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Old 09-26-2013, 09:23 PM   #1
walkingbear OP
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new airhead

http://www.asphaltandrubber.com/bike...os/#more-47663

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Old 09-26-2013, 10:49 PM   #2
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Are we sure that's an airhead not a oil head or (cringe) water head. Speaking of, anyone been keeping up to speed with the 2014 Harley Davidson water cooled twins? What a trip.

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Old 09-27-2013, 12:39 AM   #3
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The new water cooled Harley will only be certain models for now. Have not seen any bikes in the wild yet.

The new Airhead BMW will have a valve cover that looks like the modern bikes. Have also not seen one of these in person
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Old 09-27-2013, 05:01 AM   #4
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They won't build a new airhead.

It will use the last of the 1200 oil head engines....a bit like a 1200R, but retro styled. It's just another BMW special using up the Old engines whilst production gets ramped up spreading the watercooled engines throughout the range. A bit like the Rockster.

Noise and emissions mean no more new airheads
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Old 09-27-2013, 01:19 PM   #5
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Originally Posted by chasbmw View Post
Noise and emissions mean no more new airheads
Not so. It's still very possible to make an air cooled engine that meets noise and emissions standards. Hell, I'd even bet that the original airheads probably still meet modern noise standards. If guzzi and harley can still sell air cooled engines, there's no reason BMW can't.
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Old 09-27-2013, 02:49 PM   #6
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It's a mixture of power output, noise and emissions......there is a new set of euro emissions regs coming our way and this might have something to do with BMWs move to limited water cooling rather than the oil cooling used on the previous range of models.
BMW seem to have found that in order to produce high horsepower AND meet regs they have had to go to water cooling. I'm sure it's easy enough to get by with air cooling if you are producing a 65 BHP Bonneville or a 55 HP Motguzzi V7, but if you want to compete at the top table then it looks as if water cooling is becoming a requirement.

The day of a simple carbed bike meeting regs is long gone, even Royal Enfild have gone to FI.
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Old 09-27-2013, 03:07 PM   #7
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Originally Posted by chasbmw View Post
It's a mixture of power output, noise and emissions......there is a new set of euro emissions regs coming our way and this might have something to do with BMWs move to limited water cooling rather than the oil cooling used on the previous range of models.
BMW seem to have found that in order to produce high horsepower AND meet regs they have had to go to water cooling. I'm sure it's easy enough to get by with air cooling if you are producing a 65 BHP Bonneville or a 55 HP Motguzzi V7, but if you want to compete at the top table then it looks as if water cooling is becoming a requirement.

The day of a simple carbed bike meeting regs is long gone, even Royal Enfild have gone to FI.
Making best power has always required water cooling. For the most part, two strokes were the first to go there and they certainly didn't do it to meet reg's.
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Old 09-27-2013, 03:45 PM   #8
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Originally Posted by chasbmw View Post
....there is a new set of euro emissions regs coming our way and this might have something to do with BMWs move to limited water cooling rather than the oil cooling used on the previous range of models.
Water cooling vs air or oil has no advantage in terms of emissions. FI and cats, yes, but the main point of water cooling is to allow higher compression ratios (more power per unit displacement) without pinging as well as running tighter piston to cylinder clearances due to lower and more stable temperature.
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Old 09-27-2013, 10:16 PM   #9
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Originally Posted by Airhead Wrangler View Post
Water cooling vs air or oil has no advantage in terms of emissions. FI and cats, yes, but the main point of water cooling is to allow higher compression ratios (more power per unit displacement) without pinging as well as running tighter piston to cylinder clearances due to lower and more stable temperature.
The temp bit is where the emissions come in. You use a certain amount of your fuel for cooling. Run it stoichiometric and it'll get so hot it melts. That extra fuel goes out the pipes. With more cooling you can run it leaner and get lower emissions. The idea is to raise combustion chamber temps without raising head temps. So you water cool the heads.
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Old 09-27-2013, 10:34 PM   #10
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The temp bit is where the emissions come in. You use a certain amount of your fuel for cooling. Run it stoichiometric and it'll get so hot it melts. That extra fuel goes out the pipes. With more cooling you can run it leaner and get lower emissions. The idea is to raise combustion chamber temps without raising head temps. So you water cool the heads.
Depends on the bike. Some have enough fin area that they don't need to run overly rich for cooling sake. The idea is not to raise temp it's to raise pressure. Higher temps are a side effect of higher pressure. Pressure pushes pistons, not heat. All that's moot though. The idea that airheads can't be made anymore due to emissions reasons just doesn't hold any water because there are plenty of air cooled bikes with carburetors still available new for sale.
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Old 09-27-2013, 11:28 PM   #11
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Old 09-27-2013, 11:53 PM   #12
Plaka
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Originally Posted by Airhead Wrangler View Post
Depends on the bike. Some have enough fin area that they don't need to run overly rich for cooling sake. The idea is not to raise temp it's to raise pressure. Higher temps are a side effect of higher pressure. Pressure pushes pistons, not heat. All that's moot though. The idea that airheads can't be made anymore due to emissions reasons just doesn't hold any water because there are plenty of air cooled bikes with carburetors still available new for sale.
Actually, it is common to all engines and the laws of thermodynamics. PV=nRT. Unless you want to get all quantum about it (know your pistons and rods constantly measure a different lenght as they go through their stroke? ) you can't get around it. Pressure and temperature are intimately related. If you throw out V, n and R as constants you get P=T. Change the pressure and you change the temperature. increase the pressure and your gas gets hotter (stick you hand on your compressor output). Increase the temperature and you increase the pressure. Increasing the temperature by actually burrning the gas itself is the little trick that makes internal combustion engines(note word: Internal) work. External combustion engines heat the gas elsewhere and pipe it under pressure to the cylinder and piston. Google: Steam engine.


BMW stopped making airheads because they didn't think they could sell them profitably. They misgauged the market once resulting in that "Last Edition" mess. But once they had a twins lineup To go with the k's, it was the end. A small cult following, which is what airheads have, don't support the marketing plans of a big company. They wanted to compete with the folks that had been stomping on them in a lot of markets for years. And thy are doing exactly that, with a turn as most powerful machine on the street thrown in. I know people that don't blink at heading cross country on an R69 or older. Even as aged as they are. That sold them back in the day. No longer. They needed new blood in the ownership, LOTS of it. How many people go down to the dealership and pick out a new car because it's easy to work on? or it'll last a long time?

To go back to emissions, I have a California spec truck. it gives away a lot of power over 49 state models just to run it's emissions gear. It's part motor, part emissions processing plant. BMW started down that road with the fresh air feed to the exhaust port in the head. But I suspect they saw the end in sight. The rest of the motor could only take so much and it was maxed out. You want more power you do the usual: Displacement, fuel management, compression, ignition and cooling. One fuel injected, 13:1, oil cooled, computer timed hex head coming up.

The problem with cooling fins is that heat can only travel so fast through the metal. You can't make the fins bigger, the heat path gets too long. You have to make them thinner and use more of them. There is an ideal ratio of length to thickness. You can't use it, the fins become too fragile..especially if you are going to hang them out in the breeze. On the other hand you can do it if you protect the fins and put them in a protected location. Then you carry the heat over to them and dump it there. Look at your oil cooler or any radiator. That's what liquid cooling is all about, the huge quantities of very fine fins.

Air cooled aircraft engines are an interesting study. They run continously at high output, unlike auto engines. They use all the tricks, like sodium filled valves at a couple hundred a pop. But they also have continuous and massive airflow. You don't idle them at lights or get stuck in traffic.
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Old 09-28-2013, 02:18 AM   #13
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Originally Posted by chasbmw View Post
BMW seem to have found that in order to produce high horsepower AND meet regs they have had to go to water cooling. I'm sure it's easy enough to get by with air cooling if you are producing a 65 BHP Bonneville or a 55 HP Motguzzi V7, but if you want to compete at the top table then it looks as if water cooling is becoming a requirement.
isn't this the point, BMW have for some reason chosen not to go down the "vintage series" route.

They could have easily competed head on with the Bonneville range by producing their own air-cooled but fuel injected range that was not aiming at competing with Jap bikes on BHP.

To my mind a missed opportunity for them, given how many Triumph twins you see across Europe.


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there is a new set of euro emissions regs coming our way
we are always craving for more Euro regs - as if there were not bigger problems to solve on this continent
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Old 09-28-2013, 02:23 AM   #14
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isn't this the point, BMW have for some reason chosen not to go down the "vintage series" route.

They could have easily competed head on with the Bonneville range by producing their own air-cooled but fuel injected range that was not aiming at competing with Jap bikes on BHP.

To my mind a missed opportunity for them, given how many Triumph twins you see across Europe.




we are always craving for more Euro regs - as if there were not bigger problems to solve on this continent

BMW also Produce smaller bikes, but to take the 800 as an example Bmw have chosen to make a small bike that produces significantly more power than the Bonneville, but uses less fuel in the process.
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Old 09-28-2013, 02:26 AM   #15
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Originally Posted by Airhead Wrangler View Post
Water cooling vs air or oil has no advantage in terms of emissions. FI and cats, yes, but the main point of water cooling is to allow higher compression ratios (more power per unit displacement) without pinging as well as running tighter piston to cylinder clearances due to lower and more stable temperature.
As I said its a mixture of Power noise and emissions......if you want all three then water cooling seems to be part of the solution
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