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Compression ratio

  • Aviatordan
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Aviatordan created the topic: Compression ratio

Man, compression ratio, that's a topic that's a little hard to get your head around.

Quick question, on page 1.13, when you're describing the term swept volume, a reference is given to fig 1.26. However, fig 1.26 is on the next page and is a flow chart of factors affecting engine output. There is, however, a little figure on page 1.32 (as part of the question answers). Is that the fig 1.26 that you were talking about?

Cheers!
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bobtait replied the topic: Re: Compression ratio

Don't stress about all that compression ratio stuff. I happen to know that it's not examined in any depth. It's really some rather old fashioned terms for what is really pretty simple. The swept volume is simply the portion of the cylinder that the piston travels in. That is, the piston sweeps that volume as it travels from BDC to TDC and back again. The simplest way to think of compression ratio is to compare the volume above the piston when it is a BDC with the volume above the piston when it is at TDC. Most GA engines have a compression ratio of between 8 to 1 and 10 to 1.

I have modified the diagram to make it more clear. See attached and thanks for the feed-back.

File Attachment:

File Name: SECTION1.13.pdf
File Size:218 KB
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  • Aviatordan
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Aviatordan replied the topic: Re: Compression ratio

Thanks heaps for the explanation, Bob. It made a lot more sense =].
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