Im just wondering what an efficient range is for cruising, in the 20-25 in of vac range. Ive got a stock-port engine and an LT8S. Right now Im seeing 25-30 deg BTDC and Im wondering if I can go for more, like 30-40 degrees advance. I want to squeeze some mileage out of it for a 2000 mile trip next week!

 

i run a wolf, but that shouldnt matter

med-high vac tapers from 20ish sub 3k to 40deg to probably 6k slowly droping to 30's iirc

was getting almost 20mpg on long highway drives keeping my foot out of boost most of the time

stock port cosmo re with a t04s

 

OK so as long as Im in a high vacuum range then 40 deg of advance is ok? Ive searched for more specifics on timing advance (and retard under boost) and I didnt find much. A lot of people say, "well every engine and setup is different" but there must be some general range

 

Well the ignition depends on engine revs and loads. Your example of 40° advanced may be OK for high RPM ( past 4500RPM) but them may be not OK for lower engine speeds. (while Rotor-speeds increase but the fuel still takes the same time to ignite and burn)

Next point, what do you mean with high vacuum?

My advice to you would be to visit a good tuner and let them setup your car. Of course it will cost you, but it is also so much trouble- free!

REgards
Iwan

 

i ment 30+ kpa, possibly a little less but am not 100% sure

 

under 2k come to around 25 degrees. from 2k-3k go to 35 degrees and over 3k come to 40 degrees.

at all vaccum ranges from 20HG to 05HG.

 

rx72c,

with little better flowing intake manifold and full street port
do I run this steup or can I get away with little more timing

thanx
tony

 

You can go with some more timing. In some areas it will help in some it wont make any difference.