Why does liquid cooling allow for more power?
Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
Scarey thought. HD comes out with a big *** HP water cooled motor for the Tour/Dyna/Softail frames. They will have to redesign the frames so the bike can be ridden and handle the HP and get thru the corners.
Big Kahuna HDF Member
Joined: Feb 2006
Posts: 23,881
Likes: 34
From: USA
Nothing scary about it. They could easily beef up the suspension on the existing platforms with just the available aftermarket mods out now enough to do the job. (true-track etc.) They could also just water cool the heads like Kawasaki does with it's Vulcan engine without changing the look much at all. Most of the heat is in the heads. Cool the heads and add a radiator/oil cooler combo that increases the oil capacity by 1 quart and you are there.
Ultimate HDF Member
Joined: Sep 2007
Posts: 8,831
Likes: 15
From: Nomad
Comparing modern motorcycle engine design to 60+ year old aircraft engine design? Really?
The technology of liquid-cooling has progressed a bit since then. How many motorcycles are crippled on the side of the interstate because a piece of gravel from a truck took out the radiator, only to be humiliated by a Harley cruising by no problem on one cylinder?
(And, the radiator in the P-51 was behind the cockpit; the intake was ventral. Plenty of P-51s in the Pacific, too.)
The technology of liquid-cooling has progressed a bit since then. How many motorcycles are crippled on the side of the interstate because a piece of gravel from a truck took out the radiator, only to be humiliated by a Harley cruising by no problem on one cylinder?
(And, the radiator in the P-51 was behind the cockpit; the intake was ventral. Plenty of P-51s in the Pacific, too.)
Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
Tourer
Joined: Mar 2009
Posts: 270
Likes: 0
so in english... why does harley stick with air cooled?
it sounds like the water cooled is faster, more efficient, and more power... along with "more advanced" and therefore "better".
is willie g. (the lead designer) just a dinosour who is living in the 60s and doing more to hurt harley than help it?
it sounds like the water cooled is faster, more efficient, and more power... along with "more advanced" and therefore "better".
is willie g. (the lead designer) just a dinosour who is living in the 60s and doing more to hurt harley than help it?
Club Member
Joined: Feb 2008
Posts: 18,575
Likes: 4
From: Norfolk, VA
That's the answer. The tolerances in Harley engines are sloppy by comparison (because they have to allow for expansion at lower RPMs). Because liquid-cooled engines can keep their temperatures and expansion under better control, you can design them to run at considerably higher RPMs (eventually, the heat generated will overcome the cooling system's capacity, so there is a limit with those engines, too).
So, tighter tolerances that allow for higher RPMs, which require more exact valves, cams, etc....it all adds to a lot more HP. Eventually, the increase in HP makes the lack of proportional increase in TQ irrelevant.
That's why sportbikes with comparatively weak torque curves can redline at 13,000 RPMs and still put any Harley to shame.
Interesting engines are the Ducati air-cooled L-twins. They use modern technology in valves, cams, etc., and can, therefore, still wring out more HP and TQ than an air-cooled Harley V-Twin of comparable displacement.
But that's not why we buy Harleys, is it?
So, tighter tolerances that allow for higher RPMs, which require more exact valves, cams, etc....it all adds to a lot more HP. Eventually, the increase in HP makes the lack of proportional increase in TQ irrelevant.
That's why sportbikes with comparatively weak torque curves can redline at 13,000 RPMs and still put any Harley to shame.
Interesting engines are the Ducati air-cooled L-twins. They use modern technology in valves, cams, etc., and can, therefore, still wring out more HP and TQ than an air-cooled Harley V-Twin of comparable displacement.
But that's not why we buy Harleys, is it?
Higher piston speeds = more heat. Liquid is a good medium to transfer heat from engine parts.
BTW, I love that desmodromic Ducati valve train! Shaft driven...Oh Yeah!
Cruiser
Joined: Dec 2007
Posts: 223
Likes: 0
From: upstate NY
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