increasing mpg
Postmaster
Joined: Apr 2003
Posts: 2,703
Likes: 4
From: Harrisburg, NE
Originally posted by pdqford
A well tuned distributor has quite a bit of timing advance built into it at light to moderate cruise because the combination of EGR (inert gases) + air/fuel needs more time to burn and you need to complete the combustion process by about 23 degrees ATDC to maintain reasonable power AND fuel mileage. Thats also why EGR equipped engines are very prone to serious pinging if the EGR valve fails (or is blocked off, or the internal passages become plugged with carbon deposits.)
A well tuned distributor has quite a bit of timing advance built into it at light to moderate cruise because the combination of EGR (inert gases) + air/fuel needs more time to burn and you need to complete the combustion process by about 23 degrees ATDC to maintain reasonable power AND fuel mileage. Thats also why EGR equipped engines are very prone to serious pinging if the EGR valve fails (or is blocked off, or the internal passages become plugged with carbon deposits.)
Logistics Pro
Joined: Jan 2001
Posts: 3,740
Likes: 37
From: Central NYS
Originally posted by muscletruck7379
HA! my bronco will barely run with that little advance!
HA! my bronco will barely run with that little advance!
Postmaster
Joined: Apr 2003
Posts: 2,703
Likes: 4
From: Harrisburg, NE
Originally posted by pdqford
How much advance you need is as much as it takes to complete the combustion process by 23 degrees AFTER top-dead-center. If your Bronco has slow burn heads, low compression, and good EGR flow at light throttle, it may need 50 to 60 degrees advance at the crank (thats mechanical advance + vacuum advance + base timing) so that the combustion process is completed by 23* ATDC.
How much advance you need is as much as it takes to complete the combustion process by 23 degrees AFTER top-dead-center. If your Bronco has slow burn heads, low compression, and good EGR flow at light throttle, it may need 50 to 60 degrees advance at the crank (thats mechanical advance + vacuum advance + base timing) so that the combustion process is completed by 23* ATDC.
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