Compression test values for 4.5 liter
04-24-2013, 10:39 AM
#1
Banned
Thread Starter
Compression test values for 4.5 liter
The 82 I recently purchased had a compression check done about 2000 miles ago. Anyone have the stock values for this engine? Thanks!
04-24-2013, 11:43 AM
#2
Advanced
Join Date: Mar 2013
Location: Sierra foothills, CA
Posts: 78
Likes: 0
Received 0 Likes
on
0 Posts
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.
04-24-2013, 12:39 PM
#3
Banned
Thread Starter
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?
04-24-2013, 02:07 PM
#4
Race Director
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
04-24-2013, 02:35 PM
#5
Man of many SIGs
Rennlist Member
Rennlist Member
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
04-24-2013, 11:15 PM
#6
Banned
Thread Starter
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!