Why does liquid cooling allow for more power?
Road Master
Joined: Jan 2009
Posts: 866
Likes: 0
From: Houston, TX
Water cooling produces a more stable operating temperature range and thus tighter tolerances can be held. Air cooling isn't really worse than water cooling from a power standpoint, but tighter tolerances allow you to get more power because you can shed heat more easily (as the others said). It's hard to add heat-shedding power to an air-cooled engine without making it bigger. If it's water-cooled, you can just make the radiator larger.
Tourer
Joined: Nov 2005
Posts: 364
Likes: 0
From: Chicago Suburbs
Water cooling allows more constant and regulated temperatures which, as already metioned, allows tighter tolerances. tighter tolerances make a tighter engine which will produce more power.
Don't worry about how water cooling will affect the sound. If you water cool a Harley v-twin it will sound the same, maybe lose some mechanical engine noise (good) but not the harley sound.
Honda and suzuki both have liquid cooled transverse v-twins like Ducati... sound almost the same. The distinctive Harley sound is more more a function of the firing order and off-set crank pin than how it is cooled.
Don't worry about how water cooling will affect the sound. If you water cool a Harley v-twin it will sound the same, maybe lose some mechanical engine noise (good) but not the harley sound.
Honda and suzuki both have liquid cooled transverse v-twins like Ducati... sound almost the same. The distinctive Harley sound is more more a function of the firing order and off-set crank pin than how it is cooled.
Cruiser
Joined: Jul 2008
Posts: 224
Likes: 0
From: Oregon Coast
Cooling does a lot towards increasing horse power, but the real reason liquid cooled engines develope more power is because they allow higher combustion chamber pressures.
That's my story and I'm sticking to it.
That's my story and I'm sticking to it.
Ultimate HDF Member
Joined: Sep 2007
Posts: 8,831
Likes: 15
From: Nomad
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?
Road Master
Joined: Jun 2005
Posts: 1,008
Likes: 8
From: Dogtown, Oakland, CA
Road Warrior
Joined: May 2006
Posts: 1,423
Likes: 0
From: Southern California High Desert, here and there....
Water cooling allows more constant and regulated temperatures which, as already metioned, allows tighter tolerances. tighter tolerances make a tighter engine which will produce more power.
Don't worry about how water cooling will affect the sound. If you water cool a Harley v-twin it will sound the same, maybe lose some mechanical engine noise (good) but not the harley sound.
Honda and suzuki both have liquid cooled transverse v-twins like Ducati... sound almost the same. The distinctive Harley sound is more more a function of the firing order and off-set crank pin than how it is cooled.
Don't worry about how water cooling will affect the sound. If you water cool a Harley v-twin it will sound the same, maybe lose some mechanical engine noise (good) but not the harley sound.
Honda and suzuki both have liquid cooled transverse v-twins like Ducati... sound almost the same. The distinctive Harley sound is more more a function of the firing order and off-set crank pin than how it is cooled.
Tourer
Joined: Nov 2008
Posts: 472
Likes: 0
Because the amount of energy generated by the combustion is higher, since u r starting from much lower temperature (comparing to a hot engine) towards a high temperature (combustion moment).
Hot engine
Combustion temp <<<<<<<<<<<<<< prior combustion temp (hot)
x---------------------------------------------------x
Cold engine
Combustion temp <<<<<<<<<<<<<<< prior combustion temp (slightly colder)
x----------------------------------------------------------------x
The length of the line represents the amount of combustion energy which gets converted to dynamic energy through the piston, crank, gears then the belt, so the bigger the better.
Hot engine
Combustion temp <<<<<<<<<<<<<< prior combustion temp (hot)
x---------------------------------------------------x
Cold engine
Combustion temp <<<<<<<<<<<<<<< prior combustion temp (slightly colder)
x----------------------------------------------------------------x
The length of the line represents the amount of combustion energy which gets converted to dynamic energy through the piston, crank, gears then the belt, so the bigger the better.
Last edited by QS78; Apr 9, 2009 at 05:01 AM.
Road Warrior
Joined: Feb 2007
Posts: 1,785
Likes: 4
From: Oklahoma
Let me ask a related question. Why is water cooled better for EPA emissions purposes? Is it because the higher temps produce more complete combustion? or what?
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