Does altitude have any effect on compression ratio? I'm at 5200 feet.
- posted
19 years ago
Does altitude have any effect on compression ratio? I'm at 5200 feet.
It lowers compression, but the ratio is the same. :)
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
.................There's a strict age limit.
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.
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 1.2723examples 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.
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