What's the conversion for..., This is a hard one... |
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What's the conversion for..., This is a hard one... |
iiibdsiil |
Feb 17 2005, 08:27 PM
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#1
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
PSI to the compression ratio?
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Jake Raby |
Feb 17 2005, 08:28 PM
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#2
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Their really isn't one...
The cam and so many other factors effect cylinder filling and that effects cranking compression... |
redshift |
Feb 17 2005, 08:35 PM
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#3
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Bless the Hell out of you! Group: Members Posts: 10,926 Joined: 29-June 03 Member No.: 869 |
Happy Belated Birthday ANYHOW!
(IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) Didn't see you around. M |
iiibdsiil |
Feb 17 2005, 08:36 PM
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#4
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
Miles, thank you sir.
Jake, You are killing me here. I guess that is the right answer though, I'm just not happy about it. |
Jake Raby |
Feb 17 2005, 08:39 PM
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#5
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Pop off a head, measure the deck and cc the chamber...
Thats the only for sure way to know... |
TimT |
Feb 17 2005, 08:39 PM
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#6
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
Rough work around,
say 8.5:1CR 8.5*14.7=124.9psi so you could take psi and divide by 14.7 to tell you a rough CR if that what your looking for.. Like Jake says to many other variables. Cam Timing,profile etc. |
iiibdsiil |
Feb 17 2005, 08:49 PM
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#7
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
Thanks guys. Explains why I couldn't get a straight answer on google.
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Jake Raby |
Feb 17 2005, 09:18 PM
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#8
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Elevation effects air density and air density effects cranking PSI....
So someone in Florida can compression test their engine, drive it to Colorado and re-test it and get two drastic different readings... The higher the altitude the LESS PSI you will see. I set engines that are going to High Altitude 20% higher than normal as an average number..... |
iiibdsiil |
Feb 17 2005, 09:38 PM
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#9
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
That makes sense. I never thought about it being that deep. Makes perfect sense.
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john rogers |
Feb 17 2005, 10:19 PM
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#10
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Senior Member Group: Members Posts: 1,525 Joined: 4-March 03 From: Chula Vista CA Member No.: 391 |
The answer about cam overlap and the affects on compression is spot on. At one of our vintage races a guy from AZ has a 1969 Z28 and it cranks over like there are no heads on it. I asked him what the c/r was and he said 13:1 but with the cam overlap he could maybe get 100# when doing a compression test! Boy it sure ran good though once it fired up!
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Gint |
Feb 17 2005, 11:11 PM
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#11
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Mike Ginter Group: Admin Posts: 16,082 Joined: 26-December 02 From: Denver CO. Member No.: 20 Region Association: Rocky Mountains |
And 20% is just about the right number for the difference between sea level and Denver at 5K altitude. |
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Jake Raby |
Feb 18 2005, 01:25 AM
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#12
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
You got it....
When I say that i build engines for the application- Its not BS (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif) |
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