[alvaro84]

Originally Posted by paul_g

How do cold temps affect mpg? There is more oxygen density in cold air, I think. So, does that make the engine burn cleaner or richer? I have a Teknic jacket with a thermal liner that permits me to ride down into the low 20's for good distances without feeling so much as a hint of cold. But I don't recall it affected my mileage at all. Still 65-70. Now... dropping down to 4,000 ft elevation did take a toll on my mileage. That, and the fact it took place in a city with lots of starts and stops...

AFAIK the engine needs extra fuel when cold, just to keep the right fuel:air ratio, so the shorter the trips (more cold starts) the heavier the effect on FE (FAS - forced auto stop - prolongs warm ups too, so I mostly give up on it when cold). They also say that colder air also denser enough to affect aero drag, and cold rubber has more rolling resistance (this is something I don't understand - why are we inflating them hard if it hurts?). I really don't know the amounts, but it seems that I can't coast as long as I can do in the summer.

Do you know if engine rpm plays a role in efficiency? I've heard bikers say it doesn't play a role. But I usually try to keep the rpm's in the sweet spot, figuring the bike has to work harder at either the low or high end of each gear. Not sure what the science is there.

The science would be a proper BSFC diagram which I haven't seen about this particular engine - or any motorcycle engines Anyway, I try to keep my RPMs as low as possible without feeling the engine trying too hard, rewarding me with strange noises. This is somewhere ~2500rpm in 2nd-3rd, less in 1st, a bit more in 4th, and ~3100-3200 when climbing a hill 2-up in 5th. It limits my experiments with DWL [the opposite of P&G on hilly roads] because the speed at 3200rpm (~80km/h, 50mph) is not much slower than my normal cruising (if I do anything like that...)

When you say "coasting" do you mean you are turning off the engine on downhill? Or shifting into neutral?

I usually just hold the clutch tight as I hear scary grinding from the gears if I try to shift out of neutral at higher speeds than ~20mph. So I don't shift into neutral unless I'm about to stop.
Sometimes I turn off the engine - when the coasting promises long enough (I know a place nearby where I can coast for 2.2km, and several ones where I stay fast enough for 600-1000m, these are mostly places where I'd slow anyway because of a town or railway crossing). Other than that the engine stays idle (and still turns much less than it would without coasting).

I ride my bike consistently pretty hard. I'm a new rider still having a love affair with the power and torque of the bike and haven't settled back into the just cruising mode. The feeling of accelerating up hill is one that is hard to resist.

I think this is the main difference. I must admit though, that Pulse&Glide (I do it pretty much on my commutes on these hilly roads) is another type of 'hard' riding considering engine/transmission wear. Revs are still not high (I usually go up from ~2800 to 3600-4500 in 5th, ~2500 to 3000-3500 in 4th and less if I have to stay in lower gears because of the PSL) but I accelerate all the time when I'm not coasting. Especially uphills - so I use the engine with decent load and have a longer glide after the crest

So I accelerate too - I just try to avoid braking at any cost Braking (including engine brake!) is for unforeseen events (and to stop), I try to anticipate and coast whenever I have to slow down not to waste momentum

When I have extra weight and I don't feel the engine 'too powerful' I use a DWL-y approach lately: I let the bike slow down uphills with constant or even easier throttle, then
a. I accelerate on the other side with the same constant throttle, helped by the gravity, getting momentum for the next hill
b. I 'pulse' right on the crest and glide down.

Unfortunately I can't often gain speed by starting slowly and gliding downhills. Motorcycles are light and have bad aero drag (especially when you sit upright), so pretty steep declines are needed to maintain (or accelerate to) highway speeds. And roads that are steep enough are usually full of sharp turns, so this is where I need some kind of braking

BMW recommends a pretty low psi for the Tourence duals. 24 for the front and 28 for the back. Probably because the bike is designed to do some off road. What pressure do you have yours pumped to?

It's ~42psi. Feels a bit harsher but grips even bad roads fine.

Huh it's long, I hope I haven't left too many typos in the text...