Compression ratio

Does altitude have any effect on compression ratio? I'm at 5200 feet.

Reply to
Volksrod70
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It lowers compression, but the ratio is the same. :)

Reply to
jjs

Hmm... Good answer as long as you mean increased altitude (all else being equal) means decreased compression. Or... at least I agree with you, so you're probably wrong. :-) I think Tim is starting up a support group for people who get unnerved by having Chris and I agree with them, so you may need to talk to him for comforting. As always, I'm ever so glad I could help. :-D

Reply to
Shaggie

.................There's a strict age limit.

Reply to
Tim Rogers

At elevation, the pressure in the combustion chamber will be lower at BDC /and/ TDC; this because you start out with less dense air: at one mile elevation, air density is only 85.5% of sea level density, so presumably when the piston is at TDC, the compressed version is 14.5% less pressure than it would be at sea level.

The compression ratio does not change: If you have an 8:1 compression ratio at sea level, it remains 8:1 in Denver. The swept volume of the piston does not change, nor does the the volume of the combustion chamber.

Reply to
Mike Rocket J. Squirrel Elliot

Multiply the sea level compression reading by the FACTOR to see what it would be at the ALTITUDE. Multiply the altitude compression reading by the INVERSE to see what it will be at sea level.

ALTITUDE FACTOR INVERSE

1000ft .9711 1.0298 2000ft .9428 1.0607 3000ft .9151 1.0928 4000ft .8881 1.1260 5000ft .8617 1.1604 6000ft .8359 1.1963 7000ft .8106 1.2336 8000ft .7860 1.2723

examples Compression in psi at sea level = 125 What would the reading be at 7000 foot elevation? 125 x .8106 = 101.325

Compression in psi at 7000 foot elevation = 115 psi. What would the compression reading be at sea level? 115 x 1.2336 = 141.864.

Reply to
Robert

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