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Old 11-06-2010, 05:25 PM   #218 (permalink)
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Location: Taos, New Mexico
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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...

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.

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

If you are getting 75 easy at less than 500 ft... I imagine you'd get amazing mpg at 7k feet where I am.

If you've got the same engine, then the prime difference between our riding factors are:

tires: advantage alvaro
fairing: advantage alvaro
rider weight: advantage alvaro
bike weight: advantage paul_g
altitude: advantage paul_g
riding style: advantage alvaro
body design: no advantage?

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.

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?

Originally Posted by alvaro84 View Post
Oh, you can call them one-offs... my typical FE ranges from ~64 to ~92mpgUS.
Having a passenger and a topcase full of books makes a difference, so does rain, cold (down to mild frost), head/sidewind... Teresa's a real workhorse, I often can't choose the weather I'm riding in.
Speed is another important factor, prolonged rides at freeway speeds could bring the FE under 60mpg (once I tried it too), so I don't do it. But at ~110km/h (~70mph) she gave me ~73mpg in the summer, which I feel much better. For ~90 mpg I need hilly area, nice weather and 1-up riding, mostly low speed in highest possible gear (only a few pulses over 55mph), and much coasting (or agressive pulse&glide on the flat which can be tiring).

I'm usually 146...150lbs (plus my riding gear, of course), of course it makes a little difference. Typical altitude is 100-200m here (~330-650ft) so the air is pretty dense. It's not even easy to find any road over 4-500m nearby.

And she's another thumper, not a twin, with the same 4-valve 652cc Rotax engine (some batches are built in Taiwan though) - a little modified compared to the old Aprilia one, which has 5 valves. (Oh, wait a minute, we have a twin too and gets similar mileage, but it's a 250cc twin )

As for tires, I've been using Metzeler Z6 (strictly road) since day one, it's the second set on, now at 22000km (I got the first pair already equipped since I bought Teresa used, and had them for ~21100km, replaced together), and inflated to sidewall max instead of BMW recommended.
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