I'd never heard of this till a few days ago. I was wondering how this one 03 Cobra got rebuilt with 9.7:1 compression ratio from the stock 8.5:1 compression ratio and was still running high boost. The guy said because of his aftermarket cams the dynamic CR was still fairly stock. Around 7.7 if I remember correctly.
Interesting read.
http://cochise.uia.net/pkelley2/DynamicCR.html
Dynamic compression ratio
Moderator: MalcolmV8
- MalcolmV8
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Dynamic compression ratio
92 302 Ranger - sold
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85
Tuned by MD Racing
https://www.youtube.com/c/MalcolmV8
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85
Tuned by MD Racing
https://www.youtube.com/c/MalcolmV8
Re: Dynamic compression ratio
thats true and very few people really catch the concept of it, while your mechanical compression maybe 9.7 to one, that is assuming 100% cyclinder filling and trapping of those gases in the cylinder,obviousely that doesnt happen in the real world, pumping losses and camshaft centerline/duration/ overlap and blowdown time on the exhaust valve cycle reduce the eficiency of the engine by 1.5- 2 points, thats why in the 60's and 70's when a lot of guys put a monster cam in theyre engine they had to bump the compression a couple of points to ragain lost efficiency from the new cam install, your cobra motor that might have 10.1static right now only has 8.1 dynamic, hope this helps
twin turbo v8 menace
- MalcolmV8
- Supporting Member
- Posts: 2597
- Joined: Fri Dec 10, 2004 4:50 pm
- SM: Yes
- Location: Kansas City, MO
Re: Dynamic compression ratio
Yeah it was something I never realized until recently myself.
92 302 Ranger - sold
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85
Tuned by MD Racing
https://www.youtube.com/c/MalcolmV8
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85
Tuned by MD Racing
https://www.youtube.com/c/MalcolmV8