► Fuel efficiency, range and octane questions

[birdseye]

the implication of having to have the bike adjusted is that 87 octane is outside the range of the bikes systems which do adapt to various octane levels ie it then wont cope with 98 octane without adjustment back.

lower octane fuel burns quicker so the spark has to be retarded to cope. nothing to do with the quantity of fuel injected. if you then use 95 octane, the ignition will be over retarded and I seem to remember that this can cause overheating.

so I reckon it wont work and could harm the bike.

 

[Tim Cullis]

US 87 octane is equivalent to European 91 octane, so much scope for confusion here...

The 800GS is set up for 95 octane which is called super unleaded in some countries but in the UK is referred to as normal unleaded (more chance for confusion).

The 650GS is set up for 91 octane which is called normal in some countries and isn't even sold in the UK, so we stick in 95 octane instead.

The 800GS can be mapped for 91 octane (87 octane in the US). Yes, fuel economy might suffer slightly but probably more than offset by the lower petrol price. IMHO the change to 91 octane won't have any impact on the stalling issue.

Again IMHO, sticking 97 or 98 octane (super unleaded in the UK, probably stratospheric unleaded in the USA) in either bike won't improve economy or performance. Believe me, if it did BMW would specify that for the statutory economy tests and the performance testing.

Tim

 

[WoodWorks]

thank you for the input. If one uses US 87 octane in an f800 GS NOT mapped for the lower octane fuel what happens? Just wondering if I'm out of fuel in Podunk if I can refuel with whatever is available without risk of damage.

If you're gentle on the throttle, and don't lug the engine or wring its neck (especially don't lug it), probably nothing. But if you ride the thing like some testosterone-poisoned cretin, you could be looking at a holed piston, a busted con-rod, or worse. On these modern bikes, you'd have to almost intentionally abuse the engine to do any damage at all. It's not something I'm going to lose any sleep over. If I find myself with an empty tank out in eastern Podunkistan and 87 octane is all that's on tap, well then, fill 'er up! No worries.

David

 

[Tim Cullis]

Sorry, I see I'm being redundant here.

Your confirmation is valuable.

atlatl
1. only stick as much low grade fuel in as is necessary
2. top up with high grade fuel as soon as possible
3. ride gently
4. don't allow the engine to 'pink', so no pulling from low revs

 

[tip]

does anyone have their bike set up for 87 octane fuel? my understanding is fuel economy goes down set up this way, but perhaps if one is using more fuel it would help reduce the chance of unexplained stalls. also is there any harm to being set up to run lower octane fuel but instead running higher octane when available?

I'm planning on having my ECM setup (timing retarded) to allow the bike to run on regular (87 octane in Canada). Doing this for two reasons, (1.) the dealer is a 1500 km away so it's kind of a one shot deal for me and (2.) there are lots of places around here where you simply can not get supreme (91 octane) gas. Not ideal but there's not much choice.

As for running it on both types of gas I think you'd be rolling the dice and taking your chances, especially when it came to warranty issues if you holed a piston or fried a crank/main bearings.

 

[birdseye]

There may be some confusion here about the way octane is calculated in the U.S. (Average of RON & MON) vs. Europe (RON). So the optional (lower) setting of 91 European octane is roughly equivalent to 86 US octane, which makes 87 well within the fuel mapping range here in the U.S.

Sorry, I see I'm being redundant here. Can't figure out how to delete a message.

David

You're right - I wasnt aware that American measure things differently.

But leaving that aside, whether you use the US figure of 87 octane or the EU figure of 91 octane, BMW still say the bike has to be adjusted for the change from the standard US 91 octane or EU 95 octane. To my mind that means that the anti knock sensors that normally adjust the ignition automatically to take account of octane rating are not capable of adjusting for that big a difference - if indeed they are fitted to the 800 as they are to the 1200.

If you are out of fuel in the middle of nowhere, you havent got much choice. But personally, without the adjustment completed I wouldnt deliberately use US 87 when US 91 (or whatever) is specified as standard. You may get away with it. Or you may not. The risk, particularly if you run at speed for a longish time, is that you burn through a piston.

 

[samuelsnow]

Increasing Range

Saw the pics of the Touratech test ride through Africa and noticed the big fuel cannister strapped to the zega's. being the 800 manages to do 200+ on 16 litres I reckoned an emergency a couple of litres would take you at least 30ish? Found these:

http://www.amazon.co.uk/Primus-Fuel...sr_1_2?ie=UTF8&s=sports&qid=1216995040&sr=8-2

and this:

http://www.touratech.com/shops/008/...=4865&osCsid=4a7f69fc59a8493d9e1ea9b9593e38b9

on touratech uk site looks like you could carry 3 litres (2x 1.5l bottles) with ease. Has anyone tried this?

 

[Wizard]

http://www.touratech.com/shops/008/...=6560&osCsid=4a7f69fc59a8493d9e1ea9b9593e38b9

Much better idea..... holds a 2L petrol can.... £8 for the can

 

[Wizard]

1) You mount them to the back of the pannier, so they're very unlikely to take a dig in an off
2) Filled, plastic is less suceptable to puncture damage. That's why it's being used for more and more vehicle fuel tanks
3) You're much less likely to mistake a mini jerrycan for a water bottle

 

[everywherevirtually]

5L Jerry Can

How about these...

http://www.overland-solutions.com/shoppingcart/products/jerrycans/087-0000.htm

5L on either side and they are black so match the bike well.

or these from the US

http://www.hummerhub.com/Wedco_Jerrycans.html

 

[samuelsnow]

Yeah I guess for true range that would give you well into the 300+ miles. I was more thinking of an emergency 30 miles. In terms of the 5 litre option I had spotted these on an enduro site...

http://www.dkoffroad.co.uk/dkoffroad/accessories/workshop.php?product_id=84&variant_id=

black AND yellow! perfect!

BTW that american site had a great history of the Jerry Can! I read the whole thing does that make me a nerd?!

 

[chrisjk]

Why mess about - fit a proper tank! This is an Iron Butt mod. No passenger but lots of fuel - 5.5 US gallons or 21 litres

and another - no top box but can take a passenger.

 

[Wildman]

How are you thinking about an emergency I wonder? I suppose in my book it's when you have planned for fuel stops that for some reason don't work out. In the third world or simply through bad luck in a sparsely inhabited area, this could be the lone fuel pump in xyz place that is out of fuel, no electricity and lost the pump handle, owner gone fishing etc etc. It could easily be 150 miles to the next one..

If your emergency is simply an inaccurate fuel gauge, then a 30 mile reserve might be enough.

For me, being prepared for an emergency is not covering all eventualities but making reasonable provision for the unforseen circumstance of, as you say, faulty gauge, broken pump, miscalculation etc. Carrying an extra 5 ltrs on my trip next month to the Pyrenees and Alps is prudent and to my mind, not excessive.

 

[Tim Cullis]

85 mpg at 62 mph average speed

The weather yesterday in France was bad and we decided to to a blast back to Calais a day early. We cleared Paris and got onto the motorway only to find the first services were closed. By the time we saw a sign for the next services at 53 km (33 miles) away my fuel computer was predicting 20 miles range.

I didn't want to slow too much as we were trying to get the 5:15 Speedferries crossing, so I waved Martin (who's 6'4") ahead on his 1200GSA and I slipstreamed him at 70mph. Martin is a very steady rider (IAM Observer) and I was able to keep one bike length behind him and watched in awe as the fuel consumption plummeted.

Out of interest I reset the average MPH/MPG readouts to see what could be achieved. As I got closer to the services the range was getting critical and we dropped the speed to 60mph and at times I was getting over 100mpg showing on the instantaneous readout.

The fuel computer eventually went to zero a couple of miles short of the services but I made it OK and put in 17.6 litres.

Tim

 

[Tim Cullis]

Three more lots of fuel comparisons from the Pyrenees trip (all with full luggage).

#1: 145 miles of mixed motorway/roads
650GS 55 mpg (11.8 litres)
1200GS 44 mpg (14.0 litres)
1150GSA 38 mpg (15.9 litres)

#2: 168 miles of slower roads (av speed ~40 mph)
650GS 68 mpg (11.1 litres)
1200GS 54 mpg (14.4 litres)
1150GSA 41 mpg (18.4 litres)

#3: motorway high speed, average speed 71 mph
650GS 206 miles on a 16 (17.5+) litre tank with 6 miles range left
1200GS 206 miles on a 20 (22.5+) litre tank with 25 miles range left

The 650 has its greatest fuel advantage on twisties. On high-speed constant cruising on motorways with luggage the major cause of fuel consumption is air resistance and there's not such a great difference between the bikes.

Obviously there are differences in rider styles; Steve on the 1150GSA likes to hear the sound of his Remus so loud blips on downshifts, and loves the sound in tunnels. I prefer to avoid brakes so I tend cut the gas earlier on roundabouts which probably saves a little.

Tim

 

[haydenvn]

I ran out of fuel with no low fuel light on and 50 miles left to go.

Luckly I had a friend riding with me who could go for fuel. Next time no more than 200 miles before refueling.

 

[sijohnston]

This problem is really hacking me off as I ran out of juice AGAIN yesterday.

I phoned charles hurst bmw about it on fri who were s'posed to get back to me . i ran out of fuel yesterday with 50 odd miles left.

As I wrote in this post http://www.ukgser.com/forums/showpost.php?p=1499306&postcount=28it's happened too many times. Apparently it can be recalibrated, but if it can't there's sod all point in having a trip computer!

 

[Bullwinkle]

How do you fill the tank?

Okay, obviously I know where the filler hole is, and how to work a petrol pump, but I'm having problems with splash while filling.

With my R12GS, I could stick the nozzle all the way in (the plastic bit was removed) and pump at full open nozzle until the tank was almost full. With the F650GS, I cannot stick the nozzle all the way in. If it is pulled back even a little while at full open, the resulting spray is all over me and the bike. DAMHIK

If I keep the nozzle forced in as far as it will go, I can't fill with the nozzle at full open, because the breather holes at the back of the opening start bubbling and spitting all over the seat.

So, for the 2 tanks of petrol I've had the pleasure of putting in my new bike, I have fiddled with various nozzle openings (full, half, 1/4, etc.) and numerous angles of attack and positions for the nozzle. The most efficient way I've found to fill the tank, seems to be at half nozzle or below, in as far as it will go, and perpendicular to the opening. Has anyone found any other way that works better?

You tend to lose some bragging rights for your better fuel economy if you wind up covered in petrol, and it takes you twice as long to fill up.

 

[tim dew]

Fill up on the side or centre stand 800gs?

The manual for my 800GS states that I should fill the bike on the side stand, does this allow me to use all the capacity?

I am on my 2nd fill up only (god these bikes are good on fuel!)

Thanks

Tim

 

[F650Dakar_Norway]

My 800GS appears to fill up best when on the sidestand, which also seems logical considering the shape of the under-seat tank. This bike is a bit more complex to fill up than my F650GS Dakar and requires a carefull angle on the fuel hose nozzle and a cautious use of the pressure lever. I prefer to dip the nozzle 3/4 in and slanting it towards the bike while keeping a careful watch for overflows, thus allowing escaping air from the tank to pass mostly at the starboard edge of the tank opening.