Which is hotter?
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Tourer
Joined: Apr 2007
Posts: 264
Likes: 38
From: S. California
Which is hotter?
When riding in this blast furnace desert where I live and its 112 degrees, which is better for engine temps: 1) ride faster? ...Produces more cooling air but engine is making more heat...
Or
2) slow down?, less cooling air but engine also making less heat.
Or
2) slow down?, less cooling air but engine also making less heat.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
my own testing shows a cooler motor with fairing lowers on. vents closed
( ambient temps 105ş, avg speed 60 MPH an 18 mile loop. oil temps in the oil tank about 20ş lower)
the ordered air across the motor removes heat...but also can contribute to the rider "blow dryer effect"--- so the motor may be cooler, but the rider is more affected by the heat that is removed.
higher rpms equal more oiling ( incl oil spray at bottoms of pistons) which removes more heat from the motor internals.
high heat operation can increase the chances of pinging, so octane is a factor to reduce pre-ignition and detonation
my usual rpms are 2800~3200 if that is any guide to you ( rpms may drop some on a dead flat road with no headwind)
mike
( ambient temps 105ş, avg speed 60 MPH an 18 mile loop. oil temps in the oil tank about 20ş lower)
the ordered air across the motor removes heat...but also can contribute to the rider "blow dryer effect"--- so the motor may be cooler, but the rider is more affected by the heat that is removed.
higher rpms equal more oiling ( incl oil spray at bottoms of pistons) which removes more heat from the motor internals.
high heat operation can increase the chances of pinging, so octane is a factor to reduce pre-ignition and detonation
my usual rpms are 2800~3200 if that is any guide to you ( rpms may drop some on a dead flat road with no headwind)
mike
Supporter
Joined: Aug 2008
Posts: 5,189
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From: N.E. Wisconsin
Ambient air temp will only cool to a point, faster air over the engine surface takes away heat faster but usually a 10 to 20 degree temp drop from present air temperature will be realized. About 50% of engine heat dissipates from your exhaust, about 10% goes to the oil. Richer AFR. Running a more open exhaust. Plus staying in your power zone, oil cooler and channeled air are about the only things you can do to cool. Ppphysics is Ppphysics...... Sylvester says ! 
Elite HDF Member
Joined: Nov 2010
Posts: 3,846
Likes: 173
From: Simi Valley, CA
I don't have any hard data to support this opinion of mine, but here it is nonetheless...
If you're talking about riding down the road at 90 mph vs. 75 mph, I would bet the engine and engine oil temps would be lower at 75 mph.
I think the increased load on the engine at higher speeds is a bigger player in heating up the engine than the increased airflow will be at cooling it down.
If you're talking about riding down the road at 90 mph vs. 75 mph, I would bet the engine and engine oil temps would be lower at 75 mph.
I think the increased load on the engine at higher speeds is a bigger player in heating up the engine than the increased airflow will be at cooling it down.
Road Master
Joined: Apr 2011
Posts: 1,145
Likes: 98
From: Colorado Springs
I don't have any hard data to support this opinion of mine, but here it is nonetheless...
If you're talking about riding down the road at 90 mph vs. 75 mph, I would bet the engine and engine oil temps would be lower at 75 mph.
I think the increased load on the engine at higher speeds is a bigger player in heating up the engine than the increased airflow will be at cooling it down.
If you're talking about riding down the road at 90 mph vs. 75 mph, I would bet the engine and engine oil temps would be lower at 75 mph.
I think the increased load on the engine at higher speeds is a bigger player in heating up the engine than the increased airflow will be at cooling it down.
...
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From: Glendale AZ
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