► Fuel efficiency, range and octane questions

[Tom Murphy]

I've done a couple of tests on my 650 twin.
On each I managed just over 210 miles from full to when the fuel light comes on. [I'm assuming that the trip meter is accurate.]
The OBC shows about 65 km at that stage, though I haven't tested this.
Hope this helps.

 

[Ross Dean]

F800 fuel?

The salesman at my dealers and a number of people here have talked about the pros and cons of getting the F800GS sparking/fueling (I am no mechanic) changed to cope with lower octance fuels.

Two questions:

I cannot find any mention of it in the user manual/service book supplied with the bike. Anyone know where I can find a BMW reference for this?

The mechanics at my dealers have not heard of this option and say that the bikes system will compensate automatically when it encounters lower grade fuel. Other posts imply that there is no need provided care is taken when riding with lower octane and even leaded fuel. Am I fussing about nothing?

Thanks

 

[Ross Dean]

Sad as it is to reply to my own post, this is the bottom line as far as Ocean of Plymouth is concerned:

The F800GS does not require any alteration to run on lower grade fuel. It compensates ignition or whatever (I remind you I am no mechanic) for the fuel it uses automatically. BMW does not have a procedure for altering the ignition or fuel mapping of the F800GS to account for lower octane level fuels and none is needed.

 

[CourtFisher]

F800 fuel ("octane setting"?)

Sad as it is to reply to my own post, this is the bottom line as far as Ocean of Plymouth is concerned:

The F800GS does not require any alteration to run on lower grade fuel. It compensates ignition or whatever (I remind you I am no mechanic) for the fuel it uses automatically. BMW does not have a procedure for altering the ignition or fuel mapping of the F800GS to account for lower octane level fuels and none is needed.

The original (Nov 2007) BMW press kit for the 8GS, and the current 8GS "Technical Data" text on the International, US and UK website(s),
http://www.bmw-motorrad.co.uk/uk/en/index.html (click thru to F800GS Technical Data) reads:

"Fuel type Unleaded super, minimum octane rating 95 (RON); with optional engine mapping compatible with 91 RON"

The original press kit isn't explicit, but implies that this "optional engine mapping" is available only as a factory-installed modification (at the time a new bike is ordered), rather than a modification that can made by a dealer or owner. That may explain why Ocean or any dealer doesn't know about it.

Experience suggests that the 8GS can be run temporarily/ once-in-a-while with lower octane fuel, without harm, that the engine "adjusts." I suspect (don't know) that the factory-installed mod is only for bikes being sold in markets around the world where higher octane is simply not usually available, or where the owner knows in advance that's where most riding will be done.

 

[jimbob59]

Octane

I saw that in the press kit and "assumed" the modification could be made by the dealer..... maybe not....

On the back cover of the manual it says:

91 ROZ/RON, Regular unleaded
(fuel grade, usable with power and
consumption-related restrictions)


but I could not find and explanation of the "restrictions" ....

I understand that some of the higher end BMWs have knock sensors and can dynamically adjust ignition timing to compensate for lower quality gas, but that the F800GS/F658GS do not have this sensor.
(I could be wrong here....)

 

[tip]

Engine Remapping and what BMW Canada told me

I was going to have the engine remapped to run on North American Regular Pump Gas. This is an option available from the dealer. They install a new mapping program in the CPU and retard the timing. YOu can also have the factory install the software during production. Your choice.

For my situation supreme gas is readily available here <u>but</u> it's not available in many of the more interesting places. Hence the problem

So after a lot of reading of forums filled with opinions on the matter I decided to call BMW Canada and get some facts. I spoke with their lead tech guy and he told me that the remap was only worth it if one was planning to drive across Africa where there would be no supreme gas. So, if you were going to run the bike <u>exclusively</u> on regular pump gas, then get the remap done.

So, where does that leave me? I was also told that you could run on regular pump gas for a few tanks and that it should not harm anything. Worst case, add some octane booster to the tank of regular pump gas.

I was also told that the bike does not have knock sensors (which allow the cpu to adjust for poor grade fuel) because the cylinders were so close together that the sensors wouldn't fucntion correctly as they wouldn't know which cylinder the knock (detonation) came from.

So, I decided to leave the bike stock and take my chances on running on regular if I'm left with no option.

The original press kit isn't explicit, but implies that this "optional engine mapping" is available only as a factory-installed modification (at the time a new bike is ordered), rather than a modification that can made by a dealer or owner. That may explain why Ocean or any dealer doesn't know about it.

Experience suggests that the 8GS can be run temporarily/ once-in-a-while with lower octane fuel, without harm, that the engine "adjusts." I suspect (don't know) that the factory-installed mod is only for bikes being sold in markets around the world where higher octane is simply not usually available, or where the owner knows in advance that's where most riding will be done.

 

[John Armstrong]

I've noticed the sharp intake of air both times I've opened the filler cap. I wasn't aware of the tank drawing in.

Tim

Mine seems to be doing that now. Did you find out why Tim?

BTW filling up on the side stand gets the most fuel into the tank

 

[Klanky]

Sad as it is to reply to my own post, this is the bottom line as far as Ocean of Plymouth is concerned:

The F800GS does not require any alteration to run on lower grade fuel. It compensates ignition or whatever (I remind you I am no mechanic) for the fuel it uses automatically. BMW does not have a procedure for altering the ignition or fuel mapping of the F800GS to account for lower octane level fuels and none is needed.

I can say that after topping up my bike with diesel and having emptied most of the fuel out before topping up with 'fresh', the bike ran fine but would not let me rev hard or use the upper rev range. It just pootled along at about half power. Which is still plenty.

After diluting the mix even further the bike returned to full power with no aparrent ill effects.

So if it'll run on diesel, it should be fine with rough fuel.

 

[jimbob59]

gas gauge / tank venting issues...

Just a pointer ... BMW apparently has "PUMA" tech. bulletin out that covers various fuel system issues...
I don't know what "PUMA" stands for ... maybe somebody on your side of the pond can fill us in?

See this thread for details:

http://www.advrider.com/forums/showthread.php?p=9482043#post9482043

Jim

 

[Blobby]

65 mpg

Well I was very impressed with the F800GS yesterday. 225 miles up/down hills riding mainly wiggly tarmac lanes with lots of stop/starts in Wales and got 65mpg. Pretty damn good in my book and very easy of your wallet. It's a good little motor.

 

[freeloader]

Just a pointer ... BMW apparently has "PUMA" tech. bulletin out that covers various fuel system issues...
I don't know what "PUMA" stands for ... maybe somebody on your side of the pond can fill us in?

See this thread for details:

http://www.advrider.com/forums/showthread.php?p=9482043#post9482043

Jim

I can't remember what "PuMa" stands for, but it's easily Google-able...

In a nutshell, I think it's where a technical problem has foxed your local techs and they've got BMW themselves onto the case to help them investigate.

And that's possibly an oversimplification, so don't quote me, I left 5 minutes ago...

 

[mark2jag]

Fuel consumption...........

1000+ miles and averaging 58 mpg mainly on country lanes

Well now, theres a question. My 800 has about 3000 miles on it,and seems to make no difference whether i nail it or bimble round in high gear and low revs(which it doesn't like!!!!)the onboard fuel computer tells me im doing 51 MPG. Ive tried resetting it dozens of times and riding at different speeds, but it always comes back to 51 MPG, how very odd!!

 

[Manxlad]

Well I was very impressed with the F800GS yesterday. 225 miles up/down hills riding mainly wiggly tarmac lanes with lots of stop/starts in Wales and got 65mpg. Pretty damn good in my book and very easy of your wallet. It's a good little motor.

Hey blobby....Was you two up and heading through coed gelert / beddgelert in snowdonia on the A498??????????
I saw a bumblebee going pass while a sat having a coffee and giving my f800
a good rest after 589 miles in 2 days around wales!!! A crackin bike.

 

[divelandy]

Well now, theres a question. My 800 has about 3000 miles on it,and seems to make no difference whether i nail it or bimble round in high gear and low revs(which it doesn't like!!!!)the onboard fuel computer tells me im doing 51 MPG. Ive tried resetting it dozens of times and riding at different speeds, but it always comes back to 51 MPG, how very odd!!

Have you ever reset the average MPG-ometer?
Influencing your average MPG over 3k of measurements during a short ride is going to be tough!

Steve

 

[Hexme]

Milage?

Whats the most miles you've got from a full tank on your 650/800?

 

[freeloader]

Not sure, but the fewest miles I've had was 198.9 at motorway speeds. When the engine cut out, the "miles remaining" counter claimed I could go on for a further 8 miles.

And that's the only time I've run the tank to empty, so, dunno. However, I've just had a software update which is supposed to make the range counter more accurate (and the fuel gauge less so , but that's what the tech told me). Once the bike's had all its warranty work done I'll have to run it to empty again, just to check on that range counter, but I'll be carrying a spare 5 litres with me.

 

[mvs tony]

tank range

Whats the most miles you've got from a full tank on your 650/800?

had just over 200 miles without running dry, showing 18 miles left on range on my gs800

 

[freeloader]

Not sure, but the fewest miles I've had was 198.9 at motorway speeds. When the engine cut out, the "miles remaining" counter claimed I could go on for a further 8 miles.

And that's the only time I've run the tank to empty, so, dunno. However, I've just had a software update which is supposed to make the range counter more accurate (and the fuel gauge less so , but that's what the tech told me). Once the bike's had all its warranty work done I'll have to run it to empty again, just to check on that range counter, but I'll be carrying a spare 5 litres with me.

And I should have mentioned, that's on an 800, not a 650.

 

[Greggers]

220 mixed miles for me - but I'm not particularly gentle with it... Even though the 'miles left to empty' counter said zero I managed an extra 10 miles before spluttering to a halt (I had a 5L can with me..!). I need to do that a couple more times before trusting it though...

Interestingly, after my last software update the average mpg went from 49 up to 58 though ...

Greg

 

[freeloader]

Interestingly, after my last software update the average mpg went from 49 up to 58 though ...

Greg

Is that as displayed on the OBC, or did you do the calculations? I tend to view the OBC's readouts as approximations.

But if those are figures that you've worked out yourself, I'm impressed. I hope I get the same result.