Compression, Not your average Engine |
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Compression, Not your average Engine |
Mblizzard |
Oct 16 2018, 06:44 AM
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#1
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
Ok so as many know, I an building my dream engine. With lots of Type 4 Store goodies including Nickies, 78 mm crank, and 102mm P/Cs, LE-200 heads and a decent cam, I am looking at where I want my compression to be.
With a normal engine and quality components it seems that 8.5 to 9.5 is about the limit before heat and detonation become issues. Don't have any measurements yet but playing around with some calculations and assuming a low deck height because I have a slight dish and or valve pockets in the pistons I could easily get to over 11 to 1. But I am think that might not be a long lasting engine. Looking at going for 10 to 10.5. Thoughts? (IMG:style_emoticons/default/blowup.gif) |
VaccaRabite |
Oct 16 2018, 08:05 AM
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#2
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En Garde! Group: Admin Posts: 13,444 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
Its somewhat apples and oranges since my engine is a 2056, but in this most recent iteration I backed the compression from 9.2:1 down to 8.8:1. The engine has responded very positively to that. Not as punchy, yes, but head heat was an issue on the highway unless I kept it in 4th until about 70mph. With the slightly lower compression, I'm generating a lot less heat. (measuring heat on a Dakota Digital CHT tied to Cyl 3 spark plug.)
I think going 10:1 with the thin cylinder walls is going to be a challenge, unless you have a system in place to REALLY move that heat out of the cylinders and heads. Zach |
Mblizzard |
Oct 16 2018, 08:54 AM
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#3
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Advanced Member Group: Members Posts: 3,033 Joined: 28-January 13 From: Knoxville Tn Member No.: 15,438 Region Association: South East States |
Its somewhat apples and oranges since my engine is a 2056, but in this most recent iteration I backed the compression from 9.2:1 down to 8.8:1. The engine has responded very positively to that. Not as punchy, yes, but head heat was an issue on the highway unless I kept it in 4th until about 70mph. With the slightly lower compression, I'm generating a lot less heat. (measuring heat on a Dakota Digital CHT tied to Cyl 3 spark plug.) I think going 10:1 with the thin cylinder walls is going to be a challenge, unless you have a system in place to REALLY move that heat out of the cylinders and heads. Zach Zach You are completely correct. The 10 to 1 was a bit tongue in cheek with the exploding icon. Certainly I see now that was not clear. However higher compression can lead to more efficient combustion and up to a point does not equate to higher head temperatures. Problem is, for each engine and build that point is different. Reading back through a huge amount of information with some of it written by Jake, the reality seems that 9 to 9.5 is the range. but that is just a guess on my part. |
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