decrease performance. Our experience is that the engine will run smoothest at approximately 13:1, a slightly richer fuel mixture. The Motronic can be tricked into delivering this richer fuel mixture by manipulating the input signals, such as the air temperature measurement. Colder air is heavier and contains more oxygen. The ReCyclizer manipulates the air temperature measurement input by lowering the temperature, and thus fools the Motronic to think the air mass has increased. The Motronic will react by injecting more fuel to balance air-fuel ratio to 14,7:1. Because the air mass hasn't really changed, the air-fuel ratio will be 13:1, resulting in a smoother running and more powerful engine, with increased gas response.
http://www.novitech.nl/abouteng.html
Yes I noticed the corrosion - but seem to remember that's quite an old GS and they were only using it to test a specific design for using the boxer engine in microlight aircraft.
