Touratech Compares GS wethead to oilhead

[John Ranalletta]

RideApart

[AndyS]

An interesting article

I stumbled upon the Premium fuel issue recently.

I was looking for a fun small car. I test drove a load, but fell in love with a little Smart Brabus Cabrio. Well all is good. however, whilst doing my homework, I omitted to spot that the little Brab only drinks the high quality stuff. Now the point is, I still love driving the car, but the fuel cost difference is now mounting up against the running costs of the slightly less hot Smart Turbo.

Likewise, it is a shame that they didn't make this 'World' bike run on 'World' fuel.

 

[Guest Kakugo]

An interesting article

I stumbled upon the Premium fuel issue recently.

I was looking for a fun small car. I test drove a load, but fell in love with a little Smart Brabus Cabrio. Well all is good. however, whilst doing my homework, I omitted to spot that the little Brab only drinks the high quality stuff. Now the point is, I still love driving the car, but the fuel cost difference is now mounting up against the running costs of the slightly less hot Smart Turbo.

Likewise, it is a shame that they didn't make this 'World' bike run on 'World' fuel.

 

The new R1200GS has a "91 RON option" available at no extra cost here in Europe. I suspect it's probably just a firmware upgrade for the ignition/injection control module. It's more of a gimmick than anything else as 91 RON is rare (only a few fuel stations in Germany and Austria carry it these days) and exactly the same price as 95 RON (equivalent to 91 AKI).

91 RON is roughly equivalent to 87 AKI fuel so I am surprised BMW doesn't offer this option in the US.

[smiller]

Doesn't the wethead engine have knock sensors? I would expect that any engine with a 12.5:1 compression ratio would. The K-bikes have a 13:1 ratio and definitely like high octane, but will also run fine on regular fuel if necessary. I would expect the same from the wethead.

[Guest Kakugo]

Doesn't the wethead engine have knock sensors? I would expect that any engine with a 12.5:1 compression ratio would. The K-bikes have a 13:1 ratio and definitely like high octane, but will also run fine on regular fuel if necessary. I would expect the same from the wethead.

 

They surely do have a knock sensor, as do Hexheads and Camheads.

I remember when the Hexhead came out it had a sticker on fuel cap saying something along the lines "Use 98RON fuel only, 95RON allowed on emergency".

Around 2007 it changed to something along the lines of "Use 95RON only" and owner's manuals had something along the lines "Run 98RON for full power".

 

Having run a variety of fuels, I came to the conclusion 98-100RON is a waste of money. Not only the engine feels exactly the same, but fuel consumption increases by a fair bit (probably because of additives to aid fuel vaporization and hence improve throttle response).

I remember talking many years ago to Castrol engineer from their R&D center in Swindon and he said commonly available 98-100RON fuels are not designed for bike use in mind and there's no other benefit than better anti-knocking properties.

He also said they run a few dyno engine tests and their bike engines (mostly Honda's) did not see any performance improvement.

[smiller]

Yes, I would agree with all of that. People like to freak out when anyone suggests using regular fuel in high-compression engines but modern bikes with knock sensors will generally accommodate it with no problem. I do think there is more likely to be a fuel mileage increase with the higher-octane fuel (only in an engine that can make advantage of it) rather than a decrease, but since premium fuel usually costs about 10% more than regular and I doubt you'd see mileage gains anywhere near that then there's no real offset there. No doubt that there is more power available when the engine has higher-octane fuel and can use more ignition advance, the issue is what the magnitude of the real-world gains really are and whether they really advantage the rider enough to offset the increased fuel cost. Under extreme or performance conditions, perhaps, under routine riding conditions, probably not. But the price difference isn't all that much and many riders like to use premium fuel either to eek out maximum performance, or take whatever mileage increase they can get, or just because the manual says so, and that's OK. But in most cases using regular fuel is OK too.

 

[Guest Kakugo]

Here in old Europe, fuel price makes the difference: 98-100 RON fuel is usually 20% more expensive than regular 95 RON (except in France, where they are pretty much the same price, or at least were last time I was there). This also leads to fuel sitting longer in tanks and hence chances of getting deteriorated gasoline drastically go up.

 

If I'd really want to see performance increases from fuel I would just buy some oxygenated fuel from Elf or VP. Nasty stuff (though manufacturers swear it's nowhere near as nasty as a decade ago) but you can see a real power increase already without any mapping/jetting.

[lkchris]

More and more engines will require premium as fuel economy rules toughen. High compression is the key to efficiency and is the reason there are now so many turbos on smaller displacement/fewer cylinders engines. Ecotech anyone?

 

It's pretty much physically impossible to detune an engine for regular fuels and not lose performance and economy. Knock sensor "detunes" by retarding timing. The fact someone says he "can't feel it" is anecdotal. As are statements about fuel economy not tested in controlled environment.

 

Just understand that fuel economy regulations are NOT focussed on cost, they're geared toward consumption.

[mnTwin]

More and more engines will require premium as fuel economy rules toughen. High compression is the key to efficiency and is the reason there are now so many turbos on smaller displacement/fewer cylinders engines. Ecotech anyone?

 

It's pretty much physically impossible to detune an engine for regular fuels and not lose performance and economy. Knock sensor "detunes" by retarding timing. The fact someone says he "can't feel it" is anecdotal. As are statements about fuel economy not tested in controlled environment.

 

Just understand that fuel economy regulations are NOT focussed on cost, they're geared toward consumption.

 

My 2012 Mazda 3 with SkyActive has GDI, gas direct injection. It runs 14:1 compression on regular unleaded gas. As a daily driver, this summer I've gotten 40+ mpg, most recently going 500 miles on 12 gallons. Not only does it get about 10 to 15 percent better mileage than my previous Mazda 3, it has more horsepower. I really liked my older 3 and was a bit skeptical of the newer model. However, in my experience, they took a great car and made it even better. (And I'm paying less for this one than the last one!)

 

No affiliation, just a happy customer.

[Roamer]

The fact someone says he "can't feel it" is anecdotal. As are statements about fuel economy not tested in controlled environment.

 

I have a R1200RT and record every scrap of fuel that goes in. I've always done this over a succession of BMWs. I also use regular and premium and can say that whilst I accept that there must be a difference, I cannot actually statistically detect it despite monitoring over thousands of miles.

 

So the differences must be fairly small.

 

I would have hoped to see a clear difference.

[fourteenfour]

so from what I have found, it gained forty pounds or more? Is that strictly because of the new engine?

[AndyS]

so from what I have found, it gained forty pounds or more? Is that strictly because of the new engine?

 

Hi Chris, I don't understand what you mean. Can you expand on it?

[fourteenfour]

so from what I have found, it gained forty pounds or more? Is that strictly because of the new engine?

 

Hi Chris, I don't understand what you mean. Can you expand on it?

 

I was comparing the weights provided by BMW for the 2012 and 2013 models and it appears there is a forty pound weight increase, is that strictly from the new engine? As in, is water cooling adding that much weight?

[Guest Kakugo]

so from what I have found, it gained forty pounds or more? Is that strictly because of the new engine?

 

BMW gives "wet" weight as 238kg according to 93/93/CE specs, meaning the bike must be "ready to roll" (all fluids, OE tyres etc) and with a full tank of gas. The Camhead GS tipped the scales at 229kg according to the same specs. 9kg difference. If memory serves me right the bike also has a smaller tank (20L vs 22) because the new engine is very fuel efficient and no doubt to shave off a few pounds there.

 

Now, 93/93/CE is not some questionable internal standard but mandatory in the EU and the bike must be weighed in during the homologation process. It was lobbied for by European manufacturers after the Japanese started advertising some extremely unrealistic "dry weights" in the late '90s.

While they weren't lying outright, they were stretching reality quite a bit, as bikes were weighed with no fuel, no oil, no coolant, no tyres and, often, no brake and fork fluids as well.

[Huzband]

We'll have to wait (weight? ) for independent wieghts, i.e. Cycle World, Motorcyclist, etc.

[John Bentall]

The fact someone says he "can't feel it" is anecdotal. As are statements about fuel economy not tested in controlled environment.

 

I have a R1200RT and record every scrap of fuel that goes in. I've always done this over a succession of BMWs. I also use regular and premium and can say that whilst I accept that there must be a difference, I cannot actually statistically detect it despite monitoring over thousands of miles.

 

So the differences must be fairly small.

 

I would have hoped to see a clear difference.

 

Extreme conditions

Going up an Alp or two recently - 1st and 2nd gear up-hill hairpins - I could clearly tell the difference between regular and premium fuel by the onset of knocking.

 

[racer7]

With euro fuel costs and high taxes on everything else I guess I understand the premise.

But in the US with maybe $0.20 gal difference on a $20K bike- you gotta be kidding. I've been known to spend more for a good dinner than I'd save in a year and way more on farkles...

Maybe if I lived south of the border....

[smiller]

It's more like .50/gallon here ($3.39 for regular, $3.89 for premium), and I'm also in NC. So $2-$3 on a fill up, not a huge amount but then again whether the bike costs $2k or $200k has no relevance in the basic premise, i.e. either you need the additional octane or you don't.

[tallman]

Short term, usually not.

 

Long term, probably.

 

I feel very strongly about this.

 

Personally, almost all the time, premium.

[smiller]

Note that I'm not saying it's OK to use regular on a constant basis in a modern K-bike because I really don't know, I'm only saying that the pertinent factors are compression ratio, cam profile, cylinder pressures, etc., not 'the bike cost x dollars.'

 

As for me, I do use premium most of the time although like most of the others I cannot honestly discern any difference in power or mileage. My suspicion is that it doesn't really matter much when cruising out on the open road (at any reasonable speed) and at other relatively light loads, but might be beneficial in sport mode, i.e. pulling out of corners at lower engine speeds and high throttle openings, and other such operating conditions that produce high cylinder pressure. Under those conditions the knock sensors should safely limit ignition advance, but at some cost in power output. Enough to notice? Who knows.

[Ponch]

I had to run on 87 once. I could tell the difference. Still, the gas is so bad in AZ that I get pinging with 91 sometimes. I'd love to be able to put 93/94 in it just to see how it runs, meaning better. So, may be you won't notice if you ride like an old man and keep the RPMs under 5000, but otherwise, I think it's noticeable. This bike isn't a 9.x:1 compression ration cruiser. It's 12:1. That's a big difference. The fact it can run on low octane fuel without self-destructing is amazing.

[CoarsegoldKid]

I wouldn't worry about the low octane fuel around the world. Certainly BMW would use available technology on this engine. My KTM 690 Enduro R has a switch to select for poor fuel use as in low octane. BMW may actually sense the burning of non-high octane and compensate automatically.

Bye the way a good friend of mine has a wethead GS. I rode it and can say damn the bike is powerful.