At 03:44 PM 8/28/2000 -0600, James Nazarian Jr wrote:
>Does anyone know how compression varries with altitude? I should think
that a compression check will not yeild the same numbers at 6k feet as it
will at sea level.
Inversely proportional to atmospheric pressure (but not directly
proportional). This should be a step in the right direction.
Check here:
http://www.ntsource.com/~barneymg/mgtech/air.gif
This is from Mark's Standard Handbook for Mechanical Engineers. It gives
atmospheric temperature, pressure and density changes with altitude.
Also check here:
http://www.ntsource.com/~barneymg/mgtech/air2.gif
This is the formula for adiabatic expansion and compression of air.
>Also is there a relationship of compression to horsepower? For example if
compression is increased 10% then hp will increase by x%?
Generally speaking, yes. Higher compression will usually yield a little
higher efficiency, meaning more power and better economy, but it depends on
lots of other things, like the grade of fuel being used and spark and cam
timing. The net result on torque can be appreciable with a nicely matching
set of adjustments. The net result on fuel economy could be just slightly
positive, but the improved torque is usually accompanied by a heavier foot,
so the net result is more often increased accelleration at the expense of
fuel economy.
Baeney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
|
