A motor cycle is not generating a heck of a lot of power going 70 MPH.

Paul I beg to differ, the average motorcycle has terrible aerodynamics. Even the swoopy fairing
wearing models have a poorer CD than the average car. A little less plate drag but parasitic drag
up the wazoo. The fans are only used at idle and in traffic. I didn't mean to imply they helped at
speed, I meant they probably become something of an impediment to flow at high speed. As a long
time roadracer I know that lots of time went into getting enough radiator to handle the big
engines at high output. I think you have probably heard of this as a sideline to your car building
experience. The radiator in my FZR 1000 wasn't big enough stock, that engine made 160 rear wheel
HP on the dyno. Top speed was "around 200" so it was similar to some of our planes. I used the
Kawasaki ZX-7 radiator as it was 15% bigger than the Yamaha. That radiator worked fine on the
track with 160 HP running at least 80% all the time. No fan was used at all.
Bill Jepson

You are forgetting a motor cycle Frontal Area is 20% as much as a car Bill.
Sure the Cd is bad but aero drag is Cd X FA.

Not to mention tire rolling drag is much less 
due to the much lower weight.

A car needs only 40 HP or less to go 70 MPH.

Anyway, anything that can go 200 MPH on 160 HP cannot have all that much
drag. I stand by my statement.

BTW There is no magic in heat exchangers. Nobody can build one that
is appreciable better than anyone else can build one. The magic is 
in how they are installed and ducted. I highly recommend the book 
Compact Heat Exchangers by Kays & London.

Paul Lamar
 
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