Forums > Maintenance > Octane issues with the 2008 R1200GS and R1200GSA

 

Although higher-octane fuels are the most appropriate to run through a modern, computer-controlled engine with an O2 sensor, maybe I'm crazy, but it's my experience that beemers (at least the boxers) will run on pretty much anything.

I'd stay away from leaded fuels if you're running the stock catalytic converter.  Leaded fuels will destroy the media in the converter.  I don't know if the media melts and blows out the pipe (which isn't such a bad thing), or if the media just clogs-up in the box.

C

 

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Another sunrise, These bright and crystal moments, Crow flies overhead.

The 2008 boxers were upgraded to 105 bhp.   I believe the compression ratio was changed, and the feature of using premium fuel was added according to the salesman I talked to last year.

A modern engine with a closed loop control (oxygen sensor feedback to the ecu) can really only deal with knock issues if it has a knock sensor.... but reliable knock sensors are very very expensive.  Modestly priced knock sensors are generally unreliable, either because they fail to detect the transient vibration with consistency, or because they just outright fail.  Most motorcycle engines do not include knock sensors.  FWIW, if there were a knock sensor, its function would be to detect the transient spike associated with the first sign of knock, and retard the timing enough to reduce or eliminate it.

So....

Maybe BMW is blowing smoke about the need for premium gas.  I would think on a GS or GSA type bike it would be better braggin' rights to be able to advertise that it will run on skunk p*s than to have to advertise that it requires premium.

If they really need premium, do these engines have knock sensors and the necessary feedback to the ecu to retard timing?

If they don't, does BMW offer ecu modifications to retard timing and eliminate the need for premium octane levels?

FWIW, on the K1200Rsport model BMW does offer an alternate ecu that is significantly detuned.  Apparantly the reason for this is the cost of insurance, taxes, and the level of license required for operation in some other parts of the world.

 

 

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Die Entropie des Motorrads wird immer groesser. Most roaches are created unintentionally. IBA #27546

I believe that it is advertised to have alternative fuel mapping, so when in a situation say foreign country, that it WILL RUN on lesser Octane fuel.

But runs best in the US on the HIGHER stuff !!

JC

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06 Ducati 620 Multistrada [Rabbit] ;

when we went to alaska last year there were lots of places through Canada and the US where 87 octane was all I could get.  Sophie (2007 K12GT) didn't seem to mind.  It may be that she didn't run as well, but frankly, I didn't notice a difference.  Perhaps just having a bigillion horsepower covers up little issues?  I always buy the highest octane/premium gas for her that I can, but I can definitely say that she will run just fine on regular old 87 octane unleaded.  I have NO experience with "leaded".  She doesn't seem to mind the ethanol added stuff either tho.

As I write this it occurs to me that Sophie is like my dog.  she just likes to go wherever I'm going and she (as well as the dog) will do whatever it takes and put up with whatever I dish out just to get to go with me.  What more could one hope for?

laissez le bon temps rouler, yall.

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jean

WHat is the compression ratio on the R12's? That would probably be what is causing BMW to recommend the higher octane fuel. All the higher octane fuel will do is reduce the pre-detonation by burning at a cooler temp than lower octane fuel. Its recommended, but not absolutely required. They (BMW) most likely just set the written standard to 91 octane so that 99% of pre-det problems dont occur. Regarding premium gas- If the motor aint pinging, why bother? Thats all premium gas was for, I thought- to eliminate pinging.

Can one even FIND leaded gas anymore, even if you Wanted it?

There is no lead in any of the gas these days, neither in premium nor in regular.  The octane boosters that are in common use are MMT and Fecene.  Lead was phased out entirely for street fuels in 1995, at least in the US.

Yes, it is the compression ratio that is at the root of the issue.... but the ignition timing and the octane are generally the ways to control knock, and since compression ratio is fixed, you go after knock by retarding timing.

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Die Entropie des Motorrads wird immer groesser. Most roaches are created unintentionally. IBA #27546

Ditto. I believe the ECU compensates for lower octane. I have used mid grade (when premium not available) and 10% ethanol with no noticable difference. I guess if you timed it on the drag strip you could measure a difference but it is very hard to use all of the KGT power (without getting speeding tickets).

1.  The 07 was a less powerful engine and was supposed to run on regular.  The 08's were bumped up by about 10 bhp and had higher compression ratios.

2.  The ecu can't compensate for lower octane unless it is getting feedback from a knock sensor, which would be unusual for a motorcycle engine. Most do not have knock sensors.

3.  Ethanol is an octane booster and generally does not cause problems when mixed at the gasohol normal rate, i.e., 10% ethanol to 90 % straight run gasoline.

4.  You generally do not get more power out of premium gasoline. The calorific value of premium gasoline is not generally higher than the calorific value of regular grade.

5.  Ethanol does have a lower calorific value than gasoline, so gasohol generally gives slightly lower mpg figures compared to straight run gasoline.

6.  There is no lead in any of our street legal gasoline at this point.  Lead was banned by the EPA in 1995.  Other octane boosters are used today.  MMT, for example, includes magnesium instead of lead.  EPA regulates the rates of dosing with MMT to no more than 1/32nd gram of magnesium in a US gallon.  This works out to about 1/8 gram of MMT per gallon as the maximum.  On the bright side, MMT works as an octane booster at rates that are measured in ppm.  I know that some brands of gas call their regular grade "unleaded."  This is a holdover from the transition period which began with the inclusion of catalytic convertors back in the early 1970's.  All gasoline you buy at road pumps in the US are lead free.

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Die Entropie des Motorrads wird immer groesser. Most roaches are created unintentionally. IBA #27546

The GS and the RT have a 12:1 compression ratio and 110 HP on the RT.  On occasion, I've had to run 87 in it and it ran just fine.  I didn't hear any knock or have any problems.  For what it's worth.

Robo

I run leaded in my 1972 Norton Commando (13.2:1 compression).  I use Aviation fuel which still has lead.  When I am not on the R1200R or the Norton I race motocross, and I have noticed a difference in performance between pump gas.  We always run Shell premium when we run pump gas for pratice.  We run VP "Ultimate 4" for races, no lead but highly oxygenated.  Have not tried this in the R12 yet.