Compression test values for 4.5 liter
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Joined: Mar 2013
Posts: 78
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From: Sierra foothills, CA
Plenty of good info in this thread:
https://rennlist.com/forums/928-foru...st-values.html
One of the key bits of info is that the actual numbers are less important than consistency across cylinders.
https://rennlist.com/forums/928-foru...st-values.html
One of the key bits of info is that the actual numbers are less important than consistency across cylinders.
Thread Starter
Banned
Joined: Apr 2013
Posts: 850
Likes: 6
From: Humble, TX
Mine are 160 across the board plus or minus 5. The engine has 83K and has never been cracked open for any reason. Wouldn't the compression test numbers be different on the newer engines (5.0/5.4 liter) due to the factory increase of compression ratio?
Race Director
Joined: Sep 2004
Posts: 16,271
Likes: 82
From: Stockton, CA
Static compression ratio of 9.0:1.
Effective stroke is 2.71 inches.
Your dynamic compression ratio is 7.98:1 .
Your dynamic cranking pressure is 158.46 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.98 :1.
V/P (Volume to Pressure Index) is 113
Man of many SIGs
Rennlist Member
Rennlist Member
Joined: May 2005
Posts: 8,724
Likes: 12
From: Florida, USA
those are solid numbers for an 82 L jet....its a factory 9-1 CR engine and with cam timing factored in the ideal cranking pressure is about perfect
Static compression ratio of 9.0:1.
Effective stroke is 2.71 inches.
Your dynamic compression ratio is 7.98:1 .
Your dynamic cranking pressure is 158.46 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.98 :1.
V/P (Volume to Pressure Index) is 113
Static compression ratio of 9.0:1.
Effective stroke is 2.71 inches.
Your dynamic compression ratio is 7.98:1 .
Your dynamic cranking pressure is 158.46 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 7.98 :1.
V/P (Volume to Pressure Index) is 113
Thread Starter
Banned
Joined: Apr 2013
Posts: 850
Likes: 6
From: Humble, TX
Sorry, I looked at the test sheet wrong. My numbers are 155 average with 150 as the low and 160 as the high. So according to your calculations, right on the money. Good news anyway. Thanks!
Race Director
Joined: Sep 2004
Posts: 16,271
Likes: 82
From: Stockton, CA
i got the calculator from www.wallaceracing.com Lots and lots of calculators on there....stuff I don't understand at all
